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Updated: 1 hour 15 min ago

Where to Watch the Solar Eclipse Online

19 hours 7 min ago

Multiple organizations are live-streaming the total solar eclipse in incredible and unique ways — take a look!

Total solar eclipse

Rick Fienberg / S&T Online Photo Gallery

A solar eclipse ought to be seen in person — whether it’s awe-inspiring totality or a captivating partially covered Sun. So, if at all possible, go outside and take a look, making sure to use approved solar viewers or a homemade pinhole projector during the partial phases of the eclipse.

But life happens. Maybe you’re stuck in the office, were unlucky with the weather, or you’re just in the wrong part of the world for this particular event. Don’t worry, we’ve got you covered.

Multiple organizations are live-streaming the eclipse in incredible and unique ways. (Not to mention the 90-minute movies that the Megamovie Project and Citizen CATE organizations are creating, which will be available shortly after the eclipse is done.)

Browse the following list for live-stream eclipse webcasts:

  • NASA: 12 p.m. to 4 p.m. EDT, will include live coverage from 12 locations, featuring live views of the eclipse as well as eclipse activities taking place across the country. There are multiple ways to watch, including NASA's website, Facebook live, and YouTube.
  • Exploratorium: This science museum in San Francisco will be begin its eclipse webcast at 12 p.m. EDT, featuring telescopes based in Oregon and Wyoming. At 12:15 p.m. EDT, listen in to experience the Kronos Quartet's sonification of the solar eclipse. You can also watch using Exploratorium's free Android and iPhone apps.
  • CNN: CNN is teaming up with Volvo to present Eclipse of the Century, which will present the eclipse from viewing locations across the path of totality with live, 360° coverage.
  • Montana State University: Watch the eclipse from an entirely different perspective — 55 high-altitude balloon teams are teaming up with NASA to provide coverage of the solar eclipse from the stratosphere. Learn more about how and why they're doing it — and watch the live webcast on August 21st — from the Eclipse Across America website.
  • Slooh: Beginning at 11:30 a.m. EDT, Slooh will provide live coverage of the total solar eclipse from Stanley, Idaho, with additional telescope feeds all along the path of totality.
  • TimeandDate.com: Watch the eclipse's progress starting at 11:30 a.m. EDT, with live footage from multiple locations and real-time updates on the current location of the Moon's shadow.

The post Where to Watch the Solar Eclipse Online appeared first on Sky & Telescope.

Categories: Astronomy Headlines

This Week’s Sky at a Glance, August 18 – 26

21 hours 35 min ago

 

Moon and Venus in early dawn, Aug 18-19, 2017

The waning Moon thins in the dawn as it heads down toward our line of sight to the Sun . . .

Friday, August 18

• As dawn begins to break on Saturday morning the 19th, look for the waning Moon hanging under Venus low in the east, as shown here. Find Pollux and Castor, much fainter, to Venus's left or upper left.

Saturday, August 19

• August is prime Milky Way time, and the dark night is now moonless. After dark the Milky Way runs from Sagittarius in the south, up and left across Aquila and through the big Summer Triangle very high in the east, and on down through Cassiopeia to Perseus rising low in the north-northeast.

Sunday, August 20

• With the Moon obviously out of the night sky getting ready for tomorrow's command performance, this would be a fine evening to look far away from the Sun into the Cygnus Milky Way, high overhead. Hunt out the telescopic deep-sky sights there that Sue French highlights in the August Sky & Telescope, page 54, with finder charts, photo, and eyepiece sketches.

Stars and Mars close to the eclipsed Sun, Aug 21, 2017

. . . which it crosses when new on Monday . . .

Monday, August 21

• In case you didn't hear, there's an eclipse of the Sun today. Not in the path of totality? You'll get a partial eclipse from anywhere in North or Central America, the Caribbean, and northern South America. Here are all our eclipse topics, including how to take photographs. Shortcut to NASA's clickable map to get your local timetable.

• If a solar eclipse is happening, you know it's new Moon today.

Tuesday, August 22

• After dusk as August nears its end, the Great Square of Pegasus looms up in the east, balancing on one corner. Its stars are only 2nd and 3rd magnitude. Extending leftward from the Square's left corner is the main line of the constellation Andromeda, made of stars about the same brightness.

This whole giant pattern was named "the Andromegasus Dipper" by the late Sky & Telescope columnist George Lovi. Shaped somewhat like a giant Little Dipper, it currently scoops upward.

Wednesday, August 23

• The actual Little Dipper, meanwhile, is tipping over leftward in the north. It's only 40% as long as the Andromegasus Dipper, and most of it is much fainter. As always, it's rotated about 90° counterclockwise from Andromegasus.

Moon and Jupiter, Aug 24 - 26, 2017

. . . and then the Moon reappears in the evening sky as a waxing crescent, retreating farther from our sunward line of sight every day. (The Moon here is positioned for the middle of North America; your aspect may vary a bit.)

Thursday, August 24

• After causing so much fuss on Monday, the Moon now gleams shyly low in the west after sunset, as shown here. Almost a fist-width to its left is Jupiter, and fainter Spica is farther left or lower left.

Friday, August 25

• Look low in the west in twilight for the waxing crescent Moon. It forms a triangle with Jupiter and Spica below it, as shown here.

Saturday, August 26

• The thickening crescent Moon, no longer so shy now, points its round side down nearly toward Jupiter low in twilight.

________________________

Want to become a better astronomer? Learn your way around the constellations! They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy.

Pocket Sky Atlas, jumbo edition

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae. Shown above is the Jumbo Edition for easier reading in the night. Larger view. Sample chart.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The basic standard is the Pocket Sky Atlas (in either the original or Jumbo Edition), which shows stars to magnitude 7.6.

Next up is the larger and deeper Sky Atlas 2000.0, plotting stars to magnitude 8.5; nearly three times as many. The next up, once you know your way around, is the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, or the bigger Night Sky Observer's Guide by Kepple and Sanner.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (meaning heavy and expensive). And as Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

This Week's Planet Roundup

Mercury is hidden in the glare of the Sun.

Venus (magnitude –3.9) shines brightly in the east before and during dawn. Look for Pollux and Castor, much fainter, to its upper left. They form a gently curving arc with Venus that straightens out during the course of the week. The arc becomes a straight line on the morning of the 26th.

Earth, best visible in the daytime, is centered below you. Its disk is a remarkable 180° in apparent diameter, 20,000 times larger than Jupiter: the planet currently in second place in this regard. But local details usually complicate the limb, and perspective effects limit how much of the planet is visible at once. A telescope is not required.

Mars is hidden deep in the glow of sunrise.

Jupiter (magnitude –1.8, in Virgo) is very low in the west-southwest during twilight. Look for fainter Spica (magnitude +1.0) 5° left or lower left of it. Binoculars help.

Saturn (magnitude +0.4, in the legs of Ophiuchus) glows steadily in the south-southwest at nightfall. Antares, less bright, twinkles 12° to Saturn's lower right.

Uranus (magnitude 5.8, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are in the southeastern sky in the early hours of the morning. Finder charts.

______________________

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.

______________________

"This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours."
— Neil deGrasse Tyson, 2014

______________________

"Objective reality exists. Facts are often determinable. Carbon dioxide warms the globe. Bacteria evolve when challenged by antibiotics. Science and critical thinking are no political conspiracy. They are how we discover reality. Civilization's survival depends on our ability, and willingness, to do so."
— Alan MacRobert, your Sky at a Glance editor

______________________

"Facts are stubborn things; and whatever may be our wishes, our inclinations, or the dictates of our passions, they cannot alter the state of facts and evidence."
— John Adams, 1770

 

The post This Week’s Sky at a Glance, August 18 – 26 appeared first on Sky & Telescope.

Categories: Astronomy Headlines

The White Dwarf That Survived

Thu, 08/17/2017 - 13:10

A peculiar white dwarf could be what’s left after a failed supernova explosion.

classical nova system

A white dwarf siphons gas from a companion star until it triggers thermonuclear reactions that lead to a bright explosion.
NASA/JPL-Caltech

A recently found white dwarf — the burnt leftover of a star like our Sun — could be the remnant of a failed Type Ia supernova explosion.

One of the characteristics that make Type Ia supernovae interesting for science — apart from the fact that they are exploding stars whose death flashes shine 5 billion times brighter than our Sun — is that they all have the same intrinsic brightness. That means that they act like reference points scattered around the universe for astronomers, who can use them to measure distances. Once one of them pops up in a far-away galaxy, an observer can just measure how bright the exploding star appears to be and determine how distant the supernova — and its host galaxy — must be for it to look that faint.

The reason these events’ brightnesses are so reliable is because they are all created when a white dwarf steals too much material from a companion star. When the white dwarf reaches 1.4 solar masses (a point called the Chandrasekhar limit) its internal pressure causes a nuclear chain reaction that destroys the white dwarf.

