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Inside the January 2015 Issue

Tue, 11/25/2014 - 10:06
PURCHASE PRINT ISSUE | PURCHASE DIGITAL ISSUE | DOWNLOAD BACK ISSUES | SUBSCRIBE

FC-2014-12-172pxBig Scopes, Hot Products, & Observing Treats

We live in the age of Big Astronomy, where it seems every new telescope is bigger, and supposedly better than the last. But January's cover story issues a cautionary tale. Contributing editor Robert Zimmerman describes the challenges facing four huge scopes — now they serve as potent lessons for the upcoming generation of megatelescopes. We also found that "bigger is better" doesn't necessarily apply to astronomy equipment: in this issue, you'll find your ultimate gear guide to 28 of the hottest products for 2015. Drool over an $15,000 astrograph or pick up that free planetarium app — there's something here for everyone. And January holds many opportunities to use that telescope and all its gadgets, whether they be old or new: check out variable star R Geminorum, eclipsing binary Alpha Comae Berenices, or deep-sky objects galore. Brave the cold and embrace the winter sky!

Feature ArticlesAbell 2744, the first of the Hubble Space Telescope Frontier Fields

Abell 2744, the first of Hubble's Frontier Fields.
NASA / ESA / J. Lotz / M. Mountain / A. Koekemoer / HFF Team (STScI)

Hubble Goes the Distance
Using nature's gravitational lenses, astronomers are pushing the space telescope to its very limits to reveal primordial galaxies.
By Govert Schilling

Hot Products for 2015
Our 17th annual roundup of Hot Products highlights the most intriguing new astronomer gear on the market.
By the Editors of Sky & Telescope

The Backyard Sky: Winter
Embrace the cold nights of winter to observe these seasonal delights.
By Rod Mollise

Flawed Giants
The world's largest optical telescopes have had to overcome serious hurdles, delaying their scientific successes.
By Robert Zimmerman

Composing the Universe
Planning your composition can raise your imaging to a whole new level.
By Robert Gendler

Beyond the Printed PageJupiter with Io and Europa in the foreground

NASA / JPL

Mutual Events Among Jupiter's Moons
Find out how to watch Jovian moons eclipse and occult one another.

Mergers Create Pancake Galaxies by Camille M. Carlisle
Watch two galaxies collide, and see what radio a.

Fighting for Dark Skies
Learn more about one club's battle against light pollution.

Lunar Librations by Sean Walker
Librations and other lunar data for January 2015.

ALSO IN THIS ISSUEmoon venus mercury small 11

Dhruv Paranjpye took this image of the Moon, Venus, and Mercury on December 11, 2012.
Dhruv Paranjpye / Sky & Telescope Online Photo Gallery

Venus and Mercury Draw Close
Nightfall reveals a planetary pairing.
By Fred Schaaf

Vigil for a Unique Stellar Eclipse
Against incredible odds, this naked-eye star may self-eclipse for the first time seen.
By Alan MacRobert

An Observational Mystery
What causes Io's enigmatic brightening?
By Thomas A. Dobbins

Table of Contents
See what else December's issue has to offer.

The post Inside the January 2015 Issue appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Bright Spot in Uranus’s Atmosphere

Tue, 11/25/2014 - 06:32

Amateur astronomers have confirmed the presence of a large, bright storm cloud on Uranus.

There have been many dull moments on our solar system’s blue-green ice giant, but these days Uranus is pretty hopping. For the past few years, astronomers have seen the Uranian weather ramp up, producing spots, scalloped edges, and other cloud features.

Uranus storm

Australian amateur astronomer Anthony Wesley took these optical images of Uranus on September 19th and October 2nd, showing the dramatic appearance of a bright storm on a planet that normally displays only a diffuse bright polar region.
Anthony Wesley

Recent storms have been so large that amateur astronomers are spotting them, too. When Imke de Pater (University of California, Berkeley) and her colleagues detected eight large storms in the planet’s northern hemisphere on August 5th and 6th, several amateurs also started looking.

Among the successful observers was Australian amateur Anthony Wesley, who caught the bright spot in the optical images at right on October 2nd. French amateur Marc Delcroix also saw it in infrared observations he took on October 3rd and 4th. (Delcroix went looking after he processed images by amateur Régis De-Bénedictis and others from September and October that revealed the storm.)

The storm clouds are likely so bright due to high reflectivity. They’re probably made of condensations of methane ice or other compounds.

The storm the amateurs detected is fairly deep in the planet’s atmosphere, tucked below the highest layer of methane ice. The professional team saw the same storm at the near-infrared wavelength of 1.6 microns back in August, using the 10-meter Keck II scope on Mauna Kea. Some other features de Pater’s team also detected at the longer 2.2 microns, meaning they’re higher in the cloud deck, just below the tropopause. (The tropopause is the boundary between the thinner stratosphere above and the troposphere below, where weather generally happens.) On Uranus, the atmospheric pressure at the tropopause is about half that at Earth’s surface.

As the detailed press release from UC Berkeley explains, the amateurs’ storm could be part of a tall vortex anchored deep in the planet’s atmosphere, similar to the Great Red Spot and other features on Jupiter.

Anyone else spot storms? Let us know in the comment section below!

Use our free JavaScript utility to find several of Uranus's moons with your telescope.

The post Bright Spot in Uranus’s Atmosphere appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Watch Asteroid Juno Occult a Star

Mon, 11/24/2014 - 07:54

Watch an asteroid approach a star and block its light, all in a fraction of a second.

Have you ever seen a stellar occultation? If not, Jennifer West, Ian Cameron (University of Manitoba, Canada), and Jay Anderson (Royal Astronomical Society of Canada) shares their excellent video of asteroid Juno as it occults the 7th-magnitude star SAO 117176 in Hydra on November 19th, at 6:50 UT.

West writes: “Early this morning, our team observed the 9th-magnitude asteroid Juno as it occulted SAO 117176 (HIP 43357) from the Glenlea Astronomical Observatory in Manitoba, Canada. Manitoba was the only location in North America where the event was visible under clear skies. We recorded the entire event using the observatory’s 16-inch telescope and an Apogee AP47 CCD camera. The entire occultation lasted approximately 20 seconds, though our time-lapse sequence has been sped up about 20 times real speed. Watch it here (actual occultation occurs around 0:35):

Their excellent work really gives viewers a feel for how quickly an occultation “blinks out” a star; nearly all stars appear as a tiny pin-prick of light as seen from Earth, so they take a fraction of a second to disappear behind an occulting object in our solar system. Reappearance is just as abrupt.

Occultations are fun to observe, and good science can be had by recording the event. Precise timing of the disappearance and reappearance of the star from multiple locations help astronomers build an accurate shape profile of the asteroid. And in rare cases, tiny moons of these larger asteroids have been discovered during occultations when the star unexpectedly winked out twice.

Sky & Telescope magazine will alert you to major occultations, and other exciting celestial events -  subscribe now!

The post Watch Asteroid Juno Occult a Star appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Contact Lost with Sun-watching Stereo B

Fri, 11/21/2014 - 06:27

Despite rescue efforts, no one has heard from one of two NASA spacecraft on the far side of the Sun since October 1st.

