Orion the Hunter is arguably the most recognizable constellation in the world. Orion lies on the celestial equator, making it visible from both the Northern and Southern Hemispheres. Orion’s shape is easy to pick out because of its many bright stars and signature Orion’s Belt: three stars close together in a nearly straight line.
Orion the Hunter – visible to both hemispheres – rises in the east on December evenings.
In many drawings of the constellation Orion, the Hunter looks to be battling his neighbor, Taurus the Bull. Yet there is no such story in the mythology of Orion. Some stories have Orion pursuing the seven sisters of the Pleiades, which is a star cluster in the constellation Taurus. On the other side of Orion are his hunting dogs, Canis Major and Canis Minor (not to be confused with Canes Venatici, a different constellation with the actual nickname of the Hunting Dogs).
Mythology says that a scorpion killed Orion; that’s why Orion is on one side of the sky while Scorpius the Scorpion is on the opposite side. As Scorpius is about to rise in the east, Orion makes a hurried exit from the sky in the west.
Orion the Hunter, as depicted in Urania’s Mirror, a set of constellation cards from around 1825. Image via Wikimedia Commons (public domain).
Brightest stars in Orion
The brightest star in Orion is the bluish Rigel, which marks his western knee or foot. Rigel is a blue supergiant 770 light-years away with a magnitude of 0.2. Rigel is the seventh brightest star in the entire sky. The star marking the other knee or foot of Orion is Saiph, a magnitude 2.1 star. It’s a blue supergiant, 720 light-years distant.
The second brightest star in Orion is reddish-orange Betelgeuse, which marks one shoulder. Betelgeuse is the 10th brightest star in the sky at magnitude 0.5. It’s a red supergiant 550 light-years away and a whopping 800 times larger than our sun. If we substituted Betelgeuse for our sun, it would swallow up all the inner planets.
The third brightest star of Orion, which marks his other shoulder, is Bellatrix. Bellatrix, a blue supergiant shining at magnitude 1.6, is the 22nd brightest star in the sky and lies 245 light-years away.
View at EarthSky Community Photos. | Amr Elsayed of Egypt submitted this photo on December 6, 2024, and wrote: “One of the brightest stars of winter in the Orion constellation, one of the most recognizable due to the 3 stars that form a line in the center. The image also shows the Orion Nebula, a gas and dust cloud about 1,500 light-years away, and includes the orange star Betelgeuse, which is expected to end its life soon, and will potentially be visible as bright as the moon.” Thank you, Amr!
Other stars in Orion
Extending out from Bellatrix is Orion’s arm, where he is holding either a shield or an animal, depending on the artist’s concept. The brighter stars marking this object are all of 3rd and 4th magnitude.
Extending upward from Betelgeuse is Orion’s other arm, which holds a club or sword. The brightest stars in the arm and club are all 4th magnitude.
The stars that make up Orion’s head are a test of your sky’s darkness. They range from 3rd magnitude to 6th magnitude. The more stars you can see, the better your skies are.
View at EarthSky Community Photos. | Sergei Timofeevski shared this image from November 13, 2023. Sergei wrote: “The constellation Orion the Hunter and the star Sirius rising just above the eastern horizon in the Anza-Borrego Desert State Park, California.” Thank you, Sergei! Note bright Sirius is on the bottom, and Orion’s Belt pointing to it.
Nebulae of Orion the Hunter
The stars in the Sword that hangs down from the Belt are part of the Orion Nebula (M42). Yes, you can see the nebula, or cloud of gas, without optical aid as a hazy, 4th-magnitude patch. Using magnification reveals a quadruple star at the center of the nebula. These four newborn stars – the Trapezium Cluster – light up their dusty cocoon, making its glow visible to us here on Earth, a vast 1,400 light-years away.
The famous Horsehead Nebula lies near the Belt star Alnitak. This dark nebula is a faint target even for most amateur telescopes; your best bet is to view it in a picture compliments of an astrophotographer. (Learn more about dark nebulae.)
Along Orion’s side between Alnitak and Betelgeuse (but closer to the belt stars) is the 8th-magnitude nebula M78. M78 has the awkward title of “brightest diffuse reflection nebula in the sky.” One more notable nebula in Orion is near Rigel and crosses into Eridanus the River. IC 2118, the Witch Head Nebula, is extremely faint but also extremely large, spanning six full moons.
View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured this telescopic view of the Orion Nebula on October 4, 2024. Andy wrote: “I recently took a pic of Orion [look here] using an Antlia RGB enhancer. This photo turned out much bluer. Both pics are fun and I think I like the bluer one better. Orion is such a wonderful object to explore.” It definitely is, thank you, Andy!
More EarthSky Community Photos of Orion
View at EarthSky Community Photos. | Catherine Hyde in Cambria, California, captured these nebulae in Orion on January 5, 2024. Catherine wrote: “This is essentially first light on my new Redcat 51 scope, the smallest scope I’ve ever had. The short focal length allowed me to frame the belt and sword of Orion in one image. Included are the Flame and Horsehead Nebulae, and the iconic Orion Nebula with the Running Man above it.” Thank you, Catherine!View at EarthSky Community Photos. | Harshwardhan Pathak of India used a large remote telescope in Australia to capture the Orion Nebula on October 5, 2023. Harshwardhan wrote: “Popularly called the Orion Nebula, this stellar nursery has been known to many different cultures throughout human history. The nebula is only 1,400 light-years away, making it the closest large star-forming region to Earth … This is the target which every astrophotographer wants to shoot in winter’s night sky.” A beautiful capture. Thank you, Harshwardhan!View at EarthSky Community Photos. | Tameem Altameemi in the Ras Al Khaimah Mountains, United Arab Emirates (UAE), captured this telescopic view of the Horsehead Nebula in the constellation Orion on November 18, 2023. Tameem wrote: “My astrophotography from the sky of UAE. The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 900 to 1,500 light-years away, and the Horsehead Nebula, a small dark nebula in the constellation Orion.” Thank you, Tameem!
Bottom line: Orion the Hunter may be the most recognizable constellation in the world. It’s visible from the north in winter and from the south in summer. And it’s full of many deep-sky treasures.
Orion the Hunter is arguably the most recognizable constellation in the world. Orion lies on the celestial equator, making it visible from both the Northern and Southern Hemispheres. Orion’s shape is easy to pick out because of its many bright stars and signature Orion’s Belt: three stars close together in a nearly straight line.
Orion the Hunter – visible to both hemispheres – rises in the east on December evenings.
In many drawings of the constellation Orion, the Hunter looks to be battling his neighbor, Taurus the Bull. Yet there is no such story in the mythology of Orion. Some stories have Orion pursuing the seven sisters of the Pleiades, which is a star cluster in the constellation Taurus. On the other side of Orion are his hunting dogs, Canis Major and Canis Minor (not to be confused with Canes Venatici, a different constellation with the actual nickname of the Hunting Dogs).
Mythology says that a scorpion killed Orion; that’s why Orion is on one side of the sky while Scorpius the Scorpion is on the opposite side. As Scorpius is about to rise in the east, Orion makes a hurried exit from the sky in the west.
Orion the Hunter, as depicted in Urania’s Mirror, a set of constellation cards from around 1825. Image via Wikimedia Commons (public domain).
Brightest stars in Orion
The brightest star in Orion is the bluish Rigel, which marks his western knee or foot. Rigel is a blue supergiant 770 light-years away with a magnitude of 0.2. Rigel is the seventh brightest star in the entire sky. The star marking the other knee or foot of Orion is Saiph, a magnitude 2.1 star. It’s a blue supergiant, 720 light-years distant.
The second brightest star in Orion is reddish-orange Betelgeuse, which marks one shoulder. Betelgeuse is the 10th brightest star in the sky at magnitude 0.5. It’s a red supergiant 550 light-years away and a whopping 800 times larger than our sun. If we substituted Betelgeuse for our sun, it would swallow up all the inner planets.
The third brightest star of Orion, which marks his other shoulder, is Bellatrix. Bellatrix, a blue supergiant shining at magnitude 1.6, is the 22nd brightest star in the sky and lies 245 light-years away.
View at EarthSky Community Photos. | Amr Elsayed of Egypt submitted this photo on December 6, 2024, and wrote: “One of the brightest stars of winter in the Orion constellation, one of the most recognizable due to the 3 stars that form a line in the center. The image also shows the Orion Nebula, a gas and dust cloud about 1,500 light-years away, and includes the orange star Betelgeuse, which is expected to end its life soon, and will potentially be visible as bright as the moon.” Thank you, Amr!
Other stars in Orion
Extending out from Bellatrix is Orion’s arm, where he is holding either a shield or an animal, depending on the artist’s concept. The brighter stars marking this object are all of 3rd and 4th magnitude.
Extending upward from Betelgeuse is Orion’s other arm, which holds a club or sword. The brightest stars in the arm and club are all 4th magnitude.
The stars that make up Orion’s head are a test of your sky’s darkness. They range from 3rd magnitude to 6th magnitude. The more stars you can see, the better your skies are.
View at EarthSky Community Photos. | Sergei Timofeevski shared this image from November 13, 2023. Sergei wrote: “The constellation Orion the Hunter and the star Sirius rising just above the eastern horizon in the Anza-Borrego Desert State Park, California.” Thank you, Sergei! Note bright Sirius is on the bottom, and Orion’s Belt pointing to it.
Nebulae of Orion the Hunter
The stars in the Sword that hangs down from the Belt are part of the Orion Nebula (M42). Yes, you can see the nebula, or cloud of gas, without optical aid as a hazy, 4th-magnitude patch. Using magnification reveals a quadruple star at the center of the nebula. These four newborn stars – the Trapezium Cluster – light up their dusty cocoon, making its glow visible to us here on Earth, a vast 1,400 light-years away.
