The Japanese space agency (JAXA) just shared an image from the Hayabusa2 mission to asteroid Torifune. On July 5, 2026, the space probe flew within 6.2 miles (10 km) of the asteroid and sent back the image above. The asteroid appears to be what astronomers call a contact binary, or 2 asteroids stuck together. Just days earlier, the Chinese space agency also made a flyby of a different asteroid, 2016 HO3 Kamo’oalewa. See the pic below. These 2 asteroid flybys came within 3 days of each other. Torifune image via JAXA, The University of Tokyo, Chiba Institute of Technology, Tokyo University of Science, National Institute of Advanced Industrial Science and Technology, Paris Observatory, Canary Islands Institute for Astrophysics.
2 asteroid flybys yield new closeup images
Space agencies from both China and Japan have just shared images from flybys of two different asteroids in our solar system. On July 2, 2026, China’s Tianwen-2 probe flew past asteroid Kamo’oalewa from a distance of just 12.5 miles (20 km). Then on July 5, 2026, Japan’s Hayabusa2 flew past asteroid Torifune from a mere 6.2 miles (10 km) distant.
Both space agencies caught images of the asteroids. Kamo’oalewa might be a chunk of the moon ejected in a giant impact. And Torifune revealed itself to be two rubble piles joined together, or what astronomers call a contact binary.
Flyby of asteroid Kamo’oalewa
On July 6, 2026, the China National Space Administration said:
The Tianwen-2 probe has arrived at its target asteroid and begun scientific exploration.
Tianwen-2’s target is the asteroid Kamo’oalewa, which is a near-Earth asteroid. The asteroid has a strange orbit that keeps it in unison with Earth. This resonant orbit makes it a quasi-satellite of Earth. A 2024 study showed Kamo’oalewa might have once been a part of the moon that blasted off during an impact that formed the lunar crater Giordano Bruno.
China’s mission to the asteroid began back on May 29, 2025, with the launch of Tianwen-2. After a journey of what the space agency called about 400 days and 1 billion kilometers (621 million miles), Tianwen-2 will now:
… conduct more detailed scientific explorations to obtain information on the asteroid’s shape, material composition, and internal structure, providing support for preparations for sampling.
The China National Space Administration said on July 6, 2026, that it had recently captured this image of the asteroid Kamo’oalewa. Tianwen-2 took this image on July 2, 2026. Image via China National Space Administration.
Flyby of asteroid Torifune
Hayabusa2’s journey to Torifune has taken much longer. The mission launched to space in December 2014. At that time, its target was the asteroid Ryugu. In 2020, Hayabusa2 rendezvoused with Ryugu and took samples that it sent back to Earth. Analysis of the samples show they are rich in primitive organic material.
After Ryugu, JAXA sent the Hayabusa2 probe on an extended mission to Torifune. The probe arrived at 18:30 Japan Standard Time on July 5, 2026. Hayabusa2 made several observations during its flyby. JAXA is still acquiring this data, so expect more revelations about the asteroid to come!
But Hayabusa2’s extended mission is not over. After a couple swings past Earth, the space probe is headed for the tiny asteroid 1998 KY26. The asteroid is just 11 meters (36 feet) in diameter. Hayabusa2 should arrive at the asteroid in 2031.
Bottom line: Japanese and Chinese space agencies both completed asteroid flybys in early July, 2026. See the closeup images here.
The Japanese space agency (JAXA) just shared an image from the Hayabusa2 mission to asteroid Torifune. On July 5, 2026, the space probe flew within 6.2 miles (10 km) of the asteroid and sent back the image above. The asteroid appears to be what astronomers call a contact binary, or 2 asteroids stuck together. Just days earlier, the Chinese space agency also made a flyby of a different asteroid, 2016 HO3 Kamo’oalewa. See the pic below. These 2 asteroid flybys came within 3 days of each other. Torifune image via JAXA, The University of Tokyo, Chiba Institute of Technology, Tokyo University of Science, National Institute of Advanced Industrial Science and Technology, Paris Observatory, Canary Islands Institute for Astrophysics.
2 asteroid flybys yield new closeup images
Space agencies from both China and Japan have just shared images from flybys of two different asteroids in our solar system. On July 2, 2026, China’s Tianwen-2 probe flew past asteroid Kamo’oalewa from a distance of just 12.5 miles (20 km). Then on July 5, 2026, Japan’s Hayabusa2 flew past asteroid Torifune from a mere 6.2 miles (10 km) distant.
Both space agencies caught images of the asteroids. Kamo’oalewa might be a chunk of the moon ejected in a giant impact. And Torifune revealed itself to be two rubble piles joined together, or what astronomers call a contact binary.
Flyby of asteroid Kamo’oalewa
On July 6, 2026, the China National Space Administration said:
The Tianwen-2 probe has arrived at its target asteroid and begun scientific exploration.
Tianwen-2’s target is the asteroid Kamo’oalewa, which is a near-Earth asteroid. The asteroid has a strange orbit that keeps it in unison with Earth. This resonant orbit makes it a quasi-satellite of Earth. A 2024 study showed Kamo’oalewa might have once been a part of the moon that blasted off during an impact that formed the lunar crater Giordano Bruno.
China’s mission to the asteroid began back on May 29, 2025, with the launch of Tianwen-2. After a journey of what the space agency called about 400 days and 1 billion kilometers (621 million miles), Tianwen-2 will now:
… conduct more detailed scientific explorations to obtain information on the asteroid’s shape, material composition, and internal structure, providing support for preparations for sampling.
The China National Space Administration said on July 6, 2026, that it had recently captured this image of the asteroid Kamo’oalewa. Tianwen-2 took this image on July 2, 2026. Image via China National Space Administration.
Flyby of asteroid Torifune
Hayabusa2’s journey to Torifune has taken much longer. The mission launched to space in December 2014. At that time, its target was the asteroid Ryugu. In 2020, Hayabusa2 rendezvoused with Ryugu and took samples that it sent back to Earth. Analysis of the samples show they are rich in primitive organic material.
After Ryugu, JAXA sent the Hayabusa2 probe on an extended mission to Torifune. The probe arrived at 18:30 Japan Standard Time on July 5, 2026. Hayabusa2 made several observations during its flyby. JAXA is still acquiring this data, so expect more revelations about the asteroid to come!
But Hayabusa2’s extended mission is not over. After a couple swings past Earth, the space probe is headed for the tiny asteroid 1998 KY26. The asteroid is just 11 meters (36 feet) in diameter. Hayabusa2 should arrive at the asteroid in 2031.
Bottom line: Japanese and Chinese space agencies both completed asteroid flybys in early July, 2026. See the closeup images here.
Circinus the Drawing Compass is shaped like a pair of tweezers. Chart via EarthSky.
Circinus the Drawing Compass is a dim constellation of the Southern Hemisphere. Its biggest claim to fame is that it’s located next to Alpha Centauri, the third brightest star in our sky and closest star system to Earth.
Both Circinus and Alpha Centauri lie near the south celestial pole. And so, from the Southern Hemisphere, Circinus never sets. It’s circumpolar, meaning its visible throughout the night all year round in the southern sky.
Circinus may be dim, with only one star brighter than magnitude 4, but the presence of Alpha Centauri next door makes it easy to find. As the third-brightest star in the sky, Alpha Centauri is easy to find. This magnitude -0.27 star is so far south that to even get a glimpse of it from the Northern Hemisphere, you have to be south of 29 degrees north latitude. Of course, in the Southern Hemisphere, you just have to look up.
On the opposite side of Circinus from Alpha Centauri is Triangulum Australe, the Southern Triangle. Indeed, Triangulum Australe does resemble a triangle, with its brightest corner star farthest from Circinus.
Stars and star clusters in the Drawing Compass
Circinus’ brightest star, Alpha Circini, is magnitude 3.19 and lies 53 light-years away. And its second brightest star, Beta Circini, lies 7 1/2 degrees from Alpha and shines at magnitude 4.07. It’s 97 light-years from Earth.
