Bar-headed geese in India

Photo Credit: Abhinav Singhai. Visit his Flickr page

EarthSky Facebook friend Abhinav Singhai in India captured this evocative shot of bar-headed geese over Basai Wetlands, a well-known destination for birders near Delhi, India. He said there were hundreds of geese over the wetlands that day.

Thank you, Abhihav!

The bar-headed goose is a fascinating bird, by the way, and one of the world’s highest-flying birds. It’s been heard flying across Mount Makalu – the fifth highest mountain on Earth at 8,481 meters (27,825 ft). The British explorer George Lowe is said to have reported seeing bar-headed geese flying over Mount Everest – 8,848 meters (29,029 ft)! You’ll find mention of Lowe’s tale about the geese here.

According to Wikipedia, the bar-headed goose is:

… a goose that breeds in Central Asia in colonies of thousands near mountain lakes and winters in South Asia, as far south as peninsular India …

The bird is pale grey and is easily distinguished from any of the other grey geese of the genus Anser by the black bars on its head.

A Bar-headed Goose in St James’s Park, London, England. Photo by DAVID ILIFF. License: CC-BY-SA 3.0 via Wikipedia.

Bottom line: A beautiful shot of bar-headed geese flying over a wetlands in India in November 2014. Photo by Abhinav Singhai.

from EarthSky http://earthsky.org/todays-image/bar-headed-geese-in-india

Photo Credit: Abhinav Singhai. Visit his Flickr page

EarthSky Facebook friend Abhinav Singhai in India captured this evocative shot of bar-headed geese over Basai Wetlands, a well-known destination for birders near Delhi, India. He said there were hundreds of geese over the wetlands that day.

Thank you, Abhihav!

The bar-headed goose is a fascinating bird, by the way, and one of the world’s highest-flying birds. It’s been heard flying across Mount Makalu – the fifth highest mountain on Earth at 8,481 meters (27,825 ft). The British explorer George Lowe is said to have reported seeing bar-headed geese flying over Mount Everest – 8,848 meters (29,029 ft)! You’ll find mention of Lowe’s tale about the geese here.

According to Wikipedia, the bar-headed goose is:

… a goose that breeds in Central Asia in colonies of thousands near mountain lakes and winters in South Asia, as far south as peninsular India …

The bird is pale grey and is easily distinguished from any of the other grey geese of the genus Anser by the black bars on its head.

A Bar-headed Goose in St James’s Park, London, England. Photo by DAVID ILIFF. License: CC-BY-SA 3.0 via Wikipedia.

Bottom line: A beautiful shot of bar-headed geese flying over a wetlands in India in November 2014. Photo by Abhinav Singhai.

from EarthSky http://earthsky.org/todays-image/bar-headed-geese-in-india

Sun in constellation Ophiuchus November 30 to December 18

If you could see the stars during the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius today. At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the Zodiac, and every year the sun passes in front of Ophiuchus from about November 29 until December 18.

This year, in 2014, the sun enters the constellation Ophiuchus on November 30, at 1:00 a.m. CST in the central U.S. By Universal Time, that’s 7:00 on November 30.

How do I translate Universal Time into my time?

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

Need the perfect gift? Check out these 2015 moon calendars.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned. No one ever claims to be an Ophiuchus. There are the 12 traditional zodiacal constellations. But the sun passes through Ophiuchus as surely as it does the others.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

from EarthSky http://earthsky.org/tonight/sun-in-ophiuchus-november-30-to-december-18

If you could see the stars during the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius today. At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the Zodiac, and every year the sun passes in front of Ophiuchus from about November 29 until December 18.

This year, in 2014, the sun enters the constellation Ophiuchus on November 30, at 1:00 a.m. CST in the central U.S. By Universal Time, that’s 7:00 on November 30.

How do I translate Universal Time into my time?

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

Need the perfect gift? Check out these 2015 moon calendars.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned. No one ever claims to be an Ophiuchus. There are the 12 traditional zodiacal constellations. But the sun passes through Ophiuchus as surely as it does the others.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

from EarthSky http://earthsky.org/tonight/sun-in-ophiuchus-november-30-to-december-18

M33: Triangulum Galaxy

How to find it

Although long-exposure photographs show the Triangulum galaxy (Messier 33) as a pinwheel of swarming suns, this face-on spiral galaxy looks rather lackluster in binoculars or even the telescope. The Triangulum galaxy has a low surface brightness that makes this faint object a major challenge, with or without optics.

