How to know your eclipse glasses are safe

It is safe to view an eclipse through eclipse glasses if the glasses come from a reputable vendor. EarthSky glasses comes from Rainbow Symphony, which is on the AAS-approved list of reputable venders.

The American Astronomical Society (AAS) issued the following statement on August 1, 2017, prior to the August 21 total solar eclipse.

How can you tell if your eclipse glasses or handheld solar viewers are safe? It is no longer sufficient to look for the logo of the International Organization for Standardization (ISO) and a label indicating that the product meets the ISO 12312-2 international safety standard for filters for direct viewing of the sun’s bright face. Why not? Because it now appears that some companies are printing the ISO logo and certification label on fake eclipse glasses and handheld solar viewers made with materials that do not block enough of the sun’s ultraviolet, visible, and infrared radiation to make them truly safe.

Some sellers are even displaying fake test results on their websites to support their bogus claim of compliance with the ISO safety standard.

Given this unfortunate situation, the only way you can be sure your solar viewer is safe is to verify that it comes from a reputable manufacturer or one of their authorized dealers. The AAS Solar Eclipse Task Force has been working diligently to compile a list of such vendors, now posted on its Reputable Vendors of Solar Filters & Viewers page.

Task-force members have checked manufacturers’ ISO paperwork to make sure it is complete and that it comes from an accredited testing facility, and they’ve asked manufacturers to identify their authorized resellers and dealers to identify the source of the products they’re selling. Only when everything checks out does the AAS add a vendor to its listing. AAS Press Officer and task-force representative Rick Fienberg said:

If we don’t list a supplier, that doesn’t mean their products are unsafe. It just means that we have no knowledge of them or that we haven’t convinced ourselves they’re safe.

Click here for the AAS list of reputable vendors of solar filters and viewers.

Read more from the AAS about purchasing safe solar filters.

Read more from the AAS on how to safely view a solar eclipse

Bottom line: Be sure your eclipse glasses come from a reputable supplier, such as a planetarium, science museum or other longstanding science organization. Did you purchase eclipse glasses from EarthSky? Our supplier – Rainbow Symphony – is on the AAS-approved list.

from EarthSky http://ift.tt/2uUOBs0

It is safe to view an eclipse through eclipse glasses if the glasses come from a reputable vendor. EarthSky glasses comes from Rainbow Symphony, which is on the AAS-approved list of reputable venders.

The American Astronomical Society (AAS) issued the following statement on August 1, 2017, prior to the August 21 total solar eclipse.

How can you tell if your eclipse glasses or handheld solar viewers are safe? It is no longer sufficient to look for the logo of the International Organization for Standardization (ISO) and a label indicating that the product meets the ISO 12312-2 international safety standard for filters for direct viewing of the sun’s bright face. Why not? Because it now appears that some companies are printing the ISO logo and certification label on fake eclipse glasses and handheld solar viewers made with materials that do not block enough of the sun’s ultraviolet, visible, and infrared radiation to make them truly safe.

Some sellers are even displaying fake test results on their websites to support their bogus claim of compliance with the ISO safety standard.

Given this unfortunate situation, the only way you can be sure your solar viewer is safe is to verify that it comes from a reputable manufacturer or one of their authorized dealers. The AAS Solar Eclipse Task Force has been working diligently to compile a list of such vendors, now posted on its Reputable Vendors of Solar Filters & Viewers page.

Task-force members have checked manufacturers’ ISO paperwork to make sure it is complete and that it comes from an accredited testing facility, and they’ve asked manufacturers to identify their authorized resellers and dealers to identify the source of the products they’re selling. Only when everything checks out does the AAS add a vendor to its listing. AAS Press Officer and task-force representative Rick Fienberg said:

If we don’t list a supplier, that doesn’t mean their products are unsafe. It just means that we have no knowledge of them or that we haven’t convinced ourselves they’re safe.

Click here for the AAS list of reputable vendors of solar filters and viewers.

Read more from the AAS about purchasing safe solar filters.

Read more from the AAS on how to safely view a solar eclipse

Bottom line: Be sure your eclipse glasses come from a reputable supplier, such as a planetarium, science museum or other longstanding science organization. Did you purchase eclipse glasses from EarthSky? Our supplier – Rainbow Symphony – is on the AAS-approved list.

from EarthSky http://ift.tt/2uUOBs0

Sun’s core rotates 4x faster than surface

Our local star, the sun. Image via UCLA.

Our star, the sun, isn’t a solid body but instead a huge, shining ball of gas. Astronomers have long known it doesn’t rotate, or spin, as a single rigid mass. They’ve known, for example, that gases in the sun’s outer layers move around at different speeds depending on their latitude, with the equator spinning faster than the higher latitudes. The rotation of the sun’s outer layers varies from 25 days at the equator to 35 days at the poles. But what of the sun’s core? For decades, scientists have suspected the core moves faster than the surface, but, until now, no measurement was possible. Now an international team of astronomers, using data from a long-lived spacecraft called the Solar and Heliospheric Observatory (SoHO), has measured the rotation of the sun’s core and found it rotates nearly four times faster than the surface. The sun’s core spins once in about an earthly week, these researchers said. The study is published August 1, 2017 in the peer-reviewed journal Astronomy and Astrophysics.

