Watch for Sirius, sky’s brightest star

Is October 4, 2017 the Harvest Moon? Click here to find out!

Also, be sure to watch for Mars and Venus during their close conjunction on the morning of October 5. Click here for more info. And know that you can see these two worlds – still close – throughout this weekend.

And – if you’re up early watching for Venus and Mars – take a moment to see the sky’s brightest star, Sirius, on these October mornings. This star is so brilliant that you can easily see it on a moonlit night in from a light-polluted city. Click here to find out when Sirius will rise tonight from your part of the world.

Andy wrote:

Early this morning, looking southeast, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Sirius is now rising in the southeast in the hours after midnight and can be found in the south at dawn. Notice that a line from Orion’s Belt points to Sirius.

EarthSky tees are back! Learn how your purchase helps support worthy causes, and use code ESFRIENDS for $5 off.

View larger. | Brightest star Sirius on left, with constellation Orion. See how three stars of Orion’s Belt point to Sirius? This photo from EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan!

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius, which is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

More about Sirius: Dog Star and brightest star

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the star Sirius in the constellation Canis Major, brightest star in the sky. The bright planet Venus is also up before dawn now. But you’ll know Sirius, because Orion’s Belt always points to it.

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from EarthSky http://ift.tt/18IK0am

Is October 4, 2017 the Harvest Moon? Click here to find out!

Also, be sure to watch for Mars and Venus during their close conjunction on the morning of October 5. Click here for more info. And know that you can see these two worlds – still close – throughout this weekend.

And – if you’re up early watching for Venus and Mars – take a moment to see the sky’s brightest star, Sirius, on these October mornings. This star is so brilliant that you can easily see it on a moonlit night in from a light-polluted city. Click here to find out when Sirius will rise tonight from your part of the world.

Andy wrote:

Early this morning, looking southeast, I saw a beautiful star, bright and multicolored … Can you identify it for me?

And Paula wrote:

This morning two of us got up early. We found a pulsing star straight down the sky below Orion’s Belt. It was pulsing the colors of green, yellow, blue and red like a strobe light. I will search for it every morning as it was so enchanting.

This star is enchanting, so much so that – every year, beginning in Northern Hemisphere autumn – we get many, many questions about a multicolored star twinkling in the southeastern to southern sky after midnight. This star typically turns out to be Sirius, which is in the constellation Canis Major the Greater Dog and is sometimes called the Dog Star.

Sirius is now rising in the southeast in the hours after midnight and can be found in the south at dawn. Notice that a line from Orion’s Belt points to Sirius.

EarthSky tees are back! Learn how your purchase helps support worthy causes, and use code ESFRIENDS for $5 off.

View larger. | Brightest star Sirius on left, with constellation Orion. See how three stars of Orion’s Belt point to Sirius? This photo from EarthSky Facebook friend Susan Jensen in Odessa, Washington. Thank you, Susan!

Sirius appears to flash different colors when it’s low in the sky. Really, all the stars are flashing different colors, because light is composed of all the colors of a rainbow, and the journey through our atmosphere breaks starlight into its component colors via refraction. But you don’t notice the colors of the other stars much, because they’re not as bright as Sirius, which is the brightest star visible from anywhere on Earth.

Since our atmosphere is causing the light to break into its colors, and since Sirius is often seen low in the sky now (where you are peering at it through a thicker layer of atmosphere than when it’s overhead), the flashing colors of Sirius are very obvious. When Sirius is higher in the sky – which it is close to dawn in the month of October – or in the evening sky in January and February – you’ll find that Sirius shines with a steadier, whiter light.

So, on these October mornings, watch as Sirius winks at you in the wee hours before dawn!

More about Sirius: Dog Star and brightest star

Bottom line: We get many questions about a bright, colorful, twinkling star on these October mornings. It’s the star Sirius in the constellation Canis Major, brightest star in the sky. The bright planet Venus is also up before dawn now. But you’ll know Sirius, because Orion’s Belt always points to it.

