• Get an online sneak peek at Comet ISON, potential 'comet of the century'

    Watch Slooh Space Camera's live show about Comet ISON and other comets.

    By Tariq Malik, Space.com

    The much-anticipated incoming Comet ISON, which some scientists hope will become the "comet of the century" later this year, may not be visible to the naked eye yet, but you don't have to wait months to see this icy wanderer. The comet takes center stage in an online telescope webcast on Sunday.

    Comet ISON was first discovered last year and is currently expected to swing extremely close by the sun in late November, when it will be at its best and brightest of the year. In anticipation of the comet's arrival, the online Slooh Space Camera will offer live telescope views of the object beginning at 4:45 p.m. ET.

    You can watch the Comet ISON webcast live on Space.com, courtesy of Slooh Space Camera. [See more amazing photos of Comet ISON]

    The webcast marks Slooh's fourth monthly webcast dedicated to tracking Comet ISON's progress through the solar system. During Sunday's 30-minute live show, Slooh officials will provide views of Comet ISON from the firm's remotely operated telescopes in the Canary Islands, off the west coast of Africa.

    Senior space scientist Padma Yanamandra-Fisher of the Space Science Institute in Boulder, Colo., will join Slooh producer Paul Cox in the comet webcast. Yanamandra-Fisher is helping coordinate NASA's Comet ISON Observing Campaign to track the comet. The international campaign is bringing together scientists around the world to plan out observations of ISON.

    NASA has already used several spacecraft, including sun-watching Stereo probes and the Hubble Space Telescope, to observe ISON. An unmanned balloon mission is also among the expeditions planned to observe ISON.

    J.-Y. Li (PSI) / NASA / ESA

    Comet ISON glows in a picture from the Hubble Space Telescope, captured in April.

    Comet ISON has drawn worldwide attention from stargazers and scientists, including NASA, because of its close approach to the sun on Nov. 28, when it will be just 730,000 miles (1.2 million kilometers) from the sun. During that close encounter with the sun, Comet ISON could become one of the brightest comets in decades. However, the comet could also fizzle out.

    Comet ISON was discovered last September by Russian amateur astronomers Artyom Novichonok and Vitali Nevski using the International Scientific Optical Network (ISON) of remotely operated telescopes. The comet is officially known by the identification C/2012 S1 (ISON).

    On April 10, scientists used the Hubble Space Telescope to observe Comet ISON. At the time it was about 386 million miles (621 million kilometers) from the sun and 394 million miles (634 million kilometers) from Earth.

    When observed by Hubble, the comet's nucleus was about 3 miles (5 kilometers) across with a dusty tail that stretched more than 57,000 miles (92,000 kilometers) long.

    If you have an amazing picture of Comet ISON or any other night sky view that you'd like to share for a possible story or image gallery, send photos, comments and your name and location to managing editor Tariq Malik at spacephotos@space.com.

    To follow the Slooh webcast directly using Slooh's iPad app or the Slooh website, visit: http://www.slooh.com.

    Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

    Copyright 2013 Space.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • Water on Earth, moon tied to same source

    John Armstrong / Geophysical Laboratory, Carnegie Institution of Washington

    Backscatter electron image of a lunar melt inclusion from Apollo 17 sample 74220, enclosed within an olivine crystal. Skeletal crystals within the melt inclusion are a fine mixture of olivine and ilmenite. Dark area in the lower-left is an ion microprobe sputter crater.

    By Charles Q. Choi
    Space.com

    Water deep inside Earth and the moon may originate from the same source: ancient meteorites, scientists say.

    The findings hint that water may have existed on Earth before the giant impact the planet received that created the moon, and that the moon possessed water from its earliest moments, scientists added. It remains a mystery exactly how water found within the moon survived this violent collision, though.

    Water is vital to life as we know it, with organisms found virtually everywhere there is water on Earth. When Earth was born, the ingredients of the planet's water most likely would have formed beyond the orbit of Earth. As such, all the water on the planet must have come from either comets or meteorites hurtling inward from the outer solar system.

    Until recently, scientists thought the interior of the moon was bone-dry, originating as the moon did from the molten debris of a giant impact of a Mars-size protoplanet against Earth about 4.5 billion years ago. The heat of this collision should have baked all the ingredients of water out of the moon. However, five years ago, the first evidence of hydrogen was discovered in lunar samples from the Apollo missions. Hydrogen is a main ingredient of water, along with oxygen. [Water on the Moon: The Search in Photos]

    To discover the origins of this water, scientists analyzed crystals and glass beads from the moon rocks brought to Earth by the Apollo 15 and 17 missions. These crystals and beads possessed tiny pieces of glass that serve as records of the moon's geological history.

