Astronomy & Science

Near-Earth Asteroid Tally Reaches 15,000

Sky&Telescope -

Thanks to two aggressive search programs, the count of near-Earth asteroids has soared past the 15,000-object milestone.

On August 13, 1898, Carl Gustav Witt discovered a medium-size asteroid that circled the Sun much closer than its siblings did. In fact, what came to be called 433 Eros actually crosses the orbit of Mars during its 1.8-year solar circuit, and it can come as close to the Sun as 1.13 astronomical units (170 million kilometers).

From that modest beginning, the hunt for near-Earth asteroids (NEAs) — those that venture within 1.3 a.u. of the Sun — has evolved from sporadic, inadvertent pickups to dedicated searches that net hundreds of new objects every month.

Near-Earth asteroids as of November 2016

A plot of all known near-Earth asteroids (NEAs) looks scary, but the risk of collision is actually quite low.
Minor Planet Center

A week ago, the International Astronomical Union's Minor Planet Center (just a few blocks from Sky & Telescope's offices) announced the discovery of asteroid 2016 TB57. With that find, the MPC's catalog of all known NEAs reached a new threshold: 15,000.

Much like the steady climb of the stock market with time, there's no particular significance to a count of 15,000 (it's already zoomed to 15,197 as I write this) or to 2016 TB57. Observers participating in the NASA-funded Catalina Sky Survey discovered it on October 13th as it neared Earth. Rather small, roughly 15 to 35 m across, it passed by at a very safe distance of 2,010,000 km (more than five times the Moon's distance) on October 31st.

Most NEAs are found, as their name implies, someplace near Earth. Generally they're too small to be spotted far away, and it's only within the week or so when they skim near our planet that they make their existence know. These days almost all NEAs are swept up by the Catalina survey or by Pan-STARRS 1, a wide-field telescope on Haleakala in Hawai'i. (That name is a contraction of Panoramic Survey Telescope & Rapid Response System.)

Dynamicists break down NEAs into four types, each named for an archetype asteroid in that class. Amors (like Eros) cross the orbit of Mars but come no closer than 1.017 a.u. to the Sun (Earth's aphelion distance). Apollos have semimajor axes (their mean heliocentric distance) greater than 1.0 a.u. but still cross Earth's orbit at their closest. Atens have semimajor axes of less than 1 a.u. but likewise cross Earth's orbit (our planet's perihelion distance is 0.983 a.u.). At its most recent count, the MPC had tallied 6,537 Amors, 7,449 Apollos, and 1,120 Atens.

Apohele asteroids (sometimes called Atiras) are the newest and smallest group — only a dozen or so have been confirmed — and their entire orbits lie entirely inside of Earth's.

Eros seen close-up

NASA's NEAR-Shoemaker spacecraft recorded this view of its final destination, asteroid 433 Eros, on February 12, 2000.
NASA / JHU-APL

With all those space rocks flying around, you'd think that Earth might be in grave and imminent danger of a collision. But space is a big place, and neither NASA's Near-Earth Object Program nor its European Space Agency counterpart lists any object with a cumulative probability (that is, the risk over dozens of close approaches) lower than about 1 in 1,000. That dubious honor goes to the object 2011 AM37, and it's only about 4 m (15 feet) across — almost certainly too small make it through the atmosphere.

Meanwhile, 433 Eros has hardly been relegated to the back shelf of asteroid discoveries. A highly elongated body about 34 km long, Eros played host to NASA's NEAR-Shoemaker spacecraft, which orbited it for a year in 2000–01.

The post Near-Earth Asteroid Tally Reaches 15,000 appeared first on Sky & Telescope.

This Week’s Sky at a Glance, November 4 – 12

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Moon and Mars, Nov. 5-6, 2016

The waxing Moon passes over Mars Saturday and Sunday the 5th and 6th.