Circinus’ best open cluster is NGC 5823. This cluster is magnitude 7.9. Also, about 3 1/2 degrees away is another cluster for telescope observers, NGC 5715, at magnitude 10.
Circinus lies along the Milky Way, which makes it a rich hunting ground for simply scanning with a telescope and seeing what pops up.
Circinus the Drawing Compass is a constellation best seen from southern skies. The dim constellation lies near the bright star Alpha Centauri. Image via IAU/ Sky and Telescope/ Wikimedia Commons (CC BY 3.0).
Bottom line: Circinus the Drawing Compass is a dim constellation located next to the third brightest star in the sky, Alpha Centauri.
Circinus the Drawing Compass is shaped like a pair of tweezers. Chart via EarthSky.
Circinus the Drawing Compass is a dim constellation of the Southern Hemisphere. Its biggest claim to fame is that it’s located next to Alpha Centauri, the third brightest star in our sky and closest star system to Earth.
Both Circinus and Alpha Centauri lie near the south celestial pole. And so, from the Southern Hemisphere, Circinus never sets. It’s circumpolar, meaning its visible throughout the night all year round in the southern sky.
Circinus may be dim, with only one star brighter than magnitude 4, but the presence of Alpha Centauri next door makes it easy to find. As the third-brightest star in the sky, Alpha Centauri is easy to find. This magnitude -0.27 star is so far south that to even get a glimpse of it from the Northern Hemisphere, you have to be south of 29 degrees north latitude. Of course, in the Southern Hemisphere, you just have to look up.
On the opposite side of Circinus from Alpha Centauri is Triangulum Australe, the Southern Triangle. Indeed, Triangulum Australe does resemble a triangle, with its brightest corner star farthest from Circinus.
Stars and star clusters in the Drawing Compass
Circinus’ brightest star, Alpha Circini, is magnitude 3.19 and lies 53 light-years away. And its second brightest star, Beta Circini, lies 7 1/2 degrees from Alpha and shines at magnitude 4.07. It’s 97 light-years from Earth.
Circinus’ best open cluster is NGC 5823. This cluster is magnitude 7.9. Also, about 3 1/2 degrees away is another cluster for telescope observers, NGC 5715, at magnitude 10.
Circinus lies along the Milky Way, which makes it a rich hunting ground for simply scanning with a telescope and seeing what pops up.
Circinus the Drawing Compass is a constellation best seen from southern skies. The dim constellation lies near the bright star Alpha Centauri. Image via IAU/ Sky and Telescope/ Wikimedia Commons (CC BY 3.0).
Bottom line: Circinus the Drawing Compass is a dim constellation located next to the third brightest star in the sky, Alpha Centauri.
View larger. | Artist’s concept of the 2 “super-puff” planets, TOI-791 b and TOI-791 c. They are the puffiest exoplanets ever found so far, with densities like cotton candy. Image via NASA/ Daniel Rutter/ University of Oxford.
Astronomers have discovered two more “super-puff” exoplanets, both 1,113 light-years from Earth.
The planets, TOI-791 b and TOI-791 c, are close to the size of Jupiter. But their densities are like that of cotton candy.
These unusual worlds are the puffiest exoplanets astronomers have yet found.
Just like those in our solar system, planets orbiting other stars come in a wide range of sizes and masses. You might expect the largest planets to also be the most massive … but that’s not always the case.
On June 26, 2026, an international team of researchers led by the University of Oxford in the U.K. said that they have discovered two new “super-puff” planets, TOI-791 b and TOI-791 c. These planets are giants, similar in size to Jupiter, but their masses are very low. In fact, their densities are similar to that of cotton candy!
The researchers used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) mission to make the discovery. Astronomers first identified TOI-791 b and TOI-791 c as candidate planets in 2019 and 2023 respectively.
Astronomers have found similar puffy planets before, but these new ones are the lightest.
The researchers published their peer-reviewed findings in the Monthly Notices of the Royal Astronomical Society on June 25, 2026.
Cotton candy worlds
These planets are unlike any in our solar system. Even though they are about the same size as Jupiter, they are much less dense. More specifically, TOI-791 b is nearly the same size as Jupiter but has just 3.0% of Jupiter’s mass. TOI-791 c is a bit larger than Jupiter but contains just 5.9% of Jupiter’s mass. Their densities are similar to cotton candy, which typically has a density of about 3 pounds per cubic foot (0.05 grams per cubic centimeter).
The planets orbit the sun-like star TOI-791, which is 1,113 light-years from Earth.
How did the researchers find these intriguing worlds? TESS found them using the transit method. When the planets passed in front of their star, as seen from Earth, the light from the star dipped slightly in brightness. TESS recognized the dips as coming from transiting planets. And notably, the researchers weren’t even expecting to find them.
Jon Jenkins is the science lead for the Science Processing Operations Center at NASA’s Ames Research Center in California. He explained:
The main reason these planets are interesting to study is that we didn’t expect to see them at all. They represent a puzzle for us to solve about how giant planets like Jupiter and the super-puffs form.
View larger. | Comparison of TOI-791 b and TOI-791 c with Earth and the gas and ice giants in our solar system. Image via NASA/ Daniel Rutter/ University of Oxford.
Unusual orbits
The two super-puffs also have odd orbits. TOI-791 b takes 139 days to complete an orbit and TOI-791 c takes 232 days. Planets on longer orbits require more telescopic observations to gather data. Overall, TESS gathered 1,122 days of observations over seven years.
Also, the two planets are locked together gravitationally. They alternate pulling on each other as they orbit their star. This affects when they transit the star. The researchers used those variations in timing to calculate the planets’ masses. And that’s how their super-low densities were determined.
Just a handful of super-puffs
Astronomers still only know of a few of these super-puff planets. The two new ones are just the latest. Plus, astronomers currently know of only four other planetary systems that have multiple super-puff planets. Lead author George Dransfield at Oxford University in the U.K. said:
Only a handful of these super-puffy planets are known, and it is even rarer to find two in the same system. Their extremely low densities make them fascinating targets for understanding how planetary systems form and evolve.
Amaury Triaud at the University of Birmingham in the U.K. and co-author of the study, said:
This system offers a unique laboratory for understanding how super-puff planets form and evolve. We propose to carry out space-based observations using the James Webb Space Telescope to assess if the puffy atmosphere contains carbon-, nitrogen-, and oxygen-bearing species, revealing new insight into how these unusual planets formed.
Tristan Guillot at the Université Côte d’Azur and another co-author of the study, added:
These multi-planetary systems are complex, with gravitational interactions between the planets that evolve over very long periods, tens of years or more. This discovery highlights the importance of continued international collaboration in astronomy. Bringing together observations from Antarctica, space telescopes and observatories across several continents was essential to revealing the true nature of these extraordinary planets.
George Dransfield at the University of Oxford in the U.K. is the lead author of the new study about super-puff planets. Image via University of Oxford.
Previous super-puffs
Astronomers have only found a handful of super-puff planets so far. One of them is WASP-107 b. In 2024, the researchers studied that one using the James Webb Space Telescope, plus previous data from the Hubble Space Telescope. It is 210 light-years away and about 3/4 the size of Jupiter but only 1/10 the mass.
Researchers found that it must be hotter on the inside, and have a more massive core, than previously thought. They also found surprisingly low levels of methane in its atmosphere, only about 1/1000 of the expected amount.
View larger. | Artist’s concept of WASP-107 b, another super-puff planet. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
Another planet, a hot Neptune, TIC365102760 b, is also puffy. Discovered in 2024, it is 1,840 light-years from Earth and is 6.2 times larger than our planet. And this one orbits a red giant star. It’s the smallest planet so far found orbiting a red giant. And somehow it survived when its original star began dying and expanded into a red giant.