    The researchers focused on isotopes of the hydrogen found in this lunar magma. All isotopes of an element have the same number of protons, but each has a different number of neutrons. For instance, regular hydrogen has no neutrons, while the hydrogen isotope known as deuterium has one neutron. In general, objects formed closer to the sun have less deuterium than bodies that formed farther out.

    The ratio of deuterium to hydrogen seen in meteorites known as carbonaceous chondrites is similar to that seen in water on Earth, suggesting that as much as 98 percent of Earth water may have come from those space rocks instead of comets. Now, researchers find the ratio of deuterium to hydrogen in moon rocks is similar to that seen on Earth as well.

    Altogether, these findings suggest that water on the moon and Earth share a common origin in carbonaceous chondrites, meteorites found in the asteroid belt between Mars and Jupiter that are thought to be among the oldest objects in the solar system.

    "With a good degree of certainty, we know that the water came to the moon and Earth from primitive meteorites now located in the outer parts of the asteroidal belt," said study lead author Alberto Saal, a geochemist at Brown University. He and his colleagues detailed their findings online Thursday in the journal Science.

    The simplest explanation for this commonality between the moon and Earth is that "the Earth from its birth had water," Saal told Space.com. "And it got to the moon during the giant impact without completely being lost by this event." After the moon-forming impact about 100 million years after Earth formed, our planet apparently did not receive significantly more water, he added.

    If the water in the Earth and moon was indeed there before the impact that formed the moon, it remains uncertain why the heat of the impact did not bake off all this water. One possibility is that the vaporized rock the impact generated could trap gas in it like soda, Saal said. This factor, along with the Earth's gravity, may have helped the planet keep hydrogen and thus water.

    "The problem with that idea is the moon, which has much lower mass and therefore gravity," Saal said. "Although the moon has maybe five to 10 times less water than the Earth, that's still a significant amount of water it retained. That's a problem I don't think we know the answer to yet."

    Other scientists maintain that Earth water might have come from comets. Planetary scientist Paul Hartogh at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, and his colleagues had previously discovered the ratio of deuterium to hydrogen seen in comets very closely matched that found in Earth water. If comets did bring water to Earth, they might also have done so later in time than Saal and his colleagues propose, meaning that Earth and the moon did not have water inside them from the start.

    "I wonder whether Saal and his colleagues can exclude that the samples they investigated contain cometary water," Hartogh told Space.com.

    The European Space Agency's Rosetta mission might be able to resolve the question of whether comets or meteorites are the origins of water in Earth and the moon when it reaches the comet 67P/Churyumov-Gerasimenko in 2014, Hartogh said. Rosetta, which launched in March 2004, will analyze the comet's isotope ratios to see how closely they match those of the Earth and the moon.

    Follow Space.com @Spacedotcom. We're also on Facebook and Google+. Original story on Space.com.

    Copyright 2013 Space.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • Hubble telescope catches an early glimpse of 'Comet of the Century'

    J.-Y. Li (PSI) / NASA / ESA

    Comet C/2012 S1 (ISON) takes on a fuzzy glow in an April 10 image from the Hubble Space Telescope. The blue tint has been added to the black-and-white imagery.

    By Alan Boyle, Science Editor, NBC News


    Comet ISON, the long-traveling iceball that skywatchers hope will turn into the "Comet of the Century," takes on a fuzzy glow in an image captured two weeks ago by the Hubble Space Telescope and unveiled on Tuesday.

    The picture was taken on April 10, using Hubble's Wide Field Camera 3, when the comet was 386 million miles (621 million kilometers) from the sun and 394 million miles (634 million kilometers) from Earth. That's just inside the orbit of Jupiter. Right now, the comet's brightness is roughly magnitude-16, which means it can only be seen with telescopes. But comet-watchers are hoping that ISON will get dramatically brighter as it swings around the sun in late November. Some have said the comet could match the brightness of Venus or even the full moon.

    The reason for those hopes — and the reason for all the "coulds" and "mights" — is that ISON appears to be a long-period comet, coming in from the far reaches of the solar system for the first time in living memory. Such comets are unpredictable: Will they shed lots of dust and glowing gas, or will they turn out to be duds? ISON's orbit is due to bring it within 700,000 miles (1.2 million kilometers) of the sun's surface. That could cause ISON to crumble like Comet Elenin did in 2011, or it could spark a flare-up of Comet Lovejoy proportions.

    Unlike Comet Lovejoy, which lit up the Southern Hemisphere's skies during 2011's holiday season, Comet ISON should be visible from the Northern Hemisphere — which means Americans might get an eyeful during this year's winter holidays. (There's that pesky "might"!)

    The picture from Hubble helps astronomers get a better fix on the current state of Comet ISON: The nucleus appears to be no larger than three or four miles (five to seven kilometers) across. In Tuesday's image release, the Hubble team says that's "remarkably small, considering the high level of activity observed in the comet so far." The comet's fuzzy head, known as the coma, measures about 3,100 miles (5,000 kilometers) across, or a little less than the distance from New York to Dublin. ISON's tail extends more than 57,000 miles, far beyond Hubble's field of view.