Friday, November 4

• As the stars come out, look off to the Moon's left or upper left for Mars, and high above the Moon for Altair. Deneb still remains near the zenith. Brighter Vega shines high in the west. And look for Arcturus twinkling ever lower toward the west-northwest horizon.

Saturday, November 5

• Mars shines orange to the left or lower of the Moon in early evening, as shown here. Mars is twice the Moon's diameter in reality, but as of tonight, it's 485 times farther away.

• After dark this week Capella calls attention in the northeast, and the Pleiades are well up in the east-northeast three fists to Capella's right. As evening grows later, you'll find orange Aldebaran climbing up below the Pleiades. Then by around 10 p.m. (depending on your location), Orion begins clearing the eastern horizon below Aldebaran.

• Daylight-saving time ends at 2 a.m. Sunday morning; standard time returns. Clocks fall back an hour. Remember when we adjusted them all by hand?

Sunday, November 6

• Now Mars is lower right of the thickening Moon in early evening, as shown above. And look closer to the Moon's upper right for Beta and then Alpha Capricorni. Alpha Cap is a naked-eye double star if you have sharp eyes. Binoculars split it widely — and may reveal Beta as a more difficult, uneven double.

Monday, November 7

• First-quarter Moon (exact at 2:51 p.m. EST). The Moon shines in the south at dusk, just above dim Capricornus. Mars is now far to its lower right. Altair is twice as far to the Moon's upper right.

Tuesday, November 8

• Now the Moon is in Aquarius. Look to the Moon's lower left for Fomalhaut, the Autumn Star, the lonely mouth of Piscis Austrinus the Southern Fish. Half as far above the Moon is the horizontal Water Jar asterism of Aquarius, fairly dim.

• Algol in Perseus shines at its minimum brightness, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 7:19 p.m. EST.

Wednesday, November 9

• Happy 82nd birthday, Carl Sagan (November 9, 1934 – December 20, 1996). If only.

Thursday, November 10

• Around 8 or 9 p.m., depending on where you live, zero-magnitude Capella rises exactly as high in the northeast as zero-magnitude Vega has sunk in the west-northwest.

Venus, Mars and Saturn, mid-November 2016

Can you still see Saturn? And in the coming weeks and months, watch Venus and Mars draw closer together.

Friday, November 11

• Saturn is falling ever farther away to the lower right of Venus at dusk, while far to the upper left of Venus, Mars is drawing closer to it very, very gradually. The scene above is exact for viewers at 40° north latitude. Far south or north of there, you'll see the view higher or lower and slightly tilted with respect to how it's drawn here.

• By about 8 p.m. now, 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.

Saturday, November 12

• The waxing gibbous Moon shines in the southeast this evening. Upper left of it by about 15° are the two or three leading stars of Aries. About the same distance lower left of the Moon is Menkar, Alpha Ceti, the only brightish star (magnitude 2.5) in Cetus's head.

_________________________

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 new Jumbo Edition for easier reading in the night. Click image for larger view.

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 new 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 Jupiter at dawn, Nov. 5, 2016

The week starts with Jupiter easily visible at dawn and Spica very low. . .

Jupiter at dawn, Nov. 12, 2016

. . .and ends with both of them higher. But Jupiter isn't quite keeping up with the stars; compare its position with faint Gamma (γ) Virginis (3rd magnitude) in the background.

Mercury is hidden in the glare of the Sun.

Venus (magnitude –4.0) shines brightly in the southwest during evening twilight. It's now setting a good half hour after the end of twilight.

Mars (magnitude +0.4) still glows in the south-southwest at dusk, about 35° upper left of Venus. In a telescope, Mars has shrunk to a mere 7 arcseconds in diameter.

Jupiter (magnitude –1.7) shines brightly in the east-southeast in early dawn. Look for Spica about 12° below it.