Donate: Your support means the world to us

from EarthSky http://ift.tt/18IK0am

New Cybersecurity Projects for Students

New student projects explore a diverse set of cybersecurity issues that involve social science, physics, and computer programming.

from Science Buddies Blog http://ift.tt/2xOruSa

New student projects explore a diverse set of cybersecurity issues that involve social science, physics, and computer programming.

from Science Buddies Blog http://ift.tt/2xOruSa

In 2017, China’s Mid-Autumn Festival on October 4

Sky lanterns at the Mid-Autumn Festival in Vietnam, where the festival is called Tet-Trung-Thu. Image via OhMyAsian! on Tumblr

Many Asian friends will be wishing each other a happy Mid-Autumn Festival on September 4, 2017. For us in the U.S. and elsewhere in the Northern Hemisphere, this week’s Harvest Moon and last month’s autumnal equinox are signs that autumn is here. Meanwhile, in China, Taiwan, Vietnam and other parts of Asia, the focus is on the annual Mid-Autumn Festival, which by tradition also carries a strong connection to the full moon. It’s sometimes called the Moon Festival in honor of this moon. It’s also called the Mooncake Festival for a traditional baked delicacy exchanged among family and friends.

Chinese mooncake is an traditional food for the Mid-Autumn Festival.

This mooncake is filled with a lotus seed paste. Image via Wikimedia Commons.

The date of the Mid-Autumn Festival falls on the 15th day of the eighth month in the Chinese calendar. That timing places the festival in September or early October in the Gregorian calendar, close to the autumnal equinox, every year.

The Mid-Autumn Festival or Moon Festival features the beautiful idea that we all see the same moon phase on or around the same date. There are some small differences due to time zone, but, for the most part, the moon looks the same to all of us as night falls across the globe. The website Chinese-Fortune-Calendar.com said:

The Moon Festival is a holiday in China. It’s an occasion for family reunion. Chinese families like to get together to eat the mooncakes and watch the moon at the Moon Festival night. For the people are out of town or for Chinese are from China stay in USA, they miss their family or the lover at home and share the same moon at the night of the Moon Festival before the Internet gets popular.

Another tradition at the Mid-Autumn Festival is lanterns, both in the sky and on the ground. After a family dinner, Asian children are said to carry lanterns and stroll in parks or gardens. As part of the festival, lanterns are also released into the sky.

Legends associated with the Mid-Autumn Festival

And, traditionally, matchmaking has been part of the Mid-Autumn Festival. Some parts of China are said to feature dances held to help young men and women find partners, although I don’t know how widely this tradition is practiced in today’s world. According to Wikipedia:

Young women are encouraged to throw their handkerchiefs to the crowd. The young man who catches and returns the handkerchief has a chance of romance.

On the night of the Mid-Autumn Festival, people gaze at the moon and think of their loved ones far away, who might also be gazing at the same moon. Image via EarthSky Facebook friend Lee Capps

Bottom line: Happy Harvest Moon this week to friends in the western hemisphere, and to our friends in Asia … happy Mid-Autumn Festival!

from EarthSky http://ift.tt/2xVMLZn

Sky lanterns at the Mid-Autumn Festival in Vietnam, where the festival is called Tet-Trung-Thu. Image via OhMyAsian! on Tumblr

Many Asian friends will be wishing each other a happy Mid-Autumn Festival on September 4, 2017. For us in the U.S. and elsewhere in the Northern Hemisphere, this week’s Harvest Moon and last month’s autumnal equinox are signs that autumn is here. Meanwhile, in China, Taiwan, Vietnam and other parts of Asia, the focus is on the annual Mid-Autumn Festival, which by tradition also carries a strong connection to the full moon. It’s sometimes called the Moon Festival in honor of this moon. It’s also called the Mooncake Festival for a traditional baked delicacy exchanged among family and friends.

Chinese mooncake is an traditional food for the Mid-Autumn Festival.

This mooncake is filled with a lotus seed paste. Image via Wikimedia Commons.

The date of the Mid-Autumn Festival falls on the 15th day of the eighth month in the Chinese calendar. That timing places the festival in September or early October in the Gregorian calendar, close to the autumnal equinox, every year.