Or maybe not. Recent findings show that Type Ia supernovae do not always happen in such clockwork fashion. Sometimes things get messed up along the way and the explosion does not completely obliterate the white dwarf, resulting in subluminous supernovae. Astronomers think these failed detonations lie behind  a subclass called Type Iax — with 53 known objects at a recent count — that show lower luminosities, lower ejecta velocities, and more variable characteristics than normal Type Ia supernovae.

In an article published August 18th in Science, an international group of astronomers describes an object called LP 40-365 that, they think, might be the remnant of a white dwarf after ones of explosions.

LP 40-365 is a tiny star: The team estimates that it has only 0.14 solar mass and is a mere 8% as wide as the Sun, or about 8½ times larger than Earth. Spectral analysis shows an absence of hydrogen, helium, and carbon on its surface. This could be consistent with a white dwarf that expelled what was left of the star’s outer layers of hydrogen and helium into space in a subluminous supernova. The carbon could have been converted into heavier elements, or maybe sank deep inside the core.

This partially detonated, burnt cadaver of a Sun-like star is also travelling at a speed greater than the escape velocity of the Milky Way, a speed best explained by a powerful explosion that gave it a mighty kick, the authors suggest.

“There are other ways to propel a star at a very high velocity, such as an encounter with the galactic center or dynamical instabilities in a triple system, but neither could explain the strange surface of this object,” said principal author Stephane Vennes (Czech Academy of Sciences). “It is extremely difficult to peel off [the outer layers of] a dense, compact white dwarf unless a vast amount of energy is invested. The thermonuclear explosion of a white dwarf star does just that.”

Ryan Foley (University of California, Santa Cruz), an astronomer familiar with Iax supernovae who was not involved in this study, is puzzled by the absence of carbon in the star’s surface. But he considers the new observations consistent with the SN Iax scenario, where a white dwarf explodes but not as strongly as in a Type Ia supernova. “We think that in at least some cases the white dwarf doesn’t get completely disrupted and there is a gravitationally bound, battered and bruised star left behind,” Foley said. “We call these ‘zombie stars’ since they died in the explosion, but keep on ‘living.’”

According to Foley, there could be many zombie stars in the Milky Way, with an expected rate of creation of one about every 300 to 1,000 years. “If this is one, it could help us start to understand this new population of objects in our galaxy,” Foley said.

The new study also adds to a long-standing debate about the origin of Type Ia supernovae. There are two main accepted scenarios to produce one of these mighty explosions. In one of them, called the single-degenerate model, the white dwarf siphons gas form an ordinary star companion until it reaches the Chandrasekhar limit. In the second model, called the double-degenerate model, two white dwarfs merge, reaching an unstable mass that triggers the explosion.

According to Vennes, the finding of this putative supernova remnant is only consistent with the single-degenerate model. “The merger of two white dwarfs and subsequent explosion cannot leave any left-over. All the matter is consumed,” he said. A single-degenerate situation, however, should sometimes leave a remnant with properties similar to that of the white dwarf LP 40-365.

 

References:

S. Vennes et al. “An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova.” Science. August 2017.

S. Jha. “Type Iax Supernovae.” Handbook of Supernovae. July 2017.

The post The White Dwarf That Survived appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Solar Eclipse Activities for Kids and Families

Thu, 08/17/2017 - 07:19

Enrich the eclipse experience — especially the long, partial phases — with solar eclipse activities for kids and families.

Of the people who will be viewing an eclipse — total or partial — on August 21st, many will be young. Young enough that you'll want to double- and triple-check their solar viewers before letting them look up at the Sun, and young enough, too, that you'll want other activities for them (and you!) as the Sun makes its way through the long partial phases. Not to mention, young enough that this will be their very first eclipse, and you'll want to make every moment count!

Viewing the Eclipse with Kids

The first and simplest activity is to make an eclipse viewer to see the Sun. Note: Don't look at the Sun directly or through anything other than safe solar viewers or No. 14 arc-welder's glass during the partial phases of the eclipse. It's completely safe to look at the blocked Sun during totality though.

If you weren't able to procure a pair of glasses, there are other options: Pinhole projectors works just as well, if not better, to view the Sun, and they come with the side benefit that they only work when you face your back to the Sun — eye safety guaranteed.

Find a cereal box, scissors, some tin foil, a pushpin or toothpick, and tape, and you'll have everything you need to make a pinhole projector to view the solar eclipse. Watch NASA's video for the easy-to-follow instructions:

There are lots of different ways to make pinhole projectors, and this is just one of them. Just remember: The smaller the hole, the sharper the image will be, but the dimmer it will be too. So experiment — some have had fun creating pinhole projectors out of other items, such as boxes big enough to fit your head or cardboard tubes.

Solar Eclipse Activities - Make your own pinhole projector

Sky & Telescope

Planetary Society's Emily Lakdawalla has taken things one step further. The basic idea behind this fantastic concept: why create just one projection of the solar eclipse when you can create many? Go to town with that pushpin and create a work of eclipse art. Find Lakdawalla's full set of instructions at The Planetary Society's website.

In addition to creating your own multiple-pinhole projector, you might find nature making its own works of art. Take a moment during the partial phases to hunt for crescent Suns in the shade of trees or manmade objects around you.

During the partial eclipse, two crossed hands create many holes that act as pinhole projectors, creating tiny crescent Sun images in the shadow below. Using a thumbtack, a piece of foil, and your imagination, you can create your own art project using the same concept.
J. Kelly Beatty

Another fun art project that can also make eclipse glasses safer and more comfortable is to tape them onto a paper plate to create a face cover. Besides being fun to personalize, this can help keep the Sun out of wayward eyes — it might surprise you that very young children don't always know or want to look through glasses! Have an adult cut out a slice of the plate to make room for the nose, then cut out holes for where you'll tape the solar glasses. Give kids art materials such as markers and beads and enjoy the results!

Make Your Own Totality Prediction

If you're in the path of totality, you might talk with your kids about the corona — a mysterious part of the Sun that no humans can see for themselves except during a total solar eclipse. The appearance of the Sun's atmosphere changes constantly depending on what the Sun's magnetic field is doing, and while we have predictions as to the corona's appearance on Monday, everyone will experience it differently according to their eye's response.

Solar Eclipse Activities - Chalk Art

NASA

Have kids predict what they'll see with a bit of chalk. NASA has full instructions here, but the best part of this project is that it's so simple. Place a glass, pail, or other cylindrical object upside down on a piece of black or dark blue paper and trace the cylinder's outline with a thick line of chalk. Then, being careful not to move the cylinder, smear the chalk to create your own version of the corona. Remove the cylinder and voila — you've drawn your own version of the solar corona!

Act It Out

If the kids, especially the younger ones, are getting antsy, make a game of it and have them act out a solar eclipse. In a group of three, have one person each identify as the Sun, Moon, and Earth. Then, after asking the Sun and Earth to stay (relatively) still, direct the Moon to walk between the Sun and Earth. They can all take turns as Earth, relating what they see as the Moon passes between Earth and the Sun.

For older children, you can add the additional complexity of orbits: have the Moon walk around Earth as Earth walks around the Sun. Switch it up by asking the kids what will happen if there's a lunar eclipse instead of a solar eclipse — the results may be entertaining!

Visit the Library

Upwards of 7,000 libraries will be hosting special eclipse-day events. In addition to activities for the young and young at heart, they'll have knowledgeable people in attendance who can answer any questions that come up during the event.

Look for the library event nearest you.

Libraries hosting eclipse events

More than 7,000 libraries are hosting eclipse-related events on August 21, 2017.
STAR_Net's NASA@ My Library initiative / Space Science Institute / Gordon and Betty Moore Foundation / NASA / Google

I can tell you from personal experience that, even if you're not in the path of totality, this won't be an event that you or the kids you're with will soon forget.

The post Solar Eclipse Activities for Kids and Families appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Eclipse Planning: Explore Weather Model Forecasts

Wed, 08/16/2017 - 10:02

Five days to go until America's total solar eclipse and there is a palpable excitement in the air. All the talk is now focused on the weather. Will we have to move? How good is the forecast? Is this the best forecast? What model is the best?

Wide view of solar eclipse from Ternate

"The total solar eclipse over Ternate and the neighboring volcanic islands in Indonesia, Pacific Ocean, was a stunning sight this morning," writes globe-trotting photographer Babak Tafreshi. "Due to clouds I was not sure until the last minute if totality would be visible — but it was spectacular sight and the solar corona appeared through thin clouds."

Before we begin, never lose sight of the fact that you are working in the virtual world of weather modeling and that the model is, at this stage, an estimate. Nevertheless, an estimate now can pay off in your planning.

Which Weather Model to Use and How to Use It

You can play with many models, but in the end, you will probably be no wiser and certainly no happier. They won’t all agree with each other, and they won’t make the same forecast the next time they run (every 6 to 12 hours). I don’t need that kind of grief, so I pick one model and follow it, trying to decipher a consistent message in its otherwise messy prognostications. That model is the NWS Global Forecast System (GFS) model, which is constructed to make long-range forecasts of the larger-scale systems. (It’s not tuned to handle thunderstorms, though it does make and move them.)