Have you ever seen the Great Andromeda Galaxy (Messier 31)? If not, try finding the Andromeda galaxy before you take on the Triangulum galaxy. Shining 8 to 9 times more brightly than the Triangulum galaxy, the Andromeda galaxy is the most distant object that you can easily see with the unaided eye. Fortunately, the Triangulum and Andromeda galaxies are a relatively close 15 degrees apart. (For reference, a fist-width at an arm length approximates 10 degrees.)

Star-hop to the Andromeda galaxy to orient yourself to the Triangulum galaxy. As seen on the sky chart, the star Mirach stands about midway between the two galaxies. Our Andromeda galaxy sky chart shows you how to star-hop to the Andromeda galaxy. Once you’ve found it, the Andromeda galaxy and Mirach point in the general direction of the Triangulum galaxy.

The constellation Triangulum

Learn the constellation Triangulum, the small triangle made of three rather faint yet visible stars. Look eastward on some autumn evening, placing the star Alpha Triangulum at about the “7 o’clock” position in your binoculars. The Triangulum galaxy appears at the opposite side of the binouclar field, somewhere around 1 or 2 o’clock.

Now for a word of warning: even if you’re staring right at the Triangulum galaxy, it’s still possible to miss it. You won’t see the galaxy’s stars at all. Sometimes, this galaxy looks almost transparent, like a water spot on a window. The small blob in your binocular field might resemble an unwashed spot on an otherwide clean window. If you’ve never seen this deep-sky object before, it’s hard to know what to look for. Once you finally spot the Triangulum galaxy, you may wonder how you overlooked it so easily so many times before.

Science

At a distance of about 2.7 million light-years, the Triangulum galaxy might be a satellite galaxy of the Andromeda galaxy. The diameter of the Triangulum galaxy is about 50,000 light-years, or about one-half that of our Milky Way. After the Milky Way and Andromeda galaxies, the Triangulum galaxy ranks as the third largest of the few dozen galaxies inhabiting our Local Group of Galaxies.

from EarthSky http://earthsky.org/clusters-nebulae-galaxies/triangulum-galaxy-m33-a-binocular-challenge

How to find it

Although long-exposure photographs show the Triangulum galaxy (Messier 33) as a pinwheel of swarming suns, this face-on spiral galaxy looks rather lackluster in binoculars or even the telescope. The Triangulum galaxy has a low surface brightness that makes this faint object a major challenge, with or without optics.

Have you ever seen the Great Andromeda Galaxy (Messier 31)? If not, try finding the Andromeda galaxy before you take on the Triangulum galaxy. Shining 8 to 9 times more brightly than the Triangulum galaxy, the Andromeda galaxy is the most distant object that you can easily see with the unaided eye. Fortunately, the Triangulum and Andromeda galaxies are a relatively close 15 degrees apart. (For reference, a fist-width at an arm length approximates 10 degrees.)

Star-hop to the Andromeda galaxy to orient yourself to the Triangulum galaxy. As seen on the sky chart, the star Mirach stands about midway between the two galaxies. Our Andromeda galaxy sky chart shows you how to star-hop to the Andromeda galaxy. Once you’ve found it, the Andromeda galaxy and Mirach point in the general direction of the Triangulum galaxy.

The constellation Triangulum

Learn the constellation Triangulum, the small triangle made of three rather faint yet visible stars. Look eastward on some autumn evening, placing the star Alpha Triangulum at about the “7 o’clock” position in your binoculars. The Triangulum galaxy appears at the opposite side of the binouclar field, somewhere around 1 or 2 o’clock.

Now for a word of warning: even if you’re staring right at the Triangulum galaxy, it’s still possible to miss it. You won’t see the galaxy’s stars at all. Sometimes, this galaxy looks almost transparent, like a water spot on a window. The small blob in your binocular field might resemble an unwashed spot on an otherwide clean window. If you’ve never seen this deep-sky object before, it’s hard to know what to look for. Once you finally spot the Triangulum galaxy, you may wonder how you overlooked it so easily so many times before.