Bottom line: Astronomers have discovered the two puffiest exoplanets known so far. They are similar in size to Jupiter, but have the density of cotton candy.
View larger. | Artist’s concept of the 2 “super-puff” planets, TOI-791 b and TOI-791 c. They are the puffiest exoplanets ever found so far, with densities like cotton candy. Image via NASA/ Daniel Rutter/ University of Oxford.
Astronomers have discovered two more “super-puff” exoplanets, both 1,113 light-years from Earth.
The planets, TOI-791 b and TOI-791 c, are close to the size of Jupiter. But their densities are like that of cotton candy.
These unusual worlds are the puffiest exoplanets astronomers have yet found.
Just like those in our solar system, planets orbiting other stars come in a wide range of sizes and masses. You might expect the largest planets to also be the most massive … but that’s not always the case.
On June 26, 2026, an international team of researchers led by the University of Oxford in the U.K. said that they have discovered two new “super-puff” planets, TOI-791 b and TOI-791 c. These planets are giants, similar in size to Jupiter, but their masses are very low. In fact, their densities are similar to that of cotton candy!
The researchers used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) mission to make the discovery. Astronomers first identified TOI-791 b and TOI-791 c as candidate planets in 2019 and 2023 respectively.
Astronomers have found similar puffy planets before, but these new ones are the lightest.
The researchers published their peer-reviewed findings in the Monthly Notices of the Royal Astronomical Society on June 25, 2026.
Cotton candy worlds
These planets are unlike any in our solar system. Even though they are about the same size as Jupiter, they are much less dense. More specifically, TOI-791 b is nearly the same size as Jupiter but has just 3.0% of Jupiter’s mass. TOI-791 c is a bit larger than Jupiter but contains just 5.9% of Jupiter’s mass. Their densities are similar to cotton candy, which typically has a density of about 3 pounds per cubic foot (0.05 grams per cubic centimeter).
The planets orbit the sun-like star TOI-791, which is 1,113 light-years from Earth.
How did the researchers find these intriguing worlds? TESS found them using the transit method. When the planets passed in front of their star, as seen from Earth, the light from the star dipped slightly in brightness. TESS recognized the dips as coming from transiting planets. And notably, the researchers weren’t even expecting to find them.
Jon Jenkins is the science lead for the Science Processing Operations Center at NASA’s Ames Research Center in California. He explained:
The main reason these planets are interesting to study is that we didn’t expect to see them at all. They represent a puzzle for us to solve about how giant planets like Jupiter and the super-puffs form.
View larger. | Comparison of TOI-791 b and TOI-791 c with Earth and the gas and ice giants in our solar system. Image via NASA/ Daniel Rutter/ University of Oxford.
Unusual orbits
The two super-puffs also have odd orbits. TOI-791 b takes 139 days to complete an orbit and TOI-791 c takes 232 days. Planets on longer orbits require more telescopic observations to gather data. Overall, TESS gathered 1,122 days of observations over seven years.
Also, the two planets are locked together gravitationally. They alternate pulling on each other as they orbit their star. This affects when they transit the star. The researchers used those variations in timing to calculate the planets’ masses. And that’s how their super-low densities were determined.
Just a handful of super-puffs
Astronomers still only know of a few of these super-puff planets. The two new ones are just the latest. Plus, astronomers currently know of only four other planetary systems that have multiple super-puff planets. Lead author George Dransfield at Oxford University in the U.K. said:
Only a handful of these super-puffy planets are known, and it is even rarer to find two in the same system. Their extremely low densities make them fascinating targets for understanding how planetary systems form and evolve.
Amaury Triaud at the University of Birmingham in the U.K. and co-author of the study, said:
This system offers a unique laboratory for understanding how super-puff planets form and evolve. We propose to carry out space-based observations using the James Webb Space Telescope to assess if the puffy atmosphere contains carbon-, nitrogen-, and oxygen-bearing species, revealing new insight into how these unusual planets formed.
Tristan Guillot at the Université Côte d’Azur and another co-author of the study, added:
These multi-planetary systems are complex, with gravitational interactions between the planets that evolve over very long periods, tens of years or more. This discovery highlights the importance of continued international collaboration in astronomy. Bringing together observations from Antarctica, space telescopes and observatories across several continents was essential to revealing the true nature of these extraordinary planets.
George Dransfield at the University of Oxford in the U.K. is the lead author of the new study about super-puff planets. Image via University of Oxford.
Previous super-puffs
Astronomers have only found a handful of super-puff planets so far. One of them is WASP-107 b. In 2024, the researchers studied that one using the James Webb Space Telescope, plus previous data from the Hubble Space Telescope. It is 210 light-years away and about 3/4 the size of Jupiter but only 1/10 the mass.
Researchers found that it must be hotter on the inside, and have a more massive core, than previously thought. They also found surprisingly low levels of methane in its atmosphere, only about 1/1000 of the expected amount.
View larger. | Artist’s concept of WASP-107 b, another super-puff planet. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
Another planet, a hot Neptune, TIC365102760 b, is also puffy. Discovered in 2024, it is 1,840 light-years from Earth and is 6.2 times larger than our planet. And this one orbits a red giant star. It’s the smallest planet so far found orbiting a red giant. And somehow it survived when its original star began dying and expanded into a red giant.
Bottom line: Astronomers have discovered the two puffiest exoplanets known so far. They are similar in size to Jupiter, but have the density of cotton candy.
Artist’s concept of the exoplanet WD 1856 b. It’s a gas giant, similar to Jupiter. A new study said the planet survived the death of its sunlike star billions of years ago. Now the planet orbits the remains of the star, a white dwarf, 50 times closer than Earth orbits the sun. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
A Jupiter-like exoplanet survived the death of its sunlike star, and now orbits the star’s white dwarf remnant 50 times closer than Earth orbits the sun.
The planet shouldn’t have survived: when its star expanded into a red giant, anything this close should have been destroyed.
New James Webb Space Telescope data reveal the planet actually migrated into its close orbit after the star died, and was heated by the white dwarf’s gravity along the way.
A survivor 50 times closer to its star than Earth
On July 1, 2026, NASA said the James Webb Space Telescope investigated a gas giant planet that not only survived the death of its sunlike star, but is also 50 times closer to its star than Earth is to the sun.
The planet in question (or exoplanet, as we call it when it orbits a star other than the sun) is named WD 1856 b, and it’s orbiting a white dwarf star. When the star was a red giant, it should have destroyed any nearby planet. But this gas giant exoplanet still orbits its star once every 34 hours from less than 2 million miles (3 million km or 0.02 astronomical units) away.
Someday, several billion years from now, our sun will expand into the last phase of its life when it becomes a red giant. When it does, it will engulf most of the inner planets in its swollen atmosphere. Eventually, all that will be left of the sun is its dense core: a white dwarf star. Will Earth survive? That’s still a matter of debate.
The researchers published their peer-reviewed study in the journal Nature on July 1, 2026.
How Webb investigated the surviving planet
To find out how a planet so close to its star could have survived the star’s red giant phase, a team of astronomers turned Webb on it. From the telescope’s point of view, the planet passes right in front of the star in what’s called a transit. During a transit, astronomers can get a look at the planet’s atmosphere. The team analyzed the atmosphere’s composition and measured its temperature.
Even though its star is now a slowly cooling white dwarf, the planet itself was warmer than astronomers expected. They determined its atmosphere was a toasty 260 degrees Fahrenheit (126 C). That’s hotter than it would be if the star were the sole source of heat.
The team also managed to discern a bit of the planetary atmosphere’s chemical composition. Co-author Victoria Boehm of Cornell University said:
We saw the telltale signatures of small cloud particles and hydrocarbons, most likely methane, which is the first time we have seen an atmosphere on a planet transiting a dead star.
