Saturn riding the Dark Horse

Image via project nightflight.

The Dark Horse Nebula is a huge dark nebula that obscures part of the brightest regions of our Milky Way galaxy. In this project nightflight image the horse even has a rider – the bright planet Saturn. Turn sideways to see Saturn horseback-riding on the nape of the neck of the silhouetted horse. It was shot in June 2017, when Saturn passed through the constellation Ophiuchus, the Serpent Bearer.

You can only see the Dark Horse Nebula from very dark places. Any amount of light pollution or moonlight will obscure this large region of dust. Haze or other moisture in the atmosphere will also prevent you from seeing it in the night sky. If it’s visible, it’s really big. It stretches across nearly 10 degrees in the upper bulge of the Milky Way and resembles the silhouette of a prancing horse as seen from the side. Ten degrees is about the size of your fist with your arm stretched out. Currently, the Great Galactic Horse is visible in the south to the right of the Milky Way’s center at astronomical dusk.

Our friends at project nightflight said:

What makes this image even more special is that it was photographed with a DSLR and a 50mm lens without using any type of tracking device. We used a special technique we developed for untracked astrophotography. The idea is to shoot a lot of similar exposures at very high ISO ratings and keep the single exposures so short that no tracking is needed. In a stacking program the individual frames can then be digitally combined to create a final noise-free picture.

Want to know more about how to shoot untracked astro-images like this one? There’s a complete PDF tutorial from project nightlight here.

from EarthSky http://ift.tt/2gLBSU1

Image via project nightflight.

The Dark Horse Nebula is a huge dark nebula that obscures part of the brightest regions of our Milky Way galaxy. In this project nightflight image the horse even has a rider – the bright planet Saturn. Turn sideways to see Saturn horseback-riding on the nape of the neck of the silhouetted horse. It was shot in June 2017, when Saturn passed through the constellation Ophiuchus, the Serpent Bearer.

You can only see the Dark Horse Nebula from very dark places. Any amount of light pollution or moonlight will obscure this large region of dust. Haze or other moisture in the atmosphere will also prevent you from seeing it in the night sky. If it’s visible, it’s really big. It stretches across nearly 10 degrees in the upper bulge of the Milky Way and resembles the silhouette of a prancing horse as seen from the side. Ten degrees is about the size of your fist with your arm stretched out. Currently, the Great Galactic Horse is visible in the south to the right of the Milky Way’s center at astronomical dusk.

Our friends at project nightflight said:

What makes this image even more special is that it was photographed with a DSLR and a 50mm lens without using any type of tracking device. We used a special technique we developed for untracked astrophotography. The idea is to shoot a lot of similar exposures at very high ISO ratings and keep the single exposures so short that no tracking is needed. In a stacking program the individual frames can then be digitally combined to create a final noise-free picture.

Want to know more about how to shoot untracked astro-images like this one? There’s a complete PDF tutorial from project nightlight here.

from EarthSky http://ift.tt/2gLBSU1

Full Corn Moon on September 6

Above: Moonrise over Saltsjöbaden, Sweden. Image via Indranil Sinha.

Today – September 6, 2017 – presents the third and final full moon of northern summer (southern winter). In other words, this is the third of three full moons to occur in between the June 21 solstice and the September 22 equinox.

Click here to know the moonrise time, remembering to check the moonrise and moonset box.

Frequently, the September full moon provides the Northern Hemisphere with its Harvest Moon, because the September full moon – more often than not – is the closest full moon to the autumn equinox. But, in 2017, the October full moon happens closer to this equinox, so it’s this year’s Harvest Moon. When the September full moon is not the Harvest Moon, we in North America commonly call it the Fruit Moon, Corn Moon or Barley Moon.

The moon turns precisely full on September 6, 2017, at 7:03 UTC. At North American time zones, that translates to 4:03 a.m. ADT, 3:03 a.m. EDT, 2:03 a.m. CDT, 1:03 a.m. MDT, 12:03 a.m. PDT – and on September 5, at 11:03 p.m. ADKT and 9:03 p.m. HST. By the time that some of you are reading this post, this full moon instant will have passed.

Worldwide map via the US Naval Observatory. Day and night sides of Earth at the instant of the full moon (September 6, 2017 at 7:03 UTC). The shadow line passing to the left of Africa depicts sunrise on September 6, 2017, and the shadow line to the right of Australia represents sunset on September 6.

Astronomically speaking, the full moon occurs at a well-defined instant: when the moon is exactly 180^o from the sun in ecliptic longitude (also called celestial longitude). That means the moon stands opposite the sun as measured along the ecliptic – the sun’s annual pathway through constellations of the zodiac. Another way of putting it: at the instant of full moon, the moon-sun elongation equals 180^o. Click here to find out the present moon-sun elongation (if the number is negative, that means the moon is waning).

To the eye, though, the moon appears full for up to two or three days. So, no matter where you reside on the great globe of Earth, look for tonight’s moon to appear plenty full and colorful as it rises over the eastern horizon at dusk or very early evening.

Thereafter, the brilliant moon will beam all night long!

Bottom line: Full moon is September 6 at 7:03 UTC. So the crest of the moon’s full phase may have already passed, for you. Still, since the moon looks full for several days, we all can enjoy this 3rd and final full moon of northern summer (southern winter) tonight.

from EarthSky http://ift.tt/2f2nBhS

Above: Moonrise over Saltsjöbaden, Sweden. Image via Indranil Sinha.

Today – September 6, 2017 – presents the third and final full moon of northern summer (southern winter). In other words, this is the third of three full moons to occur in between the June 21 solstice and the September 22 equinox.

Click here to know the moonrise time, remembering to check the moonrise and moonset box.

Frequently, the September full moon provides the Northern Hemisphere with its Harvest Moon, because the September full moon – more often than not – is the closest full moon to the autumn equinox. But, in 2017, the October full moon happens closer to this equinox, so it’s this year’s Harvest Moon. When the September full moon is not the Harvest Moon, we in North America commonly call it the Fruit Moon, Corn Moon or Barley Moon.