The College of DuPage's website provides a sample of models to choose from, all created by the National Weather Service. For the time being, we will use the GFS models (if you click through, click on the GFS tab), as the other models won’t come into play until Friday. You can select one of the four regions along the eclipse track, or simply look at the whole USA by just selecting a feature to display from the tabs on the left.

When it comes to long-range forecasting, I like to pay a lot of attention to the upper-level winds and the jet stream, largely because the models tend to be a little more reliable in the upper regions than down close to the surface, where mountains and other complex features influence the forecasts. In the past five days, I’ve been paying particular attention to the 250-millibar pressure level, which is the flow about 10 km above the surface. You will find it, labeled as “250mb” on the CoD model site, with a choice of either winds or humidity. I use the winds to evaluate the model’s stability and reliability. A slider along the top of the map display will allow you to go ahead to “18Z MON AUG 21 2017,” the approximate time of the eclipse.

Winds at the 250 mb level have been on a roller-coaster ride recently, but in the past two days, the GFS model seems to be getting a clearer view of eclipse day. Upper-level ridges and troughs – the ups and downs in the contour lines on the 250-mb map – have recently begun to repeat from one model run to the other. That’s a sign that the model thinks it has a handle on how the future weather will evolve.

You can have a look at how it’s been changing by following the tab “Compare to Previous Runs” on the bottom of the CoD map – just explore the various options that come up until you get the hang of it.

Weather Predictions for August 21, 2017

So, what do I see in the current (12:00 p.m. EDT, August 15th) model run?

The eclipse track can potentially be affected by two jet-stream flows. One, the polar jet, lies up around the Canadian border, and won’t have too much influence on the eclipse track if the model is correct. The other wind flow – the sub-tropical jet – arcs from southern California to Kansas and Nebraska and then heads eastward across Kentucky and out to the Atlantic.

Jet streams tend to carry a lot of upper-level cloud and they also give energy to both larger-scale weather systems and to thunderstorm development. We don’t have to guess about the impact of these two jets, as they’ve pretty much had the same pattern for the past two weeks: daily thunderstorms over the western mountains and the Great Plains.

To compound our problems, in the lower atmosphere, a persistent high-pressure cell has camped out in Texas, pushing moisture (fuel for thunderstorms) from the sub-tropical Pacific and the Gulf of Mexico northward toward the eclipse track. The whole situation is messy and it looks like it’s going to continue to be messy through eclipse day.

So, what is the model telling us for eclipse day? This figure shows the flow predicted for eclipse day, 144 hours in the future:

Eclipse Weather from NWS

The 250-mb wind flow for eclipse day forecast by the GFS model. Note the trough extending into Idaho and Oregon from Canada and the jet stream flow (green areas) in Canada and across the Midwest. The small ripples in the flow lines are small, upper disturbances that will probably trigger thunderstorms.
College of DuPage / NWS

 

In the northwest, the polar jet stream is mostly over Canada, but there is a trough extending southward into Idaho at eclipse time that’s causing me some concern. It’s trouble, because the region ahead of that trough will probably be pretty cloudy and may even have rain. In the past few forecasts, that trough has always been there, but it changes in strength and position: sometimes over Oregon, sometimes as far east as Wyoming. I’m going to be in Wyoming, and it looks like it might bite me.

The Great Plains part of the eclipse track lies under the sub-tropical ridge, which is normally good; but this is a pretty flat ridge and we’ve already seen that it’s responsible for the high moisture content across the plains. Though I don’t want to believe that the GFS has it all figured out, it fires up thunderstorms over Nebraska every night from the 19th to the 22nd. It’s worth thinking about, but don’t lose sight of the fact that these are virtual thunderstorms at this stage, not real ones. If the GFS and some other models yet to come online, are doing that on the 19th, we’ll have to deal with it.

From the Missouri River to the Appalachians, there is a modest ripple in the upper flow that will set off thunderstorms, but the ripple is too weak to put much reliance on its actual position. However, those Nebraska night-time storms have to go somewhere, and that is into Illinois and Missouri, carried by those upper winds in the sub-tropical jet. South Carolina has a whole other problem – a low in northern Florida that floods the eclipse track with cloud and rain.

I’m just looking at the upper-level flow in the models to see if they are becoming more reliable, but if Pandora is tempting you too strongly, you can explore the other fields as well. You will find “Average Cloud Cover” under the Precipitation Products menu (shown above). Keep watching, but don’t make any plans just yet. Another weather model, known as the Canadian Model, has a completely different pattern for eclipse day.

Cloud Forecast for Eclipse Day

OK, I've captured the cloud forecast for you.
College of DuPage / NWS

The post Eclipse Planning: Explore Weather Model Forecasts appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Orbital Path Podcast: Holy Sheet!

Wed, 08/16/2017 - 07:25


A large circular sea ice floe covered with melt ponds and surrounded by smaller floes, as seen from an Operation IceBridge flight on July 17, 2017.
NASA/Nathan Kurtz

One of NASA’s key goals is to observe and explore our solar system ­— and beyond. But a key part to understanding how other celestial bodies might support life is to understand what’s happening on a pale blue dot orbiting a yellow star in the Orion spur of our galaxy — a planet we call home.

While NASA launches myriad spacecraft to study objects beyond Earth, it also supports several missions that study our own planet. In this episode, Michelle Thaller visits with two key members of NASA’s Operation IceBridge: Christy Hansen, Airborne Sciences Manager at NASA’s Goddard Space Flight Center, and Joe MacGregor, Deputy Project Scientist for Operation IceBridge.

Join Thaller as she learns about the IceBridge mission, the tools it is using to study Earth’s polar ice sheets, and the scientific discoveries it is making. How many ice sheets does Earth have? What impact will a recently calved iceberg the size of Delaware have on Antarctica’s the West Antarctic ice sheet? Why did Navy pilots using radar altimeters think they were further above the ground than they actually were? How many tons of ice are melting every second? How high will the sea level rise by the end of the century? What effect does melting ice have on the ocean’s temperature? What does Antarctica look like under all that ice?

Hear the answers and more in the latest installment of Orbital Path.

Orbital Path is produced by PRX and supported by the Alfred P. Sloan Foundation. Don't miss PRX's other science podcasts: Transistor and Outside Magazine.

The post Orbital Path Podcast: Holy Sheet! appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Will Monday’s Total Eclipse Change Your Life?

Wed, 08/16/2017 - 06:37

Total solar eclipses have the power to touch us deeply and reverberate through our life in unexpected ways.

Three times under the shadow

I've witnessed three total eclipses. From left: July 11, 1991; February 26, 1979; and February 26, 1998.
Bob King (left, center) and Greg Furtman

Whether this is your first or your 30th total solar eclipse, we all share one desire — to let the awe of this extraordinarily rare experience wash over us. You never know how 161 seconds of darkness in the middle of day may change your life. I've attempted to see five solar eclipses and succeeded three times. Each one has enlarged my spirit, become a touchstone moment, and set me off on new adventures as I confidently predict the August 21st event will for you.

March 7, 1970

I joined members of the Chicago Astronomical Society for my first eclipse on March 7, 1970. After a long bus ride a couple days before the event, we arrived in Fort Stewart, Georgia, just outside of Savannah. I was 16 years old and hanging with a crew that included men who still wore coats and ties to club meetings. The younger set, who'd recently let their sideburns grow, were heavily into optics and electronics. One amateur's scope featured a tube decorated with a wrap of black and white Moire interference patterns, a nod to the psychedelic spirit of the time.

We were allowed to set up our telescopes in a big field at the Army base. Eclipse day began mostly clear but clouds gradually moved in and temperatures dropped, especially as the 12:38 p.m. totality approached. While we experienced several minutes of darkness much like early twilight on a gray, northern-winter afternoon, no one saw the totally-eclipsed sun. Naturally, we were all disappointed but I came away from the whole experience with a wild sense of freedom after traveling so far from home and across parts of the country I'd never before seen. I also got my first taste of the southern stars. One of the nights was clear, and there beneath Sirius I spotted a twinkling Canopus. That alone put me in heaven.

July 10, 1972 Eclipse in the crater's shadow

The pin is about where my friends attempted to see the 1972 eclipse in the remote Canadian wilderness. Someday, I'd like to drive all the way to the crater. Not shown on the map are the billions of insects that made our stay challenging.
Google

In college now and working a summer job scooping ice cream in northern Wisconsin, my school friends, Rick and Larry, and I planned a trip to Canada's Quebec Province to see the total eclipse. We took Larry's green Vega for the 1,340-mile drive to Baie-Comeau on the St. Lawrence River and from there another 150 miles north to Manicouagan Crater, one of the oldest and most recognizable impact structures on Earth. I hope I never travel long distances in a Vega again.

We weren't much for meticulous planning. One night in Quebec there was nowhere to lodge, so we pulled over and slept in a farmer's field. The next morning the owner was there bright and early to greet us, but instead of kicking our butts, once he learned of our eclipse plans, invited us to breakfast with the family. I remember yellow sunlight streaming through the tidy home's windows, great food, and lively conversation in both French and English.