    Detailed readings from Hubble could unlock the secrets of ISON's origins, University of Maryland astronomer Michael A'Hearn said in a news release. "We want to look for the ratio of the three dominant ices, water, frozen carbon monoxide, and frozen carbon dioxide, or dry ice," A'Hearn said. "That can tell us the temperature at which the comet formed, and with that temperature, we can then say where in the solar system it formed."  

    Comet ISON was discovered last September and is formally known as C/2012 S1 (ISON). It takes its name from the International Scientific Optical Network, a group of observatories in 10 countries managed by Russia's Keldysh Institute of Applied Mathematics.

    J.-Y. Li (PSI) / NASA / ESA

    This contrast-enhanced image was produced from Hubble's view of Comet ISON to reveal the subtle structure in the inner coma of the comet. Such enhancements help astronomers determine the comet's shape and evolution, plus the spin of its solid nucleus.

    More about comets:

    The image was created from Hubble data from proposal 13198: J.-Y. Li (Planetary Science Institute), P. Lamy (Laboratoire d'Astrophysique de Marseille), H. Weaver (JHU/APL), M. A'Hearn and M. Kelley (University of Maryland), M. Knight (Lowell Observatory), T. Farnham (University of Maryland), and I. Toth (Hungarian Academy of Sciences).

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • Predicting comet brightness: Why some of them don't exactly pan out

    Victor C. Rogus

    Astrophotographer Victor C. Rogus sent in a photo of Comet Pan-STARRS taken March 20, 2013, in Jadwin, Mo. He writes: "As I look over my collection of images starting with March 11 until now, I see nightly changes in the comet. The direction of the tail comes to mind first, always away from the sun. Changes in color, at times, and also changes in the size of the coma."

    By Joe Rao
    Space.com

    The newfound Comet ISON has the potential to be one of the brightest ever seen when it streaks through the inner solar system this November, but whether it will live up to the hype is anybody's guess.

    Astronomers have a tough time forecasting the brightness of incoming comets. Ballyhooed "comet of the century" candidates sometimes fizzle out, as Kohoutek did in 1973, while some icy wanderers put on a surprisingly good show for skywatchers.

    Why is it so difficult to predict comet behavior? For starters, comets are like snowflakes — no two are alike.

    Dirty snowballs
    While comets have been called "dirty snowballs," recent observations by unmanned space probes suggest that they may not be too different from asteroids on the outside. Comets appear to have rocky surfaces that in most cases are probably not much more than several miles across. [Amazing Comet Photos of 2013]

    What makes them much different from asteroids, however, is that frozen reservoirs icy material are hidden beneath the crust or contained in fissures and craters that pockmark the surface. 

    Such comet "snow" is composed of ordinary water ice plus frozen ammonia and some other more exotic compounds, with dust grains of different sizes and compositions mixed in. These pools of volatile materials are called "active regions." 

    Comets spend most of their time far out in space, billions of miles from the sun. Out there, the nucleus is completely stable because it’s in a state of deep freeze where temperatures barely hover above absolute zero (minus 460 degrees Fahrenheit, or minus 273 degrees Celsius).  

    But when a comet nears the sun, its frozen gases react to the increasing heat by vaporizing and expanding into a huge tenuous cloud around the nucleus called the coma. The nucleus and the coma make up the head of the comet, which may swell to more than 100,000 miles across.

    It is sunlight that causes the comet's head to shine, in much the same manner that luminous paint reacts to ultraviolet light. The comet’s tail is produced by the solar wind — a thin supersonic breeze of atomic particles blowing from the sun — and the pressure of sunlight, which pushes the gas and dust out ahead of the coma.

    Old versus new
    One clue about how a comet will ultimately perform is whether it’s a "new" comet, making its very first approach to the sun, or whether it’s an "old" one that has zoomed close to our star before. 

    New comets might be covered with a load of very light, volatile material such as frozen nitrogen, carbon monoxide and carbon dioxide. Such ices can vaporize far from the sun, giving a distant comet a short-lived surge in brightness that can raise unrealistic expectations. This happened with ultimately disappointing comets such as Cunningham in 1940, Kohoutek 1973 and Austin in 1990.

    But some new comets live up to the hype. In January 2007, for instance, Comet McNaught became the brightest comet in more than 40 years, eventually becoming luminous enough to be visible in broad daylight.

    Unpredictable!
    Some small, faint comets have suddenly and unexpectedly become incredibly bright literally overnight. In October 2007, Comet Holmes brightened by a factor of 500,000 in less than two days, going from an object visible only with very large telescopes to becoming easily visible to the naked eye. 