The Mid-Autumn Festival or Moon Festival features the beautiful idea that we all see the same moon phase on or around the same date. There are some small differences due to time zone, but, for the most part, the moon looks the same to all of us as night falls across the globe. The website Chinese-Fortune-Calendar.com said:

The Moon Festival is a holiday in China. It’s an occasion for family reunion. Chinese families like to get together to eat the mooncakes and watch the moon at the Moon Festival night. For the people are out of town or for Chinese are from China stay in USA, they miss their family or the lover at home and share the same moon at the night of the Moon Festival before the Internet gets popular.

Another tradition at the Mid-Autumn Festival is lanterns, both in the sky and on the ground. After a family dinner, Asian children are said to carry lanterns and stroll in parks or gardens. As part of the festival, lanterns are also released into the sky.

Legends associated with the Mid-Autumn Festival

And, traditionally, matchmaking has been part of the Mid-Autumn Festival. Some parts of China are said to feature dances held to help young men and women find partners, although I don’t know how widely this tradition is practiced in today’s world. According to Wikipedia:

Young women are encouraged to throw their handkerchiefs to the crowd. The young man who catches and returns the handkerchief has a chance of romance.

On the night of the Mid-Autumn Festival, people gaze at the moon and think of their loved ones far away, who might also be gazing at the same moon. Image via EarthSky Facebook friend Lee Capps

Bottom line: Happy Harvest Moon this week to friends in the western hemisphere, and to our friends in Asia … happy Mid-Autumn Festival!

from EarthSky http://ift.tt/2xVMLZn

Large storm on sun sparked global aurora on Mars

This animation shows the sudden appearance of a bright aurora on Mars during a solar storm. The purple-white color scheme shows the intensity of ultraviolet light over the course of the event, from observations on September 12 and 13, 2017, by the Imaging Ultraviolet Spectrograph on NASA’s MAVEN orbiter. Image via NASA.

Just before mid-September, 2017, an event on the sun caused a coronal mass ejection, sending charged solar particles hurtling into space, toward Mars. When the charged particles arrived at Mars on September 12 and 13, they sparked a global aurora more than 25 times brighter than any previously seen by the MAVEN orbiter, which has been studying the martian atmosphere’s interaction with the solar wind since 2014. Sonal Jain at CU Boulder (@jain_sonal on Twitter) is a member of MAVEN’s Imaging Ultraviolet Spectrograph instrument team. He commented in a statement:

When a solar storm hits the martian atmosphere, it can trigger auroras that light up the whole planet in ultraviolet light. The recent one lit up Mars like a light bulb.

He explained:

An aurora on Mars can envelope the entire planet because Mars has no strong magnetic field like Earth’s to concentrate the aurora near polar regions.

Other Mars missions also observed the event, including the Curiosity rover on Mars’ surface. Its Radiation Assessment Detector, or RAD, measured radiation levels at the surface more than double any it had measured since landing in 2012. The high readings lasted more than two days. RAD Principal Investigator Don Hassler said:

This is exactly the type of event both missions were designed to study, and it’s the biggest we’ve seen on the surface so far.

Energetic particles from the large solar storm in September 2017 were seen both in Mars orbit by NASA’s MAVEN orbiter, and on the surface of Mars by NASA’s Curiosity Mars rover. Read more about this image, which is via NASA/GSFC/JPL-Caltech/UC Boulder/SwRI-Boulder/UC Berkeley.

NASA said observations like these aid both the planning for safety of future astronauts on Mars as well as in understanding of drastic environmental change that likely occurred on Mars, early in its history.

As long as we’re on Earth, events such as these don’t affect our human bodies (although they do have the potential to affect human technologies, such as electric grids and satellites in orbit). That’s because our thick atmosphere protects us.

But Mars’ atmosphere is much thinner than Earth’s, and so, on Mars, things are different. There, increased radiation from the sun can interact with the atmosphere to produce additional, secondary particles with the potential to harm unshielded human explorers. Hassler said:

If you were outdoors on a Mars walk and learned that an event like this was imminent, you would definitely want to take shelter, just as you would if you were on a space walk outside the International Space Station. To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there.