We arrived at our "site" somewhere near a dam called Manic-5 and set up camp. During the early afternoon on eclipse day, the sky was just partly cloudy, but as the Moon's shadow approached, clouds drifted in front of the Sun at just the critical time, blocking totality from view. We just drove 1,500 miles for this! How could a few clouds just take it all away?

I recall hiking down a path lit by the invisible corona slapping black flies, which were so thick, they literally chased us out of the forest. We took down our camp in a hurry immediately after the eclipse, threw everything in the car, and sped back down to the coast. I was in such pain from fly bites on the back of my neck and head, I soaked in our hotel room tub, nursing my neck well into the night.

February 26, 1979 Success at last!

The Sun in total eclipse at 10:55 a.m. local time on February 26, 1979, from Lake Winnipeg.
Bob King

Finally, sweet success! And it only took nine years. I was living in Urbana, Illinois, at the time and drove solo up to Winnipeg Beach, Manitoba, on the southern end of Lake Winnipeg, a jaunt of just over 1,000 miles. En route, I passed through Duluth, Minnesota, and was so struck by the snowy, icy beauty of the place that I ended up moving there some five months later.

The story's more complicated than that, but I'd been considering moving north to escape the sweaty Illinois summers. Seeing Duluth for the first time proved the tipping point. One wonders whether things would have turned out differently had I passed through the city in mid-June with temperatures in the 40s and 30 mph winds blasting off Lake Superior.

Weather uncertainty seasons every eclipse with a certain amount of tension, especially if you've traveled a long distance, so when I woke up in my Winnipeg hotel room on the big day and saw the Sun through the curtains, I stopped holding my breath.

Although Winnipeg lay in the path of totality, I wanted to be closer to the centerline. After a quick breakfast I hopped in my Honda and headed north. My original destination was the town of Gimli, but Winnipeg Beach, a community 75 miles north of Winnipeg and tucked along the shore of Lake Winnipeg, seemed a fine place to stop and park. I walked my 6-inch Edmund reflecting telescope out onto the snow-covered expanse and made quick friends with a group of amateurs from Minnesota.

Fiery Edge

Lots of prominences dot the lunar limb during the 1979 eclipse, the last to cross parts of the United States
Bob King

The cirrus hardly bothered the Sun as the light turned faint on the snow and shadows sharpened. I remember the diamond ring effect, the Moon covering the last beads of sunlight in real time, and striking red prominences poking up along the Moon's limb.

Mercury, Mars, and Venus were strung out on either side of the Sun, so I had this visceral sense of standing on planet Earth looking out across the entire solar system. How incredible that human beings are privy to such a profound sense of place.

The landscape during totality was brighter than expected — I'm sure the snow helped — but I recall my surprise at seeing sunset-early twilight colors all around the horizon. The event stirred a lot of emotions inside me from tinges of fear at the fading light to an irrepressible joy at the onset of totality.

I returned home with a new determination to follow my heart to the North. In September that year I made the move and Duluth's been my home ever since.

July 11, 1991 A Painter's Touch

The corona during the 1991 eclipse hints at the wealth of fine, brush-like detail visible with the naked eye and especially binoculars. Bring binoculars and keep them around your neck for great views of the corona. Magnetic fields align the corona's silky filaments much like a magnet makes iron filings trace out its magnetic field.
Bob King

My wife, Linda, and I joined a tour group and traveled to La Paz in Baja California, Mexico, to see one of the longest totalities ever — all of 6 minutes 27 seconds from our beachfront location. But as many eclipse chasers will confide, every totality feels like it lasts under a minute. When you're watching the eclipse on Monday, remember you're on UT — umbra time — when both the clock and heart seem to tick at an accelerated rate.

This eclipse coincided with the pins and needles experience of waiting for the Colombia adoption referral for our first daughter. In a referral, the couple receives photos and other information about the child and decides to proceed with the legal side of the adoption process. Every day, we'd check at the hotel front desk for a call from home with the news that the "packet" had arrived.

Crescent on the Cob

The narrow spaces along the rib of a palm frond cast neat rows of solar crescents on the sand below.
Bob King

The Sun stood high in a cloudless, blue sky during the eclipse as I set up a small telescope and camera on a blanket on the beach. My wife relaxed in a reclining chair, welder's glass at the ready as tiny crescent Suns spilled from gaps in the palm fronds onto the sand below. At this eclipse, the eeriness of the light caught my fancy more than at any other. A bizarre combination of sunshine and darkness, it makes you feel like you're slowly losing your sight. Perhaps more than at any other time, that final minute before totality intimately connects us to our most distant ancestors, who likely feared for the worst. Get ready for chills up and down your spine.

My best memory of the eclipse was viewing the corona through binoculars that gently bounced to the rhythm of my pumping heart. It looked alive! I couldn't believe the detail, the silkiness of the thread-like streamers. Few photos show this well, but wait till you see this silvery diadem for yourself — you'll never forget it. I know this sounds impossible, but I could have sworn the streamers were moving like glowing tentacles quivering in ultra-slow motion. Has anyone else experienced this or was it just my overactive brain?

Before and during an eclipse

The photo at left was taken only a minute or two before total eclipse and gives a rough idea of the darkish daylight and saturated, deep blue sky. The image at right was made during totality.
Bob King

The temperature dropped at least 10° in the mid-day twilight, lending the six-plus minutes of totality a relaxing, after-dinner feel that was further enhanced by the oranges and pinks around the horizon where the Sun was only partially (albeit deeply) eclipsed. Once again, powerful emotions took hold. I couldn't help but associate the eclipse with the beginning of my life as a new dad. Like the Moon's shadow, that life was swiftly approaching, and as any parent knows, raising a child becomes its own totality.

The final phase of our eclipse adventure took place on the return trip, upon our arrival in Los Angeles. We made a call from airport back to Minnesota and learned that the referral had just arrived. My wife's father would meet us at the airport with a picture of and details about our soon-to-be daughter.

February 26, 1998 Close call

Oh no! Clouds teased with totality at northwestern end of the island of Aruba on February 26, 1998.
Bob King

"It is the only natural event that I have experienced that felt supernatural." That's how my friend Greg Furtman described the 1998 eclipse we saw from Renaissance Beach on the island of Aruba.

But moments before totality, we both experienced another emotion: terror. Cooling temperatures brought on with the approach of totality caused masses of clouds to materialize in the blue sky only minutes before the total eclipse. Suddenly, it became apparent that we might miss the best part of the show. Luckily, the clouds only partially eclipsed the totally-eclipsed Sun — we still got great views of the prominences and corona in the sucker holes.

Up to this time, I'd viewed solar eclipses — two totals and two annulars — from a frozen lake, a hotel beach, a science museum, and a cemetery, but this was my first experience at an "adult" beach. Let's just say that clothing was an option here. Eyes may have wandered during the partial eclipse, but all were transfixed on what was happening overhead for 3 minutes and 45 seconds.

If all goes well, this will be my fourth totality, and I'm looking forward to every second of it. This one will complete a great circle in my life because both of our adopted daughters will join my wife and I in the Nebraska hinterlands. Cosmic events touch our lives in many ways. Every total eclipse is a personal journey. I hope this one will reverberate through your life in ways you never expected.

For more information about the eclipse, visit our 2017 total solar eclipse landing page.

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Categories: Astronomy Headlines

kappa-Cygnid

Tue, 08/15/2017 - 13:15

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Curiosity Rover Watches Clouds on Mars

Tue, 08/15/2017 - 13:03

Barely visible water-ice clouds coast across Mars’s skies in new videos from the Curiosity rover.

Thin clouds float above NASA’s Curiosity Mars Rover last July.

Thin clouds float above NASA’s Curiosity Mars Rover last July. This videos is made from eight still images each taken over a period of four minutes by Curiosity’s Navcam camera. 
NASA / JPL-Caltech / York University

Every now and then, the operators of NASA’s Mars Science Laboratory mission Curiosity take a break from avoiding sand traps and analyzing rocks for signs of ancient, habitable environments and instead point the rover’s robotic eyes to the sky to look at the clouds.

That’s what they did last month on July 17th, when early in the Martian morning they pointed Curiosity’s Navigation Camera (Navcam) up to capture two image sequences of feathery clouds as they drifted overhead.

The first clip shows smoky thin clouds moving from left to right as they pass right above the rover. In the second, the camera is aimed to the southern horizon line, revealing how a thin layer of similarly wispy clouds floats above two rounded hills. The Martian clouds shown in the videos look strikingly familiar and Earth-like. According to NASA, these cloud images are the “most clearly visible so far from Curiosity.”

Each sequence is made of eight images taken over a 4-minute time span. They have been processed to adjust for sensitivity differences among pixels in the camera’s sensor and to remove lens artifacts and then creating an “average” of all the frames and subtracting it from each individual frame. These corrections enhance the changes caused by movement and lightning – at the cost of adding some extra grain – making the clouds easier to see. NASA also published a version of the first video without enhancements where the clouds are much less noticeable.