Scientists knew the outer part of the sun rotates at varying speeds, with gases nearer the equator moving around faster. But the sun’s core rotation had remained elusive for decades. Image via NASA.

These researchers – led by astronomer Eric Fossat of the Observatoire de la Côte d’Azur in Nice, France – studied acoustic waves, essentially sound waves, in the sun’s atmosphere. These are longitudinal waves; that is, the waves have the same direction of vibration as their direction of travel, and they move at the speed of sound. A statement from the European Space Agency explained more:

Just as seismology reveals Earth’s interior structure by the way in which waves generated by earthquakes travel through it, solar physicists use ‘helioseismology’ to probe the solar interior by studying sound waves reverberating through it. On Earth, it is usually one event that is responsible for generating the seismic waves at a given time, but the sun is continuously ‘ringing’ owing to the convective motions inside the giant gaseous body.

Higher frequency waves, known as pressure waves (or p-waves), are easily detected as surface oscillations owing to sound waves rumbling through the upper layers of the sun. They pass very quickly through deeper layers and are therefore not sensitive to the sun’s core rotation.

Conversely, lower frequency gravity waves (g-waves) that represent oscillations of the deep solar interior have no clear signature at the surface, and thus present a challenge to detect directly.

Scientists had been searching for these elusive gravity waves in the sun for over 40 years, the ESA statement said, and although earlier attempts have hinted at detections, none were definitive.

This new study represents scientists’ success at unambiguously extracting the signature of the gravity waves, and thus being able to measure how fast the sun’s core rotates.

How do we know what’s going on inside the sun? Luckily, the sun is continuously ‘ringing’ like a bell, owing to its internal convective motions. Scientist able to study various forms of sound waves generated within the sun’s interior, to learn what’s there. Image via UCLA.

Eric Fossat said:

G-modes have been detected in other stars, and now thanks to SOHO we have finally found convincing proof of them in our own star. It is really special to see into the core of our own sun to get a first indirect measurement of its rotation speed. But, even though this decades-long search is over, a new window of solar physics now begins.

The researchers used 16 years of observations from an instrument called GOLF (Global Oscillations at Low Frequency) on the SoHO spacecraft. The method was developed by the researchers. SoHO – a joint project of ESA and NASA – was launched on December 2, 1995 to study the sun from its core to the outer corona and the solar wind; the spacecraft continues to operate.

Roger Ulrich is a UCLA professor emeritus of astronomy, who has studied the sun’s interior for more than 40 years and is a study co-author. He pointed out in a statement from UCLA that it’s likely the sun’s core rotation is:

… left over from the period when the sun formed, some 4.6 billion years ago. It’s a surprise, and exciting to think we might have uncovered a relic of what the sun was like when it first formed.

Ulrich said the new measurement of the rotation of the sun’s core might provides clues to how the sun formed. After the sun formed, the solar wind likely slowed the rotation of the outer part of the sun, he said. The rotation might also affect sunspots, which move on the sun’s surface along with the rotation of its outer gases.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Artist’s concept of SoHO spacecraft.

Bottom line: An international team of astronomers using data from SoHO has found that the sun’s core rotates or spins four times faster than its surface layers.

Via ESA and UCLA.

from EarthSky http://ift.tt/2vsSCW1

Our local star, the sun. Image via UCLA.

Our star, the sun, isn’t a solid body but instead a huge, shining ball of gas. Astronomers have long known it doesn’t rotate, or spin, as a single rigid mass. They’ve known, for example, that gases in the sun’s outer layers move around at different speeds depending on their latitude, with the equator spinning faster than the higher latitudes. The rotation of the sun’s outer layers varies from 25 days at the equator to 35 days at the poles. But what of the sun’s core? For decades, scientists have suspected the core moves faster than the surface, but, until now, no measurement was possible. Now an international team of astronomers, using data from a long-lived spacecraft called the Solar and Heliospheric Observatory (SoHO), has measured the rotation of the sun’s core and found it rotates nearly four times faster than the surface. The sun’s core spins once in about an earthly week, these researchers said. The study is published August 1, 2017 in the peer-reviewed journal Astronomy and Astrophysics.

Scientists knew the outer part of the sun rotates at varying speeds, with gases nearer the equator moving around faster. But the sun’s core rotation had remained elusive for decades. Image via NASA.

These researchers – led by astronomer Eric Fossat of the Observatoire de la Côte d’Azur in Nice, France – studied acoustic waves, essentially sound waves, in the sun’s atmosphere. These are longitudinal waves; that is, the waves have the same direction of vibration as their direction of travel, and they move at the speed of sound. A statement from the European Space Agency explained more:

Just as seismology reveals Earth’s interior structure by the way in which waves generated by earthquakes travel through it, solar physicists use ‘helioseismology’ to probe the solar interior by studying sound waves reverberating through it. On Earth, it is usually one event that is responsible for generating the seismic waves at a given time, but the sun is continuously ‘ringing’ owing to the convective motions inside the giant gaseous body.

Higher frequency waves, known as pressure waves (or p-waves), are easily detected as surface oscillations owing to sound waves rumbling through the upper layers of the sun. They pass very quickly through deeper layers and are therefore not sensitive to the sun’s core rotation.