Science

At a distance of about 2.7 million light-years, the Triangulum galaxy might be a satellite galaxy of the Andromeda galaxy. The diameter of the Triangulum galaxy is about 50,000 light-years, or about one-half that of our Milky Way. After the Milky Way and Andromeda galaxies, the Triangulum galaxy ranks as the third largest of the few dozen galaxies inhabiting our Local Group of Galaxies.

from EarthSky http://earthsky.org/clusters-nebulae-galaxies/triangulum-galaxy-m33-a-binocular-challenge

News digest – obesity and diets, the immune system, stats galore and more

• In another big week for research on the immune system and cancer, the journal Nature published five separate papers on the subject. And one of those papers looking at bladder cancer caught the eye of the BBC, Mail Online and the Telegraph. We also covered the studies on our news feed.


• New estimates revealed that almost half a million new cancer cases worldwide in adults each year are linked to excess bodyweight. We covered this, and here’s the Mail Online and the Telegraph’s take on the findings.


• Continuing with statistics, a new study found that, although things are improving, the UK cancer survival still lags behind the best in the world – particularly for lung cancer. The Guardian has more.


• And in even more stats news, smoking rates in Britain have more than halved in the last 40 years. Look at the data in our news report, and the Mail Online had this take.


• US researchers discovered that the presence of particular genetic faults in the DNA of blood cells may be an indicator for the development of blood cancers later in life. TIME has more on this.


• The BBC took a graphic look at the changing face of Australian cigarette packing.


• This piece in the Independent, by GP Margaret McCartney, discussed the importance of end-of-life care.


• The Mail Online covered a new trial looking to test an advanced imaging technique that could help diagnose prostate cancer.


• This article in The Conversation debunks the hype around research on cannabis and cancer.


• This overhyped article appeared in the Telegraph following some interesting early research looking to develop a ‘breath test’ for lung cancer. It’s still too early to say if this could be used to diagnose people earlier.

And finally

New research sparked a couple of news reports on the perceived health benefits of the 5:2 diet and claims it could prevent diseases like Alzheimer’s and cancer. But the study actually found there’s not enough evidence to reach make those conclusions. Read this NHS Choices article for a more balanced analysis.

from Cancer Research UK - Science blog http://feedproxy.google.com/~r/cancerresearchuk/SHhE/~3/x6KzXF4iAzc/

• In another big week for research on the immune system and cancer, the journal Nature published five separate papers on the subject. And one of those papers looking at bladder cancer caught the eye of the BBC, Mail Online and the Telegraph. We also covered the studies on our news feed.


• New estimates revealed that almost half a million new cancer cases worldwide in adults each year are linked to excess bodyweight. We covered this, and here’s the Mail Online and the Telegraph’s take on the findings.


• Continuing with statistics, a new study found that, although things are improving, the UK cancer survival still lags behind the best in the world – particularly for lung cancer. The Guardian has more.


• And in even more stats news, smoking rates in Britain have more than halved in the last 40 years. Look at the data in our news report, and the Mail Online had this take.


• US researchers discovered that the presence of particular genetic faults in the DNA of blood cells may be an indicator for the development of blood cancers later in life. TIME has more on this.


• The BBC took a graphic look at the changing face of Australian cigarette packing.


• This piece in the Independent, by GP Margaret McCartney, discussed the importance of end-of-life care.


• The Mail Online covered a new trial looking to test an advanced imaging technique that could help diagnose prostate cancer.


• This article in The Conversation debunks the hype around research on cannabis and cancer.


• This overhyped article appeared in the Telegraph following some interesting early research looking to develop a ‘breath test’ for lung cancer. It’s still too early to say if this could be used to diagnose people earlier.

And finally

New research sparked a couple of news reports on the perceived health benefits of the 5:2 diet and claims it could prevent diseases like Alzheimer’s and cancer. But the study actually found there’s not enough evidence to reach make those conclusions. Read this NHS Choices article for a more balanced analysis.

from Cancer Research UK - Science blog http://feedproxy.google.com/~r/cancerresearchuk/SHhE/~3/x6KzXF4iAzc/

A famous variable star in the constellation Cepheus

Tonight … come to know Delta Cephei, a famous variable star in the constellation Cepheus. With clock-like precision, this rather faint star doubles in brightness every 5.36 days. You can see the brightness change best if you contrast this star to others nearby.