Solar physicists always worry about the damage to Earth that might occur if the Sun were to unleash a titanic flare and zap our planet with a potent blast wave of energetic particles. So, during the past two decades, NASA has launched a series of spacecraft designed to keep tabs on the Sun and the "space weather" it creates.

Locations of Stereo A and B on November 21, 2014

NASA's Stereo A and B spacecraft circle the Sun in orbits very similar to Earth's. This plot shows their location on November 21, 2014.
NASA / JPL Horizons

Key to this plan is Stereo, the Solar Terrestrial Relations Observatory. Launched in 2006, Stereo A looped around the Moon and swung into a heliocentric orbit "ahead" of Earth, while Stereo B took up a solar orbit "behind" the Earth. They provide views of the Sun and its surroundings from angles we can't see.

Both Stereo craft have drifted to the far side of the Sun, meaning that their dish-shaped radio antennas must point near the Sun to communicate with Earth. To protect these from overheating, mission controllers devised a plan to point each craft away from the Sun (and Earth) and to put it in safe-mode hibernation for about a year.

Tests of these new procedures took place over the past few months. Stereo A checked out fine and began its "time out" on August 20th. A month later engineers were completing Stereo B's final tests, which involved commanding the craft to go into its safe mode and then resume normal operations.Then something went wrong.

Stereo A and B before launch

Technicians prepare NASA's twin Solar Terrestrial Relations Observatory (Stereo) spacecraft prior to their 2006 launch.
NASA / JHU-APL

There's been no radio contact with the Stereo B spacecraft since October 1st, the day it was supposed to "wake up". Its radio signal came in weakly and then quickly faded away. Up to that point, telemetry showed no indication that anything was amiss.

But now it appears that the spacecraft suffered a double whammy: first the star tracker could not lock onto its correct guide stars, and then a laser gyro in Stereo B's Inertial Measurement Unit, which senses the craft's orientation, failed and started providing bad data to the attitude-control system.

The upshot is that there's no way to know exactly where Stereo B is pointed or the state of its systems. Over the past few weeks, astronomers have been borrowing the giant, 100-meter-wide Green Bank Telescope to try to detect the spacecraft's radio signal, so far without success. The 70-m dishes of NASA's Deep Space Network are also trying to reestablish contact.

Stereo A image of the Sun

Even though contact with its twin has been lost, Stereo A continues to supply solar researchers with images of the Sun from it unique orbital perspective.
NASA / Goddard Space Flight Center

All hope is not lost. In 1998, the Solar and Heliospheric Observatory also went AWOL, putting itself in a slow spin with its solar-cell arrays pointed away from the Sun. Eventually, orbital geometry provided enough sunlight on the arrays, and enough electricity, to power the craft, and mission controllers eventually regained control. That was 16 years ago, and SOHO continues to provide daily images of the Sun and its surrounding.

But, at this point, recovery options are few. According to Joseph Gurman, Stereo project scientist at NASA's Goddard Space Flight Center, simulations are under way to deduce the spacecraft's attitude and roll rate based on the few final bits of telemetry received. NASA will then create a review board to brainstorm other recovery schemes — and to make sure this unexpected failure doesn't occur again In particular, they'll doublecheck the safe-mode programming of Stereo A, which will be out of contact with Earth for about four months beginning in March 2015.

Could Earth ever fall victim to a "solar superstorm"? Gets the odds of that happening — and the consequences if it does — in the February 2011 issue of Sky & Telescope.

The post Contact Lost with Sun-watching Stereo B appeared first on Sky & Telescope.

Categories: Astronomy Headlines

This Week’s Sky at a Glance, November 21–29

Fri, 11/21/2014 - 01:05
Some daily sky sights among the ever-changing Moon, planets, and stars.Moon and Mars in twilight, Nov. 24-26, 2014

Track the growth of the waxing crescent Moon as it passes Mars in the evening twilight. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times its actual apparent size.)

Friday, November 21

Does night already seem to be falling about as early as it ever will? You're right! We're still a whole month away from the winter solstice — but the Sun sets its earliest around December 7th, and right now it already sets within only about 5 minutes of that time (if you're near latitude 40° north). A surprising result of this: The Sun actually sets a trace earlier on Thanksgiving than on Christmas, even though Christmas is around solstice time.

This offset is made up for by the opposite happening at sunrise: the Sun doesn't come up its latest for the year until January 7th. You can blame the tilt of Earth's axis and the eccentricity of its orbit.

Saturday, November 22

High in the northeast, the W pattern of Cassiopeia stands on end as early as 6 p.m. now. Whenever this happens, the dim handle of the Little Dipper (far lower left of Cassiopeia) extends straight left from Polaris.

Algol in Perseus should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 11:50 p.m. EST (8:50 p.m. PST). Algol takes several hours to fade beforehand and to rebrighten after.

New Moon (exact at 7:32 a.m. EST).

Sunday, November 23

We're two thirds of the way through fall, so Capella shines well up in the northeast as soon as the stars come out. As night grows darker, look to its right by about three fists at arm's length for the frosty little Pleiades cluster, the size of your fingertip at arm's length.

Monday, November 24

With the waxing Moon still thin, plan some deep-sky observing while the evenings are still dark! Around the spilling water bucket of Aquarius are the Helix Nebula, the R Aquarii nebula, a little-known globular cluster, and some galaxies in the 11th- and 12th-magnitude range — as told in depth by Sue French in her Deep-Sky Wonders column in the November Sky & Telescope, page 56, with map and photos.

Tuesday, November 25

Look for Mars left of the crescent Moon in twilight, as shown above.

Algol is at minimum light for a couple hours centered on 8:39 p.m. EST.

Wednesday, November 26

The Moon now shines near Alpha and Beta Capricorni at nightfall, as shown above (depending on your location). Both Alpha and Beta Cap are wide double stars for binoculars. Alpha is easy to resolve; Beta is somewhat less so with its narrower separation and greater brightness difference.

It's still Summer Triangle season. The Triangle's brightest star is Vega, well up in the west-northwest after dinnertime. The brightest star above Vega is Deneb. The Triangle's third star, Altair, is farther to Vega's left.

Thursday, November 27

Whenever Fomalhaut is "southing" (crossing the meridian due south, which it does around 6 or 7 p.m. this week), you know that the first stars of Orion are just about to rise in the east, and the Pointers of the Big Dipper stand directly below Polaris (if you're in the world's mid-northern latitudes).

Friday, November 28

First-quarter Moon (exactly so at 5:06 a.m. Saturday morning EST). Look for Fomalhaut far to its lower left, and Enif, the nose of Pegasus, almost as far to the Moon's upper right.

Saturday, November 29

The Moon stands high in the south soon after nightfall, with the western side of the Great Square of Pegasus pointing down at it from above.

By 10 or 11 p.m. now (depending in how far east or west you live in your time zone), the dim Little Dipper hangs straight down from Polaris.

________________________________

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. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Pocket Sky Atlas

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's still less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, 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, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

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 (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). 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 RoundupJupiter with Red Spot on Nov. 8, 2014

Jupiter is always changing. Here it is on November 8th. . .