Conversely, lower frequency gravity waves (g-waves) that represent oscillations of the deep solar interior have no clear signature at the surface, and thus present a challenge to detect directly.

Scientists had been searching for these elusive gravity waves in the sun for over 40 years, the ESA statement said, and although earlier attempts have hinted at detections, none were definitive.

This new study represents scientists’ success at unambiguously extracting the signature of the gravity waves, and thus being able to measure how fast the sun’s core rotates.

How do we know what’s going on inside the sun? Luckily, the sun is continuously ‘ringing’ like a bell, owing to its internal convective motions. Scientist able to study various forms of sound waves generated within the sun’s interior, to learn what’s there. Image via UCLA.

Eric Fossat said:

G-modes have been detected in other stars, and now thanks to SOHO we have finally found convincing proof of them in our own star. It is really special to see into the core of our own sun to get a first indirect measurement of its rotation speed. But, even though this decades-long search is over, a new window of solar physics now begins.

The researchers used 16 years of observations from an instrument called GOLF (Global Oscillations at Low Frequency) on the SoHO spacecraft. The method was developed by the researchers. SoHO – a joint project of ESA and NASA – was launched on December 2, 1995 to study the sun from its core to the outer corona and the solar wind; the spacecraft continues to operate.

Roger Ulrich is a UCLA professor emeritus of astronomy, who has studied the sun’s interior for more than 40 years and is a study co-author. He pointed out in a statement from UCLA that it’s likely the sun’s core rotation is:

… left over from the period when the sun formed, some 4.6 billion years ago. It’s a surprise, and exciting to think we might have uncovered a relic of what the sun was like when it first formed.

Ulrich said the new measurement of the rotation of the sun’s core might provides clues to how the sun formed. After the sun formed, the solar wind likely slowed the rotation of the outer part of the sun, he said. The rotation might also affect sunspots, which move on the sun’s surface along with the rotation of its outer gases.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Artist’s concept of SoHO spacecraft.

Bottom line: An international team of astronomers using data from SoHO has found that the sun’s core rotates or spins four times faster than its surface layers.

Via ESA and UCLA.

from EarthSky http://ift.tt/2vsSCW1

Lots of water inside the moon?

Image via Brown University.

A new study of satellite data suggests that the moon’s interior is surprisingly water-rich.

The research, published July 24, 2017 in Nature Geoscience, finds that numerous volcanic deposits across the surface of the moon contain unusually high amounts of trapped water.

Scientists believe the ancient deposits consist of glass beads that were formed by the eruption of magma exploding from the deep lunar interior.

Scientists had assumed for years that the interior of the moon had been largely depleted of water and other volatile compounds. That idea began to change in 2008, when a research team detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 moon missions. In 2011, further study of tiny crystalline formations within those beads revealed that they actually contain similar amounts of water as some basalts on Earth. That suggests that at least parts of the moon’s mantle — the interior between its crust and the core – contain as much water as Earth’s.

Lunar volcanic glasses gathered by the Apollo 15 mission. Image via Brown University.

Ralph Milliken is lead author of the new research and an associate professor in Brown University’s Department of Earth, Environmental and Planetary Sciences. Milliken said in a statement:

The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle. By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions. The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the moon is wet.

Colored areas indicate elevated water content compared with surrounding terrains. Yellows and reds indicate the richest water content. Image via Milliken lab / Brown University.

Detecting the water content of lunar volcanic deposits using orbital instruments is no easy task. Read more about how the researchers did their study.

The researchers found evidence of water in nearly all of the large pyroclastic deposits – that is, deposits of rock fragments erupted by a volcano – that had been previously mapped across the moon’s surface, including deposits near the Apollo 15 and 17 landing sites where the water-bearing glass bead samples were collected.

Milliken said:

The distribution of these water-rich deposits is the key thing. They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off.

The idea that the interior of the moon is water-rich raises interesting questions about the moon’s formation, say the researchers. For example, scientists think the moon formed from debris left behind after an object about the size of Mars slammed into the Earth very early in solar system history. One of the reasons scientists had assumed the moon’s interior should be dry is that it seems unlikely that any of the hydrogen needed to form water could have survived the heat of that impact.

Shuai Li is a postdoctoral researcher at the University of Hawaii and co-author of the study. Li said:

The growing evidence for water inside the moon suggest that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the moon had completely solidified. The exact origin of water in the lunar interior is still a big question.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Bottom line: New research The research, published in Nature Geoscience, finds that numerous volcanic deposits across the surface of the moon contain unusually high amounts of trapped water.

Read more from Brown University

from EarthSky http://ift.tt/2uYbR6G

Image via Brown University.

A new study of satellite data suggests that the moon’s interior is surprisingly water-rich.

The research, published July 24, 2017 in Nature Geoscience, finds that numerous volcanic deposits across the surface of the moon contain unusually high amounts of trapped water.

Scientists believe the ancient deposits consist of glass beads that were formed by the eruption of magma exploding from the deep lunar interior.