The constellation Cepheus requires a dark sky to be seen, so it’ll be more obvious after moonset tonight. But if you can spot this constellation, you might be able to find the variable star. You’ll find it high in your northern sky on November and December evenings. The pattern of stars in Cepheus resembles a stick house, the kind we all drew as children. The variable star – Delta Cephei – is located near the bottom corner of the house pattern.

Black Friday to Cyber Monday! 50% off your 2015 EarthSky Lunar Calendar today!

Cepheid variable stars are a class of stars named in honor of Delta Cephei. They are known as pulsating variables. The image at right is what astronomers call a “light curve” of a variable star. Each point represents the brightness of the star at a particular time. You can see that the star’s brightness changes in a regular way over a period of days.

The brightness of a Cepheid variable star changes because the star is actually expanding and contracting in size. The radius of a Cepheid variable star changes by several million kilometers (30%) as the star expands and shrinks. There is a very precise relationship between a Cepheid variable’s luminosity, or true brightness, and pulsation period. The greater the intrinsic brightness of the star, the longer the period. For that reason, these variable stars serve as standard candles – in other words, their true brightness is known, so astronomers can see how bright they look to measure the distances to the stars – and hence to faraway galaxies.

Now look again at the chart showing the constellations Cepheus the King and Cassiopeia the Queen at the top of this page. In the actual sky, the two stars near Delta Cephei – Epsilon Cephei and Zeta Cephei – mark the low and high ends of Delta Cephei’s brightness scale. At its faintest, the variable star Delta Cephei is as dim as the fainter star, Epsilon Cephei. At its brightest, Delta Cephei matches the brightness of Zeta Cephei.

Cepheid variable stars enabled the astronomer Edwin Hubble to figure out that the Andromeda galaxy lies outside the bounds of our local galaxy, the Milky Way.

Bottom line: Delta Cephei is a famous variable star in the constellation Cepheus. With clock-like precision, this rather faint star doubles in brightness every 5.36 days.

Easily locate stars and constellations during any day and time with EarthSky’s Planisphere.

from EarthSky http://ift.tt/1rEXMHE

Tonight … come to know Delta Cephei, a famous variable star in the constellation Cepheus. With clock-like precision, this rather faint star doubles in brightness every 5.36 days. You can see the brightness change best if you contrast this star to others nearby.

The constellation Cepheus requires a dark sky to be seen, so it’ll be more obvious after moonset tonight. But if you can spot this constellation, you might be able to find the variable star. You’ll find it high in your northern sky on November and December evenings. The pattern of stars in Cepheus resembles a stick house, the kind we all drew as children. The variable star – Delta Cephei – is located near the bottom corner of the house pattern.

Black Friday to Cyber Monday! 50% off your 2015 EarthSky Lunar Calendar today!

Cepheid variable stars are a class of stars named in honor of Delta Cephei. They are known as pulsating variables. The image at right is what astronomers call a “light curve” of a variable star. Each point represents the brightness of the star at a particular time. You can see that the star’s brightness changes in a regular way over a period of days.

The brightness of a Cepheid variable star changes because the star is actually expanding and contracting in size. The radius of a Cepheid variable star changes by several million kilometers (30%) as the star expands and shrinks. There is a very precise relationship between a Cepheid variable’s luminosity, or true brightness, and pulsation period. The greater the intrinsic brightness of the star, the longer the period. For that reason, these variable stars serve as standard candles – in other words, their true brightness is known, so astronomers can see how bright they look to measure the distances to the stars – and hence to faraway galaxies.

Now look again at the chart showing the constellations Cepheus the King and Cassiopeia the Queen at the top of this page. In the actual sky, the two stars near Delta Cephei – Epsilon Cephei and Zeta Cephei – mark the low and high ends of Delta Cephei’s brightness scale. At its faintest, the variable star Delta Cephei is as dim as the fainter star, Epsilon Cephei. At its brightest, Delta Cephei matches the brightness of Zeta Cephei.