NASA’s Transiting Exoplanet Survey Satellite (TESS) originally discovered the planet orbiting the star in 2020. The pair are 80 light-years away. Interestingly, now that the star is in its white dwarf phase, the planet is much larger than the star. Lead author Ryan MacDonald of the University of St. Andrews in the U.K. said:
The planet is about the size of Jupiter, but the white dwarf it orbits is the size of Earth, so the planet is 7 times larger than its star.
How did this close planet survive?
The planet is simply too close to its star to have survived there during the red giant phase. So astronomers reasoned that it migrated into that position sometime after the red giant phase ended. Looking closer at the temperature of the planet helped them crack the case.
The white dwarf doesn’t provide enough heat to account for the temperature of the planet, so there must be internal heat from an earlier time. Co-author Christopher O’Connor of Northwestern University modeled the heat of the planet backward to determine how long it took it to cool down. This would help astronomers know how long ago the planet acquired its heat. What they really wanted to know is whether the planet heated up due to the red giant phase of its star or as a consequence of its journey closer to the star.
And the calculations showed the planet heated up between 3 and 5.5 billion years after the star became a white dwarf, which couldn’t have resulted from the red giant phase. Originally, the scientists said, the planet was far enough away from the star in its orbit that it didn’t heat up as the stellar atmosphere swelled. But, O’Connor said:
As the planet moved inward, its interactions with the strong gravity of the white dwarf will have caused it to warm up considerably, and it has been cooling ever since.
The James Webb Space Telescope was able to detect molecules in the exoplanet WD 1856 b’s atmosphere as it passed in front of, or transited, its star. Its star is a white dwarf, and only about the size of Earth. So when the planet passes in front of the star, it blocks more than half the star’s light. The red bars show the methane Webb detected. Image via NASA/ ESA/ CSA/ Joseph Olmsted (STScI).
What’s next for the surviving planet?
The exoplanet WD 1856 b will continue to slowly cool over the next few billion years. If there were any form of life on the planet, there’s no telling how it fared during the planet’s wild ride inward toward its star: first heating up as gravity took hold, then slowly cooling ever since.
Perhaps the future of Jupiter or one of the other gas giant planets in our solar system will resemble that of WD 1856 b. MacDonald said:
We’re used to looking back in time when we use telescopes, but this is the first time we have been able to look forward to what might happen to the outer planets around the remnant of a sunlike star. It’s like using a time machine to peer into the distant future of our solar system.
Bottom line: A Jupiter-like exoplanet survived the death of its sunlike star and now orbits the star’s white dwarf remnant 50 times closer than Earth orbits the sun. New Webb data show the planet migrated inward after the star’s death, rather than surviving its scorching red giant phase in place.
Artist’s concept of the exoplanet WD 1856 b. It’s a gas giant, similar to Jupiter. A new study said the planet survived the death of its sunlike star billions of years ago. Now the planet orbits the remains of the star, a white dwarf, 50 times closer than Earth orbits the sun. Image via NASA/ ESA/ CSA/ Ralf Crawford (STScI).
A Jupiter-like exoplanet survived the death of its sunlike star, and now orbits the star’s white dwarf remnant 50 times closer than Earth orbits the sun.
The planet shouldn’t have survived: when its star expanded into a red giant, anything this close should have been destroyed.
New James Webb Space Telescope data reveal the planet actually migrated into its close orbit after the star died, and was heated by the white dwarf’s gravity along the way.
A survivor 50 times closer to its star than Earth
On July 1, 2026, NASA said the James Webb Space Telescope investigated a gas giant planet that not only survived the death of its sunlike star, but is also 50 times closer to its star than Earth is to the sun.
The planet in question (or exoplanet, as we call it when it orbits a star other than the sun) is named WD 1856 b, and it’s orbiting a white dwarf star. When the star was a red giant, it should have destroyed any nearby planet. But this gas giant exoplanet still orbits its star once every 34 hours from less than 2 million miles (3 million km or 0.02 astronomical units) away.
Someday, several billion years from now, our sun will expand into the last phase of its life when it becomes a red giant. When it does, it will engulf most of the inner planets in its swollen atmosphere. Eventually, all that will be left of the sun is its dense core: a white dwarf star. Will Earth survive? That’s still a matter of debate.
The researchers published their peer-reviewed study in the journal Nature on July 1, 2026.
How Webb investigated the surviving planet
To find out how a planet so close to its star could have survived the star’s red giant phase, a team of astronomers turned Webb on it. From the telescope’s point of view, the planet passes right in front of the star in what’s called a transit. During a transit, astronomers can get a look at the planet’s atmosphere. The team analyzed the atmosphere’s composition and measured its temperature.
Even though its star is now a slowly cooling white dwarf, the planet itself was warmer than astronomers expected. They determined its atmosphere was a toasty 260 degrees Fahrenheit (126 C). That’s hotter than it would be if the star were the sole source of heat.
The team also managed to discern a bit of the planetary atmosphere’s chemical composition. Co-author Victoria Boehm of Cornell University said:
We saw the telltale signatures of small cloud particles and hydrocarbons, most likely methane, which is the first time we have seen an atmosphere on a planet transiting a dead star.
NASA’s Transiting Exoplanet Survey Satellite (TESS) originally discovered the planet orbiting the star in 2020. The pair are 80 light-years away. Interestingly, now that the star is in its white dwarf phase, the planet is much larger than the star. Lead author Ryan MacDonald of the University of St. Andrews in the U.K. said:
The planet is about the size of Jupiter, but the white dwarf it orbits is the size of Earth, so the planet is 7 times larger than its star.
How did this close planet survive?
The planet is simply too close to its star to have survived there during the red giant phase. So astronomers reasoned that it migrated into that position sometime after the red giant phase ended. Looking closer at the temperature of the planet helped them crack the case.
The white dwarf doesn’t provide enough heat to account for the temperature of the planet, so there must be internal heat from an earlier time. Co-author Christopher O’Connor of Northwestern University modeled the heat of the planet backward to determine how long it took it to cool down. This would help astronomers know how long ago the planet acquired its heat. What they really wanted to know is whether the planet heated up due to the red giant phase of its star or as a consequence of its journey closer to the star.
And the calculations showed the planet heated up between 3 and 5.5 billion years after the star became a white dwarf, which couldn’t have resulted from the red giant phase. Originally, the scientists said, the planet was far enough away from the star in its orbit that it didn’t heat up as the stellar atmosphere swelled. But, O’Connor said:
As the planet moved inward, its interactions with the strong gravity of the white dwarf will have caused it to warm up considerably, and it has been cooling ever since.
The James Webb Space Telescope was able to detect molecules in the exoplanet WD 1856 b’s atmosphere as it passed in front of, or transited, its star. Its star is a white dwarf, and only about the size of Earth. So when the planet passes in front of the star, it blocks more than half the star’s light. The red bars show the methane Webb detected. Image via NASA/ ESA/ CSA/ Joseph Olmsted (STScI).
What’s next for the surviving planet?
The exoplanet WD 1856 b will continue to slowly cool over the next few billion years. If there were any form of life on the planet, there’s no telling how it fared during the planet’s wild ride inward toward its star: first heating up as gravity took hold, then slowly cooling ever since.
Perhaps the future of Jupiter or one of the other gas giant planets in our solar system will resemble that of WD 1856 b. MacDonald said:
We’re used to looking back in time when we use telescopes, but this is the first time we have been able to look forward to what might happen to the outer planets around the remnant of a sunlike star. It’s like using a time machine to peer into the distant future of our solar system.
Bottom line: A Jupiter-like exoplanet survived the death of its sunlike star and now orbits the star’s white dwarf remnant 50 times closer than Earth orbits the sun. New Webb data show the planet migrated inward after the star’s death, rather than surviving its scorching red giant phase in place.
Guy Ottewell is a poet and artist, as well as a master astronomy chart-maker. Here’s one of his illustrations. It shows the asterism – or noticeable star pattern – known as the Northern Cross in the night sky. Image via Guy Ottewell. Used with permission.