Jupiter on Nov. 18, 2014

. . . and 10 days later. South here is up. I've never seen the Great Red Spot looking like this: with a dark rim looping up from the Red Spot Hollow and curling all the way around the Red Spot's following end. Note how much its shape changed in 10 days. South of the Red Spot, in the South Temperate Belt, are gray-rimmed Red Spot Junior (Oval BA) and a run of smaller white ovals. Images by Christopher Go.

Mercury is disappearing deep into the glow of sunrise.

Venus is still buried deep the sunset.

Mars (magnitude 1.0) remains visible in the southwest during and after twilight. It sets around 8 p.m. local time.

Jupiter (magnitude –2.2, in western Leo) rises in the east-northeast around 10 or 11 p.m. About 45 minutes later, fainter Regulus (magnitude +1.4) rises below it. By dawn they shine high in the south, with Regulus now to Jupiter's left.

Saturn is hidden behind the glare of the Sun.

Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are high in the southeast and south, respectively, right after dark. They move westward as the evening progresses. You'll need binoculars or a small telescope and our finder charts for Uranus and Neptune.

__________________________

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 Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 hours.

"I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me."

— Isaac Newton, 1642–1727

(From the Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton, David Brewster, 1855)

The post This Week’s Sky at a Glance, November 21–29 appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Dark Matter at Long Last? Three New Experiments Ramp Up

Wed, 11/19/2014 - 19:17

Three astrophysicists discuss preparations for three recently funded dark matter experiments, and the likelihood that one of them will strike gold.

Courtesy of The Kavli Foundation, Sky & Telescope is featuring an in-depth Q&A between Kavli and three astrophysicsts involved in three different searches for dark matter. Watch the live Q&A and read the transcript of an earlier roundtable discussion below.

(And for Sky & Telescope's take on the dark debate, check out our January 2013 cover story, Closing in On Dark Matter.)

Live Q&A: Dark Matter At Long Last? Three New Experiments Ramp Up

On November 20th, from 12:00pm - 12:30pm PST, Enectali Figueroa-Feliciano (MIT), Harry Nelson (University of California, Santa Barbara), and Gray Rybka (University of Washington) debate how close we are to identifying dark matter, discuss the status of their experiments, and answer your questions.

Submit questions ahead of and during the webcast by emailing info@kavlifoundation.org or by using the hashtag #KavliLive on Twitter or Google+, and watch the Q&A below:

Earlier Q&A: New Dark Matter Experiments Prepare to Hunt the Unknown

In an earlier discussion, Enectali Figueroa-Feliciano, Harry Nelson and Gray Rybka talked about preparations for their upcoming dark matter experiments.

Three new experiments are taking significant steps in the hunt for dark matter, the elusive substance that appears to make up more than a quarter of the universe, but interacts very rarely with the matter that makes up our world. The experiments – the Axion Dark Matter eXperiment (ADMX) Gen 2, LUX-ZEPLIN (LZ)and the Super Cryogenic Dark Matter Search (SuperCDMS) at SNOLAB – learned in July that each would receive much needed funding from the U.S. Department of Energy and the U.S. National Science Foundation. Each of these second-generation experiments will be at least 10 times more sensitive than today’s dark matter detectors, increasing the likelihood that they will see the small, rare interactions between dark matter and the regular matter we all interact with every day.

As the experimental plans start to coalesce and detector equipment starts to arrive for ADMX Gen2, LZ and SuperCDMS SNOLAB, three scientists discuss the likelihood that these projects will at long last discover dark matter. The participants:

The following is an edited transcript of their roundtable discussion. The participants have been provided the opportunity to amend or edit their remarks.

THE KAVLI FOUNDATION: We know that dark matter is five times more prevalent than ordinary matter, and we're able to infer that clumps of dark matter help hold together clusters of galaxies. So this substance is a huge part of what makes up our universe and an important part of why our universe looks the way it does. Why, then, haven't we been able to observe it directly? What's holding us back?

HARRY NELSON: A big part of the challenge is that dark matter doesn't interact with us very much. We know that dark matter is passing through our galaxy all the time, but it doesn't disrupt the type of matter we're made of.

But more than that, dark matter doesn't interact with itself very much either. The matter that we see around us every day interacts with itself: Atoms form molecules, the molecules form dirt, and the dirt forms planets. But that's not the case with dark matter. Dark matter is widely dispersed, and doesn't form dense objects like we're used to. That, combined with the fact that it doesn't interact with our type of matter very often, makes it hard to detect.

ENECTALI FIGUEROA-FELICIANO: What Harry says is exactly right. In my mind, nature is being coy. There's something we just don't understand about the internal structure of how the universe works. When theorists write down all the ways dark matter might interact with our particles, they find, for the simplest models, that we should have seen it already. So even though we haven't found it yet, there's a message there, one that we're trying to decode now.

Gray Rybka

Gray Rybka leads the ADMX Gen 2 experiment as a co-spokesperson and is a research assistant professor of physics at the University of Washington.

TKF: In fact, nature is being so coy that we don't yet even know what dark matter particles look like. Gray, your experiment – ADMX – looks for a different particle altogether than the one that Tali and Harry look for. Why is that?

GRAY RYBKA: As you say, my project — the Axion Dark Matter eXperiment, or ADMX —searches for a theoretical type of dark matter particle called the axion, which is extremely lightweight with neither electric charge nor spin. Harry and Tali look for a different type of dark matter called the WIMP, for Weakly Interacting Massive Particle, which describes a number of theorized particles that interact with our world very weakly and very rarely.

Both the WIMP and the axion are really good dark matter candidates. They're especially great because they would explain both dark matter and other mysteries of physics at the same time. I suppose I like the axion because there aren't a lot of experiments looking for it. If I'm going to gamble and spend a lot of time making an experiment to look for something, I don't want to look for something that everyone else is looking for.

We've been updating the ADMX experiment since 2010 and have demonstrated that we have the tools necessary to see axions if they are out there. ADMX is a scanning experiment, where we scan the various masses this axion could have, one at a time. How fast we scan depends on how cold we can make the experiment. With Gen2, we're buying a very, very powerful refrigerator that will arrive next month. Once it arrives, we'll be able to scan very, very quickly and we feel we'll have a much better chance of finding axions – if they're out there.

TKF: And, Harry, why do you bet on the WIMP?

Harry Nelson

Harry Nelson leads the LUX-ZEPLIN experiment and is a professor of physics at the University of California, Santa Barbara. (Image: Sonia Fernandez/UCSB)

NELSON: Even though I'm betting on WIMPs, I like axions too. I even wrote some papers on axions way back when. But these days, as Gray said, I look for WIMPs. My collaboration is currently operating the Large Underground Xenon, or LUX, experiment in the famous Black Hills of South Dakota, inside a mine that was the outgrowth of the 1876 gold rush that formed the city Deadwood. This month, we start our 12-month run with LUX. We're also now carefully developing our plans to upgrade our detector to make it more than 100 times more sensitive for the new LUX-ZEPLIN project.

But to tell you the truth, I actually have a little bit of the attitude that all of these possibilities are unlikely. I'm not saying that hunting for them is worthless; that's not it at all. It's just that nature doesn't have to respect what physicists want. We desire to better understand our own strong interaction, the mechanism responsible for the strong nuclear force which holds the atomic nucleus together. The axion would help do that.