Cepheid variable stars enabled the astronomer Edwin Hubble to figure out that the Andromeda galaxy lies outside the bounds of our local galaxy, the Milky Way.

Bottom line: Delta Cephei is a famous variable star in the constellation Cepheus. With clock-like precision, this rather faint star doubles in brightness every 5.36 days.

Easily locate stars and constellations during any day and time with EarthSky’s Planisphere.

from EarthSky http://ift.tt/1rEXMHE

NASA is tracking a gargantuan iceberg, escaped from Antarctica

A first look at Antarctic iceberg B31, following the Southern Hemisphere winter. NASA’s Aqua satellite captured this image on November 22, 2014.

Winter has lifted from Antarctica’s Pine Island Bay, so that passing satellites can once again acquire sunlit views of massive iceberg B31 as it drifts in the Amundsen Sea. NASA has been tracking this iceberg – an ice island, really – since it separated from the front of Antarctica’s Pine Island Glacier a year ago (November 2013). It’s 240 square miles (over 600 square kilometers), in contrast to about 23 square miles for New York’s Manhattan Island. When southern winter fell around May 2014, darkness came to this region of Earth and the iceberg could not be seen for six months. It was thought then it would likely be swept up in the swift currents of the Southern Ocean, but, for now, it’s still in the Amundsen Sea – moving west – free now of surrounding debris and sea ice. Scientists expect that the berg will continue moving west.

Last April, just before winter darkness fell in Antarctica, Kelly Brunt, a glaciologist at NASA’s Goddard Space Flight Center, noted:

Iceberg calving is a very normal process. However, the detachment rift, or crack, that created this iceberg was well upstream of the 30-year average calving front of Pine Island Glacier, so this a region that warrants monitoring.

Pine Island Glacier itself – the source of the massive iceberg – has been the subject of intense study in the past several decades. Scientists speak of this glacier as the weak underbelly of the West Antarctic Ice Sheet. The glacier has been thinning and draining rapidly and may be one of the largest contributors to sea level rise. Read more: As ocean warms, Antarctica’s Pine Island Glacier thaws

Large icebergs like this one pose a danger to ships. Our modern shipboard technologies – radar and warning systems – can’t always prevent accidents. For example, in 2007, the MS Explorer, an Antarctic cruise ship, sank after striking an iceberg near the South Shetland Islands. Read more at CBS News.

Read more the images of B31 from NASA Visible Earth

B31 is a huge ice island, 20 miles (33 kilometers) by 12 miles (20 kilometers). Image via Jeff Schmaltz, LANCE/EOSDIS Rapid Response.

The ice island B31 broke away from Pine Island Glacier in early November, 2013.

Over the course of five months of Antarctic spring and summer – in late 2013 and early 2014 – NASA used both its Terra and Aqua satellites to capture images of the massive floating ice chunk. One of the scientists involved, Grant Bigg of the University of Sheffield, said his team was busy doing research on local ocean currents to try to explain the iceberg’s motion properly. He said, “It has been surprising how there have been periods of almost no motion, interspersed with rapid flow. There were a couple of occasions early on when there might have been partial grounding or collisions with the seafloor, as B31 bounced from one side of the Bay to the other.”

This image was acquired in April, 2014, during Antarctica’s autumn. Since about that time, the iceberg has been impossible to track visually. However, as of November 2014, NASA is tracking the iceberg again with the return of summer to Antarctica.

Bottom line: NASA is tracking the huge iceberg B31, which broke away from Antarctica’s Pine Island Glacier in November, 2013. Winter is now over in the southern part of the world, and acquired its first image in six months of B31 on November 22, 2014.

from EarthSky http://ift.tt/1gXYlRy

A first look at Antarctic iceberg B31, following the Southern Hemisphere winter. NASA’s Aqua satellite captured this image on November 22, 2014.

Winter has lifted from Antarctica’s Pine Island Bay, so that passing satellites can once again acquire sunlit views of massive iceberg B31 as it drifts in the Amundsen Sea. NASA has been tracking this iceberg – an ice island, really – since it separated from the front of Antarctica’s Pine Island Glacier a year ago (November 2013). It’s 240 square miles (over 600 square kilometers), in contrast to about 23 square miles for New York’s Manhattan Island. When southern winter fell around May 2014, darkness came to this region of Earth and the iceberg could not be seen for six months. It was thought then it would likely be swept up in the swift currents of the Southern Ocean, but, for now, it’s still in the Amundsen Sea – moving west – free now of surrounding debris and sea ice. Scientists expect that the berg will continue moving west.