Besides the observations by instruments on MAVEN and Curiosity, effects of the September solar event were also detected by instruments on NASA’s Mars Odyssey orbiter and Mars Reconnaissance Orbiter and by the European Space Agency’s Mars Express orbiter.

Read more via NASA.

Aurora caught by Sacha Layos in Fairbanks, Alaska on the night of September 7-8, 2017. Read more about this image.

The September, 2017 solar event that affected Mars took place as part of a spate of solar activity, seen from both Earth and Mars on opposite sides of the sun, last month. The activity was unexpected because we’re now heading toward solar minimum, a time of least activity in the sun’s 11-year sunspot and storm-activity cycle. Jain commented:

The current solar cycle has been an odd one, with less activity than usual during the peak, and now we have this large event as we’re approaching solar minimum.

During the specific event that caused global auroras on Mars, Earth – now on the opposite side of the sun from Mars – was not affected. However, we on Earth had our own unique brand of effects from solar activity in the form of auroras, like the one in the image above, in early September, 2017.

Bottom line: A September 2017 event on the sun sparked a global aurora on Mars, stronger than any seen before.

from EarthSky http://ift.tt/2xP2tX8

This animation shows the sudden appearance of a bright aurora on Mars during a solar storm. The purple-white color scheme shows the intensity of ultraviolet light over the course of the event, from observations on September 12 and 13, 2017, by the Imaging Ultraviolet Spectrograph on NASA’s MAVEN orbiter. Image via NASA.

Just before mid-September, 2017, an event on the sun caused a coronal mass ejection, sending charged solar particles hurtling into space, toward Mars. When the charged particles arrived at Mars on September 12 and 13, they sparked a global aurora more than 25 times brighter than any previously seen by the MAVEN orbiter, which has been studying the martian atmosphere’s interaction with the solar wind since 2014. Sonal Jain at CU Boulder (@jain_sonal on Twitter) is a member of MAVEN’s Imaging Ultraviolet Spectrograph instrument team. He commented in a statement:

When a solar storm hits the martian atmosphere, it can trigger auroras that light up the whole planet in ultraviolet light. The recent one lit up Mars like a light bulb.

He explained:

An aurora on Mars can envelope the entire planet because Mars has no strong magnetic field like Earth’s to concentrate the aurora near polar regions.

Other Mars missions also observed the event, including the Curiosity rover on Mars’ surface. Its Radiation Assessment Detector, or RAD, measured radiation levels at the surface more than double any it had measured since landing in 2012. The high readings lasted more than two days. RAD Principal Investigator Don Hassler said:

This is exactly the type of event both missions were designed to study, and it’s the biggest we’ve seen on the surface so far.

Energetic particles from the large solar storm in September 2017 were seen both in Mars orbit by NASA’s MAVEN orbiter, and on the surface of Mars by NASA’s Curiosity Mars rover. Read more about this image, which is via NASA/GSFC/JPL-Caltech/UC Boulder/SwRI-Boulder/UC Berkeley.

NASA said observations like these aid both the planning for safety of future astronauts on Mars as well as in understanding of drastic environmental change that likely occurred on Mars, early in its history.

As long as we’re on Earth, events such as these don’t affect our human bodies (although they do have the potential to affect human technologies, such as electric grids and satellites in orbit). That’s because our thick atmosphere protects us.

But Mars’ atmosphere is much thinner than Earth’s, and so, on Mars, things are different. There, increased radiation from the sun can interact with the atmosphere to produce additional, secondary particles with the potential to harm unshielded human explorers. Hassler said:

If you were outdoors on a Mars walk and learned that an event like this was imminent, you would definitely want to take shelter, just as you would if you were on a space walk outside the International Space Station. To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there.

Besides the observations by instruments on MAVEN and Curiosity, effects of the September solar event were also detected by instruments on NASA’s Mars Odyssey orbiter and Mars Reconnaissance Orbiter and by the European Space Agency’s Mars Express orbiter.