The man behind the yearly Astronomical Calendar
Beloved British astronomer Guy Ottewell turns 90 on July 4, 2026. EarthSky wishes him a warm congrats on completing another trip around the sun. Guy Ottewell is best known worldwide for his beautiful astronomy charts and hand-illustrated yearly Astronomical Calendar, of which 2026 will be the final year. Virtually every astronomy educator knows Guy’s calendar and employs it in teaching about the night sky and outer space. Millions have benefited from Ottewell’s unique view of outer space.
Ottewell’s Astronomical Calendar was popular as a printed book from 1974 to 2016. Thousands of sky-lovers in more than 100 countries purchased it. It took a hiatus beginning in 2017, but returned in 2023, in both printed and electronic formats. 2026 is the final year of Guy Ottewell’s Astronomical Calendar.
And if you’re a regular reader of EarthSky, you’ll have seen many of his charts in our sky guide and more over the years.
2026 chart showing the evening apparition of the brightest planet, Venus, by Guy Ottewell. This chart shows Venus from the Southern Hemisphere; the Northern Hemisphere path is similar, but the planet doesn’t get as high in the sky. Planet images are at the 1st, 11th, and 21st of each month. The changing phase of Venus requires a telescope to see. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.
Guy Ottewell: A well-traveled educator
Guy Ottewell spent his childhood in Warwickshire, in the UK’s West Midlands, and his adolescence in Surrey, southeast of London. He did army service in Libya and hitchhiked home from there via Greece, Yugoslavia, Venice, Holland. He said:
I had done well enough at school in Greek and Latin to earn a scholarship to Cambridge, but, while there, studied Arabic, Persian, archaeology and anthropology. On vacations, I made hitchhiking journeys to Switzerland (to work in a theater), Morocco, and Iran and Afghanistan (returning from there via central Asia and Finland).
My first extended job was at a school in Arab Jerusalem, living there with my late wife Barbara. At Manchester University, and then at UCLA, I cataloged their libraries’ books in Middle Eastern languages. While at Manchester, I was encouraged to make a study of modern Hebrew, and traveled around Israel, once living in a kibbutz. For two years, I was a teacher at a native American “demonstration” school in the Navajo reservation in Arizona. Open-air camping during my travels had inspired me to know the stars, but it was at the Navajo school that I first had use of a telescope. And I collected Navajo star lore.
Then my wife was asked to start a Montessori school at Greenville, South Carolina, so we moved. Being ready to turn from astronomy to another side of nature – plants – I grew 80 kinds of vegetables and made botanical drawings.
But I was asked by Professor Bill Brantley, of the Physics Department at Furman University, to show the stars to students. This led to his suggestion of an astronomical yearbook that the Physics department could publish. This later became the yearly Astronomical Calendar. It turned out to meet a need, and I had to teach myself trigonometry and computer programming.
The early publishing imprint Astronomical Workshop – under which the Calendar and other works were initially released – had to become Universal Workshop when I took to the printer a book about human rights. I then added publications in some of my other fields of interest – history, fiction, poetry. Though not an employee of the university, I had the use of storage space and an office for fulfilling orders.
In 2001, I moved to England with my wife, Tilly, a journalist, and continued to publish the Astronomical Calendar.
My more recent journeys have been to see solar eclipses in Canada, Kenya, Java, Mexico, West Texas, India, Mongolia, the Caribbean, Turkey, Australia; to Peru at the time of Halley’s Comet; and long cycle rides in Italy, Turkey, Greece and India.
Guy’s artistic talents extend beyond his scientific illustrations, as demonstrated by this self-portrait.
At least through the end of 2026, you can also find his charts at EarthSky’s most popular post, our visible planet and night sky guide. EarthSky founder Deborah Byrd described Guy’s contributions to astronomy this way:
Through his own efforts, unaffiliated with any large organization, Guy has conveyed astronomy to millions of people since 1974. That’s when he published the original edition of his yearly Astronomical Calendar. He has published it since then, and it has become one of the most beloved resources in astronomy.
2026 chart showing the path of Comet Encke relative to the ecliptic plane (Earth-sun plane). Comets’ paths are drawn as thicker when brighter. Ticks mark the start of days 1, 11 and 21 of each month. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.A view of Earth from space showing the timing and path of the total solar eclipse on August 12, 2026. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.A sample of Guy Ottewell’s star charts. This one shows stars within 12 light-years of our sun. The lines on the grid are 4 light-years apart. Imaginary stalks from the plane to the stars show how far north or south they are. Proxima Centauri is part of the triple star system we see as the single star Alpha Centauri. Image via Guy Ottewell. Used with permission.
A voice that inspired generations of skywatchers
EarthSky’s John Jardine Goss, who is also a former president of the Astronomical League, shared his insight on Guy:
All his works – which include a number of topical, in-depth books and beautiful wall posters – have inspired curious skywatchers and amateur astronomers to see more, and to learn more while they pursue the fascinating field of astronomy.
The late Alan Hale, co-discoverer of Comet Hale-Bopp, said this about Ottewell:
In addition to his astronomical writings and publications, Guy Ottewell has also engaged in numerous humanitarian efforts, and these infuse his writings. In so doing he is not only providing informational and educational benefits to his readers but is also demonstrating that the solar system and the universe within which we live are part of the common heritage of humanity.
And Joe Patterson, professor of astronomy at Columbia University, summed up our feelings at EarthSky when he said:
There’s nobody in Ottewell’s class.
Bottom line: Longtime astronomy educator Guy Ottewell turns 90 on July 4, 2026. Guy is best known for his beautiful astronomy charts and hand-illustrated yearly Astronomical Calendar.
Guy Ottewell is a poet and artist, as well as a master astronomy chart-maker. Here’s one of his illustrations. It shows the asterism – or noticeable star pattern – known as the Northern Cross in the night sky. Image via Guy Ottewell. Used with permission.
The man behind the yearly Astronomical Calendar
Beloved British astronomer Guy Ottewell turns 90 on July 4, 2026. EarthSky wishes him a warm congrats on completing another trip around the sun. Guy Ottewell is best known worldwide for his beautiful astronomy charts and hand-illustrated yearly Astronomical Calendar, of which 2026 will be the final year. Virtually every astronomy educator knows Guy’s calendar and employs it in teaching about the night sky and outer space. Millions have benefited from Ottewell’s unique view of outer space.
Ottewell’s Astronomical Calendar was popular as a printed book from 1974 to 2016. Thousands of sky-lovers in more than 100 countries purchased it. It took a hiatus beginning in 2017, but returned in 2023, in both printed and electronic formats. 2026 is the final year of Guy Ottewell’s Astronomical Calendar.
And if you’re a regular reader of EarthSky, you’ll have seen many of his charts in our sky guide and more over the years.
2026 chart showing the evening apparition of the brightest planet, Venus, by Guy Ottewell. This chart shows Venus from the Southern Hemisphere; the Northern Hemisphere path is similar, but the planet doesn’t get as high in the sky. Planet images are at the 1st, 11th, and 21st of each month. The changing phase of Venus requires a telescope to see. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.
Guy Ottewell: A well-traveled educator
Guy Ottewell spent his childhood in Warwickshire, in the UK’s West Midlands, and his adolescence in Surrey, southeast of London. He did army service in Libya and hitchhiked home from there via Greece, Yugoslavia, Venice, Holland. He said:
I had done well enough at school in Greek and Latin to earn a scholarship to Cambridge, but, while there, studied Arabic, Persian, archaeology and anthropology. On vacations, I made hitchhiking journeys to Switzerland (to work in a theater), Morocco, and Iran and Afghanistan (returning from there via central Asia and Finland).
My first extended job was at a school in Arab Jerusalem, living there with my late wife Barbara. At Manchester University, and then at UCLA, I cataloged their libraries’ books in Middle Eastern languages. While at Manchester, I was encouraged to make a study of modern Hebrew, and traveled around Israel, once living in a kibbutz. For two years, I was a teacher at a native American “demonstration” school in the Navajo reservation in Arizona. Open-air camping during my travels had inspired me to know the stars, but it was at the Navajo school that I first had use of a telescope. And I collected Navajo star lore.