The WIMP is great because it's consistent with the physics of the Big Bang in a straightforward way. A lot of science is based on what's called Occam's razor: We make the simplest possible assumptions and then test them very well, and only give up simplicity if we absolutely need to. I've always felt that the WIMP is a tiny bit simpler than the axion. Both are unlikely, but are still the best candidates we can think of. It's probably more likely that dark matter is somewhat different than either the WIMP or the axion, but we must start somewhere and the WIMP and axion are the best starting points we can imagine.

TKF: If you think it's unlikely that the WIMP is out there, why do you look for it?

NELSON: The WIMP and axion have the absolute best theoretical motivations. And so it's great that both WIMPs and axions have really strong experiments going after them.

Tali Figueroa-Feliciano

Enectali (Tali) Figueroa-Feliciano is a member of the SuperCDMS collaboration and an associate professor of physics at the MIT Kavli Institute for Astrophysics and Space Research.

FIGUEROA-FELICIANO: As an experimentalist, I come at this from the point of view that theorists are very clever, and have come up with an incredible array of possible scenarios for what dark matter could be. And, as Harry said, we attempt to use Occam's razor to try to weed out which of these things are more probable than the others. But that's not an infallible way to go about it. Dark matter might not follow the simplest explanation possible. So we have to be a little agnostic about it.

In a way it's like looking for gold. Harry has his pan and he's looking for gold in a deep pond, and we're looking in a slightly shallower pond, and Gray's a little upstream, looking in his own spot. We don't know who's going to find gold because we don't know where it is.

That said, I think it's really important to stress how complementary these three searches are. Together, we look in a lot of the places where dark matter could be. But we certainly don't cover all of the options. As Harry says, it could be that dark matter is there, but our three experiments will never see anything because we're looking in the wrong place – it could be in another fork of the river, where we haven't even started looking yet.

RYBKA: I look at it a bit more optimistically. Although as Tali said all the experiments could be looking in entirely the wrong place, it's also possible that they'll all find dark matter. There's nothing that would require dark matter to be made of just one type of particle except us hoping that it's that simple. Dark matter could be one-third axions, one-third heavy WIMPs and one-third light WIMPs. That would be perfectly allowable from everything we've seen.

FIGUEROA-FELICIANO: I agree. I should have said that the gold nugget we're looking for is a very valuable one. So even though the search is hard, it's worthwhile because we're looking for a very valuable thing: to understand what dark matter is made of and to discover a new part of our universe. There's a very beautiful prize at the end of this search, so it's absolutely worthwhile.

Dark matter in galaxy cluster

The inferred distribution of dark matter is superimposed in purple over this Hubble Space Telescope image of galaxy cluster Abell 1689.
NASA / ESA / E. Jullo (JPL/LAM) / P. Natarajan (Yale) / J-P. Kneib (LAM)

TKF: Tali, tell us a little about the pond where you're panning for that very valuable nugget of dark matter.

FIGUEROA-FELICIANO: My experiment is currently running in Soudan, Minnesota, inside a mine that's a bit over half a kilometer (at 2,341 feet) underground. This experiment, called SuperCDMS Soudan, was designed to demonstrate a new technology we've been developing that allows us to search for WIMPs that are on the lighter-mass side. It turns out that certain classes of WIMPs, ones that are lighter than Harry searches for, deposit very little energy into detectors. Our detectors are able to distinguish very small amounts of energy deposited in the detector from all the many different signals that we get from radioactive materials, cosmic rays, and all sorts of other things that stream though our detectors. Being able to make that separation is very important, both for SuperCDMS and for LZ.

The next step for our experiment is called SuperCDMS SNOLAB. SNOLAB is a nickel mine in Canada that's 2 kilometers (6,531 feet) deep. We've been approved to build a brand new experiment down there to search for these low-mass WIMPs. Also, if LUX or LZ sees a higher mass WIMP, we'll be able to check that measurement. Right now, we're in the process of finalizing the design and taking the first steps of putting this brand-new SNOLAB experiment together. We expect to have a first phase of detectors in the next couple of years.

TKF: If one of your experiments finds evidence of dark matter, after the celebratory champagne, what would be the next steps?

LUX

LUX physicist Jeremy Mock inspected the LUX detector before the large tank was filled with more than 70,000 gallons of ultra pure water. The water shields the detector from background radiation.
Matt Kapust / Sanford Underground Research Facility

RYBKA: Bottle it and sell it, I guess! But really, I'd say that all of the experiments would need to keep going even after such a discovery, until someone could conclusively prove that the discovered dark matter makes up 100 percent of all the dark matter in the universe.

NELSON: I would agree with that. We would also need to dig in and really try to understand what we discovered. There's an old saying in particle physics that you haven't discovered a particle until you know its mass, spin and parity, a property that's important in the quantum-mechanical description of a physical system. To really discover dark matter, we'll need to prove that it's what we think it is, and we'll need to learn its characteristics. After you discover a particle, everyone gets a lot smarter at what to do with it. This has been going on with the Higgs boson lately. Folks at the Large Hadron Collider are getting cleverer because now that they've seen the particle, they can focus on interrogating it.

When we start to do that with dark matter, we're going to see something new. That's just how scientific progress works. Right now, we can't see through the wall because we haven't figured out what the wall is made of. But once we understand what's in the wall – my analogy for dark matter – we'll see through it and see to the next thing.

FIGUEROA-FELICIANO: Let me add my two cents to that. There are three different things that I think would happen if one of our experiments saw convincing evidence for dark matter. First, we would want to confirm the discovery using a different technique. In other words, we will want as much confirmation as we can before we declare victory.

SuperCDMS

The SuperCDMS experiment at the Soudan Underground Laboratory uses five towers like the one shown here to search for WIMP dark matter particles.
SuperCDMS Soudan collaboration

Then, people will come up with 100 different ways to test the particle's properties, as Harry described. After that, a phase of "dark matter astronomy" will help us learn the particle's role in the universe. We'll want to measure how fast it's going, how much of it there is, how it behaves in a galaxy.

TKF: There's clearly a lot to be done once we find even just one type of dark matter particle. But it sounds like there could be a whole new zoo of dark particles. Do you think we're going to need a "Dark Standard Model"?

NELSON: I've often had the following thought: Here we are, in our measly 15 percent of the matter in the universe, wondering what dark matter is. If dark matter is as complex as we are, it might not even know that we exist. We're just this minority 15 percent, but somehow we think we're so important. But experiments undertaken by dark matter might not even know that we exist because we're a much smaller perturbation on dark matter's world than dark matter is on us.

The dark matter sector may be as complex – or perhaps even five times as complex – as ours. Just as we're made mostly of atoms made up of electrons and nuclei, maybe dark matter is too. In some of the searches for WIMPs, you have to be careful about that. It may be that the way these things interact with our matter is rather different than the simplest possible case that we're looking for.

ADMX

Physicists Gray Rybka (left) and Leslie Rosenberg examine ADMX's primary components.
Mary Levin / University of Washington

FIGUEROA-FELICIANO:  Harry, if you were to apply Occam's razor to our universe, how does it fare with the Standard Model?