The famous Horsehead Nebula lies near the Belt star Alnitak. This dark nebula is a faint target even for most amateur telescopes; your best bet is to view it in a picture compliments of an astrophotographer. (Learn more about dark nebulae.)
Along Orion’s side between Alnitak and Betelgeuse (but closer to the belt stars) is the 8th-magnitude nebula M78. M78 has the awkward title of “brightest diffuse reflection nebula in the sky.” One more notable nebula in Orion is near Rigel and crosses into Eridanus the River. IC 2118, the Witch Head Nebula, is extremely faint but also extremely large, spanning six full moons.
View at EarthSky Community Photos. | Andy Dungan near Cotopaxi, Colorado, captured this telescopic view of the Orion Nebula on October 4, 2024. Andy wrote: “I recently took a pic of Orion [look here] using an Antlia RGB enhancer. This photo turned out much bluer. Both pics are fun and I think I like the bluer one better. Orion is such a wonderful object to explore.” It definitely is, thank you, Andy!
More EarthSky Community Photos of Orion
View at EarthSky Community Photos. | Catherine Hyde in Cambria, California, captured these nebulae in Orion on January 5, 2024. Catherine wrote: “This is essentially first light on my new Redcat 51 scope, the smallest scope I’ve ever had. The short focal length allowed me to frame the belt and sword of Orion in one image. Included are the Flame and Horsehead Nebulae, and the iconic Orion Nebula with the Running Man above it.” Thank you, Catherine!View at EarthSky Community Photos. | Harshwardhan Pathak of India used a large remote telescope in Australia to capture the Orion Nebula on October 5, 2023. Harshwardhan wrote: “Popularly called the Orion Nebula, this stellar nursery has been known to many different cultures throughout human history. The nebula is only 1,400 light-years away, making it the closest large star-forming region to Earth … This is the target which every astrophotographer wants to shoot in winter’s night sky.” A beautiful capture. Thank you, Harshwardhan!View at EarthSky Community Photos. | Tameem Altameemi in the Ras Al Khaimah Mountains, United Arab Emirates (UAE), captured this telescopic view of the Horsehead Nebula in the constellation Orion on November 18, 2023. Tameem wrote: “My astrophotography from the sky of UAE. The Flame Nebula, designated as NGC 2024 and Sh2-277, is an emission nebula in the constellation Orion. It is about 900 to 1,500 light-years away, and the Horsehead Nebula, a small dark nebula in the constellation Orion.” Thank you, Tameem!
Bottom line: Orion the Hunter may be the most recognizable constellation in the world. It’s visible from the north in winter and from the south in summer. And it’s full of many deep-sky treasures.
View at EarthSky Community Photos. | Rob Ratkowski took this all-sky view from Haleakala Observatory in Hawaii in 2023. It shows the path of the sun across the sky at the solstices (top and bottom) and at the equinoxes (center). Thanks, Rob! Find more personal solstices below!
View at EarthSky Community Photos. | Doug Pederson in Minneapolis, Minnesota, captured this scene on December 21, 2023. Doug wrote: “We host a solstice s’mores party every year on the solstice. Seems to bring out all types in our neighborhood, and this year will be our 12th annual event. A lot of kids have grown up but still come back!” Thank you, Doug!View at EarthSky Community Photos. | Rick Williams of Woodland, California, wrote in December 2020: “This was taken one day before last year’s solstice, at noon. I have a small mirror in front of my house, which reflects the sun onto my outside wall. Every day, I mark the reflection on the wall exactly at noon, which delineates an analemma over the course of a year. It took me a couple of years to get it done. Since the sun is lower in the sky, its reflection is lower on the wall. At the solstice (sol = sun, sistere = to stand still), the sun seems to pause and reverse its course. It is directly overhead at noon at 23.5 deg S, Tropic of Capricorn.” Thank you, Rick!View at EarthSky Community Photos. | Laurel Sherrie shared this photo of herself on December 21, 2020. She wrote: “Plein air painting at Point Buchon Trail, Los Osos, California. This is a rock formation we call Stonehenge, and it never disappoints. It was magical to be there for the winter solstice. Just a cell phone. A friend took the photo of me painting a favorite coastal scene on the winter solstice. So magical!” Thank you, Laurel!
More from our community
View at EarthSky Community Photos. | Jeff Schreier captured this image on the winter solstice in Sandy Hook, New Jersey. Jeff wrote: “Treehenge is located on Sandy Hook Bay in Ft. Hancock, New Jersey. On every summer solstice, the sun sets in the center opening of this small tree. Here on the winter solstice, the sun sets far to the left, while a barge holds its position and reflects its light.” Thank you, Jeff!View at EarthSky Community Photos. | Markham Starr captured this image at the 2019 December solstice in North Stonington, Connecticut. He wrote: “Native American winter solstice sunrise wall. Sun rises over the next hilltop 7/10 of a mile away. There is a spring right where the sun rises over that ridge line, so the sun also rises over water.” Thank you, Markham!View at EarthSky Community Photos. | Leslie Scopes-Anderson in Cooperstown, New York, captured this image at the December 2017 solstice. She wrote: “Sunset on a frozen pond shows the returning of the light.” Thank you, Leslie!Judy Glattstein in New Jersey wrote in 2016, “Houses here are spread apart. No chimneys, no standing stones. But in the cold of a solstice morning the trees serve to define the rising of the sun.” Thank you, Judy!View at EarthSky Community Photos. | Raul Cortes in Monterrey, Mexico, created this personal solstices composite from images captured on December 22, 2021. He wrote: “Mountain and sun attended their annual winter solstice reunion. The sun showed over the Horse Saddle Hill exactly in the middle of the saddle on December 22 for this 2021 solstice, as seen from El Obispado Hill in Monterrey, Mexico. Once again, they met together on this day, as they did last year and will do next year.” Thank you, Raul!
Personal solstices in shadows
These next few are all about shadows. Ben Orlove wrote in 2016: “On the mornings close to the winter solstice, when the sun’s course is at its lowest and southernmost, the shadow of a chimney across the street from my building falls directly on the peak of the adjacent roof and lands on the wall next to it. Our own Stonehenge!” Thank you, Ben!Capturing the year’s longest noontime shadow – December 21, 2016 – in Hyderabad, India. Photo by PadmaSri Naidu.Athens, Greece, at noon on the day of the solstice – December 21, 2016 – by Nikolaos Pantazis. Notice the long shadows!View at EarthSky Community Photos. | Wells Shoemaker captured this image on the day of the December solstice in 2005 in Death Valley National Park. He said: “The Eureka Dunes, rising 750 feet (230 meters) above the desert floor, are among the tallest in North America. The low solstice sun casts the longest shadows of the year.” Thanks, Wells!
Bottom line: Some people like to mark the solstice with a special sunset view, or marking of shadows, or party! Personal solstices from the EarthSky community, here.
View at EarthSky Community Photos. | Rob Ratkowski took this all-sky view from Haleakala Observatory in Hawaii in 2023. It shows the path of the sun across the sky at the solstices (top and bottom) and at the equinoxes (center). Thanks, Rob! Find more personal solstices below!
View at EarthSky Community Photos. | Doug Pederson in Minneapolis, Minnesota, captured this scene on December 21, 2023. Doug wrote: “We host a solstice s’mores party every year on the solstice. Seems to bring out all types in our neighborhood, and this year will be our 12th annual event. A lot of kids have grown up but still come back!” Thank you, Doug!View at EarthSky Community Photos. | Rick Williams of Woodland, California, wrote in December 2020: “This was taken one day before last year’s solstice, at noon. I have a small mirror in front of my house, which reflects the sun onto my outside wall. Every day, I mark the reflection on the wall exactly at noon, which delineates an analemma over the course of a year. It took me a couple of years to get it done. Since the sun is lower in the sky, its reflection is lower on the wall. At the solstice (sol = sun, sistere = to stand still), the sun seems to pause and reverse its course. It is directly overhead at noon at 23.5 deg S, Tropic of Capricorn.” Thank you, Rick!View at EarthSky Community Photos. | Laurel Sherrie shared this photo of herself on December 21, 2020. She wrote: “Plein air painting at Point Buchon Trail, Los Osos, California. This is a rock formation we call Stonehenge, and it never disappoints. It was magical to be there for the winter solstice. Just a cell phone. A friend took the photo of me painting a favorite coastal scene on the winter solstice. So magical!” Thank you, Laurel!
More from our community
View at EarthSky Community Photos. | Jeff Schreier captured this image on the winter solstice in Sandy Hook, New Jersey. Jeff wrote: “Treehenge is located on Sandy Hook Bay in Ft. Hancock, New Jersey. On every summer solstice, the sun sets in the center opening of this small tree. Here on the winter solstice, the sun sets far to the left, while a barge holds its position and reflects its light.” Thank you, Jeff!View at EarthSky Community Photos. | Markham Starr captured this image at the 2019 December solstice in North Stonington, Connecticut. He wrote: “Native American winter solstice sunrise wall. Sun rises over the next hilltop 7/10 of a mile away. There is a spring right where the sun rises over that ridge line, so the sun also rises over water.” Thank you, Markham!View at EarthSky Community Photos. | Leslie Scopes-Anderson in Cooperstown, New York, captured this image at the December 2017 solstice. She wrote: “Sunset on a frozen pond shows the returning of the light.” Thank you, Leslie!Judy Glattstein in New Jersey wrote in 2016, “Houses here are spread apart. No chimneys, no standing stones. But in the cold of a solstice morning the trees serve to define the rising of the sun.” Thank you, Judy!View at EarthSky Community Photos. | Raul Cortes in Monterrey, Mexico, created this personal solstices composite from images captured on December 22, 2021. He wrote: “Mountain and sun attended their annual winter solstice reunion. The sun showed over the Horse Saddle Hill exactly in the middle of the saddle on December 22 for this 2021 solstice, as seen from El Obispado Hill in Monterrey, Mexico. Once again, they met together on this day, as they did last year and will do next year.” Thank you, Raul!