You might think this is a very poor time for seeking detail on Jupiter with a telescope. It's not only low but distant and small, a mere 32 arcseconds wide. But amateurs who are imaging Jupiter at every opportunity in support of NASA's Juno mission report that a predicted outbreak of storms in the North Temperate Belt has begun. See Jupiter Returns with a Stormy Surprise. Best viewing: early dawn, and continue watching until the sky grows too bright.

Saturn (magnitude +0.5) glimmers low in the southwest, to the right or lower right of Venus as twilight fades. It's 7° from Venus on November 4th and 11° from it a week later.

Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.9, in Aquarius) are high in the southeast and south, respectively, in early evening. Info and 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. Eastern Standard Time (EST) is UT minus 5 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

The post This Week’s Sky at a Glance, November 4 – 12 appeared first on Sky & Telescope.

S&T Webinar: Get Ready for 2017’s Total Solar Eclipse

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Mark your calendar for Wednesday, November 9th, when you'll get great background info and travel tips for America's coast-to-coast total solar eclipse.

2017 eclipse track with partial phases

The path of the Moon's shadow on August 21, 2017, will cut through or clip 14 states during its coast-to-coast crossing.
Michael Zeiler / GreatAmericanEclipse.com

Maybe you've always been curious about why everyone gets excited about total solar eclipses.

Maybe you're thinking about traveling to see the one next August 21st, but you're not sure where to go.

Maybe you'll be stuck at home but still want to enjoy views of that day's partial eclipse.

Whatever your motivation, join me next Wednesday, November 9th, at 2:00 p.m. EST (19:00 Universal Time) for a live, interactive webinar that'll give you the Why, What, Where, and How of the total solar eclipse that will cross the continental U.S. from Oregon to South Carolina next August 21st.

"But that's still more than 10 months away," some of you are saying to yourselves. That's true. But next year's eclipse is a bona fide Big Deal, and you're going to want to be part of it. It's already become an obsession with untold thousands of amateur astronomers around the world — all of whom are planning to be in the 70-mile-wide path of totality.

Total solar eclipse in 2010

The Sun's corona (tenuous atmosphere) displayed many delicate streamers during the total solar eclipse on July 11, 2010.
Sky & Telescope / Dennis Di Cicco

The buzz is totally justified. Few spectacles in nature are as dramatic as watching the Moon's silhouetted disk gradually slide across the Sun's disk and then cover it completely. Only during totality can you see the gossamer strands of the corona, the Sun's incandescent atmosphere, surrounding a black bullet hole in the sky where the Sun's disk ought to be.

It's been a long time coming. The Moon's full shadow hasn't passed over any U.S. soil since 1991 (Hawaii) nor across any part of the contiguous 48 states since 1979 (Pacific Northwest). Moreover, a total solar eclipse hasn't run coast to coast across the U.S. since 1918.

Because this eclipse occurs in America's backyard, you might be tempted just to pick a spot along the path of totality, fly to a nearby airport, and rent a car. That might work, but hotels in some well-positioned towns are already completely sold out. So if you want to stand in the Moon's shadow, start planning now!

What this Total Solar Eclipse Webinar Covers

To make that easier, my live hour-long webinar will provide a lively introduction to solar eclipses, past and future, and give you an opportunity to ask me questions about how best to observe the one next year. You'll learn:

• What causes solar eclipses
• Where the path of the Moon's shadow crosses the United States
• Which past eclipses crossed the U.S.
• How to view a solar eclipse safely
• What's the best strategy for finding a good viewing spot

. . . and plenty more. (Hint: you'll learn how to impress your friends with the word exeligmos.) Please note: This webinar will not cover specifics of how to photograph an eclipse — that's a topic for a future webinar. But if you're looking forward to enjoying this event and want some viewing help or travel tips, you'll get a lot out of this webinar.

Celebrating totality in 2009

I'm a happy guy after witnessing a total solar eclipse from a ship situated near Iwo Jima in 2009. Totality lasted 6m39s — the longest of any eclipse in the 21st century.
Cheryl Beatty

All you need is a computer or other device and an Internet connection. You’ll be able to view and hear my presentation live — and you'll get to ask questions too. If you can't join me live, the presentation will be archived so that you can download it later.