    Its sudden flare may have been caused by a buildup of gas inside the comet's nucleus that eventually broke through its surface, astronomers say. Incredibly, this all took place far out in space when the comet was nearly 230 million miles (370 million kilometers) from the sun. Who knew?

    Even the most recent skywatching sight, Comet Pan-STARRS, had some surprises in store. When the comet was discovered in June 2011, forecasts indicated it might get as bright as first or even zero magnitude — in other words, as bright as the brightest stars. 

    Then, it was surmised that the comet was "new" and might possibly lag behind the original optimistic predictions. Until recently, that seemed to be the case; PanSTARRS was running about one-quarter as bright. Some suggested it might not get much brighter than third magnitude, which would be less than half as bright as Polaris, the North Star. 

    Then without fanfare, in late February, it made a surprising comeback, reaching first magnitude as it rounded the sun on March 10.

    Be careful!
    While you might have gotten the idea by now that comets are notoriously bad actors and do not always follow their scripts, I should stress that many of them are well-behaved and do what is expected in a broad sense. Still, caution is advised when reading any predictions of their brightness.

    That brings us back to Comet ISON, which is expected to sweep less than three-quarters of a million miles above the sun’s surface on Thanksgiving Day,  Nov. 28. Already there have been a plethora of articles promoting ISON as the “Comet of the Century.”

    For an interesting analogy, baseball scouts like to catalog the talents of players by looking at five general areas of performance in which one may define potential talent. Great ballplayers can hit for average, hit with power, field, run and throw. [Photos of Comet ISON in Night Sky]

    Similarly, astronomers who catalog potential great comets look at four general areas of performance: comets that closely approach the sun, closely approach Earth, have a favorable projection angle for viewing the tail and high intrinsic brightness. 

    From these criteria, Comet ISON certainly appears to be a "can't miss" prospect, though it is a new comet, which makes it more of a wild card.

    But then again, like countless numbers of young ballplayers who had unlimited potential but failed to make the big leagues, ISON too could falter. 

    It could unexpectedly exhaust all of its volatile material, leaving just a small, dark solid lump to ultimately swing around the sun — meaning we may not see it all. Or perhaps upon passing through the sun’s outer atmosphere and being subjected to a temperature of around 1 million degrees Fahrenheit (555,000 degrees Celsius) or more, the comet nucleus might shatter or disintegrate. 

    The saga of ISON is not yet fully written, and it could still go either way. We’ll keep track of its progress in the weeks and months to come.

    In the meantime, it might be worth ending with an oft-quoted axiom by the legendary comet expert Fred Whipple: “If you must bet, bet on a horse, not a comet!”  

    Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com.

    Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

     

  • Moon pairs up with Comet PanSTARRS for big show

    Mike Massee

    Comet PanSTARRS and the crescent moon loom over a mountaintop row of wind turbines near Mojave, Calif., on Tuesday night. The pairing of the comet and the moon made for one of the year's best opportunities for astrophotography.

    By Alan Boyle, Science Editor, NBC News


    Two elusive superstars came out on Tuesday evening to greet their adoring fans — in L.A. and Vegas, as well as in California's Mojave Desert and the mountaintops of Arizona and California. As a matter of fact, observers around the world could catch a glimpse of Comet PanSTARRS and the barely lit crescent moon, as long as the skies were clear.

    Like most superstars, Comet PanSTARRS doesn't always live up to its advance billing. For months, skywatchers have been looking forward to PanSTARRS as one of the top sights in the night sky. The long-period comet is now thought to be at its brightest, due to the fact that it has just come out of its close approach to the sun. But finding it has proved more difficult than expected, because it's so easily lost in the glare of sunset.

    XCOR Aerospace's Mike Massee acknowledged that it wasn't easy to capture his comet shot, which was taken in the last light of dusk from the Mojave Air and Space Port in California, where the XCOR rocket venture has its headquarters.

    "At 7:20, neither the moon nor the comet were visible, but about five minutes later you could barely make out the sliver of the new moon. According to XCOR's resident astronomy guru, Randall Clague, the comet would appear about eight moon diameters to the left of the moon. So I set up an image with the moon on the right side of the frame and made some exposures," Massee said in an email.

    "After a few minutes I could zoom in and see the comet in my camera, but not with the naked eye," he wrote. "As the sky grew darker the comet became more and more visible, and eventually you could just make out a fuzzy spot with your naked eye, but the camera was still the best way to review it after the shot was taken."

    Over the next couple of weeks, Comet PanSTARRS will be better positioned for viewing by Northern Hemisphere observers in the western sky after sunset, but each night it's expected to grow dimmer. If there are clear evening skies, grab your binoculars and try to pick out PanSTARRS. This viewing guide can help.