Read more via NASA.

Aurora caught by Sacha Layos in Fairbanks, Alaska on the night of September 7-8, 2017. Read more about this image.

The September, 2017 solar event that affected Mars took place as part of a spate of solar activity, seen from both Earth and Mars on opposite sides of the sun, last month. The activity was unexpected because we’re now heading toward solar minimum, a time of least activity in the sun’s 11-year sunspot and storm-activity cycle. Jain commented:

The current solar cycle has been an odd one, with less activity than usual during the peak, and now we have this large event as we’re approaching solar minimum.

During the specific event that caused global auroras on Mars, Earth – now on the opposite side of the sun from Mars – was not affected. However, we on Earth had our own unique brand of effects from solar activity in the form of auroras, like the one in the image above, in early September, 2017.

Bottom line: A September 2017 event on the sun sparked a global aurora on Mars, stronger than any seen before.

from EarthSky http://ift.tt/2xP2tX8

Tactical Gaming Teaches Warfighters Real-World Scenarios

Tactical gaming won't replace boots on the ground experience, but Army instructors are using it to facilitate specific training needs.

from http://ift.tt/2xd7ODl

Tactical gaming won't replace boots on the ground experience, but Army instructors are using it to facilitate specific training needs.

from http://ift.tt/2xd7ODl

2017 was a lousy year for Mars, but wait

Artist’s concept of Earth (3rd planet from the sun) passing between the sun and Mars (4th planet from the sun). Not to scale. At such times, Mars appears opposition the sun in our sky, and astronomers say that Mars is in “opposition” to the sun. Image via NASA.

More than any other bright planet, the appearance of Mars in our night sky changes from year to year. Its wild swings in brightness are part of what make Mars a fascinating planet to watch with the eye alone. Mars has been faint throughout 2017. Now it’s still faint, in the eastern sky before dawn, having a close conjunction with dazzling Venus on October 5, 2017.

But – in 2018 – Mars will begin to brighten. At its brightest in mid-year, it’ll briefly appear brighter than the second-brightest planet, Jupiter.

Why? Why does Mars sometimes appear very bright, and sometimes very faint?

In October 2017, Mars is in the east before dawn. Here are Venus and Mars Sunday morning – October 1, 2017 – via Dennis Chabot at Posne Night Sky Astrophotography.

The first thing to realize is that Mars isn’t a very big world. It is only 4,219 miles (6,790 km), making it only slightly more than half as big as Earth at 7,922 miles (12,750 km) in diameter. So, when it’s bright, its brightness isn’t due to its bigness, as is the case with Jupiter.

The main reason for Mars’ extremes in brightness has to do with the proximity (or lack of proximity) of Earth and Mars, during the orbits of both worlds around the sun. It’s about the nearness in space of our two worlds. Sometimes Earth and Mars are on the same side of the solar system, and hence near one another. At other times, as now, Mars is far across the solar system from us.

Mars isn’t very big, so its brightness – when it is bright – isn’t due to its bigness, as is true of Jupiter. Image via Lunar and Planetary Institute.

On this depiction via Fourmilab – Mars is red and Earth is blue. In early October 2017, Mars is far across the solar system from Earth. The distance between our 2 worlds is relatively large, so Mars appears faint.

Mars orbits the sun just one step outward from Earth’s orbit. Earth takes a year to orbit the sun once. Mars takes about two years to orbit once.

In 2017, Mars was in superior conjunction – most directly behind the sun as viewed from Earth – on July 27. As stated above, the planet is now in the east before dawn; that’s where it always is after superior conjunction, as the line between us and Mars is now slightly to one side of a line between us and the sun. That is, when we look toward Mars in October, 2017, the sun is still below our horizon, just about to rise.

But, by mid-2018, Mars will appear brighter than it has in many years.

That’s because, in mid-2018, Mars and Earth will be relatively close, with Earth passing between the sun and Mars. Astronomers will call it an opposition of Mars, because then Mars and the sun will appear on opposite sides of our sky (with Mars rising in the east at sunset). It happens every two years and 50 days.