In case you're curious, I'm a veteran eclipse-chaser, having traveled to see 11 total and 6 annular eclipses. I've seen totality three times from aboard ship and three times from an airplane. These travels have taken me to Europe, Africa, Asia, and even over the North and South Poles!

So let me share my experiences — and experience — with you. Again, here's the signup link for the webinar.

The post S&T Webinar: Get Ready for 2017’s Total Solar Eclipse appeared first on Sky & Telescope.

The Merope Nebula and Its Well-Kept Secret

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Did you know that the brightest part of the Merope Nebula in the Pleiades is also the hardest to see? We'll make sense of this seeming contradiction while honing key observing skills.

Just Passing Through

The Pleiades reflection nebula, the brightest part of which surrounds the star Merope (lower center), is visible in 6-inch and larger telescopes.
Bob King

By November, the Pleiades star cluster has climbed high enough in the eastern sky to be noticed by even most casual observer. Also known as the Seven Sisters, this mini-dipper of fuzzy jewels, all moving together through space, is 444 light-years from Earth.

The cluster is dominated by hot, intermediate-aged blue stars that light up the surrounding dust as a reflection nebula. Not so long ago, it was thought that the cotton candy-like tufts of nebulosity were left over from the formation of the cluster, but the 100-million-year age of its members precludes this possibility; stars that "old" would have swept out any remaining embryonic dust long ago.

Instead, the Pleiades just happen to be passing through a dust-rich region of the interstellar medium as they make a beeline for Orion. Picture a flashlight beam moving through a fog of varying thickness, its light revealing textures and densities that change from moment to moment. In this new view of the Seven Sisters, we can imagine our distant descendants looking at a rather different nebula that the one we see.

Beacons in Interstellar Fog

The hot blue stars of the Pleiades star cluster happen to illuminate a large cloud of interstellar dust along the cluster's path. The group is moving toward the southeast at 5.5″ per century. Click for a large version.
Davide De Martin & the ESA / ESO / NASA Photoshop FITS Liberator

Visually, glare from all these gorgeous blue suns makes it difficult to tell the nebula from the oft-seen glowing aureoles around bright stars. And if your optics are dirty, it's even more challenging. But the Merope Nebula, the brightest and most extensive swish of glowing dust in the cluster, is visible in even a 6-inch telescope at low to medium magnification (25×–100×). Take care to place 4th-magnitude Merope just outside the field of view for the best view.

Merope Nebula - The Easy Part

The Merope Nebula has an attractive teardrop shape readily visible in a smaller instrument. Keep Merope (above center) out of the field of view. North is up.
Hap Griffin

I'm reminded of breath on a mirror when viewing the Merope Nebula. Maybe breath on the eyepiece paints a more accurate picture, since nights can be cold in November and observers must take care not to accidentally breathe on a lens! The larger your scope, the more obvious the nebula, but it's best on the low magnification end — an island of cosmic dust with Merope a beacon blazing along its northern shore.

Merope's Little Secret

Use this chart to help you pinpoint Barnard's Nebula about 30″ southeast of 4th-magnitude Merope. Field stars' magnitudes are shown with decimals omitted. Click for a larger version to print out for use at the telescope.
Map: Bob King, Source: Stellarium

Not to be confused with the larger, much easier to see Merope Nebula is her well-hidden sister, Barnard's Merope Nebula. This tiny 10″ patch was discovered by American astronomer Edward Emerson Barnard in 1890 using the 36-inch Lick refractor. Although 15 times brighter than the Merope Nebula proper, it's incredibly hard to spot in the fierce glare of nearby Merope, blazing only 36″ to the northwest. Here's what E. E. had to say when he first saw it:

Keen-eyed E.E.