    While you're waiting for those dark, clear skies, check out this photo album, which includes a special shout-out to the Mount Lemmon SkyCenter's Adam Block and all those who contributed through NBC News' FirstPerson photo-upload website. 

    Adam Block

    The sunset glow lingers in the skies over Mount Lemmon SkyCenter in Arizona as Comet PanSTARRS and the crescent moon shine on Tuesday night. Even the dark portion of the moon glows faintly, due to reflected "Earthshine" from our own planet.

    Gene Blevins / Reuters

    David Schaefer of Pasadena, Calif., uses an iPad to help him spot Comet PanSTARRS over Southern California. The comet should be visible from the Northern Hemisphere until the end of March in western skies after sunset.

    Gene Blevins / Reuters

    Comet PanSTARRS takes its place next to the waxing crescent moon in the skies over Los Angeles on Tuesday.

    Craig Yacks via FirstPerson

    Craig Yacks says he took this photo of Comet PanSTARRS (left) and the moon (right) from Highlands Ranch, Colo., "as the clouds opened up just after sunset." The photo was taken with a Nikon D800 camera, set for ISO 1000 with a four-second exposure. "Zoomed in to give a better view of the comet and the moon," Yacks said.

    Slideshow: Catch the coolest comets in the cosmos

    Cast your eyes on pictures featuring PanSTARRS, Hale-Bopp and other crowd-pleasing comets.

    Launch slideshow

    More PanSTARRS photos from FirstPerson fans:

    Update for 7:15 p.m. ET March 13: So where's Comet PanSTARRS now? It's well below the moon, and you'll need binoculars to spot it. To get a fix on the comet, you can consult this sky chart from SpaceWeather.com.

    Wednesday evening's images from Jens Riggelsen in Aarhus, Denmark, illustrate how tricky it can be to see the comet. The moon is high in the sky, but PanSTARRS is just a speck amid the glow of sunset. "The comet wasn't visible to the naked eye, but figured I might be able to capture it with the camera. And indeed, there it was," Riggelsen told SpaceWeather.com.

    Can you spot the comet in this brand-new view from Jamie Cooper? 

    Jamie Cooper

    Comet PanSTARRS is a glimmer in the sky after sunset, far below and to the right of the crescent moon. This picture was taken by Jamie Cooper from Northampton in England on Wednesday.

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log and NBCNews.com's science and space coverage, sign up for the Tech & Science newsletter, delivered to your email in-box. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • Look for Comet PanSTARRS near the crescent moon in western skies

    Ide Geert Koffeman

    Photographer Ide Geert Koffeman assembled this view of Comet PanSTARRS (at far left) and the crescent moon (at far right), as seen from the Dutch province of Flevoland, on Tuesday evening. Five vertical HDR images were stitched together. Click on the image for a larger version, or check SpaceWeather.com for more.

    By Joe Rao
    Space.com

    Many stargazers attempting to view the Comet PanSTARRS on recent nights have been thwarted by the comet's low position in the western sky. But on Tuesday night, the thin crescent moon will lend a hand.

    Over the past weekend countless observers across in North America and Europe tried — and for the most part failed — to see Comet PanSTARRS, in part due to its low altitude above the west-northwest horizon. The bright glare of the evening twilight sky just is also a hurdle, since it can as make the comet harder to see just after sunset.

    But fret not, comet lovers! Comet PanSTARRS' position above the horizon is noticeably higher on Tuesday evening, and the moon can be used as a benchmark to point your way.

    Step 1: Find clear skies
    The best suggestion I can make for your comet watch is to find an observing site with the least amount of obstructions in the direction of the western part of the sky. [How to see the comet]

    If you end up successfully catching a glimpse of them, the moon and the comet will not be any higher than 10 degrees above the horizon. That is about the size of your clenched held out at arm's length.

    If you have a house or some trees in your line of sight, then you're going to have to find some other viewing site.

    Step 2: Find the moon
    In order to boost your chances of seeing Comet PanSTARRS, be sure to arrive at your viewing site in time to see the sunset. Take note of where on the horizon the sun sets. 

    Now wait about 30 minutes as the sky begins to darken. Truthfully, it will still be rather bright looking toward the west a half-hour after the sunset. This was one of the main problems people have had in recent days in trying to see the comet. 

    However, first things first: Let's locate the moon. Take your clenched fist and measure off 10 degrees up from that point on the horizon where the sun disappeared about a half hour before.  Now look a bit to the right from the top of your fist. That's where the crescent moon will be. 

    Seeing the moon will be a bit of a challenge in itself because it will be very narrow, appearing only about 28 hours after passing its new phase. Because of this, the lunar disk will be only 1 percent illuminated. It will be oriented with its bright sliver down, resembling a cup or a thin smile on the sky. 

    If you can't see the moon with your unaided eye, then use binoculars. Once you pick it up with binoculars, you should be able to find it without optical aid. 