Scientists had assumed for years that the interior of the moon had been largely depleted of water and other volatile compounds. That idea began to change in 2008, when a research team detected trace amounts of water in some of the volcanic glass beads brought back to Earth from the Apollo 15 and 17 moon missions. In 2011, further study of tiny crystalline formations within those beads revealed that they actually contain similar amounts of water as some basalts on Earth. That suggests that at least parts of the moon’s mantle — the interior between its crust and the core – contain as much water as Earth’s.

Lunar volcanic glasses gathered by the Apollo 15 mission. Image via Brown University.

Ralph Milliken is lead author of the new research and an associate professor in Brown University’s Department of Earth, Environmental and Planetary Sciences. Milliken said in a statement:

The key question is whether those Apollo samples represent the bulk conditions of the lunar interior or instead represent unusual or perhaps anomalous water-rich regions within an otherwise ‘dry’ mantle. By looking at the orbital data, we can examine the large pyroclastic deposits on the Moon that were never sampled by the Apollo or Luna missions. The fact that nearly all of them exhibit signatures of water suggests that the Apollo samples are not anomalous, so it may be that the bulk interior of the moon is wet.

Colored areas indicate elevated water content compared with surrounding terrains. Yellows and reds indicate the richest water content. Image via Milliken lab / Brown University.

Detecting the water content of lunar volcanic deposits using orbital instruments is no easy task. Read more about how the researchers did their study.

The researchers found evidence of water in nearly all of the large pyroclastic deposits – that is, deposits of rock fragments erupted by a volcano – that had been previously mapped across the moon’s surface, including deposits near the Apollo 15 and 17 landing sites where the water-bearing glass bead samples were collected.

Milliken said:

The distribution of these water-rich deposits is the key thing. They’re spread across the surface, which tells us that the water found in the Apollo samples isn’t a one-off.

The idea that the interior of the moon is water-rich raises interesting questions about the moon’s formation, say the researchers. For example, scientists think the moon formed from debris left behind after an object about the size of Mars slammed into the Earth very early in solar system history. One of the reasons scientists had assumed the moon’s interior should be dry is that it seems unlikely that any of the hydrogen needed to form water could have survived the heat of that impact.

Shuai Li is a postdoctoral researcher at the University of Hawaii and co-author of the study. Li said:

The growing evidence for water inside the moon suggest that water did somehow survive, or that it was brought in shortly after the impact by asteroids or comets before the moon had completely solidified. The exact origin of water in the lunar interior is still a big question.

Enjoying EarthSky so far? Sign up for our free daily newsletter today!

Bottom line: New research The research, published in Nature Geoscience, finds that numerous volcanic deposits across the surface of the moon contain unusually high amounts of trapped water.

Read more from Brown University

from EarthSky http://ift.tt/2uYbR6G

Anticrepuscular rays with rainbow

There are actually 2 rainbows here. See the faint one above the primary bow? Photo by Janice Reynolds

Janice Reynolds in Nokomis, Saskatchewan, Canada caught two different sky phenomena in this photo from July 30, 2017. Her photo is looking east in late day, when the sun is setting – or soon to set – the west. The photo shows both a double rainbow and anticrepuscular rays, both always seen in a direction opposite the sun. Janice wrote:

I saw this looking to the east. We had just had a very bad storm with very high sudden winds, thunder, lightening and some rain. I had rushed to the barnyard to lock up my animals and got stuck in it and took shelter in the barn with the animals. After the storm cleared, I fed and locked them up and the sky was clearing as quickly as it had blown in. The sun was starting to poke through the clouds. As I was heading back to the house, I saw this image and took the photo. So strange.

Yes, strange and beautiful! Thank you, Janice!

Read more about how rainbows form.

Read more about what makes anticrepuscular rays.

from EarthSky http://ift.tt/2tYu4jq

There are actually 2 rainbows here. See the faint one above the primary bow? Photo by Janice Reynolds

Janice Reynolds in Nokomis, Saskatchewan, Canada caught two different sky phenomena in this photo from July 30, 2017. Her photo is looking east in late day, when the sun is setting – or soon to set – the west. The photo shows both a double rainbow and anticrepuscular rays, both always seen in a direction opposite the sun. Janice wrote:

I saw this looking to the east. We had just had a very bad storm with very high sudden winds, thunder, lightening and some rain. I had rushed to the barnyard to lock up my animals and got stuck in it and took shelter in the barn with the animals. After the storm cleared, I fed and locked them up and the sky was clearing as quickly as it had blown in. The sun was starting to poke through the clouds. As I was heading back to the house, I saw this image and took the photo. So strange.

Yes, strange and beautiful! Thank you, Janice!

Read more about how rainbows form.

Read more about what makes anticrepuscular rays.

from EarthSky http://ift.tt/2tYu4jq

Identify Saturn near moon on August 2

Tonight – August 2, 2017 – the moon and the ringed planet Saturn pair up together at nightfall. In the same vicinity of sky, note another bright celestial beauty: the ruddy star Antares, the brightest star in the constellation Scorpius.

Clouded out tonight? Watch for them tomorrow night, too …

Saturn and Antares are bright, both exhibiting 1st-magnitude brightness. However, you can distinguish these two celestial luminaries by color. Saturn displays a golden hue while Antares has a ruddy complexion. If it’s hard for you to discern color, try observing Saturn and Antares with binoculars.