Personal solstices in shadows
These next few are all about shadows. Ben Orlove wrote in 2016: “On the mornings close to the winter solstice, when the sun’s course is at its lowest and southernmost, the shadow of a chimney across the street from my building falls directly on the peak of the adjacent roof and lands on the wall next to it. Our own Stonehenge!” Thank you, Ben!Capturing the year’s longest noontime shadow – December 21, 2016 – in Hyderabad, India. Photo by PadmaSri Naidu.Athens, Greece, at noon on the day of the solstice – December 21, 2016 – by Nikolaos Pantazis. Notice the long shadows!View at EarthSky Community Photos. | Wells Shoemaker captured this image on the day of the December solstice in 2005 in Death Valley National Park. He said: “The Eureka Dunes, rising 750 feet (230 meters) above the desert floor, are among the tallest in North America. The low solstice sun casts the longest shadows of the year.” Thanks, Wells!
Bottom line: Some people like to mark the solstice with a special sunset view, or marking of shadows, or party! Personal solstices from the EarthSky community, here.
The December solstice (winter for the Northern Hemisphere, summer for the Southern Hemisphere) will take place at 9:21 UTC on December 21, 2024. That’s 3:21 a.m. CST.
Later, in 2025, the March equinox (start of spring for the Northern Hemisphere, autumn for the Southern Hemisphere) takes place at 9:01 UTC, March 20 (4:01 a.m. CDT).
As an illustration, a solstice marks the sun’s southernmost and northernmost points in our sky. An equinox, meanwhile, marks when the sun crosses over the Earth’s equator.
In addition, the fact that Earth’s Northern and Southern Hemispheres have their summers and winters at opposite times of the year provides a clue to the reason for Earth’s seasons. That reason is Earth’s 23 1/2-degree tilt on its axis. It’s natural, of course, to think our world’s seasons result from our changing distance from the sun. But we’re closer to the sun in northern winter, and farther from the sun in northern summer. So, it’s not Earth’s distance from the sun that causes the seasons to change. Instead, on our tilted world, the angle of sunlight striking your location shifts in a yearly cycle, as we travel around the sun.
The photos and video on this page – from NASA – show Earth’s solstices and equinoxes from space. They can help you visualize why our seasons unfold as they do, continuously, throughout each year.
Earth’s seasons result from our planet’s tilt on its axis with respect to our orbit around the sun. Here are images of the different solstices and equinoxes from space. Upper left: northern winter solstice. Lower left: northern summer solstice. Upper right: northern spring equinox. Lower right: northern autumnal equinox. Images from EUMETSAT‘s Meteosat-9 weather satellite, via the archives of NASA Earth Observatory.
Viewing the solstices and equinoxes from space
EUMETSAT‘s Meteosat-9 (a weather satellite) captured the four views above of Earth from geosynchronous orbit in 2010 and 2011. A satellite in geosynchronous orbit stays over the same point on Earth all the time. And the images above show how sunlight fell on the Earth on December 21, 2010 (upper left), March 20, 2011 (upper right), June 21, 2011 (lower left), and September 20, 2011 (lower right). Also, each image was taken at 6:12 a.m. local time.
Around 6 a.m. local time each day, the sun, Earth, and any geosynchronous satellite form a right angle. Thus, affording a straight-down view of Earth’s terminator line, that is, the line between our world’s day and night sides. The shape of this line between night and day varies with the seasons. And as a result, causes different lengths of days and differing amounts of warming sunshine.
However, while the line is actually a curve because the Earth is round, satellite images show it in two dimensions only.
The terminator
On March 21 and September 23, the terminator is a straight north-south line, and the sun sits directly above the equator. Then, on December 21, the sun resides directly over the Tropic of Capricorn when viewed from the ground, and sunlight spreads over more of the Southern Hemisphere. Next, on June 21, the sun sits above the Tropic of Cancer, spreading more sunlight in the north.
Illustration showing the Earth’s orbit around the sun during the year with the tilt of Earth’s axis and position of the Earth during each season. Image via Wikimedia Commons.
Bottom line: A video from NASA shows how sunlight falls on Earth’s surface during the solstices and equinoxes, as seen by the weather satellite Meteosat-9 in 2010 and 2011.
The December solstice (winter for the Northern Hemisphere, summer for the Southern Hemisphere) will take place at 9:21 UTC on December 21, 2024. That’s 3:21 a.m. CST.
Later, in 2025, the March equinox (start of spring for the Northern Hemisphere, autumn for the Southern Hemisphere) takes place at 9:01 UTC, March 20 (4:01 a.m. CDT).
As an illustration, a solstice marks the sun’s southernmost and northernmost points in our sky. An equinox, meanwhile, marks when the sun crosses over the Earth’s equator.
In addition, the fact that Earth’s Northern and Southern Hemispheres have their summers and winters at opposite times of the year provides a clue to the reason for Earth’s seasons. That reason is Earth’s 23 1/2-degree tilt on its axis. It’s natural, of course, to think our world’s seasons result from our changing distance from the sun. But we’re closer to the sun in northern winter, and farther from the sun in northern summer. So, it’s not Earth’s distance from the sun that causes the seasons to change. Instead, on our tilted world, the angle of sunlight striking your location shifts in a yearly cycle, as we travel around the sun.
The photos and video on this page – from NASA – show Earth’s solstices and equinoxes from space. They can help you visualize why our seasons unfold as they do, continuously, throughout each year.
Earth’s seasons result from our planet’s tilt on its axis with respect to our orbit around the sun. Here are images of the different solstices and equinoxes from space. Upper left: northern winter solstice. Lower left: northern summer solstice. Upper right: northern spring equinox. Lower right: northern autumnal equinox. Images from EUMETSAT‘s Meteosat-9 weather satellite, via the archives of NASA Earth Observatory.
Viewing the solstices and equinoxes from space
EUMETSAT‘s Meteosat-9 (a weather satellite) captured the four views above of Earth from geosynchronous orbit in 2010 and 2011. A satellite in geosynchronous orbit stays over the same point on Earth all the time. And the images above show how sunlight fell on the Earth on December 21, 2010 (upper left), March 20, 2011 (upper right), June 21, 2011 (lower left), and September 20, 2011 (lower right). Also, each image was taken at 6:12 a.m. local time.
Around 6 a.m. local time each day, the sun, Earth, and any geosynchronous satellite form a right angle. Thus, affording a straight-down view of Earth’s terminator line, that is, the line between our world’s day and night sides. The shape of this line between night and day varies with the seasons. And as a result, causes different lengths of days and differing amounts of warming sunshine.
However, while the line is actually a curve because the Earth is round, satellite images show it in two dimensions only.
The terminator
On March 21 and September 23, the terminator is a straight north-south line, and the sun sits directly above the equator. Then, on December 21, the sun resides directly over the Tropic of Capricorn when viewed from the ground, and sunlight spreads over more of the Southern Hemisphere. Next, on June 21, the sun sits above the Tropic of Cancer, spreading more sunlight in the north.
Illustration showing the Earth’s orbit around the sun during the year with the tilt of Earth’s axis and position of the Earth during each season. Image via Wikimedia Commons.
Bottom line: A video from NASA shows how sunlight falls on Earth’s surface during the solstices and equinoxes, as seen by the weather satellite Meteosat-9 in 2010 and 2011.
View larger. | This elevation map depicts the South Pole-Aitken basin on the moon. It is the moon’s largest crater. The lowest regions are in blue and purple. A new study suggested the crater is more circular in shape than scientists previously thought. Image via NASA/ GSFC/ University of Arizona.
The South Pole-Aitken basin is the largest impact crater on the moon. Its 1,550-mile (2,500-km) expanse also makes it one of the largest known impact craters in the solar system.
Scientists thought the basin was oval in shape. This is the shape that would form if the impacting asteroid hit the moon at a low angle.
But a new study shows the massive crater is more circular. The researchers studied mountains around the edge of the basin to determine its original shape.
South Pole-Aitken basin is the moon’s largest crater
The moon is covered in craters. The South Pole-Aitken basin is the largest crater on the moon, resulting from a massive impact billions of years ago. It sits on the moon’s far side, stretching from the South Pole to a crater named Aitken, thus its name. For a long time, scientists thought this huge crater was oval-shaped, forming when an asteroid hit the moon at a shallow angle. But on December 6, 2024, a research team led by the University of Maryland said the basin is more circular than scientists previously thought.
The finding, based on data from NASA’s Lunar Reconnaissance Orbiter (LRO), also has implications for NASA’s plans to send astronauts to the lunar South Pole as part of the Artemis missions.
The researchers published their peer-reviewed results in Earth and Planetary Science Letters on November 28, 2024. The paper will also be in Volume 650 of the journal, on January 25, 2025.
Moon’s largest crater rounder than previously thought
The South Pole-Aitken basin is enormous, about 1,550 miles (2,500 km) across. In fact, that’s nearly a quarter of the circumference of the moon. It’s one of the largest known impact craters in the solar system.
Scientists thought the basin was more oval shaped than circular. That would mean the impacting asteroid that created it hit the lunar surface at a shallow angle. But the new study suggests the crater is rounder. Hannes Bernhardt, an assistant research scientist in the University of Maryland’s Department of Geology is the lead author. He said:
It’s challenging to study the South Pole-Aitken basin holistically due to its sheer enormousness, which is why scientists are still trying to learn its shape and size. In addition, 4 billion years have passed since the basin was originally formed and many other impacts have obscured its original appearance. Our work challenges many existing ideas about how this massive impact occurred and distributed materials, but we are now a step closer to better understand the moon’s early history and evolution over time.