The moon turns precisely full on September 6, 2017, at 7:03 UTC. At North American time zones, that translates to 4:03 a.m. ADT, 3:03 a.m. EDT, 2:03 a.m. CDT, 1:03 a.m. MDT, 12:03 a.m. PDT – and on September 5, at 11:03 p.m. ADKT and 9:03 p.m. HST. By the time that some of you are reading this post, this full moon instant will have passed.

Worldwide map via the US Naval Observatory. Day and night sides of Earth at the instant of the full moon (September 6, 2017 at 7:03 UTC). The shadow line passing to the left of Africa depicts sunrise on September 6, 2017, and the shadow line to the right of Australia represents sunset on September 6.

Astronomically speaking, the full moon occurs at a well-defined instant: when the moon is exactly 180^o from the sun in ecliptic longitude (also called celestial longitude). That means the moon stands opposite the sun as measured along the ecliptic – the sun’s annual pathway through constellations of the zodiac. Another way of putting it: at the instant of full moon, the moon-sun elongation equals 180^o. Click here to find out the present moon-sun elongation (if the number is negative, that means the moon is waning).

To the eye, though, the moon appears full for up to two or three days. So, no matter where you reside on the great globe of Earth, look for tonight’s moon to appear plenty full and colorful as it rises over the eastern horizon at dusk or very early evening.

Thereafter, the brilliant moon will beam all night long!

Bottom line: Full moon is September 6 at 7:03 UTC. So the crest of the moon’s full phase may have already passed, for you. Still, since the moon looks full for several days, we all can enjoy this 3rd and final full moon of northern summer (southern winter) tonight.

from EarthSky http://ift.tt/2f2nBhS

How many house-sized Near-Earth Objects?

Vapor trail left by the Chelyabinsk meteor, as captured by Flickr user Alex Alishevskikh.

Many people were driving and startled to see the now-famous Chelyabinsk meteor hurtling through Earth’s atmosphere on the morning of February 15, 2013, shortly before it exploded over the Russian city of Chelyabinsk. The explosion shattered windows, and sent more than a thousand people to medical centers for injuries, mostly from flying glass. It’s thought that, when it was in space, the Chelyabinsk meteoroid was in the range of 10 to 20 meters across (30 to 60 feet across), about as big as a house. A new study whose lead investigator is the director of the Kitt Peak National Observatory, astronomer Lori Allen, looked at how many house-sized rocks – similar to the Chelyabinsk meteor – have orbits that bring them close to Earth. The study found these objects to be rarer than previously thought. Allen said:

There are around 3.5 million NEOs larger than 10 meters, a population 10 times smaller than inferred in previous studies. About 90% of these NEOs are in the Chelyabinsk size range of 10-20 meters.

Near-Earth Objects (NEOs) are asteroids or comets whose orbits bring them close to Earth’s orbit. Their close approach makes them a potential Earth-impact hazard capable of causing destruction on the scale of cities. The astronomers’ statement explained:

While very large (10 km-sized) impactors can induce mass extinction events like the event that led to the demise of the dinosaurs, much smaller impactors can also wreak havoc. The meteoroid that exploded in Chelyabinsk unleashed a powerful shock wave that destroyed buildings and blew people off their feet. Relatively petite at a ‘mere’ 17 meters in diameter, comparable to the size of a 6-story building, the impactor, when it exploded, released about 10 times the energy of the Hiroshima atomic bomb.

A dashboard camera caught the bright fireball from the Chelyabinsk meteor – February 15, 2013 – as it was exploding in the atmosphere.

To carry out their study, these astronomers directly surveyed NEOs with a wide-field CCD imager called DECam on the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile.

The study has been accepted for publication in the peer-reviewed Astronomical Journal.

The astronomers say it is:

… the first to derive, from a single observational data set with no external model assumptions, the size distribution of NEOs from 1 kilometer down to 10 meters. A similar result was obtained in an independent study that analyzed multiple data sets (Tricarico 2017).

While the surprising results do not alter the impact threat from house-sized NEOs, which is constrained by the observed rate of Chelyabinsk-like bolide events, they do lend new insights into the nature and origin of small NEOs.

Astronomer David Trilling of Northern Arizona University is the study’s first author. He explained how the study reconciled the surprisingly small number of house-sized NEOs with the observed rate of Chelyabinsk-like events:

If house-sized NEOs are responsible for Chelyabinsk-like events, our results seem to say that the average impact probability of a house-sized NEO is actually 10 times greater than the average impact probability of a large NEO. That sounds strange, but it may be telling us something interesting about the dynamical history of NEOs.

Trilling speculates:

… that the orbital distributions of large and small NEOs differ, with small NEOs concentrated in bands of collisional debris that are more likely to impact Earth. Bands of debris could be produced when larger NEOs fragment into swarms of smaller boulders. Testing this hypothesis is an interesting problem for the future.

Read more about the study from NOAO

Another shot from a dashboard camera of the Chelyabinsk meteor seen over Russia on February 15, 2013.

Bottom line: Astronomers surveyed NEOs with a wide-field CCD imager on the 4-meter Blanco telescope at Cerro Tololo in Chile, to learn that house-sized NEOs – similar to the Chelyabinsk meteor that exploded over Russia in 2013 – may be 10 times fewer in number than previously thought.

from EarthSky http://ift.tt/2vIj4LS

Vapor trail left by the Chelyabinsk meteor, as captured by Flickr user Alex Alishevskikh.

Many people were driving and startled to see the now-famous Chelyabinsk meteor hurtling through Earth’s atmosphere on the morning of February 15, 2013, shortly before it exploded over the Russian city of Chelyabinsk. The explosion shattered windows, and sent more than a thousand people to medical centers for injuries, mostly from flying glass. It’s thought that, when it was in space, the Chelyabinsk meteoroid was in the range of 10 to 20 meters across (30 to 60 feet across), about as big as a house. A new study whose lead investigator is the director of the Kitt Peak National Observatory, astronomer Lori Allen, looked at how many house-sized rocks – similar to the Chelyabinsk meteor – have orbits that bring them close to Earth. The study found these objects to be rarer than previously thought. Allen said:

There are around 3.5 million NEOs larger than 10 meters, a population 10 times smaller than inferred in previous studies. About 90% of these NEOs are in the Chelyabinsk size range of 10-20 meters.