Wispy clouds above the horizon on Mars

Wispy clouds above the horizon on Mars recorded by Curiosity’s Navcam camera. 
NASA / JPL-Caltech / York University

Although the rover’s operators most likely appreciate the change of subject, this is not a leisure activity. Researchers have been observing the Martian sky from the planet’s surface from years, using Curiosity and other previous missions such as the Phoenix Mars Lander, in order to study its climate.

Thanks to these observations as well as others by orbiting spacecraft and the Hubble Space Telescope, scientists have learned much about Mars’s cloud regime, which is driven by the planet’s elliptical orbit. When Mars is closer to the Sun, the extra sunlight it receives heats things up and can create global dust storms that may prevent cloud formation. As it moves away from our star and cools down, clouds begin to form in two major systems: made of frozen carbon dioxide on top of the colder poles and made of water-ice along a wide band following the equator.

These videos show examples of the second type – water-ice cirrus clouds similar to the ones found on Earth.

You can read more about the videos in NASA’s Jet Propulsion Laboratory’s press release.

 

Explore Mars for yourself with our Mars globes.

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Categories: Astronomy Headlines

Sky & Telescope Answers Your Eclipse Questions: Part II

Tue, 08/15/2017 - 12:39

A few weeks ago we took to Twitter and Facebook to find out what questions you wanted answered about the August 21st Total Solar Eclipse. Now we're back with Part II of the answers! (Part I)

 

Q: How much of a difference will there be between ~95% and 100%? Trying to decide if it's worth a three hour drive.
- @StylusH, Twitter

A: Very different. A total eclipse is a different animal.

 

Q: Is a 2 degree field of view enough to capture corona during totality? Have 8" Dob 1200 mm focal length (f5.9). Thinking about using 40 mm Plossl. Should give 2 degrees.
- Ernie, Facebook

A: Seems like the TFOV of the setup here is closer to 1.5°? Assuming the 40-mm Plossl has a 43° AFOV? The corona could stretch as far as 3.5° (max). So yes, in theory, 1.5° (or better 2°), you could see the corona, but you wouldn't be seeing all the corona. Keeping it narrow would be better to see the corona details and Regulus (about 1° from Sun); going wide, you could possibly see entire extent of corona.

 

Q: What is the safest way to watch the total solar eclipse?
-@JonGrummer

A: During the partial phases of this eclipse, as with any time the Sun is shining, don't look at the Sun directly unless viewing through an approved solar filter. Or you can use indirect projection of the Sun. If you're lucky enough to witness totality, you won't need any!

 

Q: Will it be visible in the southern hemisphere?
-Gerda, Facebook

A: Great question! The total solar eclipse will not be visible in the southern hemisphere, but a partial eclipse will be visible from parts of South America. There's a handy diagram in this article about viewing the partial eclipse.

 

Q: I'd like specific information on where to go to see the best views of the totality phase of the ecliipse. Thank you!
-Odette, Facebook

A: That depends on what you mean by "best." In terms of weather, we have a detailed guide of what to expect for each region, with maps and cloud statistics. (There's also a link at the bottom of the article for downloading it as a PDF.) We also recommend consulting these guides. But remember that many accommodations have completely sold out, so weather considerations aside, the "best" place might be wherever you can find a bed!

 

Q: At what percentage of the Sun being covered by the Moon does the sky become noticeably darker? I'm in the 85% partial eclipse area.
-David, Facebook

A: "Noticeably" darker for a dedicated skywatcher? I'd say at 30% obscuration of the Sun. Casual skywatcher, maybe 75%.

 

We hope you enjoyed these answers to your questions — for more information, visit our eclipse resources page about the 2017 Total Solar Eclipse.

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Categories: Astronomy Headlines

Four Exoplanets Might Orbit Nearby Sun-like Star

Tue, 08/15/2017 - 09:28

Astronomers have used an innovative technique to discover four super-Earth-size planet candidates orbiting Tau Ceti, a Sun-like star 12 light-years away.

Earth-size planet Kepler-186f

An artist's conception of an Earth-size planet in its star's habitable zone.
NASA Ames / SETI Institute / JPL-Caltech

When exoplanets were first being discovered by the handful in the 1990s, teams competed to measure the wobbles of nearby stars, induced by the gravitational tugs of orbiting planets. A star’s radial velocity (its motion toward or away from Earth) can be measured by its spectrum, where the Doppler effect will shift spectral lines as the star wobbles. The tinier the wobble, the tinier the shift — and the tinier the planet doing the tugging.

Now astronomers are testing the limits of what this planet-finding method can achieve.

Initially, the process of exoplanet discovery was relatively straightforward, albeit time-consuming and telescope-intensive. A hot Jupiter on a tight orbit induces a large wobble in its star, shifting it back and forth several meters per second over a period of days, generating a clear, regular signal. But if astronomers want to detect an Earth-size planet at an Earth-like distance from its star, they’ll need far more sensitive radial velocity measurements — around 0.1 m/s. And things get tricky when astronomers begin reaching below 1 m/s. It’s easy to confuse the motions on a star’s surface for the motion of the star itself or with internal signals generated by the instrument itself. A small planet’s signal can become lost in the noise.

Fabo Feng (University of Hertfordshire, UK) and colleagues are taking a new approach to radial velocity measurements, digging deep into the noise to get at planet-induced signals. The team examined more than 9,000 spectroscopic measurements of the star collected using the High-Accuracy Radial Velocity Planet Searcher (HARPS) instrument, a spectrograph installed on the European Southern Observatory’s 3.6-meter telescope at La Silla Observatory in Chile.

When the team removed all known sources of noise from the star’s spectra, four regular signals remained. The planet candidates are named Tau Ceti e, f, g, and h. Two of the candidates had already been suspected in a previous study, while two others (g and h, with tight orbits of 20 and 43 days) are brand-new finds. The radial velocity these planets induce on their star is around 0.2 m/s — in other words, the instrument has almost, but not quite, reached the capability to find an Earth-size planet in an Earth-like orbit.

“We realized that we could see how the star's activity differed at different wavelengths and use that information to separate this activity from signals of planets,” said Mikko Tuomi (University of Hertfordshire, UK). “No matter how we look at the star, there seems to be at least four rocky planets orbiting it.”

The results will be published in the Astronomical Journal (full text here).

Paul Robertson (Penn State), who was not involved in the study, found the method intriguing. “Regardless of whether all four candidates stand the test of time, this work represents an important effort to advance our ability to distinguish bona fide planets from astrophysical and instrumental noise,” he says.

Cooler and smaller red dwarf stars have become the target of many new planet searches for their proximity to Earth, but such stars are prone to high-energy flares and microflares that could endanger life on surrounding planets. Tau Ceti is the nearest single Sun-like star, and it doesn’t exhibit much high-energy activity. However, Tau Ceti has 10 times the comets and asteroids found in our solar system, so the chance for impacts could be considerably higher for Tau Ceti planets than on Earth. Still, it remains a popular target for SETI searches.

Two of the star’s planets, Tau Ceti e and f, orbit in the habitable zone. That means that, if the planets had solid surfaces, they’re at the right distance from the star for liquid water to exist on their surfaces. The planets have masses at least 4 times Earth’s mass, so it’s unclear if they’re more like solid super-Earths or gaseous mini-Neptunes. The planet's sizes are still unknown, so future measurements will be key to determining the planets' compositions.

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Categories: Astronomy Headlines

Astronomers Find Best Exomoon Candidate Yet

Tue, 08/15/2017 - 06:31

Astronomers have found one of the best exomoon candidates based on data collected by the Kepler spacecraft. Now they just need the Hubble observations to check if it exists.

Saturn's moons

This image from the Cassini spacecraft shows four of Saturn's moons and the outskirts of the planet's rings. Saturn's largest moon, Titan, is in the background. In front of it and above the rings at center is Dione, one of the mid-size moons. The small moon Pandora orbits beyond the rings on the right of the image. Finally, Pan peeks out as a spot in the Encke Gap of the A ring on the left of the image.
NASA / JPL-Caltech / Space Science Institute

Astronomers have found thousands of exoplanets orbiting their host stars. Yet, despite thousands of observations, one type of detection has proven elusive: the signal of an exomoon.

In our own solar system, moons are common; Jupiter and Saturn are each surrounded by dozens of them. Now, a group based in Columbia University Cool Worlds Lab have used a novel statistical technique to quantify just how many exomoons might be out there. Intriguingly, their results point out one leading candidate.

The study, conducted by Alex Teachey and David Kipping (both at Columbia University), and Allan Schmitt (a citizen scientist), used a high-quality subset of known planets to search for exomoons.The Kepler spacecraft had spotted the planets indirectly, by the dips in stars’ brightness caused when the planets transited, or passed in front of, their host stars.

Kepler can measure stars’ brightness levels with exquisite precision, detecting changes down to 40 parts per million. That’s enough to find Earth-size planets around Sun-like stars but not nearly enough to detect moons around those planets. Furthermore, hunting for individual moons is not as straightforward as detecting planets. Because the moons are orbiting the planets, their transits won’t follow the same timing as the planet’s transits. The moon could sometimes lead and sometimes lag behind its planet, and other times it might not be detected at all.