Mountains provide a clue
So, how did the researchers determine the basin is more circular? They used high-resolution images from NASA’s Lunar Reconnaissance Orbiter to study mountain formations around the edge of the basin. They found more than 200 of these mountain formations. The scientists think they’re remnants from the original impact. The new data revealed something interesting. If the original impact likely created a more circular crater, it would have spread debris across the moon’s South Pole, where the Artemis astronauts will land. As Bernhardt said:
A rounder, more circular shape indicates that an object struck the moon’s surface at a more vertical angle, possibly similar to dropping a rock straight down onto the ground. This circular impact implies that debris from the impact is more equally distributed around it than was originally thought, which means that Artemis astronauts or robots in the South Pole region may be able to closely study rocks from deep within the moon’s mantle or crust; materials that are typically impossible for us to access.
View larger. | The South Pole-Aitken basin is enormous, stretching about 1,550 miles (2,500 km) from Aitken crater to the South Pole. Image via NASA/ GSFC/ Arizona State University.
Insight into the moon’s origin
Being able to study these rocks is good news for the upcoming Artemis missions. They could provide valuable clues about the moon’s interior and how the moon first formed. The impact would have sprayed material from the moon’s lower crust and upper mantle. Much of that material should still be sitting on the surface, waiting for astronauts or robots to collect samples for study. As Bernhardt noted:
One of the most exciting implications of our research is how it is applicable to missions to the moon and beyond. Astronauts exploring the lunar South Pole might have easier access to ancient lunar materials that could help us understand how the moon and our solar system came to be.
Chandrayaan-3 mission findings support new study
In addition, India’s Chandrayaan-3 mission landed near the lunar South Pole on August 23, 2023. Among its findings, the rover discovered minerals that indicated impact debris came from the mantle close to the South Pole. This supported the theory that the impact was more head-on than at an angle.
In 2019, scientists reported the discovery of an unusual large mass of material beneath the South Pole-Aitken basin. It likely extends more than 200 miles (320 km) deep. Scientists think it consists of metal and leftover material from the asteroid impact that created the basin.
Bottom line: The South Pole-Aitken basin is the moon’s largest crater. Scientists have thought it was oval-shaped, but a new study suggests it’s more circular.
View larger. | This elevation map depicts the South Pole-Aitken basin on the moon. It is the moon’s largest crater. The lowest regions are in blue and purple. A new study suggested the crater is more circular in shape than scientists previously thought. Image via NASA/ GSFC/ University of Arizona.
The South Pole-Aitken basin is the largest impact crater on the moon. Its 1,550-mile (2,500-km) expanse also makes it one of the largest known impact craters in the solar system.
Scientists thought the basin was oval in shape. This is the shape that would form if the impacting asteroid hit the moon at a low angle.
But a new study shows the massive crater is more circular. The researchers studied mountains around the edge of the basin to determine its original shape.
South Pole-Aitken basin is the moon’s largest crater
The moon is covered in craters. The South Pole-Aitken basin is the largest crater on the moon, resulting from a massive impact billions of years ago. It sits on the moon’s far side, stretching from the South Pole to a crater named Aitken, thus its name. For a long time, scientists thought this huge crater was oval-shaped, forming when an asteroid hit the moon at a shallow angle. But on December 6, 2024, a research team led by the University of Maryland said the basin is more circular than scientists previously thought.
The finding, based on data from NASA’s Lunar Reconnaissance Orbiter (LRO), also has implications for NASA’s plans to send astronauts to the lunar South Pole as part of the Artemis missions.
The researchers published their peer-reviewed results in Earth and Planetary Science Letters on November 28, 2024. The paper will also be in Volume 650 of the journal, on January 25, 2025.
Moon’s largest crater rounder than previously thought
The South Pole-Aitken basin is enormous, about 1,550 miles (2,500 km) across. In fact, that’s nearly a quarter of the circumference of the moon. It’s one of the largest known impact craters in the solar system.
Scientists thought the basin was more oval shaped than circular. That would mean the impacting asteroid that created it hit the lunar surface at a shallow angle. But the new study suggests the crater is rounder. Hannes Bernhardt, an assistant research scientist in the University of Maryland’s Department of Geology is the lead author. He said:
It’s challenging to study the South Pole-Aitken basin holistically due to its sheer enormousness, which is why scientists are still trying to learn its shape and size. In addition, 4 billion years have passed since the basin was originally formed and many other impacts have obscured its original appearance. Our work challenges many existing ideas about how this massive impact occurred and distributed materials, but we are now a step closer to better understand the moon’s early history and evolution over time.
Mountains provide a clue
So, how did the researchers determine the basin is more circular? They used high-resolution images from NASA’s Lunar Reconnaissance Orbiter to study mountain formations around the edge of the basin. They found more than 200 of these mountain formations. The scientists think they’re remnants from the original impact. The new data revealed something interesting. If the original impact likely created a more circular crater, it would have spread debris across the moon’s South Pole, where the Artemis astronauts will land. As Bernhardt said:
A rounder, more circular shape indicates that an object struck the moon’s surface at a more vertical angle, possibly similar to dropping a rock straight down onto the ground. This circular impact implies that debris from the impact is more equally distributed around it than was originally thought, which means that Artemis astronauts or robots in the South Pole region may be able to closely study rocks from deep within the moon’s mantle or crust; materials that are typically impossible for us to access.
View larger. | The South Pole-Aitken basin is enormous, stretching about 1,550 miles (2,500 km) from Aitken crater to the South Pole. Image via NASA/ GSFC/ Arizona State University.
Insight into the moon’s origin
Being able to study these rocks is good news for the upcoming Artemis missions. They could provide valuable clues about the moon’s interior and how the moon first formed. The impact would have sprayed material from the moon’s lower crust and upper mantle. Much of that material should still be sitting on the surface, waiting for astronauts or robots to collect samples for study. As Bernhardt noted:
One of the most exciting implications of our research is how it is applicable to missions to the moon and beyond. Astronauts exploring the lunar South Pole might have easier access to ancient lunar materials that could help us understand how the moon and our solar system came to be.
Chandrayaan-3 mission findings support new study
In addition, India’s Chandrayaan-3 mission landed near the lunar South Pole on August 23, 2023. Among its findings, the rover discovered minerals that indicated impact debris came from the mantle close to the South Pole. This supported the theory that the impact was more head-on than at an angle.
In 2019, scientists reported the discovery of an unusual large mass of material beneath the South Pole-Aitken basin. It likely extends more than 200 miles (320 km) deep. Scientists think it consists of metal and leftover material from the asteroid impact that created the basin.
Bottom line: The South Pole-Aitken basin is the moon’s largest crater. Scientists have thought it was oval-shaped, but a new study suggests it’s more circular.
View at EarthSky Community Photos. | Karl Diefenderfer of Quakertown, Pennsylvania, wrote: “Vibrant winter’s solstice sunrise.” Thank you, Karl! By the way, the December solstice starts the year’s shortest season.
The year’s shortest season has begun
Did you know that Earth’s seasons are slightly different lengths? And by season, we mean the time between a solstice and an equinox. The season – between the December solstice and March equinox – is a touch shy of 89 days. So it’s Earth’s shortest season.
Here are the lengths of the astronomical seasons:
December solstice to March equinox: 88.99 days
March equinox to June solstice: 92.76 days
June solstice to September equinox: 93.65 days
September equinox to December solstice: 89.84 days
The December solstice occurs when the sun reaches its southernmost point in our sky for this year. That is what’s happening this week, at 9:21 UTC on December 21, 2024 (3:21 a.m. CST). This solstice marks an unofficial beginning of the winter season in the Northern Hemisphere, and the start of the summer season in the Southern Hemisphere. Unofficial? What? That’s correct. While no government body has decreed it shall be so, we all generally agree that the solstices and equinoxes are hallmarks of seasonal change.
So no matter where you are on Earth, the season – between the December solstice and March equinox – marks the beginning of your shortest season.
Contrast the number of days in the present season with that of Earth’s longest season – the time between the June solstice and September equinox – in other words, a Northern Hemisphere summer or Southern Hemisphere winter. Because that is Earth’s longest season and lasts 93.65 days.
But the current season is nearly five days shorter. Why?
The reason for the shortest season
As a matter of fact, every year in early January, the Earth swings closest to the sun for the year. And this nearest point is called Earth’s perihelion. Because Earth reaches perihelion in early January, our planet moves most swiftly in its orbit around now. That is just physics: Planets move faster when they are closer to the sun than when they are farther from the sun. And it’s why a Northern Hemisphere winter, or Southern Hemisphere summer, is the shortest of the four seasons. It simply takes us fewer days at this time of year to move between a solstice and an equinox.
On the other hand, in early July, Earth is at aphelion – or farthest from the sun – and moving most slowly in its orbit. So that’s why the longest season occurs at that time.
But of course, seasons change
According to the computational wizard Jean Meeus, a Northern Hemisphere winter or Southern Hemisphere summer became the shortest season after the year 1246. The astronomical season between the December solstice and the March equinox will reach a minimum value of 88.71 days around the year 3500, and will continue to reign as the shortest season until about the year 6430.
The lights of cities from the nightside of Earth. This composite image of Asia and Australia at night used data from the Suomi NPP satellite. Image via NASA.
Bottom line: Earth’s shortest season begins at the solstice on December 21, 2024. The coming season – Northern Hemisphere winter or Southern Hemisphere summer – is a touch shy of 89 days in length.