The last opposition was on May 22, 2016. Around that time, Mars was very bright indeed in Earth’s sky. See photos of Mars in May, 2016.

The image below shows Mars in mid-July, 2018, when Earth will next pass between the sun and Mars.

Earth will pass between between the sun and Mars on July 27, 2018. Then, the distance between our two worlds will be at its least for this two-year period, and Mars will appear brightest in our sky. Image via Fourmilab.

This 2018 opposition of Mars isn’t an ordinary opposition. Astronomers will call it a perihelic opposition (or perihelic apparition) of Mars. The word perihelion refers the point in Mars’ orbit when it is closest to the sun. Maybe you can see that – in years when we pass between Mars and the sun, when Mars is also closest to the sun – Earth and Mars are closest. That’s what will be happening in 2018, and it’s why the Association of Lunar and Planetary Observers (ALPO) wrote:

The 2018 perihelic apparition of Mars will prove to be one of the most favorable since the 2003 apparition when the Red Planet came closest to Earth in 59,635 years (the year 57,617 BC).

According to ALPO, in 2003, Mars came within 34.6 million miles (55.7 million km) to Earth, closer than at any time in over nearly 60 thousand years! It’ll be only 1.2 million miles (just under 2 million km) farther away in 2018. Closest approach for Mars in 2018 will take place about two weeks after the opposition date, on on July 31.

So 2017 is, indeed, a lousy year for Mars. But just wait! Mars will be grand in 2018.

Diagram by Roy L. Bishop. Copyright Royal Astronomical Society of Canada. Used with permission. Visit the RASC estore to purchase the Observers Handbook, a necessary tool for all skywatchers. Read more about this image.

Bottom line: Mars is bright when it and Earth are on the same side of the sun. It’s faint when it and Earth are on opposite sides of the sun. 2017 is one of the off-years, and Mars has been faint in our sky throughout this year. But, in 2018, we’ll have a grand view of Mars … best since 2003!

from EarthSky http://ift.tt/21Jgj1f

Artist’s concept of Earth (3rd planet from the sun) passing between the sun and Mars (4th planet from the sun). Not to scale. At such times, Mars appears opposition the sun in our sky, and astronomers say that Mars is in “opposition” to the sun. Image via NASA.

More than any other bright planet, the appearance of Mars in our night sky changes from year to year. Its wild swings in brightness are part of what make Mars a fascinating planet to watch with the eye alone. Mars has been faint throughout 2017. Now it’s still faint, in the eastern sky before dawn, having a close conjunction with dazzling Venus on October 5, 2017.

But – in 2018 – Mars will begin to brighten. At its brightest in mid-year, it’ll briefly appear brighter than the second-brightest planet, Jupiter.

Why? Why does Mars sometimes appear very bright, and sometimes very faint?

In October 2017, Mars is in the east before dawn. Here are Venus and Mars Sunday morning – October 1, 2017 – via Dennis Chabot at Posne Night Sky Astrophotography.

The first thing to realize is that Mars isn’t a very big world. It is only 4,219 miles (6,790 km), making it only slightly more than half as big as Earth at 7,922 miles (12,750 km) in diameter. So, when it’s bright, its brightness isn’t due to its bigness, as is the case with Jupiter.

The main reason for Mars’ extremes in brightness has to do with the proximity (or lack of proximity) of Earth and Mars, during the orbits of both worlds around the sun. It’s about the nearness in space of our two worlds. Sometimes Earth and Mars are on the same side of the solar system, and hence near one another. At other times, as now, Mars is far across the solar system from us.

Mars isn’t very big, so its brightness – when it is bright – isn’t due to its bigness, as is true of Jupiter. Image via Lunar and Planetary Institute.

On this depiction via Fourmilab – Mars is red and Earth is blue. In early October 2017, Mars is far across the solar system from Earth. The distance between our 2 worlds is relatively large, so Mars appears faint.

Mars orbits the sun just one step outward from Earth’s orbit. Earth takes a year to orbit the sun once. Mars takes about two years to orbit once.