Near-Earth Objects (NEOs) are asteroids or comets whose orbits bring them close to Earth’s orbit. Their close approach makes them a potential Earth-impact hazard capable of causing destruction on the scale of cities. The astronomers’ statement explained:

While very large (10 km-sized) impactors can induce mass extinction events like the event that led to the demise of the dinosaurs, much smaller impactors can also wreak havoc. The meteoroid that exploded in Chelyabinsk unleashed a powerful shock wave that destroyed buildings and blew people off their feet. Relatively petite at a ‘mere’ 17 meters in diameter, comparable to the size of a 6-story building, the impactor, when it exploded, released about 10 times the energy of the Hiroshima atomic bomb.

A dashboard camera caught the bright fireball from the Chelyabinsk meteor – February 15, 2013 – as it was exploding in the atmosphere.

To carry out their study, these astronomers directly surveyed NEOs with a wide-field CCD imager called DECam on the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile.

The study has been accepted for publication in the peer-reviewed Astronomical Journal.

The astronomers say it is:

… the first to derive, from a single observational data set with no external model assumptions, the size distribution of NEOs from 1 kilometer down to 10 meters. A similar result was obtained in an independent study that analyzed multiple data sets (Tricarico 2017).

While the surprising results do not alter the impact threat from house-sized NEOs, which is constrained by the observed rate of Chelyabinsk-like bolide events, they do lend new insights into the nature and origin of small NEOs.

Astronomer David Trilling of Northern Arizona University is the study’s first author. He explained how the study reconciled the surprisingly small number of house-sized NEOs with the observed rate of Chelyabinsk-like events:

If house-sized NEOs are responsible for Chelyabinsk-like events, our results seem to say that the average impact probability of a house-sized NEO is actually 10 times greater than the average impact probability of a large NEO. That sounds strange, but it may be telling us something interesting about the dynamical history of NEOs.

Trilling speculates:

… that the orbital distributions of large and small NEOs differ, with small NEOs concentrated in bands of collisional debris that are more likely to impact Earth. Bands of debris could be produced when larger NEOs fragment into swarms of smaller boulders. Testing this hypothesis is an interesting problem for the future.

Read more about the study from NOAO

Another shot from a dashboard camera of the Chelyabinsk meteor seen over Russia on February 15, 2013.

Bottom line: Astronomers surveyed NEOs with a wide-field CCD imager on the 4-meter Blanco telescope at Cerro Tololo in Chile, to learn that house-sized NEOs – similar to the Chelyabinsk meteor that exploded over Russia in 2013 – may be 10 times fewer in number than previously thought.

from EarthSky http://ift.tt/2vIj4LS

Watch for zodiacal light or false dawn

The zodiacal light is the diffuse cone-shaped light extending up from the horizon on the right side of this photo. Photo by Richard Hasbrouck in Truchas, New Mexico.

If you’re in the Northern Hemisphere, it’s time to start looking for the zodiacal light – or false dawn – an eerie light in the east before sunrise, visible in clear dark skies in the months around the autumn equinox. If you’re in the Southern Hemisphere in September or October, look in the west after sunset instead, for the same phenomenon, now called the false dusk. The light looks like a hazy pyramid. It’s comparable in brightness to the Milky Way, but even milkier in appearance. Follow the links below to learn more about the zodiacal light.

How I can see the zodiacal light?

Springtime? Autumn? When should I look?

What is zodiacal light?

Zodiacal light via Flickr user Robert Snache.

How I can see the zodiacal light? Maybe you’ve seen the zodiacal light in the sky already and not realized it. Maybe you glimpsed it while driving on a highway or country road. This strange light is a seasonal phenomenon. Springtime and autumn are best for seeing it, no matter where you live on Earth.

Suppose you’re driving toward the east – in the hour before dawn – in autumn. You catch sight of what you think is the light of a nearby town, just over the horizon. But it might not be a town. It might be the zodiacal light. The light looks like a hazy pyramid of light extending up from the eastern horizon, shortly before morning twilight begins. The zodiacal light can be extremely bright and easy to see from latitudes like those in the southern U.S.

We also sometimes hear from skywatchers in the northern U.S. or Canada, who’ve captured images of the zodiacal light.

You’ll need a dark sky location to see the zodiacal light, someplace where city lights aren’t obscuring the natural lights in the sky.

The zodiacal light is most visible before dawn in autumn (September or October for the Northern Hemisphere, March or April for the Southern Hemisphere) because autumn is when the ecliptic – or path of the sun and moon – stands nearly straight up with respect to your eastern horizon before dawn. Likewise, the zodiacal light is easiest to see just after true night falls in your springtime months, because then the ecliptic is most perpendicular to your western horizon in the evening.

In autumn, the zodiacal light can be seen in the hour before true dawn begins. Or, in spring, it can be seen for up to an hour after all traces of evening twilight leave the sky. Unlike true dawn or dusk, though, there’s no rosy color to the zodiacal light. The reddish skies at dawn and dusk are caused by Earth’s atmosphere, while the zodiacal light originates far outside our atmosphere, as explained below.

The darker your sky, the better your chances of seeing it. Your best bet is to pick a night when the moon is out of the sky, although it’s definitely possible, and very lovely, to see a slim crescent moon in the midst of this strange milky pyramid of light.

If you see it, let us know! If you catch a photo, submit it here.

Zodiacal light at Paranal. Image via European Southern Observatory/Y. Beletsky

Springtime? Autumn? When should I look? Is there a Northern/ Southern Hemisphere difference between the best time of year to view the zodiacal light? Yes and no. For both hemispheres, springtime is the best time to see the zodiacal light in the evening. Autumn is the best time to see it before dawn.