Then my wife was asked to start a Montessori school at Greenville, South Carolina, so we moved. Being ready to turn from astronomy to another side of nature – plants – I grew 80 kinds of vegetables and made botanical drawings.
But I was asked by Professor Bill Brantley, of the Physics Department at Furman University, to show the stars to students. This led to his suggestion of an astronomical yearbook that the Physics department could publish. This later became the yearly Astronomical Calendar. It turned out to meet a need, and I had to teach myself trigonometry and computer programming.
The early publishing imprint Astronomical Workshop – under which the Calendar and other works were initially released – had to become Universal Workshop when I took to the printer a book about human rights. I then added publications in some of my other fields of interest – history, fiction, poetry. Though not an employee of the university, I had the use of storage space and an office for fulfilling orders.
In 2001, I moved to England with my wife, Tilly, a journalist, and continued to publish the Astronomical Calendar.
My more recent journeys have been to see solar eclipses in Canada, Kenya, Java, Mexico, West Texas, India, Mongolia, the Caribbean, Turkey, Australia; to Peru at the time of Halley’s Comet; and long cycle rides in Italy, Turkey, Greece and India.
Guy’s artistic talents extend beyond his scientific illustrations, as demonstrated by this self-portrait.
At least through the end of 2026, you can also find his charts at EarthSky’s most popular post, our visible planet and night sky guide. EarthSky founder Deborah Byrd described Guy’s contributions to astronomy this way:
Through his own efforts, unaffiliated with any large organization, Guy has conveyed astronomy to millions of people since 1974. That’s when he published the original edition of his yearly Astronomical Calendar. He has published it since then, and it has become one of the most beloved resources in astronomy.
2026 chart showing the path of Comet Encke relative to the ecliptic plane (Earth-sun plane). Comets’ paths are drawn as thicker when brighter. Ticks mark the start of days 1, 11 and 21 of each month. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.A view of Earth from space showing the timing and path of the total solar eclipse on August 12, 2026. Chart via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.A sample of Guy Ottewell’s star charts. This one shows stars within 12 light-years of our sun. The lines on the grid are 4 light-years apart. Imaginary stalks from the plane to the stars show how far north or south they are. Proxima Centauri is part of the triple star system we see as the single star Alpha Centauri. Image via Guy Ottewell. Used with permission.
A voice that inspired generations of skywatchers
EarthSky’s John Jardine Goss, who is also a former president of the Astronomical League, shared his insight on Guy:
All his works – which include a number of topical, in-depth books and beautiful wall posters – have inspired curious skywatchers and amateur astronomers to see more, and to learn more while they pursue the fascinating field of astronomy.
The late Alan Hale, co-discoverer of Comet Hale-Bopp, said this about Ottewell:
In addition to his astronomical writings and publications, Guy Ottewell has also engaged in numerous humanitarian efforts, and these infuse his writings. In so doing he is not only providing informational and educational benefits to his readers but is also demonstrating that the solar system and the universe within which we live are part of the common heritage of humanity.
And Joe Patterson, professor of astronomy at Columbia University, summed up our feelings at EarthSky when he said:
There’s nobody in Ottewell’s class.
Bottom line: Longtime astronomy educator Guy Ottewell turns 90 on July 4, 2026. Guy is best known for his beautiful astronomy charts and hand-illustrated yearly Astronomical Calendar.
View at EarthSky Community Photos. | C. Gentile from Florham Park, New Jersey, captured this image of a July 4th celebration and wrote: “The sky was really this color!” Thank you! And happy 4th of July to all who celebrate it. Read what creates the beautiful colors in fireworks below.
The U.S. has a big holiday tomorrow. It’s the 250th Independence Day, aka the 4th of July. And that means it’s fireworks season!
If you watch your local fireworks display, you’ll see the reds, oranges, yellows, greens, blues and purples exploding in the skies. You’ll hear lots of “oohs” and “ahs!”
But what creates the colors of fireworks?
How to sound really smart to your friends on the 4th of July: Know what minerals create the colors in fireworks. ? ? #knowbeforepic.twitter.com/vqnr9617TO
The colors in fireworks come from a simple source. They’re created by the use of metal salts. These chemical salts are different from table salt, referring instead to any compound that contains metal and non-metal atoms. And some of these compounds produce intense colors when they burn, which makes them ideal for fireworks.
Others, like potassium nitrate, sulfur and charcoal are useful to help the fireworks burn. Nitrates, chlorates and perchlorates provide oxygen for the combustion of the fuel. Dextrin, often used as a starch, holds the mixture together. In addition, the use of chlorine-carrying chemicals strengthens some colors.
Metal salts commonly used in firework displays include: strontium carbonate (red fireworks), calcium chloride (orange fireworks), sodium nitrate (yellow fireworks), barium chloride (green fireworks) and copper chloride (blue fireworks). Purple fireworks are typically a mixture of strontium (red) and copper (blue) compounds.
Then they pack these metal salts into small pea- to plum-sized pellets called “stars” or pyrotechnic stars.
View at EarthSky Community Photos. | Ken Chan captured this image at the 4th of July celebration in San Francisco, California, in 2023. He wrote: “July 4th as celebratory fireworks erupted throughout the city.” Thank you, Ken!
What happens after fireworks ignite?
After a firework ignites, a lift charge propels it into the sky. That’s just explosive black powder in a confined space that, when lit, causes a fast increase of heat and gas that can send a firework as high as 1,000 feet (300 meters) into the air.
Meanwhile, a time-delay fuse burns slowly into the interior of the firework shell. Then, after about five seconds, as the shell is soaring overhead, the fuse kindles a charge that reaches the core of the firework, explodes and ignites the stars that contain the metal salts.
Voilà! A beautiful and colorful fireworks display.
Word of caution
By the way, the people who create fireworks are precise, expert craftsmen. If even one thing is off – too much black powder, stars that aren’t aligned correctly or a trigger that fires too soon or too late – everything can go kaboom. After all, fireworks are explosives, and working with them is best left to the professionals.
Bottom line: The red, orange, yellow, green, blue and purple colors exploding in the night sky during a fireworks festival are created by the use of metal salts.
View at EarthSky Community Photos. | C. Gentile from Florham Park, New Jersey, captured this image of a July 4th celebration and wrote: “The sky was really this color!” Thank you! And happy 4th of July to all who celebrate it. Read what creates the beautiful colors in fireworks below.
The U.S. has a big holiday tomorrow. It’s the 250th Independence Day, aka the 4th of July. And that means it’s fireworks season!
If you watch your local fireworks display, you’ll see the reds, oranges, yellows, greens, blues and purples exploding in the skies. You’ll hear lots of “oohs” and “ahs!”
But what creates the colors of fireworks?
How to sound really smart to your friends on the 4th of July: Know what minerals create the colors in fireworks. ? ? #knowbeforepic.twitter.com/vqnr9617TO
The colors in fireworks come from a simple source. They’re created by the use of metal salts. These chemical salts are different from table salt, referring instead to any compound that contains metal and non-metal atoms. And some of these compounds produce intense colors when they burn, which makes them ideal for fireworks.
Others, like potassium nitrate, sulfur and charcoal are useful to help the fireworks burn. Nitrates, chlorates and perchlorates provide oxygen for the combustion of the fuel. Dextrin, often used as a starch, holds the mixture together. In addition, the use of chlorine-carrying chemicals strengthens some colors.
Metal salts commonly used in firework displays include: strontium carbonate (red fireworks), calcium chloride (orange fireworks), sodium nitrate (yellow fireworks), barium chloride (green fireworks) and copper chloride (blue fireworks). Purple fireworks are typically a mixture of strontium (red) and copper (blue) compounds.