NELSON: Well, it doesn't do very well. The Standard Model is a lot more complex than it needs to be. So maybe the same is true for dark matter. Maybe there are even dark photons out there. The idea is interesting. With ADMX, Gray is looking for a particle that has to do with the strong interaction. Tali and I are looking for a particle that has to do with the weak interaction. And searches for the dark photon look for a relationship between the electromagnetic interaction and the dark matter sector.

The community really wants to figure out dark matter. There's a feeling of urgency about it, and we'll look for it in all the ways that we can.

RYBKA: It's true. With ADMX, we're mostly focused on the axion, but we also look for dark photons at the lower masses. There are the dark matter candidates that people are really, really excited about, like axions and WIMPs. Those get experiments built that are dedicated to them. And then there are the ideas that might be good but don't have quite as much motivation, like dark photons. People still look for ways to test those ideas, often with existing experiments.

TKF: It's clear there are a wide variety of places where we could find dark matter. We're panning for this gold wherever we can, but we're not entirely sure that it exists anywhere we're looking. What's it like searching for something that you might never find?

FIGUEROA-FELICIANO: I think that the people who work on dark matter have a certain personality, a bit of a gambler's streak. We go for the high stakes, putting all the chips in. There are other areas of physics where we would be sure to see something. Instead, we choose to look for something that we might not actually see. If we do see it, though, it's a huge deal.

We're extremely lucky that we actually get paid to try to figure out what the universe is made of. That's an incredibly wonderful thing.

NELSON: Sometimes I think of what it must have been like to be Columbus and his crew, or the explorers who first went to the Earth's poles. They were way out in the middle of the ocean, or in the ice, not quite sure what would come next. But they had set goals: India and China for Columbus, the poles for those explorers. We're explorers too, we set goals for ourselves too, to seek certain pre-defined sensitivities to dark matter. We're innovating with modern technology to reach our specific goals. And we may make it the New World or the North Pole, and that's wonderfully exciting.

— Kelen Tuttle (Fall 2014)

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Categories: Astronomy Headlines

Dark Galaxies Discovered in Coma Cluster

Wed, 11/19/2014 - 08:03

A bizarre set of galaxies in the Coma Cluster have lost most of their stars (or star-making material), making them especially rich in dark matter.

Coma Cluster

Coma Cluster
Adam Block / Mount Lemmon SkyCenter / University of Arizona

The Coma Cluster, visible in the evening skies of spring and summer, reveals its jewel box to large backyard telescopes: several thousand galaxies sardine-packed into a space only 20 million light-years across.

But there’s more to the Coma Cluster than meets the eye — or the backyard telescope.

Pieter van Dokkum (Yale University) and colleagues took a unique look at Coma through the Dragonfly Telephoto Array, eight Canon cameras armed with telephoto lenses. The Dragonfly is designed to find faint, fuzzy blobs, but what its images revealed surprised the team.

On Coma’s outskirts lurk 47 galaxies similar in size to the Milky Way — but with 1,000 times fewer stars. To survive in crowded Coma, these dark galaxies must contain 98% dark matter to hold themselves together, much higher than the fraction in the universe at large (73%).

Near or Far?Serendipitous Hubble image of "dark galaxy"

Hubble imaging picked up one of the dark galaxies serendipitously. The galaxy's smattering of red stars is barely visible against the backdrop. Click the image for a size comparison to several well known galaxies, if they were at the same distance in the Coma Cluster.
Pieter van Dokkum & others

The galaxies' size depends on their distance, so to make sure this result wasn’t just a trick of perspective, van Dokkum and colleagues had to make sure these galaxies really belonged to the Coma cluster, more than 300 million light-years away. If they turned out to live nearby, the galaxies' size would be akin to regular ol' dwarf galaxies.

Determining cluster membership was a challenge because the objects are far too faint to study in the usual ways, such as taking a spectrum to determine their distance. Nonetheless, “van Dokkum and his co-authors make quite a convincing case,” says Mark den Brok (University of Utah).

The authors initially expected the galaxies to be distributed randomly, as they would be if they lay in the foreground near the Milky Way. Instead, the galaxies cluster around the center of the image in the cluster’s periphery. The discovery of a serendipitous Hubble image of one of the galaxies strengthened the team’s case, den Brok says, definitively showing that it doesn’t have the traits of a nearby dwarf galaxy.

Starless GalaxiesDragonfly Telephoto Array

The Dragonfly Telephoto Array contains eight Canon cameras armed with telephoto lenses. The array is designed to image low surface brightness objects.
Dunlap Institute for Astronomy & Astrophysics / University of Toronto

Somehow these weirdly faint galaxies have lost their stars — or they never had many stars in the first place. Van Dokkum and colleagues suggest that these may be “failed” galaxies, having forfeited most of their star-building gas after hosting a first generation of stars.

Simulations that track the evolution of large-scale structure suggest that even normal galaxies start out with three times more star-building material than they develop into stars. So whatever process works to limit star formation in normal galaxies is working particularly well in these dark matter-rich galaxies.

“Our simulations have shown that one way to limit star formation so drastically is to use the energy stars produce when they blow up as supernovae,” says Greg Stinson (Max Planck Institute for Astronomy, Germany). “It turns out that this disruption leads directly to galaxies that look like the ones van Dokkum is seeing.”

“I was actually very much relieved to see Prof. van Dokkum’s paper,” Stinson adds. Dark matter simulations have been producing galaxies with exactly the size and matter distribution that van Dokkum’s team observed, but such galaxies are naturally difficult to observe.

It’s ironic that dark matter-rich galaxies were discovered in Coma, the birthplace of dark matter theory. Observations of the same cluster in 1933 helped Fritz Zwicky (Caltech) first conceive of the invisible matter that shapes the large-scale structure of the universe. Now ever-deeper observations continue to help astronomers understand dark matter’s role in galaxy evolution.

Reference:
Pieter van Dokkum et al. "Forty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster." Astrophysical Journal Letters, submitted.

Dark matter is one of the universe's great unknowns. Find out what else we don't know in our special publication, Astronomy's 60 Greatest Mysteries.

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Categories: Astronomy Headlines

When Algol Winks, Will You Wink Back?

Wed, 11/19/2014 - 07:55

The dark ways of Algol, the Demon Star, and what it can teach us about stellar evolution.

Algol comes from the Arabic  al-Ghul or "the ghoul"

Algol (Beta Persei) in the constellation Perseus is not only easy to see, but fun to watch during eclipse.
Bob King

What if I told you that you could stand in your front yard and watch one star eclipse another 93 light-years away from Earth with nothing but your eyeballs? As improbable as it sounds, this sight is within easy reach of northern hemisphere skywatchers once or twice a month throughout fall and winter.

Algol, nicknamed the Demon Star, resides in the constellation Perseus directly below the "W" of Cassiopeia. The name derives from Arabic "Al-Ghul," (ghoul) and may hint at its then-mysterious habit of fading away and returning to normal brightness in a matter of hours. We now understand that this evil-spirited behavior can be blamed on Algol B, its dimmer companion star. Every 2.87 days, Algol B partially eclipses the hotter and brighter Algol A. Astronomers refer to this pair as an eclipsing binary.