No matter where you live on Earth, look for the zodiacal light in the east before dawn around the time of your autumn equinox. Look for it in the west after sunset around the time of your spring equinox.

Of course, spring and autumn fall in different months for Earth’s Northern and Southern Hemispheres.

So if you’re in the Northern Hemisphere look for the zodiacal light before dawn from about late August through early November.

In those same months, if you’re in the Southern Hemisphere, look for the light in the evening.

Likewise, if you’re in the Northern Hemisphere, look for the evening zodiacal light from late February through early May. During those months, from the Southern Hemisphere, look for the light in the morning.

Zodiacal Light over the Faulkes Telescope, Haleakala, Maui. Photo credit: Rob Ratkowksi

What is zodiacal light? People used to think zodiacal light originated somehow from phenomena in Earth’s upper atmosphere, but today we understand it as sunlight reflecting off dust grains that circle the sun in the inner solar system. These grains are thought to be left over from the process that created our Earth and the other planets of our solar system 4.5 billion years ago.

These dust grains in space spread out from the sun in the same flat disc of space inhabited by Mercury, Venus, Earth, Mars and the other planets in our sun’s family. This flat space around the sun – the plane of our solar system – translates on our sky to a narrow pathway called the ecliptic. This is the same pathway traveled by the sun and moon as they journey across our sky.

The pathway of the sun and moon was called the zodiac or Pathway of Animals by our ancestors in honor of the constellations seen beyond it. The word zodiacal stems from the word zodiac.

In other words, the zodiacal light is a solar system phenomenon. The grains of dust that create it are like tiny worlds – ranging from meter-sized to micron-sized – densest around the immediate vicinity of the sun and extending outward beyond the orbit of Mars. Sunlight shines on these grains of dust to create the light we see. Since they lie in the flat sheet of space around the sun, we could, in theory, see them as a band of dust across our entire sky, marking the same path that the sun follows during the day. And indeed there are sky phenomena associated with this band of dust, such as the gegenschein.

But seeing such elusive sky phenomena as the gegenschein is difficult. Most of us see only the more obvious part of this dust band – the zodiacal light – in either spring or fall.

Milky Way on left in this photo. Zodiacal light on right. This photo is from EarthSky Facebook friend Sean Parker Photography. He captured it at Kitt Peak National Observatory in Arizona.

The zodiacal light is easier to see as you get closer to Earth’s equator. But it can be glimpsed from northerly latitudes, too. Here’s the zodiacal light seen by EarthSky Facebook friend Jim Peacock on the evening of February 5, 2013, over Lake Superior in northern Wisconsin. Thank you, Jim!

Here’s the zodiacal light as captured on film in Canada. This wonderful capture is from Robert Ede in Invermere, British Columbia.

Bottom line: The zodiacal light – sometimes called the false dawn – is a hazy pyramid of light extending up from the eastern horizon, beginning about an hour before true dawn begins to break, in autumn. It extends up from the western horizon, a couple of hours after sunset. The light is caused by sunlight reflecting on dust grains that move in the plane of the solar system.

from EarthSky http://ift.tt/1l3mMSs

The zodiacal light is the diffuse cone-shaped light extending up from the horizon on the right side of this photo. Photo by Richard Hasbrouck in Truchas, New Mexico.

If you’re in the Northern Hemisphere, it’s time to start looking for the zodiacal light – or false dawn – an eerie light in the east before sunrise, visible in clear dark skies in the months around the autumn equinox. If you’re in the Southern Hemisphere in September or October, look in the west after sunset instead, for the same phenomenon, now called the false dusk. The light looks like a hazy pyramid. It’s comparable in brightness to the Milky Way, but even milkier in appearance. Follow the links below to learn more about the zodiacal light.

How I can see the zodiacal light?

Springtime? Autumn? When should I look?

What is zodiacal light?

Zodiacal light via Flickr user Robert Snache.

How I can see the zodiacal light? Maybe you’ve seen the zodiacal light in the sky already and not realized it. Maybe you glimpsed it while driving on a highway or country road. This strange light is a seasonal phenomenon. Springtime and autumn are best for seeing it, no matter where you live on Earth.

Suppose you’re driving toward the east – in the hour before dawn – in autumn. You catch sight of what you think is the light of a nearby town, just over the horizon. But it might not be a town. It might be the zodiacal light. The light looks like a hazy pyramid of light extending up from the eastern horizon, shortly before morning twilight begins. The zodiacal light can be extremely bright and easy to see from latitudes like those in the southern U.S.

We also sometimes hear from skywatchers in the northern U.S. or Canada, who’ve captured images of the zodiacal light.

You’ll need a dark sky location to see the zodiacal light, someplace where city lights aren’t obscuring the natural lights in the sky.

The zodiacal light is most visible before dawn in autumn (September or October for the Northern Hemisphere, March or April for the Southern Hemisphere) because autumn is when the ecliptic – or path of the sun and moon – stands nearly straight up with respect to your eastern horizon before dawn. Likewise, the zodiacal light is easiest to see just after true night falls in your springtime months, because then the ecliptic is most perpendicular to your western horizon in the evening.

In autumn, the zodiacal light can be seen in the hour before true dawn begins. Or, in spring, it can be seen for up to an hour after all traces of evening twilight leave the sky. Unlike true dawn or dusk, though, there’s no rosy color to the zodiacal light. The reddish skies at dawn and dusk are caused by Earth’s atmosphere, while the zodiacal light originates far outside our atmosphere, as explained below.

The darker your sky, the better your chances of seeing it. Your best bet is to pick a night when the moon is out of the sky, although it’s definitely possible, and very lovely, to see a slim crescent moon in the midst of this strange milky pyramid of light.

If you see it, let us know! If you catch a photo, submit it here.

Zodiacal light at Paranal. Image via European Southern Observatory/Y. Beletsky

Springtime? Autumn? When should I look? Is there a Northern/ Southern Hemisphere difference between the best time of year to view the zodiacal light? Yes and no. For both hemispheres, springtime is the best time to see the zodiacal light in the evening. Autumn is the best time to see it before dawn.