Then they pack these metal salts into small pea- to plum-sized pellets called “stars” or pyrotechnic stars.
View at EarthSky Community Photos. | Ken Chan captured this image at the 4th of July celebration in San Francisco, California, in 2023. He wrote: “July 4th as celebratory fireworks erupted throughout the city.” Thank you, Ken!
What happens after fireworks ignite?
After a firework ignites, a lift charge propels it into the sky. That’s just explosive black powder in a confined space that, when lit, causes a fast increase of heat and gas that can send a firework as high as 1,000 feet (300 meters) into the air.
Meanwhile, a time-delay fuse burns slowly into the interior of the firework shell. Then, after about five seconds, as the shell is soaring overhead, the fuse kindles a charge that reaches the core of the firework, explodes and ignites the stars that contain the metal salts.
Voilà! A beautiful and colorful fireworks display.
Word of caution
By the way, the people who create fireworks are precise, expert craftsmen. If even one thing is off – too much black powder, stars that aren’t aligned correctly or a trigger that fires too soon or too late – everything can go kaboom. After all, fireworks are explosives, and working with them is best left to the professionals.
Bottom line: The red, orange, yellow, green, blue and purple colors exploding in the night sky during a fireworks festival are created by the use of metal salts.
1. Every star you see in the night sky is bigger and brighter than our sun
Of the 5,000 or so stars bright enough to see with the unaided eye (brighter than magnitude 6) only a handful of very faint stars are near the same size and brightness of our sun. All the rest are all bigger and brighter.
Of the 500 or so that are brighter than 4th magnitude – which includes essentially every star visible to the unaided eye from an urban location – all are bigger and brighter than our sun, many by a large percentage.
Of the brightest 50 stars visible to the human eye from Earth, the least intrinsically bright star is Alpha Centauri. This star still appears very bright to us, because it’s the closest star system to Earth at 4.2 light-years away. And Alpha Centauri is still more than 1.5 times more luminous than our sun.
2. You can’t see millions of stars on a dark night
Despite what you may hear in poems, songs and commercials, you cannot see a million stars … anywhere. There simply are not enough stars close enough and bright enough to equal a million.
On a really exceptional night, with no moon and far from any source of lights, a person with very good eyesight may be able to see 2,000-2,500 stars at any one time. So the next time you hear someone claim to have seen a million stars in the sky, just attribute it to wonder-inspired exaggeration.
3. Red hot, blue cool? No!
We are accustomed to referring to things that are red as hot and those that are blue as cool. This is not entirely unreasonable, since a red, glowing fireplace poker is hot; and ice, especially in glaciers and polar regions, can have a bluish cast. But we say that only because our everyday experience is limited.
In fact, heated objects change color as their temperature changes. And red represents the lowest temperature at which a heated object can glow in visible light. As it gets hotter, the color changes to white and ultimately to blue. So the red stars you see in the sky are the “coolest” (least hot), and the blue stars are the hottest!
4. Stars are black bodies
A black body is an object that absorbs 100% of all electromagnetic radiation (light, radio waves and so on) that falls on it. A common image here is that of a brick oven with the interior painted black and the only opening a small window. All light that shines through the window is absorbed by the interior of the oven and none is reflected outside the oven. It is a perfect absorber.
As it turns out, this definition of being a perfect absorber suits stars very well! But this just says that a black body absorbs all the radiant energy that hits it. And it does not forbid the black body from re-emitting the energy. In the case of a star, it absorbs all radiation that falls on it, but it also radiates back into space much more than it absorbs. Thus a star is a black body that glows with great brilliance!
An even more perfect black body is a black hole. But, unlike stars, a black hole appears truly black, and radiates no light.
5. There are no green stars
There are scattered claims for stars that appear green, including Beta Librae (Zubeneschamali). But most observers do not see green in any stars except as an optical effect from their telescopes, or else a quirk of personal vision and contrast.
Stars emit a spectrum (“rainbow”) of colors, including green. But the human eye-brain connection mixes the colors together in a manner that rarely, if ever, comes out green. One color can dominate the radiation, but within the range of wavelengths and intensities found in stars, greens get mixed with other colors. And in that case the star appears white. For stars, the general colors are, from lower to higher temperatures, red, orange, yellow, white and blue. So as far as the human eye can tell, there are no green stars.
The sun in extreme ultraviolet, converted to the false color green. The human eye cannot see ultraviolet at all. Keep reading for more cool things about stars! Image via NASA/ ESA/ SOHO.
6. Our sun is a green star
This might seem contradictory after the last fact … But our sun is a “green” star, or more specifically, a green-blue star. That is, its peak wavelength lies clearly in the transition area on the spectrum between blue and green.
This isn’t just an idle fact, but is important because the temperature of a star is related to the color of its main emission wavelength. In the sun’s case, the surface temperature is about 5,800 kelvin (about 9,900 Fahrenheit or 5,500 Celsius), or 500 nanometers, which is a green-blue. However, as we said above, when the human eye factors in the other colors around it, the sun’s apparent color comes out as yellowish white.
7. Our sun is a dwarf star
We are accustomed to think of the sun as a “normal” star. And in many respects, it is. But did you know that it is a dwarf star? Technically, as far as normal stars go, there are only dwarf stars, giant stars and supergiant stars.
The giants and supergiants represent the terminal (old age) stages of stars. But the vast majority of stars – those in the long, mature stage of evolution called the main sequence by astronomers – are all called “dwarfs.”
There is quite a bit of range in size here, but they are all much smaller than the giants and supergiants. So technically, the sun is a dwarf star … And is sometimes called a “yellow dwarf”, in contradiction to the entry above!
8. Stars don’t twinkle
Stars often appear to twinkle (“scintillate”), especially when they are near the horizon. The brightest star, Sirius, twinkles, sparkles and flashes so much sometimes that people actually report it as a UFO.
Is twinkling a property of the stars then? No. It’s a property of Earth’s turbulent atmosphere. As the light from a star passes through the atmosphere, especially when the star appears near the horizon, it must pass through many layers of often rapidly differing density. This has the effect of deflecting the light slightly like a ball in a pinball machine. The light eventually gets to your eyes, but every deflection causes it to change slightly in color and intensity. The result is “twinkling.” Above the Earth’s atmosphere, stars do not twinkle.
9. You can see 20 quadrillion miles, at least
On a good night, you can see about 19,000,000,000,000,000 miles, easily. That’s 19 quadrillion miles, the approximate distance to the bright star Deneb in the constellation Cygnus the Swan.
Cygnus is prominent in the evening skies of summer, fall and winter. And Deneb is bright enough to be seen virtually anywhere in the Northern Hemisphere and, in fact, from almost anywhere in the inhabited world.
There is another star, Eta Carinae, that is a little more than twice as far away, or about 44 quadrillion miles. But Eta Carinae is faint, and not well placed for observers in most of the Northern Hemisphere.
Of course, we’re limiting this to just stars. Both the Andromeda galaxy and the Triangulum galaxy are also visible under certain conditions, and are roughly 15 and 18 quintillion miles away! (One quintillion is 10 raised to the power of 18.)
10. Black holes don’t suck
Many writers frequently describe black holes as “sucking in” everything around them. And it is a common worry among the ill-informed that the so-far-hypothetical “mini” black holes that may be produced by the Large Hadron Collider (LHC) would suck in everything around them in an ever-increasing vortex that would consume the Earth! In the case of the LHC, it isn’t true for a number of reasons, but black holes in general do not “suck.”
This is not just a semantic distinction, but one of process and consequence as well. The word “suck” via suction, as in the way vacuum cleaners work, is not how black holes attract matter. In a vacuum cleaner, the fan produces a partial vacuum (really, just a slightly lower pressure) at the floor end of the vacuum, and regular air pressure outside, being greater, pushes the air into it, carrying along loose dirt and dust.