Not just a model, Algol's for real

The stars Algol A (center) and Algol B photographed with Georgia State University's Center for High Angular Resolution Astronomy (CHARA) interferometric array on Mount Wilson, California. The larger, fainter B star swings in front of and then behind the primary in the sequence. Click to animate.
CHARA

During eclipse, Algol fades from magnitude +2.1 (as bright as one of the Big Dipper stars) to +3.4, then returns to its original brightness. The change is dramatic, looking as if the star might disappear altogether. But as surely as the Moon releases its hold on the Sun during a solar eclipse, Algol A and B dance about their center of gravity until the primary star returns to its previous brightness. The entire cycle takes about ten hours.

Over the next week, North American observers will have a pair of opportunities to watch this ballet of suns.

 Stellarium

Finding Algol is easy. This map shows the sky facing northeast around 7 p.m. local time in late November. Locate the bright star Capella in Auriga and the Pleiades, or Seven Sisters, star cluster. They form a triangle with Perseus' brightest star, Mirfak. Algol lies just a few degrees to the right, or south, of Mirfak. Star magnitudes are shown so you can track Algol's through its cycle as it fades from magnitude +2.1 to +3.4.
Source: Stellarium

On Saturday evening, November 22, 2014, Algol reaches minimum brightness around 10:50 p.m. (CST), presenting a fine opportunity to catch the downward half of its cycle from maximum to minimum brightness. Then on Tuesday, November 25th, Algol bottoms out again, this time at 7:39 p.m. (CST). In the eastern half of the country, Algol becomes visible at the end of twilight near minimum and spends the rest of the evening rising back to maximum. West Coast observers will be able to see nearly an entire cycle, assuming they're patient enough!

The next easily observed Algol eclipse series will occur on December 13, 15 and 18, 2014. No matter where you live, you can find out when the next eclipse occurs by visiting the Sky and Telescope Minima of Algol site. It automatically detects your time zone, so all you have to do is press the "Initialize to Today" button for a list. How easy is that?

Clockwork eclipses every 2.87 days

Here's what an eclipse would look like if you could see it up close. The main eclipse (at right) occurs when the larger but dimmer companion star, a K2 orange subgiant, partially eclipses Algol A, a more massive but smaller main sequence star. A small secondary eclipse (left) is observed when the B star passes around the back of the primary.
Mike Guidry / Univ. of Tennessee

The Algol system is three-star system: Algol A, a hot, brilliant B-class star; its eclipse buddy, Algol B, a larger though fainter, orange subgiant; and Algol C, a much fainter star that orbits the AB pair every 1.86 years. Because the orbit of the two stars lies in Earth's line of sight, B glides over A like clockwork every 2 days, 20 hours and 49 minutes. Between the deep "primary" eclipses, there's a smaller dip of 1/10 magnitude when the bright star partially eclipses its companion.

To witness an eclipse, you don't have to spend ten hours in the cold. Algol remains at or near minimum for about two hours centered on the time of mid-eclipse. That means you can catch it near maximum about two hours before or after the time of minimum. For many amateurs, that's a typical observing session at the telescope, but there's an even easier way. Just step outside and note Algol's brightness at or well before minimum. Return a couple hours later for another look. I think you'll be amazed at the difference.

Goodricke was a keen observer of variable stars

John Goodricke, an English amateur astronomer, was the first person to time the regular period of Algol's eclipses.
Sky and Telescope / Royal Astronomical Society

Although Algol's variability may have been noticed by earlier generations of skywatchers, it was formally discovered in 1667 by the Italian astronomer Geminiano Montanari. It took another 115 years for anyone to notice its regular cycle. The young English observer, John Goodricke, working closely with his neighbor Edward Pigott, discovered Algol's steady heartbeat in 1782-83.

Here's Goodricke's first impression of the star, penned in his journal on November 12, 1782, when he was only 18 years old: "This night I looked at Beta Persei (Algol) and was much amazed to find its brightness altered... I observed it diligently for about an hour — I hardly believed that it changed its brightness because I never heard of any star varying so quickly in its brightness."

You'd think that after nearly 350 years of observation we'd know everything there is to know about the Algol system. Not quite. The more massive a star, the shorter its lifetime. Massive stars burn hotter and devour their fuel faster, evolving into giant stars.

Algol A, the primary star, is 3.7 times more massive than the Sun, while lightweight Algol B boasts only a mass of 0.81 solar. Yet as stars go, the primary is youthful, while its less massive companion is far older and more evolved. Astronomers call this the "Algol Paradox". The only good explanation for the disparity is that the companion star has somehow lost mass. Where did it go?

Artist conception of the eclipsing binary Algol. Gas is funneled from the companion to the smaller but more massive star. Bob King

Artist conception of the eclipsing binary Algol. Gas funnels from the companion to the smaller but more massive star, Algol A. Not to scale.
Bob King

The culprit appears to be Algol. The two stars orbit each other very closely, separated by only 4.65 million miles (7,484 million km). That's just 5% of the distance between Earth and Sun. Careful study of the stars' spectra reveal that the gravitational might of the more massive star draws a stream of matter from its hapless companion. The brighter Algol puts on pounds at Algol B's expense.

One might see a moral tale here of the mighty growing more powerful at the expense of the little guy. Sure, why not? But if that's the case, then every 2.87 days Algol gets its comeuppance when the little guy steps into the limelight and eclipses his captor.

It's remarkable how much we can see in a point of light on a dark night. Everything from eclipsing stars, to a young man's passion, to the battle of aging as played out by the stars. Next time, Algol winks at you, you can give it a knowing wink back.

Need help finding Algol? Use a Sky & Telescope Star Wheel!

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Categories: Astronomy Headlines

crescent NGC 6888

Wed, 11/19/2014 - 07:07

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Autumn Moonlight

Wed, 11/19/2014 - 07:07

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Orion party

Wed, 11/19/2014 - 07:07

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Categories: Astronomy Headlines

M13

Wed, 11/19/2014 - 07:02

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Categories: Astronomy Headlines

First Contact Polymer Solutions Optics Cleaner

Tue, 11/18/2014 - 08:00
Photonic Cleaning Technologies

P.O. Box 435, Platteville, WI 53818
608-467-5396; www.photoniccleaning.com

NPS_1stcontact3_200pxPhotonic Cleaning Technologies introduces First Contact Polymer Solutions ($110), which cleans your optical surfaces without leaving residue. Simply spray, brush, or pour the polymer solution on your telescope mirror or lens. Once dry, First Contact Polymer becomes a strong, flexible film that you can then peel off to remove any fingerprints, dust, pollen, or other contaminants without damaging delicate optical coatings. The Red First Contact Starter Kit includes a 15-millimeter bottle with applicator brush, one 29-ml dilution spray, two 29-ml refill bottles, and 30 peel tabs for removing the dried polymer film. See the manufacturer's website for larger quantities and other options.

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

Why is Jupiter’s Great Red Spot … Red?

Tue, 11/18/2014 - 07:23

Scientists think they've figured out what causes the mysterious ruddy coloring in the giant planet's enormous oval storm.

Jupiter's appearance in February 2014

Earlier this year, the Great Red Spot stood out prominently against Jupiter's bright zones and dark belts.
Damian Peach

When it comes to well-known planetary features, Jupiter's iconic Great Red Spot is near the top of everyone's list. It's truly enormous — much bigger than Earth — though its girth has shrunk over the past decade.