View at EarthSky Community Photos. | Karl Diefenderfer of Quakertown, Pennsylvania, wrote: “Vibrant winter’s solstice sunrise.” Thank you, Karl! By the way, the December solstice starts the year’s shortest season.
The year’s shortest season has begun
Did you know that Earth’s seasons are slightly different lengths? And by season, we mean the time between a solstice and an equinox. The season – between the December solstice and March equinox – is a touch shy of 89 days. So it’s Earth’s shortest season.
Here are the lengths of the astronomical seasons:
December solstice to March equinox: 88.99 days
March equinox to June solstice: 92.76 days
June solstice to September equinox: 93.65 days
September equinox to December solstice: 89.84 days
The December solstice occurs when the sun reaches its southernmost point in our sky for this year. That is what’s happening this week, at 9:21 UTC on December 21, 2024 (3:21 a.m. CST). This solstice marks an unofficial beginning of the winter season in the Northern Hemisphere, and the start of the summer season in the Southern Hemisphere. Unofficial? What? That’s correct. While no government body has decreed it shall be so, we all generally agree that the solstices and equinoxes are hallmarks of seasonal change.
So no matter where you are on Earth, the season – between the December solstice and March equinox – marks the beginning of your shortest season.
Contrast the number of days in the present season with that of Earth’s longest season – the time between the June solstice and September equinox – in other words, a Northern Hemisphere summer or Southern Hemisphere winter. Because that is Earth’s longest season and lasts 93.65 days.
But the current season is nearly five days shorter. Why?
The reason for the shortest season
As a matter of fact, every year in early January, the Earth swings closest to the sun for the year. And this nearest point is called Earth’s perihelion. Because Earth reaches perihelion in early January, our planet moves most swiftly in its orbit around now. That is just physics: Planets move faster when they are closer to the sun than when they are farther from the sun. And it’s why a Northern Hemisphere winter, or Southern Hemisphere summer, is the shortest of the four seasons. It simply takes us fewer days at this time of year to move between a solstice and an equinox.
On the other hand, in early July, Earth is at aphelion – or farthest from the sun – and moving most slowly in its orbit. So that’s why the longest season occurs at that time.
But of course, seasons change
According to the computational wizard Jean Meeus, a Northern Hemisphere winter or Southern Hemisphere summer became the shortest season after the year 1246. The astronomical season between the December solstice and the March equinox will reach a minimum value of 88.71 days around the year 3500, and will continue to reign as the shortest season until about the year 6430.
The lights of cities from the nightside of Earth. This composite image of Asia and Australia at night used data from the Suomi NPP satellite. Image via NASA.
Bottom line: Earth’s shortest season begins at the solstice on December 21, 2024. The coming season – Northern Hemisphere winter or Southern Hemisphere summer – is a touch shy of 89 days in length.
For the latest on Parker Solar Probe, watch the livestream above at 12:15 CST (18:15 UTC) on Friday, December 20, 2024, with EarthSky founder Deborah Byrd and heliophysicist C. Alex Young of NASA Goddard Spaceflight Center, co-author of EarthSky’s daily sun news update. Join us in marveling at a spacecraft that can touch the sun!
Parker Solar Probe’s closest sun flyby on December 24
On November 6, 2024, the Parker Solar Probe completed its 7th and final gravity assist with Venus, in preparation for the world’s closest encounter of a spacecraft with our sun. And that’s saying something. Already, in 2021, Parker Solar Probe became the first spacecraft ever to touch the sun, that is to fly within the sun’s corona or outer atmosphere. But it’s due to come closer still. On December 24, 2024, Parker will break its own record when it comes within 3.86 million miles (6.2 million km) of the sun’s surface.
As the spacecraft once again becomes the closest humanmade object to the sun, it will be out of contact with mission control. In fact, we won’t hear how Parker’s trip was until three days later (!), on December 27, 2024. That’s when the probe will send a beacon back to Earth. But, even then, Parker Solar Probe’s mission won’t be over. It’ll complete two more close encounters with the sun at the same distance as the December 24 event. The seven-year mission should conclude sometime in 2025.
Needless to say, the results from Parker Solar Probe’s mission will be unprecedented. And sun scientists are excited about this spacecraft’s data-gathering ability so close to our local star. At this month’s American Geophysical Union meeting in Washington, D.C., sun scientists were particularly focused on space weather. That is, they were excited about increasing their understanding of how flares on the sun can lead to conditions in near-Earth space that affect our world’s magnetic field. The effects can include beautiful auroral displays. And they can include fried satellite and power grid components. These scientists believe the results from Parker Solar Probe will help keep our human society safer from the effects of solar flares. NASA said in a statement:
The primary goals are to examine the acceleration of solar wind through the movement of heat and energy in the sun’s corona in addition to study solar energetic particles.
Dr. C. Alex Young, co-author of EarthSky’s daily sun news update, talked about Parker Solar Probe and about what scientists were buzzing about at the AGU meeting, in this EarthSky livestream:
Hear EarthSky founder Deborah Byrd – and Dr. C. Alex Young of NASA Goddard Space Flight Center, co-author of EarthSky’s daily sun news update – discuss what scientists were saying at this year’s AGU meeting, in the video above.
When Parker Solar Probe 1st touched the sun in 2021
Parker Solar Probe became the first spacecraft to literally touch the sun on April 28, 2021. Scientists made the announcement on December 14, 2021, at the American Geophysical Union meeting in New Orleans. They said the Parker Solar Probe flew through the sun’s upper atmosphere, its wispy corona. The corona is that fiery-looking outer layer of the sun that appears around the moon’s silhouette during total solar eclipses.
Parker Solar Probe has been sampling the corona’s particles and magnetic fields. It’s been making discoveries more distant spacecraft can’t make. For example, the solar wind is a stream of charged particles released from the sun’s corona. Parker Solar Probe found zigzag structures in the solar wind that scientists are calling switchbacks.
Also on December 14, 2021, the peer-reviewedPhysical Review Letterspublished the results of Parker Solar Probe’s first venture into the sun’s upper atmosphere.
Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA Headquarters in Washington, said:
Touching the sun is a monumental moment for solar science and a truly remarkable feat. Not only does this milestone provide us with deeper insights into our sun’s evolution and its impacts on our solar system, but everything we learn about our own star also teaches us more about stars in the rest of the universe.
In addition, Nour Raouafi of Johns Hopkins Applied Physics Laboratory said:
Flying so close to the sun, Parker Solar Probe now senses conditions in the magnetically dominated layer of the solar atmosphere – the corona – that we never could before. We see evidence of being in the corona in magnetic field data, solar wind data, and visually in images. We can actually see the spacecraft flying through coronal structures that can be observed during a total solar eclipse.
What does touching the sun look like? For one thing, as Parker Solar Probe passed through our sun’s corona, or wispy outer atmosphere, it flew by structures called coronal streamers. These structures are the bright features moving upward in the upper images above, and angled downward in the lower row. They are the streamers visible around the dark moon silhouette during total solar eclipses. And Parker Solar Probe touched and measured these streamers for the first time. Image via NASA/ Johns Hopkins APL/ Naval Research Laboratory.
Watch a video about when Parker Solar Probe touched the sun
Reaching the Alfvén critical surface
NASA launched Parker toward the sun in 2018. As Parker circled closer and closer during several flybys, scientists looked for indications that it had reached the Alfvén critical surface. The Alfvén critical surface is the point that marks the end of the solar atmosphere and the beginning of the solar wind. While the sun doesn’t have a solid surface, it does have a boundary. The boundary is the point at which solar material bound to the sun by gravity and magnetic forces ends.
Solar material energetic enough to cross the Alfvén critical surface becomes the solar wind, dragging magnetic field lines with it. Once the material crosses this boundary, the wind is moving too fast to ever travel back to the sun, severing the connection.
Scientists estimated the Alfvén critical surface was somewhere between 10 to 20 solar radii from the surface of the sun. This is equal to 4.3 to 8.6 million miles (7 to 13.8 million km) from the sun. When Parker finally spiraled close enough to the sun to detect that it had crossed the Alfvén critical surface, it was 18.8 solar radii (around 8 million miles or 13 million km) above the solar surface. For the first time, on April 28, 2021, Parker entered the solar atmosphere.
Justin Kasper of BWX Technologies Inc. and the University of Michigan, said:
We were fully expecting that, sooner or later, we would encounter the corona for at least a short duration of time. But it is very exciting that we’ve already reached it.
Artist’s concept shows NASA’s Parker Solar Probe. It is the 1st spacecraft to touch the sun. Image via NASA.
The peculiarities of the sun’s border
Parker Solar Probe discovered that this boundary – the Alfvén critical surface – isn’t smooth and round. The edge has wrinkles. The spacecraft passed through spikes and valleys as it dove in and out of the boundary. Parker got as close as just under 15 solar radii (around 7 million miles or 11 million km) from the sun’s surface. In this region it passed through a pseudostreamer, a feature in the corona. Pseudostreamers are towering structures that rise above the sun’s surface that we can see during solar eclipses.
Being inside the pseudostreamer was like being inside the eye of a hurricane. The conditions were quieter and slower, easing the barrage of particles on the spacecraft. In this region, magnetic fields were the dominate force over particles, providing proof that Parker was inside the Alfvén critical surface.
Parker only spent a few hours in the sun’s corona. But the spacecraft will continue to spiral closer, aiming for a distance of 8.86 solar radii (3.83 million miles or 6.1 million km) from the surface. Its next flyby, in January 2022, should dip Parker into the corona again. Nicola Fox of NASA said:
I’m excited to see what Parker finds as it repeatedly passes through the corona in the years to come. The opportunity for new discoveries is boundless.
View larger. | This graphic represents Parker Solar Probe’s distances from the sun during its milestones and discoveries. Image via NASA/ Mary P. Hrybyk-Keith.