No matter where you live on Earth, look for the zodiacal light in the east before dawn around the time of your autumn equinox. Look for it in the west after sunset around the time of your spring equinox.

Of course, spring and autumn fall in different months for Earth’s Northern and Southern Hemispheres.

So if you’re in the Northern Hemisphere look for the zodiacal light before dawn from about late August through early November.

In those same months, if you’re in the Southern Hemisphere, look for the light in the evening.

Likewise, if you’re in the Northern Hemisphere, look for the evening zodiacal light from late February through early May. During those months, from the Southern Hemisphere, look for the light in the morning.

Zodiacal Light over the Faulkes Telescope, Haleakala, Maui. Photo credit: Rob Ratkowksi

What is zodiacal light? People used to think zodiacal light originated somehow from phenomena in Earth’s upper atmosphere, but today we understand it as sunlight reflecting off dust grains that circle the sun in the inner solar system. These grains are thought to be left over from the process that created our Earth and the other planets of our solar system 4.5 billion years ago.

These dust grains in space spread out from the sun in the same flat disc of space inhabited by Mercury, Venus, Earth, Mars and the other planets in our sun’s family. This flat space around the sun – the plane of our solar system – translates on our sky to a narrow pathway called the ecliptic. This is the same pathway traveled by the sun and moon as they journey across our sky.

The pathway of the sun and moon was called the zodiac or Pathway of Animals by our ancestors in honor of the constellations seen beyond it. The word zodiacal stems from the word zodiac.

In other words, the zodiacal light is a solar system phenomenon. The grains of dust that create it are like tiny worlds – ranging from meter-sized to micron-sized – densest around the immediate vicinity of the sun and extending outward beyond the orbit of Mars. Sunlight shines on these grains of dust to create the light we see. Since they lie in the flat sheet of space around the sun, we could, in theory, see them as a band of dust across our entire sky, marking the same path that the sun follows during the day. And indeed there are sky phenomena associated with this band of dust, such as the gegenschein.

But seeing such elusive sky phenomena as the gegenschein is difficult. Most of us see only the more obvious part of this dust band – the zodiacal light – in either spring or fall.

Milky Way on left in this photo. Zodiacal light on right. This photo is from EarthSky Facebook friend Sean Parker Photography. He captured it at Kitt Peak National Observatory in Arizona.

The zodiacal light is easier to see as you get closer to Earth’s equator. But it can be glimpsed from northerly latitudes, too. Here’s the zodiacal light seen by EarthSky Facebook friend Jim Peacock on the evening of February 5, 2013, over Lake Superior in northern Wisconsin. Thank you, Jim!

Here’s the zodiacal light as captured on film in Canada. This wonderful capture is from Robert Ede in Invermere, British Columbia.

Bottom line: The zodiacal light – sometimes called the false dawn – is a hazy pyramid of light extending up from the eastern horizon, beginning about an hour before true dawn begins to break, in autumn. It extends up from the western horizon, a couple of hours after sunset. The light is caused by sunlight reflecting on dust grains that move in the plane of the solar system.

from EarthSky http://ift.tt/1l3mMSs

Army Wraps Up Autonomous Micro-robotics Research Program

Nearly 10 years of Army research has come to an end but new innovations that benefit the warfighter are just beginning.

from http://ift.tt/2eGp40e

Nearly 10 years of Army research has come to an end but new innovations that benefit the warfighter are just beginning.

from http://ift.tt/2eGp40e

Artificial intelligence probes gravity’s lens

Artist’s represenation of the use of neural networks to analyze the phenomenon of gravitational lensing, whereby massive objects cause extreme distortions in spacetime. Image via SLAC.

Manuel Gnida wrote this article for SLAC National Accelerator Laboratory in Menlo Park, California.

Researchers from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have for the first time shown that neural networks – a form of artificial intelligence – can accurately analyze the complex distortions in spacetime known as gravitational lenses 10 million times faster than traditional methods. Postdoctoral fellow Laurence Perreault Levasseur, a co-author of a study published August 30, 2017 in Nature, said:

Analyses that typically take weeks to months to complete, that require the input of experts and that are computationally demanding, can be done by neural nets within a fraction of a second, in a fully automated way and, in principle, on a cell phone’s computer chip.

The team at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of SLAC and Stanford, used neural networks to analyze images of strong gravitational lensing, where the image of a faraway galaxy is multiplied and distorted into rings and arcs by the gravity of a massive object, such as a galaxy cluster, that’s closer to us. The distortions provide important clues about how mass is distributed in space and how that distribution changes over time – properties linked to invisible dark matter that makes up 85 percent of all matter in the universe and to dark energy that’s accelerating the expansion of the universe.

Until now this type of analysis has been a tedious process that involves comparing actual images of lenses with a large number of computer simulations of mathematical lensing models. This can take weeks to months for a single lens.

But with the neural networks, the researchers were able to do the same analysis in a few seconds, which they demonstrated using real images from NASA’s Hubble Space Telescope and simulated ones.

To train the neural networks in what to look for, the researchers showed them about half a million simulated images of gravitational lenses for about a day. Once trained, the networks were able to analyze new lenses almost instantaneously with a precision that was comparable to traditional analysis methods. In a separate paper, submitted to The Astrophysical Journal Letters, the team reports how these networks can also determine the uncertainties of their analyses.

In the video below, KIPAC researcher Phil Marshall explains the optical principles of gravitational lensing using a wineglass.

The study’s lead author is Yashar Hezaveh, a NASA Hubble postdoctoral fellow at KIPAC. He said:

The neural networks we tested – three publicly available neural nets and one that we developed ourselves – were able to determine the properties of each lens, including how its mass was distributed and how much it magnified the image of the background galaxy.

This goes far beyond recent applications of neural networks in astrophysics, which were limited to solving classification problems, such as determining whether an image shows a gravitational lens or not.