    Adam Block / Caelum Observatory

    Comet PanSTARRS stands out when seen from a high-altitude vantage point. "Here is the picture I captured ... from atop Mount Lemmon (at the Mount Lemmon SkyCenter). I run the stargazing programs up here and while hosting the show for the guests I captured this picture," Arizona astrophotographer Adam Block said in an email.

    Adam Block / Caelum Observatory

    Astrophotographer Adam Block captured this view of Comet PanSTARRS amid a line of power poles near Tucson, Ariz., on March 10. For more from Block, check out the Caelum Observatory.

    StarDate Magazine

    The location of Comet Pan-STARRS low in the western horizon in March 2013 is shown in this sky map released by StarDate Magazine, a publication of McDonald Observatory at the University of Texas.

    Step 3: Find the comet
    With the moon found in the evening sky, it is time to use it as a guide to spot Comet PanSTARRS.

    The comet will be located about 5 degrees to the left of the moon. Once again, you might not initially see it with your eyes, so use binoculars if you need to. Five degrees measures roughly "half a fist" in length.

    You'll know Comet PanSTARRS when you see it. It will appear as a bright, starlike "head" with a short, stubby tail extending from the head upwards and slightly to the left from the bright end. Like the moon, once you find it with binoculars, you should, with time, be able to make it out against the bright twilight sky.  

    Comet PanSTARRS and the moon should be visible for about a half hour before they disappear into the murky haze always located near the horizon.

    Not so 'Great Comet'?
    Comet PanSTARRS was discovered in June 2011 by a team of astronomers using the Panoramic Survey Telescope and Rapid Response System (or Pan-STARRS), a telescope in Hawaii. The comet is officially designated as C/2011 L4 (PANSTARRS) and is thought to take more than 100 million years to make a single orbit around the sun. [Comet PanSTARRS Explained (Infographic)]

    Right now the brightness of Comet PanSTARRS, according to viewers who spotted it in the Southern Hemisphere, ranks at about first-magnitude on the astronomy brightness scale. That is about as bright as the brightest stars. 

    Normally, a comet as bright as this would be categorized as a "Great Comet," but most observers feel that PanSTARRS does not fall into this category because it's not visible against a fully dark sky. The bright twilight background is working against making it a prominent eye-catching sight.

    And the comet's dust tail is not breathtakingly long, but rather short and rather stubby. To the naked eye, not much of the tail may be visible at all, though in big binoculars or small telescopes, some say that PanSTARRS is a rather impressive sight.

    Comet PanSTARRS is one of at least three comets in the night sky that are sending a thrill through stargazers. Another comet (Comet Lemmon) is currently visible to observers in Southern Hemisphere, while the third object is Comet ISON.

    Comet ISON is a promising celestial object that was discovered by amateur astronomers in 2012 and is expected to make its closest approach to the sun in late November. The comet will be only 800,000 miles (1.2 million kilometers) from the sun at its closest point, and could put on a dazzling night-sky spectacle. But it could also fizzle out.

    NASA astronomers and stargazers around the world are regularly tracking Comet ISON, as well as comets PanSTARRS and Lemmon as they shine in the night sky.

    If you snap an amazing photo of Comet PanSTARRS in the night sky, or any other celestial object, and you'd like to share for a possible story or image gallery, please send images and comments, including location information, to managing editor Tariq Malik at spacephotos@space.com.

    Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. Follow us @Spacedotcom, Facebook or Google+. This article was first published on SPACE.com.

    Slideshow: Catch the coolest comets

    Cast your eyes on pictures featuring PanSTARRS, Hale-Bopp and other crowd-pleasing comets.

    Launch slideshow

    Copyright 2013 Space.com. All rights reserved.

  • Seeing Comet PanSTARRS is tricky for skywatchers, but it's easy online

    Fritz Helmut Hemmerich via SpaceWeather.com

    Comet PanSTARRS shines above the clouds on Tenerife in the Canary Islands on March 10.

    By Alan Boyle
    Science Editor, NBC News 

    Comet PanSTARRS has proved harder to spot in the Northern Hemisphere than some might have expected — but some hardy souls have captured time-lapse videos of the sparkle in the sky. 

    "Certainly not a 'great comet' by any means," astronomer Alan Hale, the co-discoverer of 1997's Comet Hale-Bopp, wrote in a posting to the Comets-ML online forum. "The visibility should hopefully improve over the next few nights as it climbs higher out of the twilight, but I don't foresee anything spectacular."

    Other veteran observers said PanSTARRS could hardly be seen with the naked eye amid the glare of sunset. As the week wears on, the comet will get progressively higher and more northerly in the sky. But it will get progressively dimmer as well.