E. E. Barnard

"... discovered a new comparatively bright, round cometary nebula close south and following Merope (23 Tauri) ... It is about 30″ in diameter, of the 13 (magnitude), gradually brighter in the middle, and very cometary in appearance."

He went on further to note that it was no surprise such a bright nebula hadn't been photographed before, since an exposure to capture the fainter parts of the Pleiades nebulosity would overexpose this nebular nubbin.

This object, also cataloged as IC 349, is one of the most challenging objects I've ever attempted to see. If it weren't for the glare of Merope, it would be far better known. In a wicked irony, the very thing that makes it the brightest part of the Pleiades nebula also thwarts its visibility.

Shredded by Merope

Compare the photo of IC 349 taken with the Hubble Space Telescope (left) to an image taken through an amateur telescope. The bizarre appearance of the nebula is cause by radiation pressure from Merope. Smaller particles pushed away by the pressure of starlight gather to the lower left, while larger particles point toward the star, which is moving toward the nebula. Click photo to see a larger Hubble image.
Left: NASA / ESA, Right: Volker Wendel, Josef Pöpsel, Stefan Binnewies: www.capella-observatory.com

On a recent night of above average seeing, I cranked up the magnification on my 15-inch Dob reflector to 428× to separate the nebula from the star as much as possible. Then I placed Merope just outside the field of view. After more than a half hour of averted vision viewing, during which time I repeatedly re-hid the drifting star, I strongly suspected a dab of nebulosity between Merope's flashing diffraction spikes and within its glowing aureole. The effort made me hungry enough to eat a steak. 

Simple Glare Blocker

To make an occulting bar, slice a narrow strip of aluminum foil and tape it over the field stop of an eyepiece. You may have to use a toothpick to bend / push the strip into the focal plane, so it comes to a sharp focus when viewed through the eye lens.
Bob King

At the next opportunity, I opted to use an occulting bar instead. I taped a thin strip of aluminum foil across the field stop of an old 12-mm Orthoscopic eyepiece and plunked it into a 2× Barlow for a magnification of 284×. After noting the direction of Merope's drift across the field, I aligned the opaque bar to hide the star and suppress its glare.

This is the preferred arrangement for spotting faint objects near bright ones. It works wonders when hunting the satellites of Uranus or attempting to see the white dwarf companion of Sirius.

Seeing wasn't nearly as good as the previous night's, but once again, I strongly suspected a cometary patch at the correct position. I've also attempted observations of the nebula in the past but never came away 100% convinced of seeing it. Until my suspicion becomes a confirmation, this tough nut will remain on my observing list!

Cosmic Filaments Reflecting Merope's Light

The main Merope Nebula resembles streaks of cirrus clouds crossing the sun in this close up view. The little blip sticking out below Merope is Barnard's Nebula, IC 349.
Hunter Wilson

Since visual observations are almost non-existent, I can't say what the minimum-size aperture would be required to see this mini-Merope but suspect that clean, well-collimated optics and steady seeing will play important roles in your attempt. I strongly encourage observers with 8-inch and larger scopes to try this one out. There's no better time than late fall and winter when the Pleiades extend an invite every moonless night.

The post The Merope Nebula and Its Well-Kept Secret appeared first on Sky & Telescope.

ALMA Images Spiral Disk Around Baby Stars

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Astronomers have imaged a third star embedded in the spiral disk around a pair of baby stars, the first direct evidence of a process of star formation known as disk fragmentation.

ALMA images three baby stars

ALMA image of the L1448 IRS3B system, where two young stars orbit each other at the center and a third orbits out in the dusty disk connected to the central pair by a long spiral arm. The spiral structure indicates instability in the disk, which led to the formation of third baby star.
Bill Saxton / ALMA (ESO / NAOJ / NRAO), NRAO / AUI / NSF

Our usual picture of star formation has stars condensing like droplets of rain out of their natal clouds of gas and dust. In fact, astronomers caught this process in action in the Perseus star-forming region a year ago.