To circumvent these challenges, Teachey and his collaborators used a powerful statistical method to examine an entire population of planets. While they lost the ability to carefully detect individual candidates, they were able to quantify the how often massive moons, like the Galilean moons of Jupiter, exist in the systems that Kepler studied.

The team looked at 284 of Kepler’s highest-quality lightcurves of known transiting planets, which show how the host star’s light changes over time as the planet passes in front of it, Then they stretched those transit signatures so that they were all roughly the same shape, and combined them. This allowed them to cleanly remove the planet transits from the average lightcurve and quantify other signals that appear around the same time, when a moon might be transiting. They found that about 1 out of 6 planets might host a massive exomoon.

But that’s not what got everyone’s attention. During the course of their analysis, the team also used a much simpler model to look for exomoons in individual systems. In doing so, the astronomers uncovered one of the best exomoon candidates to date: Kepler 1625b-i (the “b” denotes the planet and the “i” denotes its moon).

Unfortunately, Kepler had only captured three of Kepler 1625b’s transits in front of its host star, making the identification of its moon uncertain. But if the exomoon does exist, it would be huge — literally! The candidate appears to be the size of Neptune, orbiting a planet a little larger than Jupiter.

The team will test the exomoon’s existence with Hubble observations later this year, which will examine an upcoming transit of the planet and, potentially, its moon. Until those data arrive, though, the moon around Kepler 1625b will only be a tantalizing possibility.

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Categories: Astronomy Headlines

New Age Estimate for TRAPPIST-1

Tue, 08/15/2017 - 05:55

A new study suggests that the seven-planet dwarf star could be much older than the Sun.

TRAPPIST-1

This illustration gives an imaginative look at the TRAPPIST-1 system, as seen from near planet f (at right).
NASA / JPL-Caltech

Since March’s announcement that the little red dwarf star TRAPPIST-1 hosts seven small exoplanets, astronomers have been working hard to discover everything they can about the star. One of the crucial bits of information they’ve been seeking is the star’s age. But TRAPPIST-1 is coy. The star is among the smallest, faintest M dwarfs, and such stars are hard to date.

Reporting in an upcoming Astrophysical Journal, Adam Burgasser (University of California, San Diego) and Eric Mamajek (JPL and University of Rochester) pulled together several observations of TRAPPIST-1, and of red dwarfs more broadly, to tackle the age question. They considered more than a half dozen different stellar characteristics to determine which were the most illuminating. They settled on the star’s chemical composition, its motion through the galaxy, and how often it flares.

None of these parameters gave specific results, but using them the team estimates that TRAPPIST-1 is between 5.4 and 9.8 billion years old. That’s consistent with a previous estimate of between 3 and 8 billion years by Rodrigo Luger (University of Washington, Seattle) and others, based on the star’s activity level and its spin. But the new study leans more toward the higher end of the range than many had suspected.

One reason for that shift to older ages is the star’s activity. Given the star’s output of high-energy radiation, previous work had suggested that TRAPPIST-1 is fairly young. But Burgasser and Mamajek found that, when compared with more than 200 active M dwarfs in the solar neighborhood, TRAPPIST-1 is actually pretty lethargic — its relatively weak emission suggests that it’s older than at least half these stars.

The advanced age is a bit odd, because scientists had wondered whether the planetary system would be stable for more than a billion years. The dwarf’s seven exoplanets orbit in a resonant chain, their movements tightly coupled by gravity. Imbalances in this chain would easily yank planets out of line.

Although it might sound good for habitability, the passage of so many billions of years may well have done in all but the outermost exoplanets. All seven worlds orbit closer to TRAPPIST-1 than Mercury does to the Sun. So close to the star, the planets have been bombarded by dangerous radiation over the last several billion years — enough to strip the innermost worlds of Earth-like atmospheres, and perhaps enough to rip an ocean’s worth of water off all but the two outermost planets, only one of which lies in the putative habitable zone. Thick atmospheres might save the planets, but astronomers will likely have to wait for the James Webb Space Telescope, launching in late 2018, before they can clearly detect the worlds’ atmospheres.

The paper is a nice synthesis of research on TRAPPIST-1 and its place among M dwarfs, and I encourage you to read it if you’re interested in this topic. You can also read more about the result in JPL’s press release.

 

Reference: A. J. Burgasser and E. E. Mamajek. “On the Age of the TRAPPIST-1 System.” Accepted to Astrophysical Journal.

The biggest astronomy event of the year is coming: the total solar eclipse of 2017! Prepare with our comprehensive eclipse guide.

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Categories: Astronomy Headlines

Perseid Meteor Shower 2017

Tue, 08/15/2017 - 04:42

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Milky Way through my window

Tue, 08/15/2017 - 00:57

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The Solar Eclipse for the Rest of Us

Mon, 08/14/2017 - 13:14

Totality watchers get the best show, but a far greater number of people will be in partial-only territory. Here's how to make the most of it.

The Christmas 2000 eclipse was partial only. For Fred Espenak, its maximum "eclipse magnitude" (middle image) was 43%.
Fred Espenak

Over the years we’ve had a lot to say about America’s total eclipse of the Sun coming up on August 21st. You can visit our eclipse landing page, and get local maps as detailed as you want. But as the broader maps in this article show, for the vast majority of people in North America, Central America, and northern South America, the eclipse will be only partial.

The partial eclipse crosses most of the Americas. The red lines give the Universal Time of mid-eclipse. The blue lines tell the eclipse magnitude (the percent of the Sun’s diameter covered) at that time. Of totality’s 8,600-mile-long track, about 30% falls on land.
Sky & Telescope, source:
Fred Espenak

Here are ways to make the most of it — without endangering your eyes.

How to Watch

The blindingly brilliant surface of the Sun can be actually blinding, perhaps permanently, if you stare at it for any length of time. And that also goes for the bright part of a partially eclipsed Sun.

You have two basic ways to watch safely: directly through a safe solar filter, or indirectly by projection.

Direct viewing: For this you’ll need a filter that’s specifically designed for Sun viewing: one that reduces the Sun’s invisible infrared and ultraviolet rays as much as it does visible light. All of the inexpensive little “eclipse glasses” that we’ve tested do fine, but just to be sure, look for “ISO 12312-2” printed on them. Check the AAS's safe vendor guidelines to ensure your eclipse glasses aren't fakes.

For binoculars or telescopes, you can buy solar-filter material made of glass or thin, metal-coated plastic film — either as a sheet you can cut with scissors to attach over the front of your optics, or pre-mounted in a cell sized to fit firmly onto the front (don’t let it blow off!). Leave the film slack; wrinkles don’t matter, but stretching it will haze out the view and compromise safety. When we tested various glass and thin-film solar filters few years back, we liked the Baader Astro-Solar thin film the best.

Projecting the Sun. Put binoculars on a tripod and point them sunward. Adding a cardboard shield around them creates a large shaded area for viewing the projected image.

Projection means projecting an image of the Sun onto a piece of white paper and watching the paper. The oldest, simplest, but poorest projection method is to use a pinhole. For instance, take a long box, cut a hole in one end, tape aluminum foil over the hole, and put a pinhole in the foil. Tape white paper inside the other end of the box, close it up, and cut a big hole in the side so you can look at the paper. Aim the pinhole at the Sun, and an image of the Sun’s face will fall on the paper.

But the image will be very small and dim. Experiment with different sized pinholes. A large one makes the image bright but fuzzy; a small one makes it sharp but dim.

Much better is to use binoculars or a telescope to project a big, bright image, as shown on the next page. Aim the instrument at the Sun (without looking in it! Move it around until its shadow is minimized and light floods out of the eyepiece). On a telescope, use your lowest-power eyepiece. Focus the image with the focus knob and/or by moving the paper catching the image closer or farther back. If the scope’s aperture is larger than about 3 inches, cut a clean, 3-inch hole in thin cardboard and tape it over the front. You don’t want to let a damaging amount of solar heat inside.

What To Watch For

• Can you see any sunspots? Don’t get your hopes up; the Sun is well past the 2014 maximum of its 11-year activity cycle, and its face these days is pretty quiet, sometimes completely blank. But if you do see a spot or two, they will be landmarks for events coming up. If you’re projecting the Sun’s image onto paper, wiggle the paper to distinguish sunspots from tiny paper flaws.

First contact is the moment when the edge of the Moon first touches the Sun’s western edge. Find the exact time of this event for your location by clicking on this Google Map. But the Moon’s edge will take a little while after first contact to intrude enough to begin to show. How well can you time when this happens? What’s the delay as seen with your setup? Set your timepiece accurately beforehand.

• As the Moon leisurely intrudes farther onto the Sun, look for irregularities showing up on the edge of the Moon’s silhouette. These are lunar mountains and valleys seen in profile along the Moon’s limb. The Sun’s edge, by contrast, is perfectly smooth.