Better yet, try observing Saturn with a telescope. You can view Saturn’s glorious rings even with a modest backyard variety.

Patrick Prokop of Savannah, Georgia caught this shot of Saturn on July 31, 2017, using a 6-inch Celestron telescope at f10 focal length and magnified about 200X (“… about the limit for this size scope,” he said). Thanks for sharing, Patrick!

Did you know that, as seen from Earth, the orientation of Saturn’s rings appears to shift regularly, over time? This happens as we orbit the sun yearly, while Saturn orbits once every 29.5 years. In 2017 – as we gaze across space to Saturn – we are seeing the north face of Saturn’s rings. Saturn’s rings are inclined at 27^o toward Earth in 2017, which is about as wide open as they ever appear to us from our world.

We see the north face of the rings for about 15 years and 9 months, then the south face for about 13 years and 9 months. The difference is due to Saturn’s eccentric orbit, with the planet traveling most swiftly at perihelion and most slowly at aphelion.

The north side of Saturn’s rings will open up most fully on October 26, 2017, to exhibit a maximum inclination of 27^o.

Thereafter, the inclination of Saturn’s rings will slowly but surely diminish until the rings appear edge-on in the year 2025. At this juncture, Saturn’s rings will appear invisible to earthly observers for about one and one-half months. That’s because the rings are so thin, in contrast to their width.

View larger. .Saturn oppositions from 2001 to 2019 simulated by a computer program written by Tom Ruen.

This animation demonstrates the 29 year period for oppositions of Saturn from 2001 to 2029, taken from the 28 images of Saturn above.

After the year 2025, the south side of Saturn’s rings will start to show. Then some seven years later – on May 12, 2032 – the south side of Saturn’s rings will become maximally inclined (27^o) toward Earth.

Some seven years after the south side of Saturn’s rings opens up most fully, the rings will appear edge-on and return to invisibility in 2039. Some seven years after that, the north side of Saturn’s rings will become maximally inclined (27^o) toward Earth on November 15, 2046.

Contrasting the size of Saturn and its rings with our planet Earth via Hubble Heritage Team.

Saturn’s rotational axis is inclined at 27^o to its orbital plane, and – as we said above – this planet takes nearly 29.5 Earth-years to orbit the sun. Therefore, the maximum inclination of Saturn’s rings recurs in a cycle of about 29.5 years, as is shown in the table and diagram below:

Maximum inclination of Saturn’s rings in the 21st century (2001 to 2100)

2003 Apr. 7: South face inclined 27^o 01’
2017 Oct. 16: North face inclined 26^o 59’
2032 May 12: South face inclined 26^o 58’
2046 Nov. 15: North face inclined 26^o 56’
2062 Mar. 31: South face inclined 27^o 01’
2076 Oct. 9: North face inclined 27^o 00’
2091 May 4: South face inclined 26^o 59’

Source: page 295 of More Mathematical Astronomy Morsels by Jean Meeus

View larger. The astronomer Christian Huygens (1629 to 1695) explanation for the periodic disappearance of Saturn’s rings in Systemma Saturnium 1659

Bottom line: On August 2, 2017, use the moon to locate the ringed planet Saturn as darkness falls. Miss ’em tonight? Try again tomorrow night.

from EarthSky http://ift.tt/2vh0PMk

Tonight – August 2, 2017 – the moon and the ringed planet Saturn pair up together at nightfall. In the same vicinity of sky, note another bright celestial beauty: the ruddy star Antares, the brightest star in the constellation Scorpius.

Clouded out tonight? Watch for them tomorrow night, too …

Saturn and Antares are bright, both exhibiting 1st-magnitude brightness. However, you can distinguish these two celestial luminaries by color. Saturn displays a golden hue while Antares has a ruddy complexion. If it’s hard for you to discern color, try observing Saturn and Antares with binoculars.

Better yet, try observing Saturn with a telescope. You can view Saturn’s glorious rings even with a modest backyard variety.

Patrick Prokop of Savannah, Georgia caught this shot of Saturn on July 31, 2017, using a 6-inch Celestron telescope at f10 focal length and magnified about 200X (“… about the limit for this size scope,” he said). Thanks for sharing, Patrick!

Did you know that, as seen from Earth, the orientation of Saturn’s rings appears to shift regularly, over time? This happens as we orbit the sun yearly, while Saturn orbits once every 29.5 years. In 2017 – as we gaze across space to Saturn – we are seeing the north face of Saturn’s rings. Saturn’s rings are inclined at 27^o toward Earth in 2017, which is about as wide open as they ever appear to us from our world.

We see the north face of the rings for about 15 years and 9 months, then the south face for about 13 years and 9 months. The difference is due to Saturn’s eccentric orbit, with the planet traveling most swiftly at perihelion and most slowly at aphelion.

The north side of Saturn’s rings will open up most fully on October 26, 2017, to exhibit a maximum inclination of 27^o.

Thereafter, the inclination of Saturn’s rings will slowly but surely diminish until the rings appear edge-on in the year 2025. At this juncture, Saturn’s rings will appear invisible to earthly observers for about one and one-half months. That’s because the rings are so thin, in contrast to their width.