Solar maximum and switchbacks
The sun’s corona expands in size during periods of higher solar activity. The sun is currently in solar cycle 25, which should reach a peak in activity (solar maximum) around 2025. This expansion will allow Parker to spend more time inside the corona. Kasper said:
It is a really important region to get into because we think all sorts of physics potentially turn on. And now we’re getting into that region and hopefully going to start seeing some of these physics and behaviors.
One behavior of the sun that Parker is already investigating is that of strange kinks in the solar wind’s magnetic field lines. Scientists first spotted these switchbacks in the mid-1990s and thought they were limited to the sun’s polar regions. Parker encountered the zigzags in the solar wind in 2019, finding that they are common, not rare. And now that Parker is twice as close to the sun as it was in 2019, it can see where these kinky structures originate: the solar surface. Its findings confirm that the switchbacks come from the photosphere, or the visible surface of the sun.
Parker discovered that the switchbacks occur in patches and have a higher percentage of helium – a sign that they came from the photosphere – than other elements. Parker also found that the patches of switchbacks aligned with magnetic funnels that emerge from the photosphere between convection cell structures called supergranules.
Now, scientists think these magnetic funnels may also be the source of the fast solar wind. Stuart Bale of the University of California, Berkeley, said:
The structure of the regions with switchbacks matches up with a small magnetic funnel structure at the base of the corona. This is what we expect from some theories, and this pinpoints a source for the solar wind itself.
Parker Solar Probe: More mysteries
As astronomers learn more about the solar wind and switchbacks, they hope it will help them unlock a long-standing mystery in astronomy: why the corona is so much hotter than the surface of the sun. Bale said:
My instinct is, as we go deeper into the mission and lower and closer to the sun, we’re going to learn more about how magnetic funnels are connected to the switchbacks and hopefully resolve the question of what process makes them.
Scientists hope to learn more about the superheated corona and what pushes the solar wind to supersonic speeds. This will also help them understand and forecast space weather events that impact Earth’s environment and sometimes human technology.
Joseph Smith, Parker program executive at NASA Headquarters, said:
It’s really exciting to see our advanced technologies succeed in taking Parker Solar Probe closer to the sun than we’ve ever been, and to be able to return such amazing science. We look forward to seeing what else the mission discovers as it ventures even closer in the coming years.
Bottom line: The Parker Solar Probe will make its closest pass by the sun on December 24, 2024. It will be even closer than when it 1st “touched the sun” in 2021.
For the latest on Parker Solar Probe, watch the livestream above at 12:15 CST (18:15 UTC) on Friday, December 20, 2024, with EarthSky founder Deborah Byrd and heliophysicist C. Alex Young of NASA Goddard Spaceflight Center, co-author of EarthSky’s daily sun news update. Join us in marveling at a spacecraft that can touch the sun!
Parker Solar Probe’s closest sun flyby on December 24
On November 6, 2024, the Parker Solar Probe completed its 7th and final gravity assist with Venus, in preparation for the world’s closest encounter of a spacecraft with our sun. And that’s saying something. Already, in 2021, Parker Solar Probe became the first spacecraft ever to touch the sun, that is to fly within the sun’s corona or outer atmosphere. But it’s due to come closer still. On December 24, 2024, Parker will break its own record when it comes within 3.86 million miles (6.2 million km) of the sun’s surface.
As the spacecraft once again becomes the closest humanmade object to the sun, it will be out of contact with mission control. In fact, we won’t hear how Parker’s trip was until three days later (!), on December 27, 2024. That’s when the probe will send a beacon back to Earth. But, even then, Parker Solar Probe’s mission won’t be over. It’ll complete two more close encounters with the sun at the same distance as the December 24 event. The seven-year mission should conclude sometime in 2025.
Needless to say, the results from Parker Solar Probe’s mission will be unprecedented. And sun scientists are excited about this spacecraft’s data-gathering ability so close to our local star. At this month’s American Geophysical Union meeting in Washington, D.C., sun scientists were particularly focused on space weather. That is, they were excited about increasing their understanding of how flares on the sun can lead to conditions in near-Earth space that affect our world’s magnetic field. The effects can include beautiful auroral displays. And they can include fried satellite and power grid components. These scientists believe the results from Parker Solar Probe will help keep our human society safer from the effects of solar flares. NASA said in a statement:
The primary goals are to examine the acceleration of solar wind through the movement of heat and energy in the sun’s corona in addition to study solar energetic particles.
Dr. C. Alex Young, co-author of EarthSky’s daily sun news update, talked about Parker Solar Probe and about what scientists were buzzing about at the AGU meeting, in this EarthSky livestream:
Hear EarthSky founder Deborah Byrd – and Dr. C. Alex Young of NASA Goddard Space Flight Center, co-author of EarthSky’s daily sun news update – discuss what scientists were saying at this year’s AGU meeting, in the video above.
When Parker Solar Probe 1st touched the sun in 2021
Parker Solar Probe became the first spacecraft to literally touch the sun on April 28, 2021. Scientists made the announcement on December 14, 2021, at the American Geophysical Union meeting in New Orleans. They said the Parker Solar Probe flew through the sun’s upper atmosphere, its wispy corona. The corona is that fiery-looking outer layer of the sun that appears around the moon’s silhouette during total solar eclipses.
Parker Solar Probe has been sampling the corona’s particles and magnetic fields. It’s been making discoveries more distant spacecraft can’t make. For example, the solar wind is a stream of charged particles released from the sun’s corona. Parker Solar Probe found zigzag structures in the solar wind that scientists are calling switchbacks.
Also on December 14, 2021, the peer-reviewedPhysical Review Letterspublished the results of Parker Solar Probe’s first venture into the sun’s upper atmosphere.
Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA Headquarters in Washington, said:
Touching the sun is a monumental moment for solar science and a truly remarkable feat. Not only does this milestone provide us with deeper insights into our sun’s evolution and its impacts on our solar system, but everything we learn about our own star also teaches us more about stars in the rest of the universe.
In addition, Nour Raouafi of Johns Hopkins Applied Physics Laboratory said:
Flying so close to the sun, Parker Solar Probe now senses conditions in the magnetically dominated layer of the solar atmosphere – the corona – that we never could before. We see evidence of being in the corona in magnetic field data, solar wind data, and visually in images. We can actually see the spacecraft flying through coronal structures that can be observed during a total solar eclipse.
What does touching the sun look like? For one thing, as Parker Solar Probe passed through our sun’s corona, or wispy outer atmosphere, it flew by structures called coronal streamers. These structures are the bright features moving upward in the upper images above, and angled downward in the lower row. They are the streamers visible around the dark moon silhouette during total solar eclipses. And Parker Solar Probe touched and measured these streamers for the first time. Image via NASA/ Johns Hopkins APL/ Naval Research Laboratory.
Watch a video about when Parker Solar Probe touched the sun
Reaching the Alfvén critical surface
NASA launched Parker toward the sun in 2018. As Parker circled closer and closer during several flybys, scientists looked for indications that it had reached the Alfvén critical surface. The Alfvén critical surface is the point that marks the end of the solar atmosphere and the beginning of the solar wind. While the sun doesn’t have a solid surface, it does have a boundary. The boundary is the point at which solar material bound to the sun by gravity and magnetic forces ends.
Solar material energetic enough to cross the Alfvén critical surface becomes the solar wind, dragging magnetic field lines with it. Once the material crosses this boundary, the wind is moving too fast to ever travel back to the sun, severing the connection.
Scientists estimated the Alfvén critical surface was somewhere between 10 to 20 solar radii from the surface of the sun. This is equal to 4.3 to 8.6 million miles (7 to 13.8 million km) from the sun. When Parker finally spiraled close enough to the sun to detect that it had crossed the Alfvén critical surface, it was 18.8 solar radii (around 8 million miles or 13 million km) above the solar surface. For the first time, on April 28, 2021, Parker entered the solar atmosphere.
Justin Kasper of BWX Technologies Inc. and the University of Michigan, said:
We were fully expecting that, sooner or later, we would encounter the corona for at least a short duration of time. But it is very exciting that we’ve already reached it.
Artist’s concept shows NASA’s Parker Solar Probe. It is the 1st spacecraft to touch the sun. Image via NASA.
The peculiarities of the sun’s border
Parker Solar Probe discovered that this boundary – the Alfvén critical surface – isn’t smooth and round. The edge has wrinkles. The spacecraft passed through spikes and valleys as it dove in and out of the boundary. Parker got as close as just under 15 solar radii (around 7 million miles or 11 million km) from the sun’s surface. In this region it passed through a pseudostreamer, a feature in the corona. Pseudostreamers are towering structures that rise above the sun’s surface that we can see during solar eclipses.
Being inside the pseudostreamer was like being inside the eye of a hurricane. The conditions were quieter and slower, easing the barrage of particles on the spacecraft. In this region, magnetic fields were the dominate force over particles, providing proof that Parker was inside the Alfvén critical surface.
Parker only spent a few hours in the sun’s corona. But the spacecraft will continue to spiral closer, aiming for a distance of 8.86 solar radii (3.83 million miles or 6.1 million km) from the surface. Its next flyby, in January 2022, should dip Parker into the corona again. Nicola Fox of NASA said:
I’m excited to see what Parker finds as it repeatedly passes through the corona in the years to come. The opportunity for new discoveries is boundless.
View larger. | This graphic represents Parker Solar Probe’s distances from the sun during its milestones and discoveries. Image via NASA/ Mary P. Hrybyk-Keith.