• Keep an eye on those sunspots. If the black lunar silhouette approaches a big one, and if you’re looking through a fairly large filtered scope, you should be able to see that, by comparison, the sunspot’s dark umbra is not truly dark. Photos to the contrary, sunspot umbras shine with about 20% the surface brightness of the rest of the Sun. They would appear blindingly brilliant if the rest of the Sun weren’t there and dictating the density of your solar filter.

• As the eclipse progresses, look around at the landscape and blue sky. Is the blue becoming deeper and purer? You may be surprised by how much sunlight has to be lost before the world looks any different. This is a measure of how well our eyes naturally adapt to changing lighting conditions.

If the partial eclipse at your site is deep and the Sun becomes a thin crescent, watch for the landscape to take on a slightly alien, silvery look, with shadows turning crisper than usual.

How deep will the eclipse become at your location? The Google Map tells this two ways. The maximum magnitude of the partial eclipse is the percent of the Sun’s diameter that the Moon will cover. The obscuration tells what fraction of the Sun’s surface area is covered. That’s also about how much light is lost (although the Sun’s disk is a little dimmer around its edges than near its middle, a solar-atmosphere effect called limb darkening).

Venus and Jupiter may become visible if the sky turns a deep enough blue. Venus is your first try. Look for it 34° (about 3½ fists at arm’s length) to the Sun’s celestial west. Next brightest is Jupiter, 50° to the Sun’s east.

Unless the eclipse becomes total or very nearly so, you don’t have much hope for Mars (magnitude +1.8) some 8° west of the Sun, Regulus (+1.4) just 1° to the Sun’s east-southeast, and certainly not Mercury, fainter still at +3.3, 10° to the Sun’s southeast.

• Look for dim dapples of sunlight on the ground under trees. A leaf canopy may form many pinhole projectors, and during a partial eclipse each dapple will show an identical dent. Or make little holes between the fingers of your two hands laid across each other, as shown in the photo at lower left.

During the partial eclipse, cross two hands so your fingers make a waffle pattern. The holes between them act as pinhole projectors to create tiny crescent Sun images in the shadow below.
J. Kelly Beatty

And then watch everything slowly unwind in reverse, until the Moon’s last trace slides off eastward into invisibility, and last contact ends the show until next time.

And when is that?

The next North American partial eclipse happens for the northeastern U.S. and eastern Canada around sunrise on June 10, 2021. Then nearly all the continent is partially eclipsed on October 14, 2023, when an annular eclipse runs from Oregon to Texas and points south.

The next total solar eclipse awaits North Americans on April 8, 2024, running from Mexico through Texas, the Midwest, northern New England, and the Maritimes. Again, almost all of the continent will be partially eclipsed.

This article originally appeared in Sky & Telescope's August 2017 issue. For more information about the eclipse, visit our 2017 total solar eclipse landing page.

The post The Solar Eclipse for the Rest of Us appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Use Your Smartphone to Shoot a Solar Eclipse

Mon, 08/14/2017 - 12:41

Read this advice from expert eclipse-chasers before you use your smartphone to photograph a solar eclipse.

The advice many experts offer to first-time eclipse watchers is to experience totality without any lens in the way — even the longest total solar eclipse seems like the briefest moment in time. Yet many won’t be able to resist the temptation of trying to capture the rarest of photo ops: a solar eclipse.

Paul Deans / TravelQuest International

Before we begin, safety first: never look directly at the Sun without proper eye protection, using either solar viewing glasses or a No. 14 arc-welder’s glass filter when viewing the Sun naked-eye, or a special solar filter if viewing through cameras, binoculars, telescopes, and finder scopes. (Find a list of reputable vendors of solar glasses and filters here.) Do not use ordinary sunglasses, polarizing filters, or neutral-density filters — they are not safe. Failure to take proper precaution can result in serious eye injury or permanent blindness.

Using a smartphone to shoot an eclipse is appealing: smartphones are compact and easy to use, and the phone’s built-in camera can capture high-quality, high-resolution still images and video of the event, which you can then immediately share with family and friends via text message, e-mail, or social media. Just be sure your phone is fully charged, and that you’ve freed up enough memory.

If you just hold up your unfiltered smartphone to the Sun and try taking snapshots, not only is the Sun’s image going to be tiny, it's also going to be completely overexposed. There’s also the risk of damaging your phone. But there are other options.

Partial Phase Photography

Crescent Suns projected through the tiny openings between palm leaves aboard the MV Discovery, by Anthony Sanchez.

During the partial eclipse, look under leafy trees — the tiny spaces between the leaves act as natural pinholes, projecting dozens of small solar crescents on the shaded ground. Lay down a white blanket to see the crescents better. The projected solar images will be tiny, dim, and fuzzy, but they are perfectly safe to look at and to photograph with your phone camera.

Alternatively, you can create your own pinhole patterns on a piece of cardboard, or use any everyday items around the house with small perforations to project solar crescents. Get creative!!

Capture Totality with Your Smartphone

Lynn Palmer captured this wide-angle view of totality from an airplane over Antarctica during the November 23, 2003, solar eclipse.

Smartphones are perfect for capturing dramatic panoramic shots of the sky and the local scenery during totality. To add creativity to your composition, you can include people observing in the foreground, silhouetted by the sunset colors along the horizon.

You can also use the camera’s video mode to record the shadow of the Moon as it approaches and then retreats. For best results, use a bracket or some kind of tripod adapter to hold the phone and keep it steady while recording. Prior to the eclipse, practice taking twilight photos at dusk to get an idea how your smartphone will perform in low-light conditions, just like what you’ll experience during totality.

Smartphone + Telescope

If you want to take highly detailed, close-up shots of the eclipse, you’ll need a telescope to magnify the image. (Inexpensive, third-party clip-on “telephoto” lens kits are often not enough, and they can be frustratingly tricky to use.) Be sure to place a proper, safe solar filter in front of the telescope when shooting the partial phase.

Smartphone bracket

Commercial brackets, like the Meade smartphone adapter shown here, are the way to go to get steady shots of the partial eclipse through a filtered telescope. No solar filter is needed during totality.
Imelda Joson and Edwin Aguirre

The quickest and easiest way to shoot through a properly filtered telescope is by holding the phone camera in your hand. First, insert a low- to medium-power eyepiece into the focuser and focus the telescope on the Sun. Then hold your smartphone and aim its camera lens directly into the eyepiece. To prevent stray light from causing unwanted glare or reflections, try to get the lens as close to the eyepiece as possible.

Use the LCD screen to center the sun. Try not to use the camera’s “digital” zoom to enlarge the image since this can degrade the image quality. Manually focus the camera by placing your finger on the image of the Sun’s limb and tapping the screen lightly to lock the focus. Slide your finger up or down to lighten or darken the exposure, then try to hold the camera as steady as you can while clicking the shutter button or icon. Refer to your phone’s instruction manual if you’re not sure how to do this. Of course, you don’t need to use a solar filter during totality.

A better and steadier way than handholding your smartphone is to use a commercial bracket to attach the phone securely to the eyepiece barrel. For example, Meade’s phone adapter, which retails for $19.99, can accommodate several models of the iPhone 6 and Samsung Galaxy. Avid do-it-yourselfers and amateur telescope-makers can fabricate their own homemade bracket using metal or wood, as well as plastic components designed and created using CAD software and 3D printer.

To enhance your camera’s imaging capability, you can download photo apps — such as Camera+ or NightCap Pro for iPhones and iPads, as well as Camera FV-5, or Open Camera for Android phones and tablets — so you can manually fine-tune the camera’s focus, exposure settings, and much more.

The post Use Your Smartphone to Shoot a Solar Eclipse appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Perseids and the Erupting Volcano

Mon, 08/14/2017 - 10:24
Categories: Astronomy Headlines

Solar Eclipse Apps You’ll Need on Eclipse Day

Mon, 08/14/2017 - 07:42
Great American Eclipse

Eclipse Safari

Anticipation is building for the “Great American” solar eclipse of Monday, August 21st. After avoiding the continental United States for 38 years, the Moon’s dark shadow will sweep across the country from Oregon to South Carolina and give millions of residents and visitors the thrill of a lifetime. Everyone in North and Central America, and millions more in northern South America, will get at least a partial solar eclipse that day.

Would you like to know when the eclipse begins and ends in your hometown? How much of the Sun’s face the Moon will cover at maximum, and when that occurs? Maybe you’re on the verge of a last-minute decision to get yourself into the path of totality — would you like to know the quickest way to get there? Are you worried about remembering when to remove and replace your solar filters and wishing you could get a reminder at the appropriate times? Are you going to be stuck at work on the 21st and hoping to catch a live stream of the eclipse so as not to miss the event entirely?

There’s an app for that! (You probably saw that coming.)

In fact, there are surprisingly many apps for your mobile device to help you get the most out of the August 21st solar eclipse, no matter where you’ll be. Some are specific to this eclipse, while others are more general and can help you explore past and future eclipses too. Most are available for both iOS and Android, though some are specific to one or the other operating system. Most are free, none are expensive. There are also some apps that you can run from a web browser on your internet-connected smartphone, tablet, or personal computer, no matter what operating system it uses.