    That's what makes Tuesday's viewing opportunity so key: On March 12, PanSTARRS should be sitting just to the left of the crescent moon, as indicated in this sky chart from SpaceWeather.com. The moon will thus serve as a guidepost for you to turn your binoculars to the right spot just after sunset. 

    Greg Crinklaw, who writes about comets on the Skyhound website, said the expectations for sighting PanSTARRS have been stoked by "blazing headlines." Now reality is setting in.

    "There will be about a 10- to 20-minute window to catch the comet each night starting about March 12 and going through the end of the month," he wrote. "I am predicting that it will not be a naked-eye object except to expert observers at higher elevations with very little haze on their horizon."

    Fortunately, some of those expert observers have been sharing their moving pictures of PanSTARRS. Fritz Helmut Hemmerich, for example, sent SpaceWeather.com an animated sequence from Tenerife in the Canary Islands. "We went high on the Teide volcano to photograph the comet," Hemmerich said. "Each frame in the video is a 4-second exposure taken with a Canon 1100D digital camera set at ISO 400."

    Hemmerich's son, Hanoch, contributed a video to the Vimeo website, and you can watch it further on down below. I'm also including some other PanSTARRS movies from the Northern Hemisphere as well as the Southern Hemisphere, courtesy of Vimeo. In all cases, it's best if you go for the full-screen HD view. For still more comet sightings, check out the gallery on SpaceWeather.com.

    Did you see the comet? Got any tips? Please feel free to share your tips as comments below, and share your photos via our FirstPerson photo-upload page. Here's our first FirstPerson submission, from Vik Sridharan in San Pedro, Calif:

    Vik Sridharan via NBC News FirstPerson

    "Comet PanSTARRS visible above the Pacific Ocean about an hour after sunset," Vik Sridharan reported in his FirstPerson photo submission. "Visible to a camera sensor, but not the naked eye! Shot from Palos Verdes with a Canon 50D and 200mm F4L. 3-second exposure at f/4 and ISO 800."

    Comet C/2011 L4 PanSTARRS from Hanoch Hemmerich on Vimeo.

    This view of Comet PanSTARRS on Vimeo comes from Michael Zeiler in Santa Fe, N.M.

    Comet PanSTARRS setting over Australia's Henley Beach from Steven Saffi on Vimeo.

    Slideshow: Catch the coolest comets

    Cast your eyes on pictures featuring PanSTARRS, Hale-Bopp and other crowd-pleasing comets.

    Launch slideshow

    More about comets:

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • Comet Pan-STARRS is closest to Sun today: See it at sunset

    Luis Argerich/Nightscape Photography

    Astrophotographer Luis Argerich of Buenos Aires, Argentina, took this photo of Comet Pan-STARRS taken on March 2, 2013. He writes: "Comet Pan-STARRS was visible from about 8:15 pm to 9 pm above the western horizon."

    By Tariq Malik, Space.com

    A comet sailing through the inner solar system make its closest approach to the sun and will be at its brightest at sunset tonight, but the glare of twilight may make it tricky to see, NASA says.

    The Comet Pan-STARRS will be 28 million miles (45 million kilometers) from the surface of the sun when it swings around the star today, and should be bright enough to see without the aid of telescopes or binoculars, weather permitting. But the comet is also appearing low on the western horizon at sunset so some planning is needed to spot the celestial wanderer with the naked eye tonight.

    "Look too early and the sky will be too bright," said Rachel Stevenson, a NASA Postdoctoral Fellow at the agency's Jet Propulsion Laboratory in Pasadena, Calif. "Look too late, the comet will be too low and obstructed by the horizon. This comet has a relatively small window."

    Science@NASA

    The progression of comet Pan-STARRS across the night sky in March 2013 is shown in this NASA graphic.

    A good time to look is about 40 minutes after sunset. The comet may appear as a sort of exclamation point in the evening sky, with the point being the comet itself and its diffuse tail stretching nearly straight up from the horizon, JPL officials added. [How to see the comet]

    Comet Pan-STARRS, officially known as comet C/2011 L4 Pan-STARRS, was discovered in June 2011 by astronomers using the Panoramic Survey Telescope and Rapid Response System (or PAN-STARRS), a telescope atop the Haleakala volcano in Hawaii. The comet takes more than 100 million years to orbit the sun and appears to come from the Oort cloud, a vast halo of comets and icy objects at the outer edge of the solar system.

    While the comet is making its closest pass by the sun tonight, the best views of the object are still to come. NASA scientists said the comet's proximity to the sun may make it too difficult to spot tonight, but that will change over the next few days.

    "As it continues its nightly trek across the sky, the comet may get lost in the sun's glare but should return and be visible to the naked eye by March 12," JPL officials explained. "As time marches on in the month of March, the comet will begin to fade away slowly, becoming difficult to view (even with binoculars or small telescopes) by month's end."