Solar maximum and switchbacks
The sun’s corona expands in size during periods of higher solar activity. The sun is currently in solar cycle 25, which should reach a peak in activity (solar maximum) around 2025. This expansion will allow Parker to spend more time inside the corona. Kasper said:
It is a really important region to get into because we think all sorts of physics potentially turn on. And now we’re getting into that region and hopefully going to start seeing some of these physics and behaviors.
One behavior of the sun that Parker is already investigating is that of strange kinks in the solar wind’s magnetic field lines. Scientists first spotted these switchbacks in the mid-1990s and thought they were limited to the sun’s polar regions. Parker encountered the zigzags in the solar wind in 2019, finding that they are common, not rare. And now that Parker is twice as close to the sun as it was in 2019, it can see where these kinky structures originate: the solar surface. Its findings confirm that the switchbacks come from the photosphere, or the visible surface of the sun.
Parker discovered that the switchbacks occur in patches and have a higher percentage of helium – a sign that they came from the photosphere – than other elements. Parker also found that the patches of switchbacks aligned with magnetic funnels that emerge from the photosphere between convection cell structures called supergranules.
Now, scientists think these magnetic funnels may also be the source of the fast solar wind. Stuart Bale of the University of California, Berkeley, said:
The structure of the regions with switchbacks matches up with a small magnetic funnel structure at the base of the corona. This is what we expect from some theories, and this pinpoints a source for the solar wind itself.
Parker Solar Probe: More mysteries
As astronomers learn more about the solar wind and switchbacks, they hope it will help them unlock a long-standing mystery in astronomy: why the corona is so much hotter than the surface of the sun. Bale said:
My instinct is, as we go deeper into the mission and lower and closer to the sun, we’re going to learn more about how magnetic funnels are connected to the switchbacks and hopefully resolve the question of what process makes them.
Scientists hope to learn more about the superheated corona and what pushes the solar wind to supersonic speeds. This will also help them understand and forecast space weather events that impact Earth’s environment and sometimes human technology.
Joseph Smith, Parker program executive at NASA Headquarters, said:
It’s really exciting to see our advanced technologies succeed in taking Parker Solar Probe closer to the sun than we’ve ever been, and to be able to return such amazing science. We look forward to seeing what else the mission discovers as it ventures even closer in the coming years.
Bottom line: The Parker Solar Probe will make its closest pass by the sun on December 24, 2024. It will be even closer than when it 1st “touched the sun” in 2021.
We have our best views of Mars only once every 2 years. And that time is fast approaching! Watch a replay of our livestream for more information about Mars.
Mars can appear bright or faint in our sky. 2024 has been mostly a faint year, but Mars has been steadily brightening, and it’s very noticeable now, nearly as bright as the sky’s brightest star. The time to start observing Mars for this two-year period is here.
Mars is growing brighter as Earth catches up with Mars, in our smaller, faster orbit around the sun. The coming opposition of Mars – when Earth will pass between it and the sun, bringing Mars closest and brightest – will take place on January 15-16, 2025.
Start watching for Mars now. It’s up in the east by late evening, following blazing Jupiter across the sky.
Opposition for Mars last fell on December 7-8, 2022. That’s when our planet Earth last flew between Mars and the sun. Mars will reach opposition again at 3 UTC on January 16, 2025. Throughout November 2024, Mars has been growing brighter. It’s now easy to spot late at night through dawn. How to see Mars in the sky: Mars is now nearly as bright as Sirius, the sky’s brightest star. It was near the moon on December 17, 2024. Mars, Jupiter and Sirius will appear as “New Year’s stars” on December 31. Note: Mars reaches opposition about every 26 months, or about every two Earth years. It’s now racing toward its January 15-16, 2025, opposition. Wait. That’s not quite right. It’s Earth that’s racing up behind Mars, in our smaller, faster orbit around the sun.
Mars in December 2024
View at EarthSky Community Photos. | Richard Swieca at Hillsboro Beach, Florida, caught Mars and the waning moon rising over the Atlantic Ocean on the evening of December 17, 2024. Watch for Mars! It’s bright, soon to be at its brightest. Thank you, Richard! By the way, following to this view caught by Richard, the moon will occult or pass in front of Mars as seen from parts of Canada, Greenland, eastern Russia and Alaska and other locations.In December 2024, Mars lies in front of the constellation of Cancer the Crab and not far from the twin stars of Gemini: Castor and Pollux. It’s rising in mid-evening, not far behind blazing Jupiter, and is obvious in the sky before dawn. Mars will be as bright as Sirius, the sky’s brightest star, by the end of December. It will be at its closest to Earth in mid-January 2025. Chart via EarthSky.
Sometimes, Mars is faint
Mars last reached opposition on December 8, 2022. It remained bright through early 2023, then started to rapidly fade through the end of the year. Mars reached superior conjunction – when it passed behind the sun as viewed from Earth – on November 18, 2023. It began 2024 as a faint object, far across the solar system from us. But now Mars is getting bright again.
The geometry of Mars’ orbit is such that it spends much longer periods of time at large distances from the Earth than it does close to us, which provides added incentive to observe it in the weeks around opposition. When it passes opposition, every 2 years, Mars appears large and bright for only a few weeks. Here’s a comparison of the apparent size of Mars when seen at its closest opposition, around its opposition in 2025, and at its farthest opposition. Also shown is how Mars appears when it’s most distant from the Earth at solar conjunction. Image via Dominic Ford/ In-The-Sky.org. Used with permission.
Sometimes, Mars is bright
Mars’ dramatic swings in brightness (and its red color) are why the early stargazers named Mars for their god of war.
Sometimes the war god rests. And sometimes he grows fierce! These changes are part of the reason Mars is so fascinating to watch in the night sky.
When Mars passes opposition, every 2 years, it appears large and bright for only a few weeks. The panel above shows the change in Mars’ apparent size from November 20, 2024, to March 12, 2025. Mars will appear 14.6 arcseconds wide on January 15, 2025. Image via Dominic Ford/ In-The-Sky.org. Used with permission.As Mars races towards its next opposition in January 2025, it’ll grow in apparent size and increase in brightness. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
To understand why Mars varies so much in brightness in Earth’s sky, first realize that it isn’t a very big world. It’s only 4,219 miles (6,790 km) in diameter, making it only slightly more than half Earth’s size (7,922 miles or 12,750 km in diameter).
On the other hand, consider Mars in contrast to Jupiter, the biggest planet in our solar system. Jupiter is 86,881 miles (140,000 km) in diameter. As an illustration, more than 20 planets the size of Mars could be lined up side by side in front of Jupiter. Basically, Jupiter always looks bright, because it’s so big.
Not so for little Mars, however. Rather, its extremes in brightness have to do with its nearness (or lack of nearness) to Earth.
Mars isn’t very big, so its brightness – when it is bright – isn’t due to its bigness, as is true of Jupiter. Mars’ brightness, or lack of brightness, is all about how close we are to the red planet. It’s all about where Earth and Mars are, relative to each other, in their respective orbits around the sun. Image via NASA.
Future Martian oppositions
As mentioned above, the next opposition of Mars – when will appear at its brightest in Earth’s sky for that two-year period – will be January 2025. Check out the chart at C. Seligman’s Mars oppositions page that lists all oppositions of Mars from 1995 to 2037.
There’s a 15-year cycle of Mars, whereby the red planet is brighter and fainter at opposition. In July 2018, we were at the peak of the 2-year cycle – and the peak of the 15-year cycle – and Mars was very, very bright! In 2020, we were also at the peak of the 2-year cycle; however, Earth and Mars were farther apart at Mars’ opposition than they were in 2018. Still, 2020’s opposition of Mars was excellent. And, in December 2022, Mars had a good opposition but appeared smaller and dimmer than in 2020, since we were farther away from it. And the January 2025 opposition will find Mars smaller and dimmer than Mars was in 2022. Diagram by Roy L. Bishop. Copyright Royal Astronomical Society of Canada. Used with permission. Visit the RASC eStore to purchase the Observer’s Handbook, a necessary tool for all skywatchers.
EarthSky Community Photos
View at EarthSky Community Photos. | Paolo Bardelli of Italy made this composite image and said: “On January 16, 2025, Mars will be in opposition, the previous one occurred on December 8, 2022, when it became the brightest object in the night sky. During these periods, tracing the apparent motion of the red planet from evening to evening is very interesting, as a real ‘noose’ is created, with a double reversal of its movement. This put ancient sky observers in crisis at the time when the geocentric theory was dominant. Putting things in their place, it turned out to be a simple perspective effect, due to the mutual motion of Earth and Mars. This image is the sum of a sequence taken every useful evening, clouds permitting, from August 12, 2022, to March 22, 2023. The background is the sum of 22 shots of the area of the sky where Mars was located, the rich star field of the constellation del Toro (Taurus). By coincidence, in February 2023 the path of comet C/2022 E3 (ZTF) crossed the noose.” Thank you, Paolo!View at EarthSky Community Photos. | Miguel Ventura in Fafe, Portugal, captured this image on August 28, 2022, and wrote: “Every now and then and in addition to its natural beauty, the night sky and the whims of the universe offer us moments like this. With some planning and luck in the mix (truce from the clouds) I was able to photograph this magnificent alignment. We can see the Pleiades and the constellation of Taurus with the planet Mars between these 2 … below near the horizon the imposing constellation of Orion appears, announcing the autumn sky.” Thank you, Miguel!
Seeing red
Mars appears as a reddish light in the sky and, therefore, is often called the red planet. Other obvious red dots in the sky are reddish-orange Aldebaran and the famous red supergiant Betelgeuse. So, it is fun to contrast Mars’ color and intensity of red with that of Aldebaran or Betelgeuse.
And then there is red Antares. Antares is Greek for rival of Ares (Ares being the Greek name for Mars). Antares is sometimes said to be the anti-Mars due to its competing red color. For a few months every couple of years Mars is much brighter than Antares. Also, every couple of years Mars passes near Antares, as if taunting the star. Mars moves rapidly through the heavens and Antares is fixed to the starry firmament.