The ability to sift through large amounts of data and perform complex analyses very quickly and in a fully automated fashion could transform astrophysics in a way that is much needed for future sky surveys that will look deeper into the universe – and produce more data – than ever before.

The Large Synoptic Survey Telescope (LSST), for example, whose 3.2-gigapixel camera is currently under construction at SLAC, will provide unparalleled views of the universe and is expected to increase the number of known strong gravitational lenses from a few hundred today to tens of thousands. Perreault Levasseur commented:

We won’t have enough people to analyze all these data in a timely manner with the traditional methods. Neural networks will help us identify interesting objects and analyze them quickly. This will give us more time to ask the right questions about the universe.

KIPAC researchers used images of strongly lensed galaxies taken with the Hubble Space Telescope to test the performance of neural networks, which promise to speed up complex astrophysical analyses tremendously. Image via Yashar Hezaveh/ Laurence Perreault Levasseur/ Phil Marshall/ Stanford/ SLAC National Accelerator Laboratory/ NASA and ESA).

Neural networks are inspired by the architecture of the human brain, in which a dense network of neurons quickly processes and analyzes information.

In the artificial version, the neurons are single computational units that are associated with the pixels of the image being analyzed. The neurons are organized into layers, up to hundreds of layers deep. Each layer searches for features in the image. Once the first layer has found a certain feature, it transmits the information to the next layer, which then searches for another feature within that feature, and so on. KIPAC staff scientist Phil Marshall, a co-author of the paper, said:

The amazing thing is that neural networks learn by themselves what features to look for. This is comparable to the way small children learn to recognize objects. You don’t tell them exactly what a dog is; you just show them pictures of dogs.

But in this case, Hezaveh said:

It’s as if they not only picked photos of dogs from a pile of photos, but also returned information about the dogs’ weight, height and age.

Scheme of an artificial neural network, with individual computational units organized into hundreds of layers. Each layer searches for certain features in the input image (at left). The last layer provides the result of the analysis. The researchers used particular kinds of neural networks, called convolutional neural networks, in which individual computational units (neurons, gray spheres) of each layer are also organized into 2-D slabs that bundle information about the original image into larger computational units. Image via Greg Stewart/ SLAC National Accelerator Laboratory.

Although the KIPAC scientists ran their tests on the Sherlock high-performance computing cluster at the Stanford Research Computing Center, they could have done their computations on a laptop or even on a cell phone, they said. In fact, one of the neural networks they tested was designed to work on iPhones. KIPAC faculty member Roger Blandford, who was not a co-author on the paper, explained:

Neural nets have been applied to astrophysical problems in the past with mixed outcomes. But new algorithms combined with modern graphics processing units, or GPUs, can produce extremely fast and reliable results, as the gravitational lens problem tackled in this paper dramatically demonstrates. There is considerable optimism that this will become the approach of choice for many more data processing and analysis problems in astrophysics and other fields.

Part of this work was funded by the DOE Office of Science.

Bottom line: Researchers at SLAC and Stanford have for the first time shown that neural networks – a form of artificial intelligence – can accurately analyze distortions in spacetime known as gravitational lenses, 10 million times faster than traditional methods. They say the ability to sift through large amounts of data and perform complex analyses quickly and in an automated fashion could transform astrophysics.

from EarthSky http://ift.tt/2gJ7h9H

Artist’s represenation of the use of neural networks to analyze the phenomenon of gravitational lensing, whereby massive objects cause extreme distortions in spacetime. Image via SLAC.

Manuel Gnida wrote this article for SLAC National Accelerator Laboratory in Menlo Park, California.

Researchers from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have for the first time shown that neural networks – a form of artificial intelligence – can accurately analyze the complex distortions in spacetime known as gravitational lenses 10 million times faster than traditional methods. Postdoctoral fellow Laurence Perreault Levasseur, a co-author of a study published August 30, 2017 in Nature, said:

Analyses that typically take weeks to months to complete, that require the input of experts and that are computationally demanding, can be done by neural nets within a fraction of a second, in a fully automated way and, in principle, on a cell phone’s computer chip.

The team at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), a joint institute of SLAC and Stanford, used neural networks to analyze images of strong gravitational lensing, where the image of a faraway galaxy is multiplied and distorted into rings and arcs by the gravity of a massive object, such as a galaxy cluster, that’s closer to us. The distortions provide important clues about how mass is distributed in space and how that distribution changes over time – properties linked to invisible dark matter that makes up 85 percent of all matter in the universe and to dark energy that’s accelerating the expansion of the universe.

Until now this type of analysis has been a tedious process that involves comparing actual images of lenses with a large number of computer simulations of mathematical lensing models. This can take weeks to months for a single lens.

But with the neural networks, the researchers were able to do the same analysis in a few seconds, which they demonstrated using real images from NASA’s Hubble Space Telescope and simulated ones.

To train the neural networks in what to look for, the researchers showed them about half a million simulated images of gravitational lenses for about a day. Once trained, the networks were able to analyze new lenses almost instantaneously with a precision that was comparable to traditional analysis methods. In a separate paper, submitted to The Astrophysical Journal Letters, the team reports how these networks can also determine the uncertainties of their analyses.

In the video below, KIPAC researcher Phil Marshall explains the optical principles of gravitational lensing using a wineglass.

The study’s lead author is Yashar Hezaveh, a NASA Hubble postdoctoral fellow at KIPAC. He said:

The neural networks we tested – three publicly available neural nets and one that we developed ourselves – were able to determine the properties of each lens, including how its mass was distributed and how much it magnified the image of the background galaxy.

This goes far beyond recent applications of neural networks in astrophysics, which were limited to solving classification problems, such as determining whether an image shows a gravitational lens or not.

The ability to sift through large amounts of data and perform complex analyses very quickly and in a fully automated fashion could transform astrophysics in a way that is much needed for future sky surveys that will look deeper into the universe – and produce more data – than ever before.