View larger. .Saturn oppositions from 2001 to 2019 simulated by a computer program written by Tom Ruen.

This animation demonstrates the 29 year period for oppositions of Saturn from 2001 to 2029, taken from the 28 images of Saturn above.

After the year 2025, the south side of Saturn’s rings will start to show. Then some seven years later – on May 12, 2032 – the south side of Saturn’s rings will become maximally inclined (27^o) toward Earth.

Some seven years after the south side of Saturn’s rings opens up most fully, the rings will appear edge-on and return to invisibility in 2039. Some seven years after that, the north side of Saturn’s rings will become maximally inclined (27^o) toward Earth on November 15, 2046.

Contrasting the size of Saturn and its rings with our planet Earth via Hubble Heritage Team.

Saturn’s rotational axis is inclined at 27^o to its orbital plane, and – as we said above – this planet takes nearly 29.5 Earth-years to orbit the sun. Therefore, the maximum inclination of Saturn’s rings recurs in a cycle of about 29.5 years, as is shown in the table and diagram below:

Maximum inclination of Saturn’s rings in the 21st century (2001 to 2100)

2003 Apr. 7: South face inclined 27^o 01’
2017 Oct. 16: North face inclined 26^o 59’
2032 May 12: South face inclined 26^o 58’
2046 Nov. 15: North face inclined 26^o 56’
2062 Mar. 31: South face inclined 27^o 01’
2076 Oct. 9: North face inclined 27^o 00’
2091 May 4: South face inclined 26^o 59’

Source: page 295 of More Mathematical Astronomy Morsels by Jean Meeus

View larger. The astronomer Christian Huygens (1629 to 1695) explanation for the periodic disappearance of Saturn’s rings in Systemma Saturnium 1659

Bottom line: On August 2, 2017, use the moon to locate the ringed planet Saturn as darkness falls. Miss ’em tonight? Try again tomorrow night.

from EarthSky http://ift.tt/2vh0PMk

An Earth-like atmosphere for Proxima b?

Artist’s concept of the surface of the Proxima b, nearest known exoplanet. It orbits the red dwarf star Proxima Centauri, closest star to our solar system. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Image via NASA’s Goddard Space Flight Center.

In August 2016, when scientists announced the discovery of a planet orbiting the nearest known star, Proxima Centauri, people got excited. That’s largely because it’s not just any planet: it’s a planet similar in size to Earth, orbiting in its star’s habitable zone. At 4.2 light-years or 25 trillion miles from Earth, Proxima b is vastly too far away to be explored in our lifetimes (although that hasn’t stopped dreamers and visionaries like those at Breakthough Initiatives from devising plans to explore it). Still, theoretical studies are the order of the day for Proxima b. A recent one suggests that Proxima b:

…may not be able to keep a grip on its atmosphere, leaving the surface exposed to harmful stellar radiation and reducing its potential for habitability.

Habitable zone, to astronomers, means the potential for liquid water to exist on a planet’s surface. Life, as we know it, needs water. But an atmosphere is another essential ingredient for life. The team’s statement said:

Having the right atmosphere allows for climate regulation, the maintenance of a water-friendly surface pressure, shielding from hazardous space weather, and the housing of life’s chemical building blocks.

This new computer model – which was part of a NASA study, published on July 24, 2017, in the peer-reviewed Astrophysical Journal Letters – considered what would happen if Earth orbited Proxima Centauri. The study suggests Earth’s atmosphere wouldn’t survive in such close proximity to Proxima, which is an active red dwarf star that emits high-energy extreme ultraviolet radiation. This radiation has the potential to ionize gases in a planet’s atmosphere; that is, it knocks electrons off atoms and produces a swath of electrically charged particles. In this process, the newly formed electrons gain enough energy that they can readily escape a planet’s gravity and race out of the atmosphere.

On Earth, this clearly isn’t happening, but our sun is a more sedate star than Proxima. Katherine Garcia-Sage, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is lead author of the new study. She and her colleagues’ computer model used Earth’s atmosphere, magnetic field and gravity as proxies for Proxima b’s.

They also calculated how much radiation Proxima Centauri produces on average, based on observations from NASA’s Chandra X-ray Observatory.

Click to view larger. This illustration shows stars within 12 light-years of our sun, including Proxima Centauri. The lines on the grid are 4 light-years apart. Diagram via Guy Ottewell’s Astronomical Companion. Used with permission. Read more from Guy Ottewell: Where is Proxima Centauri?

In Proxima Centauri’s habitable zone, Proxima b encounters bouts of extreme ultraviolet radiation hundreds of times greater than Earth does from the sun. That radiation generates enough energy to strip away not just the lightest molecules — hydrogen — but also, over time, heavier elements such as oxygen and nitrogen. Ofer Cohen, a space scientist at the University of Massachusetts, Lowell and co-author of the study, said:

The question is, how much of the atmosphere is lost, and how quickly does that process occur?

If we estimate that time, we can calculate how long it takes the atmosphere to completely escape — and compare that to the planet’s lifetime.