But there’s more than one way to form a star.

Stars-to-be grow by gobbling gas in their vicinity. But if the disk that feeds a star grows big enough, the disk itself can wobble and collapse into a second star in a process known as disk fragmentation. Plenty of circumstantial evidence exists for this process, but astronomers have never actually seen it happen.

Until now. In a study published in the October 27th Nature, John Tobin (University of Oklahoma and Leiden University, The Netherlands) and colleagues have returned to Perseus with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the triple protostar system L1448 IRS3B. The scientists penetrated the thick shroud surrounding three protostars, imaging the disk that feeds them.

And to their surprise, they discovered that the third baby star — once thought to be the central player of the system — is actually nestled in a long spiral arm extending from the parent binary. The image is the first direct observational evidence that stars form by disk fragmentation.

Caught in the Act

Astronomers already knew there were three stars in this system, but they had a totally different mental picture of what was going on. “For a long time (going back almost 20 years), we thought that the tertiary was the center of the system because it was the brightest,” Tobin says.

But ALMA’s images reveal that that’s not the case. The array’s radio “eyes” are two times sharper and ten times more sensitive than those used in previous studies. ALMA detects emission from the carbon monoxide molecule, which acts as a tracer for the molecular hydrogen reservoir that forms stars. (Molecular hydrogen by itself is nearly impossible to detect in star-forming clouds.) The motion of carbon monoxide revealed a disk centered, surprisingly, on the other two stars.

ALMA’s image isn’t even the neatest part of the result. “The strength of this study is the attention to detail in Tobin and colleagues’ analysis,” writes Adele Plunkett (ESO, Chile), author of an accompanying perspective piece. The team modeled how stable the disk is, gravitationally speaking, and showed that it’s in fact unstable right around where the tertiary star is forming. The result confirms that the disk is collapsing in on itself in this region to make the third star.

Artist's concept of disk fragmentation

This image shows how the triple-star system develops: at left, a disk of material fragments into separate protostars, and at right, the stellar emerges after accumulating and/or dispelling the surrounding cloud. The central stars are 60 astronomical units apart (the diameter of Neptune's orbit), and the third star is 183 a.u. away from the central-most protostar.

Bill Saxton / NRAO / AUI / NSF

Amassing a Star

Astronomers can calculate the central duo’s mass by measuring how fast the disk rotates around them. Right now, the central two protostars have a combined mass equal to the Sun’s. They’ll still grow, but probably not too much more — most of the gas ALMA detects around them already effectively belongs to the stars.

The third protostar in the disk is more difficult to “weigh”: all we know at this point is that it’s in the process of gobbling down a chunk of gas worth 8.5% of the Sun’s mass. That explains why it’s the brightest object in the image: ALMA isn't seeing the star itself, but rather the glow of the cool dust and gas around it.

“I expect that the tertiary in the outer disk is likely to grow the most,” Tobin adds. Out there, the protostar has access to more raw materials than the primary pair in the central cavity. (The central two stars are mostly done growing at this point, having cleared out a cavity around them.) So while its mass may have the third protostar looking more like a brown dwarf at this point, Tobin predicts it will become a more massive, red dwarf star by the time all is said and done.

With this discovery, the question remains: how common is gravitational instability? How often do stars form in the shadow of their stellar siblings? “Fragmenting disks like the one observed by Tobin and colleagues are probably not rare,” Plunkett writes. “Rather, they are waiting to be studied in more detail using the powerful (sub-)millimeter-wavelength telescopes that are now available.”

The post ALMA Images Spiral Disk Around Baby Stars appeared first on Sky & Telescope.

Astrophotography: Cable Management

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The art of astrophotography can quickly turn into the art of cable management. Learn how to tame the cable monster and get back to photographing the night sky.