The Large Synoptic Survey Telescope (LSST), for example, whose 3.2-gigapixel camera is currently under construction at SLAC, will provide unparalleled views of the universe and is expected to increase the number of known strong gravitational lenses from a few hundred today to tens of thousands. Perreault Levasseur commented:

We won’t have enough people to analyze all these data in a timely manner with the traditional methods. Neural networks will help us identify interesting objects and analyze them quickly. This will give us more time to ask the right questions about the universe.

KIPAC researchers used images of strongly lensed galaxies taken with the Hubble Space Telescope to test the performance of neural networks, which promise to speed up complex astrophysical analyses tremendously. Image via Yashar Hezaveh/ Laurence Perreault Levasseur/ Phil Marshall/ Stanford/ SLAC National Accelerator Laboratory/ NASA and ESA).

Neural networks are inspired by the architecture of the human brain, in which a dense network of neurons quickly processes and analyzes information.

In the artificial version, the neurons are single computational units that are associated with the pixels of the image being analyzed. The neurons are organized into layers, up to hundreds of layers deep. Each layer searches for features in the image. Once the first layer has found a certain feature, it transmits the information to the next layer, which then searches for another feature within that feature, and so on. KIPAC staff scientist Phil Marshall, a co-author of the paper, said:

The amazing thing is that neural networks learn by themselves what features to look for. This is comparable to the way small children learn to recognize objects. You don’t tell them exactly what a dog is; you just show them pictures of dogs.

But in this case, Hezaveh said:

It’s as if they not only picked photos of dogs from a pile of photos, but also returned information about the dogs’ weight, height and age.

Scheme of an artificial neural network, with individual computational units organized into hundreds of layers. Each layer searches for certain features in the input image (at left). The last layer provides the result of the analysis. The researchers used particular kinds of neural networks, called convolutional neural networks, in which individual computational units (neurons, gray spheres) of each layer are also organized into 2-D slabs that bundle information about the original image into larger computational units. Image via Greg Stewart/ SLAC National Accelerator Laboratory.

Although the KIPAC scientists ran their tests on the Sherlock high-performance computing cluster at the Stanford Research Computing Center, they could have done their computations on a laptop or even on a cell phone, they said. In fact, one of the neural networks they tested was designed to work on iPhones. KIPAC faculty member Roger Blandford, who was not a co-author on the paper, explained:

Neural nets have been applied to astrophysical problems in the past with mixed outcomes. But new algorithms combined with modern graphics processing units, or GPUs, can produce extremely fast and reliable results, as the gravitational lens problem tackled in this paper dramatically demonstrates. There is considerable optimism that this will become the approach of choice for many more data processing and analysis problems in astrophysics and other fields.

Part of this work was funded by the DOE Office of Science.

Bottom line: Researchers at SLAC and Stanford have for the first time shown that neural networks – a form of artificial intelligence – can accurately analyze distortions in spacetime known as gravitational lenses, 10 million times faster than traditional methods. They say the ability to sift through large amounts of data and perform complex analyses quickly and in an automated fashion could transform astrophysics.

from EarthSky http://ift.tt/2gJ7h9H

Harvest Moon on September 5-6?

Bettina Berg in Las Vegas contributed the image above of 2016’s Harvest Moon.

Tonight – September 5, 2017 – look for the full-looking moon to beam in the east at dusk. It’ll climb highest up for the night around midnight and sit low in west at dawn September 6. For us in the Americas, the moon turns full on this night. In other time zones, full moon falls closer to the night of September 6. Either way, some will call this September 2017 full moon the Northern Hemisphere’s Harvest Moon. Others will say the 2017 Harvest Moon comes in October. More about this issue later on in this post.

First let’s talk about the date and time of full moon. The moon turns full on September 6, 2017, at 7:03 UTC. Although the full moon happens at the same instant worldwide, the clock reads differently by time zone. Here, in the contiguous United States, the moon turns precisely full on September 6, at 3:03 a.m. EDT, 2:03 a.m. CDT, 1:03 a.m. MDT and 12:03 PDT. That’s why we say the full moon falls on the night of September 5, for the Americas.

If we include the states Alaska and Hawaii, the full moon really does happen on September 5. The time is 11:03 p.m. on September 5 in Alaska and 9:03 p.m. on September 5 in Hawaii.

But we’re talking technicalities here. Technically speaking, the moon is full at the instant that it’s 180^o from the sun in ecliptic or celestial longitude. Realistically speaking, for a day or two around the exact time of full moon, the moon looks and acts full. That is, it stays more or less opposite the sun throughout the night – rising in the east at dusk, highest up around midnight and in the west at dawn – for all of us around the globe.

Worldwide map via the US Naval Observatory. Day and night sides of Earth at the instant of the full moon (2017 September 6 at 7:03 UTC). The shadow line passing to the left of Africa depicts sunrise and the shadow line to the right of Australia represents sunset.

Is the September 5-6 full moon the Harvest Moon? More often than not, the September full moon is the Northern Hemisphere’s Harvest Moon. The Harvest Moon is usually defined as the full moon closest to the autumn equinox, which – in the Northern Hemisphere – comes on or near September 22 each year.

Last year’s Harvest Moon fell in September. Next year’s Harvest Moon will, too.

But, in 2017, the September 6 full moon comes too early to be the Northern Hemisphere’s official Harvest Moon, according to the most widely accepted definition of the term. That’s because the full moon of October 5, 2017, will fall closer to this year’s September 22 equinox. The October 2017 full moon will be this year’s Harvest Moon, while the September 5-6 full moon will carry its ordinary monthly full moon name of Corn Moon or Fruit Moon in the Northern Hemisphere (and Worm Moon, Lenten Moon, Crow Moon, Sugar Moon, Chaste Moon or Sap Moon in the Southern Hemisphere). Read more about full moon names.

However, in most respects, the September 2017 and October 2017 full moons can be regarded as Harvest Moon co-stars. By that we mean that both have the characteristics of a Harvest Moon. The primary Harvest Moon characteristic has to do with the moonrise. On the average, the moon rises some 50 minutes later with each passing day. Around the time of the full Harvest Moon, the lag time between successive moonrises is reduced to a yearly low.