In the course of maintaining the American Astronomical Society’s “Solar Eclipse Across America” website, I compiled a list of every solar-eclipse-related app I could find. I’m sure I missed some, but I’m reasonably confident that I found all the ones created for use by the general public (as opposed to diehard eclipse chasers who want everything to the umpteenth decimal point).

I use an iPhone 6s, so for this article I downloaded all the iOS apps and played with them to see what they do and how they work. I wasn’t able to try out any Android-only apps, so for them I relied on what I could glean from the developers’ websites. In addition to the data in the accompanying table, I’ll describe the features common to many of the apps and highlight some products that stand out from the crowd for one reason or another.

Download the full summary of all the apps and their capabilities here.

Eclipse Circumstances Solar Eclipse App

Solar Eclipse 2017 (timeanddate.com)

Almost all of the eclipse apps I've found (listed at the AAS website) compute eclipse circumstances for your current location using your smartphone's build-in GPS receiver. The information listed always includes contact times, usually in the appropriate local time zone, and sometimes also the altitude and azimuth of the Sun in the sky at each contact.

Another important piece of information is the percentage of the Sun covered by the Moon at maximum eclipse, sometimes given as magnitude (fraction of diameter), sometimes as obscuration (fraction of area), and sometimes both. For locations within the path of totality, most apps will also report the duration of the total phase of the eclipse.

What if you want to find the same information for a different location? Most apps let you ignore the current GPS reading and specify another location — such as the site from which you plan to observe totality — using either a pull-down menu of countries and cities, a search box, or an interactive map.

Interactive Map

Most of the eclipse apps include an interactive map. It’s a lot easier to explore how the eclipse progresses differently in different places around the country if you can just point to a spot on a map and pull up the eclipse circumstances for that location. An advantage to having a map is that you can see the path of totality and where different cities and towns lie in relation to it. Some apps use a variant of Google Maps, which means you can toggle between a map view, satellite view, or hybrid view.

Eclipse Simulations

Where does the Moon take its first bite out of the Sun? It’s easier to catch the instant of “first contact” if you know exactly where on the Sun’s limb to look. Many eclipse apps provide a visual preview of the eclipse from the location you’ve specified, enabling you to see how the Moon will move across the Sun relative to your local horizon and zenith. Some apps, such as Black Sun, just show you the relative position of the Sun and Moon at each contact, and others, such as Solar Eclipse 2017, actually run a short animation. Either way, you’ll know exactly where to watch the Moon ingress, and then later egress, the Sun’s face.

Space Views

A few maps take simulation a step further and provide 2D or even 3D views of the eclipse from different perspectives. Watch the Moon’s shadow race across the country as if you were in Earth orbit. Or take a trip to the Sun and watch the whole event unfold from Old Sol’s point of view.

Black Sun did the best job of 3D simulations, in my opinion. It lets you see the long, tapering lunar umbra as it touches Earth and then races from coast to coast. If you’re having trouble visualizing solar eclipse geometry, you’ll learn a lot from Black Sun. NASA’s Eyes on Eclipse 2017 does a nice job on this too.

Routes/Directions Solar Eclipse App

Eclipse Run

You should have decided long ago to travel to the path of totality, but you procrastinated, and now it’s crunch time. What’s the quickest route to the centerline of the Moon’s shadow? Several apps will show you, providing mileage, drive time, and in some cases, turn-by-turn directions. Eclipse Run even alerts you when you cross the northern or southern limit and enter the path of totality, then tells you when you’ve reached the centerline. If you’re battling the Mother of All Traffic Jams on eclipse day, knowing you’ve crossed into the path could let you breathe a little easier — as long as the Moon’s shadow hasn’t already passed you by!

Weather

As the saying goes, climate is what you expect, but weather is what you get. Eclipse chasers will be paying close attention to weather forecasts along the path of totality in the days leading up to the big event. A few apps, such as Eclipse Explorer and Flowx, include weather forecasts from various sources — set your location, and see how things are shaping up for eclipse day.

As a wannabe private pilot, I got a special kick from Robert Urschel’s EclipseFlite, which shows all the general aviation airports within the path of totality and provides aviator-ready weather forecasts for each of them.

Traffic

One app gets special mention: Michael Zeiler’s web app Tour the Great American Eclipse of 2017. Zeiler is a geographic information systems (GIS) professional, and his website, is a masterwork of both the science and art of eclipse maps. His web app includes layer upon layer of useful information, all sensibly displayed so as not to be overwhelming.

In addition to the best route to totality from outside the path and real-time weather reports, the Tour web app also includes real-time traffic, just as Google Maps and other navigation apps do. If you’re not already inside the path of totality on eclipse day and need to drive, Zeiler’s app will help you figure out which roads to avoid and which ones might actually get you to your observing site on time.

Live Stream Solar Eclipse App

NASA's Eyes Eclipse 2017

NASA, the Exploratorium in San Francisco, and numerous other organizations will be live-streaming the eclipse from various points along the path of totality. NASA’s stream can be viewed from within two apps produced by Simulation Curriculum: Eclipse Safari and Smithsonian Eclipse 2017. You can access the Exploratorium’s stream from the museum’s own app, Total Solar Eclipse.

Not to jinx anybody, but if you’re in the path of totality and get clouded out, you can still watch the eclipse through these apps. I hope that doesn’t happen to anybody, and that everybody outside the path tunes in to get a taste for what they’re missing by settling for a partial eclipse.

Audio Prompts

I lead eclipse tours, and one of my responsibilities is to keep my traveling companions informed about what’s going to happen next, and when. This means I inevitably spend too much time looking at my watch or a timer when I should be enjoying the view overhead. On August 21st I plan to run Gordon and Angela Telepun’s Solar Eclipse Timer (available for iOS and Android). Once you’ve set your location in the app, it computes the eclipse contact times and then counts down to each upcoming event — not just on the display, but with voice-over.

I plan to listen with earphones and then shout things like “10 seconds to third contact!” and “filters on!” to my fellow eclipse watchers. But this time, I’ll be watching the eclipse, not the clock. Solar Eclipse Timer isn’t the only app with audio prompts, but I think it’s the one that makes the most effective use of the technology.

Camera Control Solar Eclipse App

Eclipse Megamovie Mobile: Solar Eclipse 2017

A growing number of eclipse photographers use specialized software to control their cameras from laptop computers. This frees them up to watch the eclipse rather than spend all of totality clicking the shutter button and missing the sky show. The paid version of Wolfgang Strickling’s EclipseDroid (available for Androids only) makes it possible to control a digital SLR camera with your smartphone via a USB connection and adapter cable. It’s the only app I’ve seen that made me want to trade in my iPhone for an Android device — almost!

Now there’s an app that automates eclipse photography with the camera built in to your smartphone. Designed for observers in the path of the Moon’s shadow, Eclipse Megamovie Mobile — out now for iOS and coming soon for Android — lets you set up your phone to shoot totality automatically while you enjoy the view. Your images will then be incorporated into the Eclipse Megamovie, a crowd-sourced record of totality as seen from one end of the country to the other.

Final Thoughts

No matter what you want to know about the August 21st solar eclipse, there’s an app that’ll tell you. The conundrum is which of these excellent resources to use?! I've compiled a list of all of the eclipse apps, noting their price and functions — download the file here.

But you don’t need to pick just one. Some apps shine at eclipse planning, while others are most useful on eclipse day itself. Since most don’t cost anything, go ahead and try as many as look appealing to you. You’ll quickly zero in in your favorites.

Clear skies to all on August 21st!

The post Solar Eclipse Apps You’ll Need on Eclipse Day appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Planetary Video Camera from Meade Instruments

Mon, 08/14/2017 - 06:00

Meade Instruments
27 Hubble
Irvine, CA 92618
800-626-3233

Meade-LPIMeade Instruments introduces a new planetary video camera. The LPI-G camera ($219.95) features the highly sensitive AR 130 CMOS detector with a 1,280-by-960 array of 3.75-micron pixels. This USB-2.0 camera is capable of recording up to 28 frames per second at full resolution, or 30 frames per second using a 640 x 480 region-of-interest. Additionally, the camera can function as an autoguider for deep-sky imagers, and it connects to your mount through an ST-4 autoguider port. The camera is available with color or monochrome detectors. Each purchase includes a 2-meter USB 2.0 cable, a guiding cable, a C-mount-to-11⁄4-inch nosepiece adapter, and a CD with ASCOM drivers and the company's Sky Capture control software.

SkyandTelescope.com's New Product Showcase is a reader service featuring innovative equipment and software of interest to amateur astronomers. The descriptions are based largely on information supplied by the manufacturers or distributors. Sky & Telescope assumes no responsibility for the accuracy of vendors statements. For further information contact the manufacturer or distributor. Announcements should be sent to nps@SkyandTelescope.com. Not all announcements will be listed.

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Categories: Astronomy Headlines

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