The Simple Life

The Simple Life
Only a couple of cables are needed when you’re starting out — one for power and one for the hand controller on the mount. Most cameras let you expose up to 30 seconds using the camera’s self-timer, so you won’t need a camera shutter release cable just yet.
Jerry Lodriguss

When we are first born, things are pretty simple. We begin with one cord attached to our mother. That cord is cut soon enough, but as we get older, we get more sophisticated and develop new attachments.

So it is with astrophotography. We start with one cable to power our mount; life is simple. We take pictures by pressing a shutter-release cable or using the self-timer. When we see the first results of a couple of seconds of exposure on the Orion Nebula, life is good. But then we get more sophisticated and start taking longer exposures of fainter objects.

For one, most of us have to take measures to combat dew. We add a dew heater, and a controller so it doesn’t run at full power continuously — only a small amount of heat keeps the glass above the dewpoint.

Next, we add an autoguider so we can shoot really long exposures with round stars. An autoguider usually requires an additional power cable, and a cable to go from the guider to your mount. Advanced models require a computer to control its functionsThat computer also needs a power cable, another cable connection between the autoguider and the computer, as well as another one connecting the computer and the mount.

 The Cable Monster

When life gets more complicated, cables start to dangle. Here, cables for power and camera control just hang off the camera. This can cause trailed stars if the cables catch on anything, or if the wind blows and makes them sway in the breeze.
Jerry Lodriguss

Then we figure that since the computer is at the scope already, we might as well run the camera with it — yet another cable that connects the imaging camera to your computer This offers some additional advantages between the guider and imaging camera that aren’t available when using stand-alone camera models, such as dithered guiding, a subject for a future column.

With every new gadget, the number of cables grows. Additional cables appear when you add a filter wheel, an electronic focuser, and even a powered USB hub if you’re shooting with multiple cameras.

Phew! Suddenly, life is complicated! We now have a bird’s nest of power and control wires running from batteries to computers to the mount and to the camera. I call this the “cable monster.” All of these cables need to be managed so they don’t catch on things or move when the wind blows, ruining our exposures.

Taming Astrophotography's "Cable Monster"

We could just get rid of most of the cables, but we want to keep our sophisticated toys, and with good reason – when mastered, they help us produce better images. So here are some alternatives.

The basic philosophy in all of these solutions is to anchor the cables at two points — one on the scope and one on the tripod or pier — and bundle all of the cables between them in a loop that can’t catch on anything.

Start taming the cable monster

Reduce the cable monster’s tangle by moving power and USB hubs to the top of the telescope, or on the mount. That way, most of them don’t move as the scope tracks the sky. Instead of a half dozen or more cables, only two — power and USB — need to move.
Jerry Lodriguss

Cable Management

Loop and secure your cables, and remember to leave enough slack to let the scope move.
Jerry Lodriguss

But first, take a good look at your rig. Is there any way to reduce the amount of cables coming off the scope?

For example, you can mount some accessories, such as a powered USB hub and your anti-dew controller right on top of your telescope tube. Then all you’d need is a single USB cable running from the computer to the hub and a single power cable from the battery to the dew zapper.

Next, bundle all of your cables together with flexible cable wraps or zip ties. Anchor the top to the declination plate or rings of your scope, and the bottom to a tripod leg.

Then create a loop with the bundled cables that is big enough so the mount can point anywhere it needs to without pulling on these cables. Anchor the other end of the loop securely to someplace near the base of the mount.

Test your cable setup by unlocking the clutches and swinging the scope around to different areas of the sky to make sure cables don’t snag as the scope tracks during your imaging session.

Of course, not every setup is this complicated or has this many cables, but in any event, don’t let the cable monster ruin your nights!

Tamed Cable Monster

High-end mounts like the Astro-Physics Mach1 offer the ultimate luxury — through-the-mount cabling. Cables run through the right-ascension axis up through the declination axis and come out under the dec plate.
Jerry Lodriguss

The post Astrophotography: Cable Management appeared first on Sky & Telescope.

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