Last April, just before winter darkness fell in Antarctica, Kelly Brunt, a glaciologist at NASA’s Goddard Space Flight Center, noted:

Iceberg calving is a very normal process. However, the detachment rift, or crack, that created this iceberg was well upstream of the 30-year average calving front of Pine Island Glacier, so this a region that warrants monitoring.

Pine Island Glacier itself – the source of the massive iceberg – has been the subject of intense study in the past several decades. Scientists speak of this glacier as the weak underbelly of the West Antarctic Ice Sheet. The glacier has been thinning and draining rapidly and may be one of the largest contributors to sea level rise. Read more: As ocean warms, Antarctica’s Pine Island Glacier thaws

Large icebergs like this one pose a danger to ships. Our modern shipboard technologies – radar and warning systems – can’t always prevent accidents. For example, in 2007, the MS Explorer, an Antarctic cruise ship, sank after striking an iceberg near the South Shetland Islands. Read more at CBS News.

Read more the images of B31 from NASA Visible Earth

B31 is a huge ice island, 20 miles (33 kilometers) by 12 miles (20 kilometers). Image via Jeff Schmaltz, LANCE/EOSDIS Rapid Response.

The ice island B31 broke away from Pine Island Glacier in early November, 2013.

Over the course of five months of Antarctic spring and summer – in late 2013 and early 2014 – NASA used both its Terra and Aqua satellites to capture images of the massive floating ice chunk. One of the scientists involved, Grant Bigg of the University of Sheffield, said his team was busy doing research on local ocean currents to try to explain the iceberg’s motion properly. He said, “It has been surprising how there have been periods of almost no motion, interspersed with rapid flow. There were a couple of occasions early on when there might have been partial grounding or collisions with the seafloor, as B31 bounced from one side of the Bay to the other.”

This image was acquired in April, 2014, during Antarctica’s autumn. Since about that time, the iceberg has been impossible to track visually. However, as of November 2014, NASA is tracking the iceberg again with the return of summer to Antarctica.

Bottom line: NASA is tracking the huge iceberg B31, which broke away from Antarctica’s Pine Island Glacier in November, 2013. Winter is now over in the southern part of the world, and acquired its first image in six months of B31 on November 22, 2014.

from EarthSky http://ift.tt/1gXYlRy

Is it true that Jupiter protects Earth?

Here’s a question we get regularly:

Is it true that Jupiter could be considered our friendliest planet because – without Jupiter – comets would be more likely to hit us?

The answer is yes … and no. Some astronomers believe that one reason Earth is habitable is that the gravity of Jupiter does help protect us from some comets. Long-period comets, in particular, enter the solar system from its outer reaches. Jupiter’s gravity is thought to sling most of these fast-moving ice balls out of the solar system before they can get close to Earth. So long-period comets are thought to strike Earth only on very long timescales of millions or tens of millions of years. Without Jupiter nearby, long-period comets would collide with our planet much more frequently.

In addition, in recent decades, astronomers have been able to see signs of comets that have crashed into Jupiter. There was Comet Shoemaker-Levy 9 in 1994. And, in 2009, astronomers observed a dark gash in one side of the giant planet, likely caused by a comet.

A NASA Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. At this point, the comet had broken into 21 icy fragments stretched stretched across 1.1 million kilometers (710 thousand miles) of space, or 3 times the distance between Earth and moon. When this picture was taken, these fragments were on a mid-July collision course with the gas giant planet Jupiter. Image via Wikimedia Commons.

Taking one for the team? Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter’s atmosphere in July 1994. Image and caption via Wikimedia Commons.

In 2009, amateur astronomer Anthony Wesley noticed a dark mark on Jupiter. It turned out to be a scar from an impact with some object, presumably a comet. Read more about the 2009 impact on Jupiter here.