The Great Red Spot is as mysterious as it is majestic. Unlike hurricanes and cyclones on Earth, which come and go in a matter of days, this iconic oval has endured for centuries. Giovanni Battista Riccioli and Gian Domenico Cassini noted it during the mid-1600s, though it could well have existed well before then.

Astronomers have long pondered what causes the GRS to be so red — at least most of the time (the intensity of its hue changes, varying from a dark salmon to nearly white).

One important clue comes from the spot's overall structure and 5-day-long rotation. Unlike terrestrial hurricanes, which are low-pressure storms, the GRS is a high-pressure (anticyclonic) system that's much taller than the clouds surrounding it. The spot's cloudy interior is also relatively opaque, meaning whatever particles are coloring it must float near the top of this giant, buoyant bubble.

Cassini's infrared view of Jupiter

The Great Red Spot's appearance at three infrared wavelengths, as recorded by Cassini in 2000, provides important clues to the big storm's characteristics.
NASA / JPL / K. Baines

For decades atmospheric chemists believed that the spot was tinted with phosphine (PH3), an unusual compound found in the Jovian atmosphere. But more recently attention has focused on sulfur and its colorful allotropes. One of Jupiter's three dense cloud layers consists of ammonium hydrosulfide (NH4SH), which, the thinking goes, could be dredged up by atmospheric convection and broken down by sunlight to form elemental sulfur.

That's what Kevin Baines, Robert Carlson, and Thomas Momary (all at the Jet Propulsion Laboratory) had in mind when they began laboratory experiments to try to replicate the coloring process. Carlson irradiated ammonium hydrosulfide with ultraviolet light, to mimic sunlight. But the resulting compounds were bright green, not red!

So the researchers instead tried irradiating a mixture of ammonia (NH3) and acetylene (C2H2), both of which exist in Jupiter's upper atmosphere. The result was a red concoction of cyanide-like molecules with the general formula HxCyNz where x, y, and z vary. Better still, the reddish particles have a spectrum that closely matches what NASA's Cassini spacecraft recorded inside the Great Red Spot when it swept by Jupiter in late 2000 while en route to Saturn.

Baines, Carlson, and Momary find that the best match involves particles just 400 nanometers across (the wavelength of blue light) thinly scattered in a layer only a few kilometers thick. The stuff looks red because it absorbs blue light strongly. "The model that fits is basically a 'crème brûlée' or 'strawberry-frosted cake' model," Baines explains, with a narrow layer of reddish material on top of the main, whitish cloud layer. So beneath its reddish veneer, created at a pressure level of roughly 300 millibars, the Great Red Spot would actually look rather bland.

Cassini's view of Great Red Spot

NASA's Cassini spacecraft captured the complex circulation inside the Great Red Spot when it swept past Jupiter (en route to Saturn) on December 29, 2000.
NASA / JPL / Space Science Inst.

The spot's rotation isolates and confines the atmospheric gases inside it, allowing these reddish colorants (impress your friends: they're technically called chromophores) to accumulate. "The GRS acts as a cauldron," Baines explains, "confining materials and letting them cook."

So why does the GRS's color vary so much over time? Apparently its hue depends on how much of ammonia and acetylene are present, their exact altitude, and how long they're exposed to sunlight. But the chemical conversion is rapid — Baines says they able to create the basic colors after just one day of "tanning" of the gas mixture in their lab tests.

The three researchers presented their findings Friday at the annual meeting of the American Astronomical Society's Division for Planetary Sciences. A full account has been submitted to Icarus, but you can also find details in this JPL press release.

Track down Jupiter and a host of other celestial sights with SkyWatch, our annual observing guide. Choose from the 2014 edition or the 2015 edition.

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Categories: Astronomy Headlines

Philae Wins Race to Return Comet Findings

Sat, 11/15/2014 - 08:15

With its battery power failing, Philae became the "little lander than could" and managed to return results from all 10 of its science instruments before slipping into hibernation.

If everything had gone according to a carefully constructed plan, the European Space Agency's Philae spacecraft would have descended from mother ship Rosetta, dropped onto its flat, wide-open landing site on Comet 67P/Churymov-Gerasimenko, relayed a rush of findings about the comet's structure and composition, and then basked in enough sunlight to continue operating for several weeks.

Philae's first bounce

Two images, taken 5 minutes apart, zero in on the spot where Philae touched down — and then bounced away — on the surface of Comet 67P/Churyumov-Gerasimenko. The landing occurred precisely where it should have, but a pair of anchoring harpoons failed to activate.
ESA / OSIRIS team

But space exploration is never easy, as engineers and scientists at ESA's control center in Darmstadt, Germany, learned this week.

Troubles began when Wednesday when the lander made a pinpoint landing on Agilkia, the Sun-drenched landing site on the "head" of the twin-lobed comet. But two systems designed to anchor the craft in the ultra-low gravity — a downward-pushing thruster and two harpoons — both failed. As a result, Philae bounced not once but twice, coming to rest hundreds of meters from its intended location.

Initial images returned to Earth showed the lander wedged in rugged terrain and deep in shadow from a nearby cliff, its legs angled awkwardly and canted some 30° from horizontal. And yet, the lander was undamaged by by this roller-coaster arrival, ending up with its radio antenna pointed skyward.

Side view of Philae lander

ESA's Philae lander is roughly the size of a washing machine and has a mass of about 215 pounds (98 kg).
ESA / ATG medialab

Getting Philae to perform as planned immediately became a race against time, made more intense because the windows of contact with Rosetta were intermittent. The lander's initial surface contact automatically triggered the start of data-gathering activities — yet for the next two hours Philae was airborne, making a 1-km-high arc above the nucleus. And the final, precarious perch made it risky to deploy the lander's mechanical probe, X-ray spectrometer, and sampling drill.

Worse, the clock was ticking. Philae was designed to complete its primary activities within 64 hours, using only the power from an on-board battery. Extended operations could follow if small solar-cell panels provided enough power. But the cliff's deep shadow exposed the landed only to 1½ hours of sunlight during the comet's 12.4-hour rotation, and some panels were pointed toward the cliff.

The Little Lander That Could

Back on Earth, the mission team worked frantically to send up new commands that would salvage as many of the scientific objectives as possible. The drama intensified the morning of November 14th when a communication session with Rosetta ended at 9:58 Universal Time, just as the drill was being deployed. Some feared the battery would die before contact could be reestablished 12 hour later.

Philae's first view from comet's surface

The first view of the comet's rugged surface (a composite of two frames) shows one of Philae's three landing legs at left.
ESA / CIVA team

But when Rosetta returned to view, radio contact resumed at 22:19 UT. Still alive, Philae immediately started relaying findings from all 10 of its instruments. Back on Earth, engineers watched helplessly as the battery voltage plummeted. The final measurements came from Ptolemy, an instrument designed to measure ratios of atomic isotopes. After 75 minutes, the transmission ended as Philae slipped into electronic hibernation.

During the frantic final communication session, the lander's various instrument groups provided moment-to-moment status in a flurry of tweets. A sample from the SD2 (drill) team: "Preliminary checks show we operated nominally, no time outs. Hopefully we caught the comet sample ever."