In the case of black holes, there is no suction involved. Instead, matter is pulled into the black hole by a very strong gravitational attraction. In one way of visualizing it, it really is a bit like falling into a hole, but not like being hoovered into it. Gravity is a fundamental force of nature, and all matter has it. When something is pulled into a black hole, the process is more like a fish being reeled in by an angler, rather than being pushed along like a rafter inexorably being dragged over a waterfall.
The difference may seem trivial, but from a physical standpoint it is fundamental. So black holes don’t suck, but they are very cool. Actually, they are cold. Very, very cold. But that’s a story for another time.
Bottom line: Here’s a collection of 10 cool things about stars that you probably didn’t know. Big stars, green stars, black holes, stars by the millions, and more!
1. Every star you see in the night sky is bigger and brighter than our sun
Of the 5,000 or so stars bright enough to see with the unaided eye (brighter than magnitude 6) only a handful of very faint stars are near the same size and brightness of our sun. All the rest are all bigger and brighter.
Of the 500 or so that are brighter than 4th magnitude – which includes essentially every star visible to the unaided eye from an urban location – all are bigger and brighter than our sun, many by a large percentage.
Of the brightest 50 stars visible to the human eye from Earth, the least intrinsically bright star is Alpha Centauri. This star still appears very bright to us, because it’s the closest star system to Earth at 4.2 light-years away. And Alpha Centauri is still more than 1.5 times more luminous than our sun.
2. You can’t see millions of stars on a dark night
Despite what you may hear in poems, songs and commercials, you cannot see a million stars … anywhere. There simply are not enough stars close enough and bright enough to equal a million.
On a really exceptional night, with no moon and far from any source of lights, a person with very good eyesight may be able to see 2,000-2,500 stars at any one time. So the next time you hear someone claim to have seen a million stars in the sky, just attribute it to wonder-inspired exaggeration.
3. Red hot, blue cool? No!
We are accustomed to referring to things that are red as hot and those that are blue as cool. This is not entirely unreasonable, since a red, glowing fireplace poker is hot; and ice, especially in glaciers and polar regions, can have a bluish cast. But we say that only because our everyday experience is limited.
In fact, heated objects change color as their temperature changes. And red represents the lowest temperature at which a heated object can glow in visible light. As it gets hotter, the color changes to white and ultimately to blue. So the red stars you see in the sky are the “coolest” (least hot), and the blue stars are the hottest!
4. Stars are black bodies
A black body is an object that absorbs 100% of all electromagnetic radiation (light, radio waves and so on) that falls on it. A common image here is that of a brick oven with the interior painted black and the only opening a small window. All light that shines through the window is absorbed by the interior of the oven and none is reflected outside the oven. It is a perfect absorber.
As it turns out, this definition of being a perfect absorber suits stars very well! But this just says that a black body absorbs all the radiant energy that hits it. And it does not forbid the black body from re-emitting the energy. In the case of a star, it absorbs all radiation that falls on it, but it also radiates back into space much more than it absorbs. Thus a star is a black body that glows with great brilliance!
An even more perfect black body is a black hole. But, unlike stars, a black hole appears truly black, and radiates no light.
5. There are no green stars
There are scattered claims for stars that appear green, including Beta Librae (Zubeneschamali). But most observers do not see green in any stars except as an optical effect from their telescopes, or else a quirk of personal vision and contrast.
Stars emit a spectrum (“rainbow”) of colors, including green. But the human eye-brain connection mixes the colors together in a manner that rarely, if ever, comes out green. One color can dominate the radiation, but within the range of wavelengths and intensities found in stars, greens get mixed with other colors. And in that case the star appears white. For stars, the general colors are, from lower to higher temperatures, red, orange, yellow, white and blue. So as far as the human eye can tell, there are no green stars.
The sun in extreme ultraviolet, converted to the false color green. The human eye cannot see ultraviolet at all. Keep reading for more cool things about stars! Image via NASA/ ESA/ SOHO.
6. Our sun is a green star
This might seem contradictory after the last fact … But our sun is a “green” star, or more specifically, a green-blue star. That is, its peak wavelength lies clearly in the transition area on the spectrum between blue and green.
This isn’t just an idle fact, but is important because the temperature of a star is related to the color of its main emission wavelength. In the sun’s case, the surface temperature is about 5,800 kelvin (about 9,900 Fahrenheit or 5,500 Celsius), or 500 nanometers, which is a green-blue. However, as we said above, when the human eye factors in the other colors around it, the sun’s apparent color comes out as yellowish white.
7. Our sun is a dwarf star
We are accustomed to think of the sun as a “normal” star. And in many respects, it is. But did you know that it is a dwarf star? Technically, as far as normal stars go, there are only dwarf stars, giant stars and supergiant stars.
The giants and supergiants represent the terminal (old age) stages of stars. But the vast majority of stars – those in the long, mature stage of evolution called the main sequence by astronomers – are all called “dwarfs.”
There is quite a bit of range in size here, but they are all much smaller than the giants and supergiants. So technically, the sun is a dwarf star … And is sometimes called a “yellow dwarf”, in contradiction to the entry above!
8. Stars don’t twinkle
Stars often appear to twinkle (“scintillate”), especially when they are near the horizon. The brightest star, Sirius, twinkles, sparkles and flashes so much sometimes that people actually report it as a UFO.
Is twinkling a property of the stars then? No. It’s a property of Earth’s turbulent atmosphere. As the light from a star passes through the atmosphere, especially when the star appears near the horizon, it must pass through many layers of often rapidly differing density. This has the effect of deflecting the light slightly like a ball in a pinball machine. The light eventually gets to your eyes, but every deflection causes it to change slightly in color and intensity. The result is “twinkling.” Above the Earth’s atmosphere, stars do not twinkle.
9. You can see 20 quadrillion miles, at least
On a good night, you can see about 19,000,000,000,000,000 miles, easily. That’s 19 quadrillion miles, the approximate distance to the bright star Deneb in the constellation Cygnus the Swan.
Cygnus is prominent in the evening skies of summer, fall and winter. And Deneb is bright enough to be seen virtually anywhere in the Northern Hemisphere and, in fact, from almost anywhere in the inhabited world.
There is another star, Eta Carinae, that is a little more than twice as far away, or about 44 quadrillion miles. But Eta Carinae is faint, and not well placed for observers in most of the Northern Hemisphere.
Of course, we’re limiting this to just stars. Both the Andromeda galaxy and the Triangulum galaxy are also visible under certain conditions, and are roughly 15 and 18 quintillion miles away! (One quintillion is 10 raised to the power of 18.)
10. Black holes don’t suck
Many writers frequently describe black holes as “sucking in” everything around them. And it is a common worry among the ill-informed that the so-far-hypothetical “mini” black holes that may be produced by the Large Hadron Collider (LHC) would suck in everything around them in an ever-increasing vortex that would consume the Earth! In the case of the LHC, it isn’t true for a number of reasons, but black holes in general do not “suck.”
This is not just a semantic distinction, but one of process and consequence as well. The word “suck” via suction, as in the way vacuum cleaners work, is not how black holes attract matter. In a vacuum cleaner, the fan produces a partial vacuum (really, just a slightly lower pressure) at the floor end of the vacuum, and regular air pressure outside, being greater, pushes the air into it, carrying along loose dirt and dust.
In the case of black holes, there is no suction involved. Instead, matter is pulled into the black hole by a very strong gravitational attraction. In one way of visualizing it, it really is a bit like falling into a hole, but not like being hoovered into it. Gravity is a fundamental force of nature, and all matter has it. When something is pulled into a black hole, the process is more like a fish being reeled in by an angler, rather than being pushed along like a rafter inexorably being dragged over a waterfall.
The difference may seem trivial, but from a physical standpoint it is fundamental. So black holes don’t suck, but they are very cool. Actually, they are cold. Very, very cold. But that’s a story for another time.
Bottom line: Here’s a collection of 10 cool things about stars that you probably didn’t know. Big stars, green stars, black holes, stars by the millions, and more!