In 2017, Mars was in superior conjunction – most directly behind the sun as viewed from Earth – on July 27. As stated above, the planet is now in the east before dawn; that’s where it always is after superior conjunction, as the line between us and Mars is now slightly to one side of a line between us and the sun. That is, when we look toward Mars in October, 2017, the sun is still below our horizon, just about to rise.

But, by mid-2018, Mars will appear brighter than it has in many years.

That’s because, in mid-2018, Mars and Earth will be relatively close, with Earth passing between the sun and Mars. Astronomers will call it an opposition of Mars, because then Mars and the sun will appear on opposite sides of our sky (with Mars rising in the east at sunset). It happens every two years and 50 days.

The last opposition was on May 22, 2016. Around that time, Mars was very bright indeed in Earth’s sky. See photos of Mars in May, 2016.

The image below shows Mars in mid-July, 2018, when Earth will next pass between the sun and Mars.

Earth will pass between between the sun and Mars on July 27, 2018. Then, the distance between our two worlds will be at its least for this two-year period, and Mars will appear brightest in our sky. Image via Fourmilab.

This 2018 opposition of Mars isn’t an ordinary opposition. Astronomers will call it a perihelic opposition (or perihelic apparition) of Mars. The word perihelion refers the point in Mars’ orbit when it is closest to the sun. Maybe you can see that – in years when we pass between Mars and the sun, when Mars is also closest to the sun – Earth and Mars are closest. That’s what will be happening in 2018, and it’s why the Association of Lunar and Planetary Observers (ALPO) wrote:

The 2018 perihelic apparition of Mars will prove to be one of the most favorable since the 2003 apparition when the Red Planet came closest to Earth in 59,635 years (the year 57,617 BC).

According to ALPO, in 2003, Mars came within 34.6 million miles (55.7 million km) to Earth, closer than at any time in over nearly 60 thousand years! It’ll be only 1.2 million miles (just under 2 million km) farther away in 2018. Closest approach for Mars in 2018 will take place about two weeks after the opposition date, on on July 31.

So 2017 is, indeed, a lousy year for Mars. But just wait! Mars will be grand in 2018.

Diagram by Roy L. Bishop. Copyright Royal Astronomical Society of Canada. Used with permission. Visit the RASC estore to purchase the Observers Handbook, a necessary tool for all skywatchers. Read more about this image.

Bottom line: Mars is bright when it and Earth are on the same side of the sun. It’s faint when it and Earth are on opposite sides of the sun. 2017 is one of the off-years, and Mars has been faint in our sky throughout this year. But, in 2018, we’ll have a grand view of Mars … best since 2003!

from EarthSky http://ift.tt/21Jgj1f

Moon and planet-rise, seen from space

With Venus and Mars gearing up for their October 5, 2017 close conjunction before dawn, the European Space Agency (ESA) just released this timelapse video. Astronaut Paolo Nespoli (@astro_paolo on Twitter) shot it from the International Space Station (ISS) on September 18. It shows the moon rising above the Earth’s horizon together with Mercury, Mars, the star Regulus, and Venus. Be sure to watch to the end of the video, when the sun rises.

ESA astronaut Paolo Nespoli is currently working and living aboard ISS as part of his long-duration Vita mission..

Connect with Paolo.

Bottom line: Timelapse video of moon and planet-rise, as seen from ISS.

Via ESA

from EarthSky http://ift.tt/2hLh2ol

With Venus and Mars gearing up for their October 5, 2017 close conjunction before dawn, the European Space Agency (ESA) just released this timelapse video. Astronaut Paolo Nespoli (@astro_paolo on Twitter) shot it from the International Space Station (ISS) on September 18. It shows the moon rising above the Earth’s horizon together with Mercury, Mars, the star Regulus, and Venus. Be sure to watch to the end of the video, when the sun rises.

ESA astronaut Paolo Nespoli is currently working and living aboard ISS as part of his long-duration Vita mission..

Connect with Paolo.

Bottom line: Timelapse video of moon and planet-rise, as seen from ISS.

Via ESA

from EarthSky http://ift.tt/2hLh2ol