Although the lander operated for nearly 57 hours, short of the hoped-for duration, it managed to return all the results from its final sequence of measurements. There was even enough juice to rotate the lander's body about 35°, to reposition the solar-cell panels to receive more direct sunlight.

"It has been a huge success," exulted a weary Stephan Ulamec, lander manager for the German aerospace company DLR, which oversaw Philae's construction. "Despite the unplanned series of three touchdowns, all of our instruments could be operated and now it's time to see what we've got."

Conceivably, the lander will again receive enough sunlight — perhaps weeks or months from now as the comet's "seasons" change and the sunlight intensifies — to recharge its battery and return to operation.

Meanwhile, the team is is still searching for Philae's exact resting place. A sequence of high-resolution images from Rosetta were fixated on the planned landing location and missed the likely endpoint along the rim of a broad crater. For now, Rosetta has moved to a somewhat higher orbit, 20 miles (30 km) above the comet, but it will move in closer on December 6th. Until then engineers hope to use a series of radio transmissions from CONSERT, a radar sounder aboard the lander, to triangulate to the final location.

ESA managers have yet not announced when Philae's initial findings will be presented. For now they are no doubt catching up on lost sleep, happy that they've made the most of a bad situation — and, of course, having made the first-ever soft landing on a comet.

Read all about the Rosetta mission in Sky & Telescope's August issue.

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Categories: Astronomy Headlines

This Week’s Sky at a Glance, November 14 – 22

Fri, 11/14/2014 - 01:05
Some daily sky sights among the ever-changing Moon, planets, and stars.Mars in the southwestern twilight, Nov. 14, 2014

Spot Mars in the southwestern twilight.

The Moon with Jupiter and the Sickle of Leo in early dawn, Nov. 14-16, 2014.

In early dawn, the Moon guides the way to Jupiter and the Sickle of Leo. How late into the brightening daylight can you follow each?

Friday, November 14

Keep an eye on little Mars in the southwest at dusk. It will keep hanging in there month after month through this winter, as constellations of the zodiac slide behind it.

Last-quarter Moon (exact at 10:16 a.m. EST). The Moon rises around midnight tonight with Jupiter to its left (for North America.) By dawn Saturday morning the 15th, the Moon is below Regulus with Jupiter now high to their upper right, as shown below.

Saturday, November 15

By about 8 p.m. Orion is clearing the eastern horizon (depending on how far east or west you live in your time zone). High above Orion shines orange Aldebaran. Above Aldebaran is the little Pleiades cluster, the size of your fingertip at arm's length. Far left of the Pleiades shines bright Capella.

Sunday, November 16

By 8 p.m. now, Great Square of Pegasus stands in its level position very high toward the south. Its right side points far down toward Fomalhaut. Its left side points less far down more or less toward Beta Ceti.

If you have an open view to a dark south horizon, and if you're no farther north than roughly New York or Denver, picture an equilateral triangle with Fomalhaut and Beta Ceti forming its top two corners. Near where the third corner would be is Alpha Phoenicis, or Ankaa, in the southern constellation Phoenix. It's magnitude 2.4, not very bright but the brightest thing in the area. Have you ever seen a star of Phoenix before?

Monday, November 17

The Leonid meteor shower should peak late tonight, but don't expect much. Even under ideal dark-sky conditions, you might see roughly a dozen per hour during the best viewing period: from about midnight or 1 a.m. tonight until the beginning of dawn. Also, keep an eye out for the very occasional Taurid fireball. For more: See November's Speedy Leonids.

Tuesday, November 18

Very high now in the north, in the fall Milky Way, is dim Cepheus: husband in myth to brighter Cassiopeia. Its constellation pattern includes two landmark variable stars, Delta (δ) and Mu (μ) Cephei, for binoculars or even the naked eye. Delta is the prototype Cepheid. Mu is one of the largest stars known. See Gary Seronik's Binocular Highlight column and chart in the November Sky & Telescope, page 45.

Wednesday, November 19

It's still Summer Triangle season. The Triangle's brightest star is Vega, still well up in the west-northwest after dinnertime. The brightest above Vega is Deneb. The Triangle's third star, Altair, is farther to Vega's left.

Thursday, November 20

Whenever Fomalhaut is "southing" (crossing the meridian due south, which it does around 7 p.m. this week), you know that the first stars of Orion are just about to rise in the east, and the Pointers of the Big Dipper stand directly below Polaris. (If you're in the world's mid-northern latitudes).

Friday, November 21

Does it seem like night is already falling about as early as it ever will? You're right. We're still a whole month from the winter solstice (in the Northern Hemisphere), but the Sun sets earliest around December 7th, and right now it sets only about 5 minutes from that time (if you're near latitude 40° north). A surprising result of this: The Sun actually sets earlier on Thanksgiving than Christmas!

This odd offset is made up for by the opposite happening at sunrise: the Sun comes up latest for the year on January 7th.

Saturday, November 22

High in the northeast, the W pattern of Cassiopeia stands on end as early as 6 or 7 p.m. now. Whenever this happens, the dim handle of the Little Dipper (far lower left of Cassiopeia) extends straight left from Polaris.

Algol in Perseus should be at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for two hours centered on 11:50 p.m. EST (8:50 p.m. PST). Algol takes several hours to fade and brighten before and after.

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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. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Pocket Sky Atlas

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's still less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, 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, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

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 (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). 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 RoundupJupiter with Red Spot on Nov. 8, 2014

Jupiter is always changing, Here it is on November 8th, imaged by Christopher Go. South here is up. I've never the Great Red Spot looking like this: with a dark rim looping up from the Red Spot Hollow and curling all the way around the Red Spot's following end. To the upper left of the Red Spot, in the South Temperate Belt, are dark-rimmed Red Spot Junior (Oval BA) and a run of smaller white ovals.

Mercury (still magnitude –0.8) is sinking away low into the sunrise. Early in the week, look for it a little above the east-southeast horizon about 30 minutes before sunrise. Bring binoculars. Don't confuse it with fainter Spica increasingly far to its upper right, or with Arcturus farther to its upper left.

Venus is hidden deep the glow on sunset.

Mars (magnitude 1.0) remains in the southwest during and after twilight. It sets around 8 p.m. local time.

Jupiter (magnitude –2.1, in western Leo) rises in the east-northeast around 11 p.m. About 40 minutes later, Regulus (magnitude +1.4) rises below it. By dawn they shine high in the south, with Regulus now to Jupiter's left.

Saturn is hidden behind the glare of the Sun.

Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are high in the southeast and south, respectively, right after dark. They move westward as the evening progresses. Use our finder charts for Uranus and Neptune.

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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 Standard Time (EST) is Universal Time (UT, UTC, or GMT) minus 5 hours.

"I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me."

— Isaac Newton, 1642–1727

(From the Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton, David Brewster, 1855)

The post This Week’s Sky at a Glance, November 14 – 22 appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Tropical Moon.

Thu, 11/13/2014 - 06:15

The post Tropical Moon. appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Milky way over Gyirong Valley

Thu, 11/13/2014 - 06:15

The post Milky way over Gyirong Valley appeared first on Sky & Telescope.

Categories: Astronomy Headlines

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