But Jupiter creates both good and bad conditions for earthly life. Consider that its powerful gravity prevented space rocks orbiting near it from coalescing into a planet, and that’s why our solar system today has an asteroid belt, consisting of hundreds of thousands of small flying chunks of debris.

Today, Jupiter’s gravity continues to affect the asteroids – only now it nudges some asteroids toward the sun, where they have the possibility of colliding with Earth.

Another interesting story comes from several centuries ago. The late Brian G. Marsden, former director of the the International Astronomical Union’s Central Bureau for Astronomical Telegrams, related it to Dennis Overbye of the New York Times in 2009, shortly after the dark gash appeared on Jupiter. It’s rare for a comet to come within 1 astronomical unit of Earth (that is, one Earth-sun distance, 92 million miles, or about 150 million kilometers). But, in the year 1770, a Comet Lexell streaked past Earth at a distance of only a million miles. Dr. Marsden told Overbye that:

… the comet had come streaking in from the outer solar system three years earlier and passed close to Jupiter, which diverted it into a new orbit and straight toward Earth.

The comet made two passes around the sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system.

‘It was as if Jupiter aimed at us and missed,’ said Dr. Marsden.

So is Jupiter Earth’s protector? The answer is … sometimes!

What’s the difference between comets and asteroids?

from EarthSky http://ift.tt/QDGsx4

Here’s a question we get regularly:

Is it true that Jupiter could be considered our friendliest planet because – without Jupiter – comets would be more likely to hit us?

The answer is yes … and no. Some astronomers believe that one reason Earth is habitable is that the gravity of Jupiter does help protect us from some comets. Long-period comets, in particular, enter the solar system from its outer reaches. Jupiter’s gravity is thought to sling most of these fast-moving ice balls out of the solar system before they can get close to Earth. So long-period comets are thought to strike Earth only on very long timescales of millions or tens of millions of years. Without Jupiter nearby, long-period comets would collide with our planet much more frequently.

In addition, in recent decades, astronomers have been able to see signs of comets that have crashed into Jupiter. There was Comet Shoemaker-Levy 9 in 1994. And, in 2009, astronomers observed a dark gash in one side of the giant planet, likely caused by a comet.

A NASA Hubble Space Telescope image of Comet Shoemaker-Levy 9, taken on May 17, 1994. At this point, the comet had broken into 21 icy fragments stretched stretched across 1.1 million kilometers (710 thousand miles) of space, or 3 times the distance between Earth and moon. When this picture was taken, these fragments were on a mid-July collision course with the gas giant planet Jupiter. Image via Wikimedia Commons.

Taking one for the team? Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter’s atmosphere in July 1994. Image and caption via Wikimedia Commons.

In 2009, amateur astronomer Anthony Wesley noticed a dark mark on Jupiter. It turned out to be a scar from an impact with some object, presumably a comet. Read more about the 2009 impact on Jupiter here.

But Jupiter creates both good and bad conditions for earthly life. Consider that its powerful gravity prevented space rocks orbiting near it from coalescing into a planet, and that’s why our solar system today has an asteroid belt, consisting of hundreds of thousands of small flying chunks of debris.

Today, Jupiter’s gravity continues to affect the asteroids – only now it nudges some asteroids toward the sun, where they have the possibility of colliding with Earth.

Another interesting story comes from several centuries ago. The late Brian G. Marsden, former director of the the International Astronomical Union’s Central Bureau for Astronomical Telegrams, related it to Dennis Overbye of the New York Times in 2009, shortly after the dark gash appeared on Jupiter. It’s rare for a comet to come within 1 astronomical unit of Earth (that is, one Earth-sun distance, 92 million miles, or about 150 million kilometers). But, in the year 1770, a Comet Lexell streaked past Earth at a distance of only a million miles. Dr. Marsden told Overbye that:

… the comet had come streaking in from the outer solar system three years earlier and passed close to Jupiter, which diverted it into a new orbit and straight toward Earth.

The comet made two passes around the sun and in 1779 again passed very close to Jupiter, which then threw it back out of the solar system.

‘It was as if Jupiter aimed at us and missed,’ said Dr. Marsden.

So is Jupiter Earth’s protector? The answer is … sometimes!

What’s the difference between comets and asteroids?

from EarthSky http://ift.tt/QDGsx4