What makes them red?
Surface temperature is what determines the colors of the stars. The hottest stars are blue and the coolest stars are red. In fact, from hottest to coolest, the colors of stars range from blue, white, yellow, orange and red. And while the colors of stars might be hard to detect, some stars – like Aldebaran, Antares and Betelgeuse – are noticeably colorful.
On the other hand, Mars appears red for a different reason. It’s red because of iron oxide in the dust that covers this desert world. Iron oxide gives rust and blood its red color. Rovers on Mars sampled the Martian dust and determined it contains three colors: reds, browns and oranges. So those three colors are what you may see when you gaze upon Mars.
Do you see red when you look at Mars, Aldebaran, Antares and Betelgeuse? Are they the same color? Do you see any other colors of stars?
Bottom line: Mars was the bright red “star” near last night’s moon. Earth is racing up behind Mars in orbit now, about to catch up with it, bringing Mars to opposition in January 2025.
We have our best views of Mars only once every 2 years. And that time is fast approaching! Watch a replay of our livestream for more information about Mars.
Mars can appear bright or faint in our sky. 2024 has been mostly a faint year, but Mars has been steadily brightening, and it’s very noticeable now, nearly as bright as the sky’s brightest star. The time to start observing Mars for this two-year period is here.
Mars is growing brighter as Earth catches up with Mars, in our smaller, faster orbit around the sun. The coming opposition of Mars – when Earth will pass between it and the sun, bringing Mars closest and brightest – will take place on January 15-16, 2025.
Start watching for Mars now. It’s up in the east by late evening, following blazing Jupiter across the sky.
Opposition for Mars last fell on December 7-8, 2022. That’s when our planet Earth last flew between Mars and the sun. Mars will reach opposition again at 3 UTC on January 16, 2025. Throughout November 2024, Mars has been growing brighter. It’s now easy to spot late at night through dawn. How to see Mars in the sky: Mars is now nearly as bright as Sirius, the sky’s brightest star. It was near the moon on December 17, 2024. Mars, Jupiter and Sirius will appear as “New Year’s stars” on December 31. Note: Mars reaches opposition about every 26 months, or about every two Earth years. It’s now racing toward its January 15-16, 2025, opposition. Wait. That’s not quite right. It’s Earth that’s racing up behind Mars, in our smaller, faster orbit around the sun.
Mars in December 2024
View at EarthSky Community Photos. | Richard Swieca at Hillsboro Beach, Florida, caught Mars and the waning moon rising over the Atlantic Ocean on the evening of December 17, 2024. Watch for Mars! It’s bright, soon to be at its brightest. Thank you, Richard! By the way, following to this view caught by Richard, the moon will occult or pass in front of Mars as seen from parts of Canada, Greenland, eastern Russia and Alaska and other locations.In December 2024, Mars lies in front of the constellation of Cancer the Crab and not far from the twin stars of Gemini: Castor and Pollux. It’s rising in mid-evening, not far behind blazing Jupiter, and is obvious in the sky before dawn. Mars will be as bright as Sirius, the sky’s brightest star, by the end of December. It will be at its closest to Earth in mid-January 2025. Chart via EarthSky.
Sometimes, Mars is faint
Mars last reached opposition on December 8, 2022. It remained bright through early 2023, then started to rapidly fade through the end of the year. Mars reached superior conjunction – when it passed behind the sun as viewed from Earth – on November 18, 2023. It began 2024 as a faint object, far across the solar system from us. But now Mars is getting bright again.
The geometry of Mars’ orbit is such that it spends much longer periods of time at large distances from the Earth than it does close to us, which provides added incentive to observe it in the weeks around opposition. When it passes opposition, every 2 years, Mars appears large and bright for only a few weeks. Here’s a comparison of the apparent size of Mars when seen at its closest opposition, around its opposition in 2025, and at its farthest opposition. Also shown is how Mars appears when it’s most distant from the Earth at solar conjunction. Image via Dominic Ford/ In-The-Sky.org. Used with permission.
Sometimes, Mars is bright
Mars’ dramatic swings in brightness (and its red color) are why the early stargazers named Mars for their god of war.
Sometimes the war god rests. And sometimes he grows fierce! These changes are part of the reason Mars is so fascinating to watch in the night sky.
When Mars passes opposition, every 2 years, it appears large and bright for only a few weeks. The panel above shows the change in Mars’ apparent size from November 20, 2024, to March 12, 2025. Mars will appear 14.6 arcseconds wide on January 15, 2025. Image via Dominic Ford/ In-The-Sky.org. Used with permission.As Mars races towards its next opposition in January 2025, it’ll grow in apparent size and increase in brightness. Chart via Guy Ottewell’s 2024 Astronomical Calendar. Used with permission.
To understand why Mars varies so much in brightness in Earth’s sky, first realize that it isn’t a very big world. It’s only 4,219 miles (6,790 km) in diameter, making it only slightly more than half Earth’s size (7,922 miles or 12,750 km in diameter).
On the other hand, consider Mars in contrast to Jupiter, the biggest planet in our solar system. Jupiter is 86,881 miles (140,000 km) in diameter. As an illustration, more than 20 planets the size of Mars could be lined up side by side in front of Jupiter. Basically, Jupiter always looks bright, because it’s so big.
Not so for little Mars, however. Rather, its extremes in brightness have to do with its nearness (or lack of nearness) to Earth.
Mars isn’t very big, so its brightness – when it is bright – isn’t due to its bigness, as is true of Jupiter. Mars’ brightness, or lack of brightness, is all about how close we are to the red planet. It’s all about where Earth and Mars are, relative to each other, in their respective orbits around the sun. Image via NASA.
Future Martian oppositions
As mentioned above, the next opposition of Mars – when will appear at its brightest in Earth’s sky for that two-year period – will be January 2025. Check out the chart at C. Seligman’s Mars oppositions page that lists all oppositions of Mars from 1995 to 2037.
There’s a 15-year cycle of Mars, whereby the red planet is brighter and fainter at opposition. In July 2018, we were at the peak of the 2-year cycle – and the peak of the 15-year cycle – and Mars was very, very bright! In 2020, we were also at the peak of the 2-year cycle; however, Earth and Mars were farther apart at Mars’ opposition than they were in 2018. Still, 2020’s opposition of Mars was excellent. And, in December 2022, Mars had a good opposition but appeared smaller and dimmer than in 2020, since we were farther away from it. And the January 2025 opposition will find Mars smaller and dimmer than Mars was in 2022. Diagram by Roy L. Bishop. Copyright Royal Astronomical Society of Canada. Used with permission. Visit the RASC eStore to purchase the Observer’s Handbook, a necessary tool for all skywatchers.
EarthSky Community Photos
View at EarthSky Community Photos. | Paolo Bardelli of Italy made this composite image and said: “On January 16, 2025, Mars will be in opposition, the previous one occurred on December 8, 2022, when it became the brightest object in the night sky. During these periods, tracing the apparent motion of the red planet from evening to evening is very interesting, as a real ‘noose’ is created, with a double reversal of its movement. This put ancient sky observers in crisis at the time when the geocentric theory was dominant. Putting things in their place, it turned out to be a simple perspective effect, due to the mutual motion of Earth and Mars. This image is the sum of a sequence taken every useful evening, clouds permitting, from August 12, 2022, to March 22, 2023. The background is the sum of 22 shots of the area of the sky where Mars was located, the rich star field of the constellation del Toro (Taurus). By coincidence, in February 2023 the path of comet C/2022 E3 (ZTF) crossed the noose.” Thank you, Paolo!View at EarthSky Community Photos. | Miguel Ventura in Fafe, Portugal, captured this image on August 28, 2022, and wrote: “Every now and then and in addition to its natural beauty, the night sky and the whims of the universe offer us moments like this. With some planning and luck in the mix (truce from the clouds) I was able to photograph this magnificent alignment. We can see the Pleiades and the constellation of Taurus with the planet Mars between these 2 … below near the horizon the imposing constellation of Orion appears, announcing the autumn sky.” Thank you, Miguel!
Seeing red
Mars appears as a reddish light in the sky and, therefore, is often called the red planet. Other obvious red dots in the sky are reddish-orange Aldebaran and the famous red supergiant Betelgeuse. So, it is fun to contrast Mars’ color and intensity of red with that of Aldebaran or Betelgeuse.
And then there is red Antares. Antares is Greek for rival of Ares (Ares being the Greek name for Mars). Antares is sometimes said to be the anti-Mars due to its competing red color. For a few months every couple of years Mars is much brighter than Antares. Also, every couple of years Mars passes near Antares, as if taunting the star. Mars moves rapidly through the heavens and Antares is fixed to the starry firmament.
What makes them red?
Surface temperature is what determines the colors of the stars. The hottest stars are blue and the coolest stars are red. In fact, from hottest to coolest, the colors of stars range from blue, white, yellow, orange and red. And while the colors of stars might be hard to detect, some stars – like Aldebaran, Antares and Betelgeuse – are noticeably colorful.
On the other hand, Mars appears red for a different reason. It’s red because of iron oxide in the dust that covers this desert world. Iron oxide gives rust and blood its red color. Rovers on Mars sampled the Martian dust and determined it contains three colors: reds, browns and oranges. So those three colors are what you may see when you gaze upon Mars.
Do you see red when you look at Mars, Aldebaran, Antares and Betelgeuse? Are they the same color? Do you see any other colors of stars?
Bottom line: Mars was the bright red “star” near last night’s moon. Earth is racing up behind Mars in orbit now, about to catch up with it, bringing Mars to opposition in January 2025.