The model shows Proxima Centauri’s powerful radiation drains the Earth-like atmosphere as much as 10,000 times faster than what happens at Earth. Garcia-Sage said:

This was a simple calculation based on average activity from the host star. It doesn’t consider variations like extreme heating in the star’s atmosphere or violent stellar disturbances to the exoplanet’s magnetic field — things we’d expect provide even more ionizing radiation and atmospheric escape.

At its orbital distance from its star Proxima Centauri, the exoplanet Proxima b – nearest known exoplanet to Earth – likely couldn’t sustain an Earth-like atmosphere, according to a new theoretical study. Image via NASA’s Goddard Space Flight Center/ Mary Pat Hrybyk-Keith.

Shawn Domagal-Goldman, a Goddard space scientist not involved in the study, said:

This study looks at an under-appreciated aspect of habitability, which is atmospheric loss in the context of stellar physics. Planets have lots of different interacting systems, and it’s important to make sure we include these interactions in our models.

The scientists show that with the highest thermosphere temperatures and a completely open magnetic field, Proxima b could lose an amount equal to the entirety of Earth’s atmosphere in 100 million years — that’s just a fraction of Proxima b’s 4 billion years thus far. When the scientists assumed the lowest temperatures and a closed magnetic field, that much mass escapes over 2 billion years. Jeremy Drake, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and co-author of the study, said:

Things can get interesting if an exoplanet holds on to its atmosphere, but Proxima b’s atmospheric loss rates here are so high that habitability is implausible. This questions the habitability of planets around such red dwarfs in general.

Another red dwarf star recently in the news is the star TRAPPIST-1. Such stars are often the target of exoplanet hunts, because they are the coolest, smallest and most common stars in the galaxy. Because they are cooler and dimmer, planets have to maintain tight orbits for liquid water to be present.

But unless the atmospheric loss is counteracted by some other process — such as a massive amount of volcanic activity or comet bombardment — this close proximity, scientists are finding more often, is not promising for an atmosphere’s survival or sustainability, these scientists say.

Bottom line: Proxima b is the nearest known exoplanet and orbits in its star’s habitable zone. But a new study suggests it might not be able to hold onto its atmosphere long enough for life to develop.

Via NASA

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

Artist’s concept of the surface of the Proxima b, nearest known exoplanet. It orbits the red dwarf star Proxima Centauri, closest star to our solar system. The double star Alpha Centauri AB also appears in the image to the upper-right of Proxima itself. Image via NASA’s Goddard Space Flight Center.

In August 2016, when scientists announced the discovery of a planet orbiting the nearest known star, Proxima Centauri, people got excited. That’s largely because it’s not just any planet: it’s a planet similar in size to Earth, orbiting in its star’s habitable zone. At 4.2 light-years or 25 trillion miles from Earth, Proxima b is vastly too far away to be explored in our lifetimes (although that hasn’t stopped dreamers and visionaries like those at Breakthough Initiatives from devising plans to explore it). Still, theoretical studies are the order of the day for Proxima b. A recent one suggests that Proxima b:

…may not be able to keep a grip on its atmosphere, leaving the surface exposed to harmful stellar radiation and reducing its potential for habitability.

Habitable zone, to astronomers, means the potential for liquid water to exist on a planet’s surface. Life, as we know it, needs water. But an atmosphere is another essential ingredient for life. The team’s statement said:

Having the right atmosphere allows for climate regulation, the maintenance of a water-friendly surface pressure, shielding from hazardous space weather, and the housing of life’s chemical building blocks.

This new computer model – which was part of a NASA study, published on July 24, 2017, in the peer-reviewed Astrophysical Journal Letters – considered what would happen if Earth orbited Proxima Centauri. The study suggests Earth’s atmosphere wouldn’t survive in such close proximity to Proxima, which is an active red dwarf star that emits high-energy extreme ultraviolet radiation. This radiation has the potential to ionize gases in a planet’s atmosphere; that is, it knocks electrons off atoms and produces a swath of electrically charged particles. In this process, the newly formed electrons gain enough energy that they can readily escape a planet’s gravity and race out of the atmosphere.

On Earth, this clearly isn’t happening, but our sun is a more sedate star than Proxima. Katherine Garcia-Sage, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is lead author of the new study. She and her colleagues’ computer model used Earth’s atmosphere, magnetic field and gravity as proxies for Proxima b’s.

They also calculated how much radiation Proxima Centauri produces on average, based on observations from NASA’s Chandra X-ray Observatory.

Click to view larger. This illustration shows stars within 12 light-years of our sun, including Proxima Centauri. The lines on the grid are 4 light-years apart. Diagram via Guy Ottewell’s Astronomical Companion. Used with permission. Read more from Guy Ottewell: Where is Proxima Centauri?

In Proxima Centauri’s habitable zone, Proxima b encounters bouts of extreme ultraviolet radiation hundreds of times greater than Earth does from the sun. That radiation generates enough energy to strip away not just the lightest molecules — hydrogen — but also, over time, heavier elements such as oxygen and nitrogen. Ofer Cohen, a space scientist at the University of Massachusetts, Lowell and co-author of the study, said:

The question is, how much of the atmosphere is lost, and how quickly does that process occur?

If we estimate that time, we can calculate how long it takes the atmosphere to completely escape — and compare that to the planet’s lifetime.