In 2017, there’s no appreciable difference between the lag in moonrise times associated with September and October full moons. In both of these months, the moon rises a shorter-than-usual time after sunset for several evenings in a row, following the date of full moon.

As the sun sets at and near the autumn equinox, the angle of the ecliptic – or sun and moon’s path – makes a narrow angle with the horizon. Image via classicalastronomy.com.

The narrow angle of the ecliptic means the moon rises noticeably farther north (left) on the horizon. For a few to several days after the full Harvest Moon, there is no long period of darkness between sunset and moonrise. Image via classicalastronomy.com.

For instance, at and near 40^o north latitude (the latitude of Denver, CO and Philadelphia, PA), the moon will rise about 35 (not 50) minutes later for the next several days after September 5. That’s virtually the same lag time that accompanies the October 2017 full Harvest Moon.

Take another example. Farther north, at Fairbanks, Alaska (65^o north latitude), the moon will rise about 10 (not 50) minutes later for the next several days after tonight (September 5). Again, that’s essentially equal to the lag time accompanying the October 2017 full Harvest Moon.

Click here to find out the moon’s rising time, remembering to check the moonrise and moonset box.

In any year when the October full moon is the Harvest Moon, the September full moon displays the characteristics of a Harvest Moon, too.

So this year we can enjoy the double feature, whereby two Harvest Moons extend the daylight hours in the season of diminishing daylight.

Bottom line: Tonight- on September 5, 2017 – watch for the full moon to light up the nighttime from dusk till dawn.

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

Bettina Berg in Las Vegas contributed the image above of 2016’s Harvest Moon.

Tonight – September 5, 2017 – look for the full-looking moon to beam in the east at dusk. It’ll climb highest up for the night around midnight and sit low in west at dawn September 6. For us in the Americas, the moon turns full on this night. In other time zones, full moon falls closer to the night of September 6. Either way, some will call this September 2017 full moon the Northern Hemisphere’s Harvest Moon. Others will say the 2017 Harvest Moon comes in October. More about this issue later on in this post.

First let’s talk about the date and time of full moon. The moon turns full on September 6, 2017, at 7:03 UTC. Although the full moon happens at the same instant worldwide, the clock reads differently by time zone. Here, in the contiguous United States, the moon turns precisely full on September 6, at 3:03 a.m. EDT, 2:03 a.m. CDT, 1:03 a.m. MDT and 12:03 PDT. That’s why we say the full moon falls on the night of September 5, for the Americas.

If we include the states Alaska and Hawaii, the full moon really does happen on September 5. The time is 11:03 p.m. on September 5 in Alaska and 9:03 p.m. on September 5 in Hawaii.

But we’re talking technicalities here. Technically speaking, the moon is full at the instant that it’s 180^o from the sun in ecliptic or celestial longitude. Realistically speaking, for a day or two around the exact time of full moon, the moon looks and acts full. That is, it stays more or less opposite the sun throughout the night – rising in the east at dusk, highest up around midnight and in the west at dawn – for all of us around the globe.

Worldwide map via the US Naval Observatory. Day and night sides of Earth at the instant of the full moon (2017 September 6 at 7:03 UTC). The shadow line passing to the left of Africa depicts sunrise and the shadow line to the right of Australia represents sunset.

Is the September 5-6 full moon the Harvest Moon? More often than not, the September full moon is the Northern Hemisphere’s Harvest Moon. The Harvest Moon is usually defined as the full moon closest to the autumn equinox, which – in the Northern Hemisphere – comes on or near September 22 each year.

Last year’s Harvest Moon fell in September. Next year’s Harvest Moon will, too.

But, in 2017, the September 6 full moon comes too early to be the Northern Hemisphere’s official Harvest Moon, according to the most widely accepted definition of the term. That’s because the full moon of October 5, 2017, will fall closer to this year’s September 22 equinox. The October 2017 full moon will be this year’s Harvest Moon, while the September 5-6 full moon will carry its ordinary monthly full moon name of Corn Moon or Fruit Moon in the Northern Hemisphere (and Worm Moon, Lenten Moon, Crow Moon, Sugar Moon, Chaste Moon or Sap Moon in the Southern Hemisphere). Read more about full moon names.

However, in most respects, the September 2017 and October 2017 full moons can be regarded as Harvest Moon co-stars. By that we mean that both have the characteristics of a Harvest Moon. The primary Harvest Moon characteristic has to do with the moonrise. On the average, the moon rises some 50 minutes later with each passing day. Around the time of the full Harvest Moon, the lag time between successive moonrises is reduced to a yearly low.

In 2017, there’s no appreciable difference between the lag in moonrise times associated with September and October full moons. In both of these months, the moon rises a shorter-than-usual time after sunset for several evenings in a row, following the date of full moon.

As the sun sets at and near the autumn equinox, the angle of the ecliptic – or sun and moon’s path – makes a narrow angle with the horizon. Image via classicalastronomy.com.

The narrow angle of the ecliptic means the moon rises noticeably farther north (left) on the horizon. For a few to several days after the full Harvest Moon, there is no long period of darkness between sunset and moonrise. Image via classicalastronomy.com.

For instance, at and near 40^o north latitude (the latitude of Denver, CO and Philadelphia, PA), the moon will rise about 35 (not 50) minutes later for the next several days after September 5. That’s virtually the same lag time that accompanies the October 2017 full Harvest Moon.

Take another example. Farther north, at Fairbanks, Alaska (65^o north latitude), the moon will rise about 10 (not 50) minutes later for the next several days after tonight (September 5). Again, that’s essentially equal to the lag time accompanying the October 2017 full Harvest Moon.

Click here to find out the moon’s rising time, remembering to check the moonrise and moonset box.

In any year when the October full moon is the Harvest Moon, the September full moon displays the characteristics of a Harvest Moon, too.

So this year we can enjoy the double feature, whereby two Harvest Moons extend the daylight hours in the season of diminishing daylight.

Bottom line: Tonight- on September 5, 2017 – watch for the full moon to light up the nighttime from dusk till dawn.

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