The model shows Proxima Centauri’s powerful radiation drains the Earth-like atmosphere as much as 10,000 times faster than what happens at Earth. Garcia-Sage said:

This was a simple calculation based on average activity from the host star. It doesn’t consider variations like extreme heating in the star’s atmosphere or violent stellar disturbances to the exoplanet’s magnetic field — things we’d expect provide even more ionizing radiation and atmospheric escape.

At its orbital distance from its star Proxima Centauri, the exoplanet Proxima b – nearest known exoplanet to Earth – likely couldn’t sustain an Earth-like atmosphere, according to a new theoretical study. Image via NASA’s Goddard Space Flight Center/ Mary Pat Hrybyk-Keith.

Shawn Domagal-Goldman, a Goddard space scientist not involved in the study, said:

This study looks at an under-appreciated aspect of habitability, which is atmospheric loss in the context of stellar physics. Planets have lots of different interacting systems, and it’s important to make sure we include these interactions in our models.

The scientists show that with the highest thermosphere temperatures and a completely open magnetic field, Proxima b could lose an amount equal to the entirety of Earth’s atmosphere in 100 million years — that’s just a fraction of Proxima b’s 4 billion years thus far. When the scientists assumed the lowest temperatures and a closed magnetic field, that much mass escapes over 2 billion years. Jeremy Drake, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics and co-author of the study, said:

Things can get interesting if an exoplanet holds on to its atmosphere, but Proxima b’s atmospheric loss rates here are so high that habitability is implausible. This questions the habitability of planets around such red dwarfs in general.

Another red dwarf star recently in the news is the star TRAPPIST-1. Such stars are often the target of exoplanet hunts, because they are the coolest, smallest and most common stars in the galaxy. Because they are cooler and dimmer, planets have to maintain tight orbits for liquid water to be present.

But unless the atmospheric loss is counteracted by some other process — such as a massive amount of volcanic activity or comet bombardment — this close proximity, scientists are finding more often, is not promising for an atmosphere’s survival or sustainability, these scientists say.

Bottom line: Proxima b is the nearest known exoplanet and orbits in its star’s habitable zone. But a new study suggests it might not be able to hold onto its atmosphere long enough for life to develop.

Via NASA

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

Maryam Mirzakhani, A Candle Illuminating The Dark (Synopsis) [Starts With A Bang]

“I think it’s rarely about what you actually learn in class. It’s mostly about things that you stay motivated to go and continue to do on your own.” -Maryam Mirzakhani, on success in mathematics

Only a few weeks ago, pioneering mathematician and the first (and only) woman to win the Fields Medal, Maryam Mirzakhani, tragically died of cancer at the young age of 40. Her brilliant work had applications to a huge variety of problems, from the periodic and/or chaotic motions of billiard balls to the question of designing a room that, even if completely covered by mirrors, could never be illuminated by a single candle.

A room where the walls, even if completely covered with mirrors, would never have every location illuminated, was a mathematically interesting conjecture that was only solved recently. Image credit: Mathematical Sciences Research Institute (MSRI) / Numberphile / Brady Haran / Howard Masur.

Her life and her work were cut short by disease, but the story of both is truly an inspiration, as well as a testament to the power of creative thinking and the capabilities of the human mind. The pursuit of knowledge knows no national, racial, or gendered borders, and Maryam Mirzakhani’s life was a testament to that.

As a young girl, Maryam Mirzakhani was more interested in reading and literature than she was in mathematics. Once she discovered her true love for mathematics, however, she couldn’t be kept from it. Image credit: Family photo from Maryam Mirzakhani’s childhood.

Paul Halpern, in his own unique style, has written a beautiful testament to the late Maryam Mirzakhani. Get to know her, and her groundbreaking work, today!

from ScienceBlogs http://ift.tt/2hk5ckg

“I think it’s rarely about what you actually learn in class. It’s mostly about things that you stay motivated to go and continue to do on your own.” -Maryam Mirzakhani, on success in mathematics

Only a few weeks ago, pioneering mathematician and the first (and only) woman to win the Fields Medal, Maryam Mirzakhani, tragically died of cancer at the young age of 40. Her brilliant work had applications to a huge variety of problems, from the periodic and/or chaotic motions of billiard balls to the question of designing a room that, even if completely covered by mirrors, could never be illuminated by a single candle.

A room where the walls, even if completely covered with mirrors, would never have every location illuminated, was a mathematically interesting conjecture that was only solved recently. Image credit: Mathematical Sciences Research Institute (MSRI) / Numberphile / Brady Haran / Howard Masur.

Her life and her work were cut short by disease, but the story of both is truly an inspiration, as well as a testament to the power of creative thinking and the capabilities of the human mind. The pursuit of knowledge knows no national, racial, or gendered borders, and Maryam Mirzakhani’s life was a testament to that.

As a young girl, Maryam Mirzakhani was more interested in reading and literature than she was in mathematics. Once she discovered her true love for mathematics, however, she couldn’t be kept from it. Image credit: Family photo from Maryam Mirzakhani’s childhood.

Paul Halpern, in his own unique style, has written a beautiful testament to the late Maryam Mirzakhani. Get to know her, and her groundbreaking work, today!

from ScienceBlogs http://ift.tt/2hk5ckg