    Astronomy Education Services / Gingin Observatory

    Close-up of comet C/2011 L4 PANSTARRS as seen from Mount Dale, Western Australia.

    And there is another reason to look for comet Pan-STARRS later this week. On Tuesday (March 12), the moon rises into the cosmic display.

    "The comet will be joined in the western sky after dark by the slender crescent moon on March 12, 13, and 14," the editors of StarDate Magazine, a stargazing publication of the McDonald Observatory at the University of Texas. "Good naked-eye views of the comet should continue for several nights, with the comet remaining visible through binoculars into April."

    Comet Pan-STARRS is one of three comets capturing the attention of stargazers this year. The Comet Lemmon C/2012 F6 is currently visible to observers in the Southern Hemisphere and at times was in the night sky at the same time, allowing stargazers to capture rare photos of two comets in the sky together.

    Meanwhile, the Comet ISON is making its way into the inner solar system and could put on a spectacular cosmic display later this year. Officially designated C/2012 S1 (ISON), Comet ISON was discovered in September 2012 by Russian amateur astronomers Vitali Nevski and Artyom Novichonok using a remotely operated International Scientific Optical Network (ISON) telescope.

    Some astronomers have billed Comet ISON as a potential "comet of the century" since it could be brighter than the full moon in daylight when it makes its closest approach to the sun on Nov. 28. At that time, Comet ISON will be much closer to the sun than Comet Pan-STARRS is now. ISON will approach within 800,000 miles (1.2 million km) of the star, making it a true sungrazing comet.

    StarDate Magazine

    The location of Comet Pan-STARRS low in the western horizon in March 2013 is shown in this sky map released by StarDate Magazine, a publication of the McDonald Observatory at the University of Texas.

    Editor's note: If you snap an amazing photo of Comet Pan-STARRS, or any other celestial object, and you'd like to share it for a possible story or image gallery, please send images and comments, including location information, to managing editor Tariq Malik at spacephotos@space.com.

    Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik and Google+. Follow us @Spacedotcom, Facebook and Google+. Original article on SPACE.com.

    Copyright 2013 SPACE.com, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

  • 'Marsageddon' comet scenario adds to concerns about space threats

    Chris Smith / NASA file

    An artist's conception shows a comet streaking through Martian skies.

    By Alan Boyle, Science Editor, NBC News


    It sounds like an "Armageddon" sequel, set on Mars instead of Earth: A supermassive doomsday comet is heading toward the planet in 2014, and there's nothing anyone can do about it. Not even Bruce Willis.

    The comet presents a good-news, bad-news situation for the Red Planet, and for us earthlings as well. NASA says Comet 2013 A1, also known as Comet Siding Spring, is almost certain to miss Mars on Oct. 19, 2014. However, there's still a chance — a less than a 1-in-600 chance — that Mars could be hit, due to the remaining uncertainty about the comet's path. That uncertainty is likely to be cleared up over the next few months, eventually resulting in an all-clear.

    Even if the comet did hit, there'd be no negative effect on Earth. However, the "Marsageddon" scenario is already adding to the concern that was generated by last month's Russian meteor blast and a near-miss by a larger asteroid.

    The case of Comet Siding Spring led Henry Vanderbilt, founder of the Space Access Society, to ask a scary what-if question. "If it was coming straight at us (no more or less likely than it coming straight at Mars), and given our existing space capabilities, could we do anything about it other than prepare to die?" he wrote in a posting to the Moon and Back blog. "The short answer is: Maybe."

    The comet's size is the most worrisome part of the story. Based on its observed brightness, astronomers estimate that the iceball could be anywhere from 9 to 30 miles (15 to 50 kilometers) in diameter. In comparison, the asteroid that's been blamed for killing off the dinosaurs 65 million years ago is thought to have been 6 miles (10 kilometers) in diameter.

    A direct hit on Mars' backside wouldn't tear the planet apart, but it would produce an explosion that Bad Astronomy's Phil Plait estimates at somewhere around a billion megatons of TNT. That would create a huge crater, blast tons of debris into space and perhaps set off a flood reminiscent of the one that washed over Marte Vallis millions of years ago.

    On Earth, the impact would be a civilization-killer.

    How do you stop something like that? Scientists have proposed a variety of deflection techniques for smaller objects, when the collision threat can be detected years or even decades in advance. Those techniques range from space-based gravity tractors, to paintball shooters, to laser blasters, to laser bees, to solar sails, to "Armageddon"-style nuclear bombs. Just this week, Iowa State University's Asteroid Deflection Research Center proposed a $500 million mission to test a nuclear-armed asteroid interceptor.

    "It's not a laughing matter," center director Bong Wie said in a news release.

    There would definitely be no one laughing if a 20-mile-wide comet were coming at us with less than two years of advance warning. In that scenario, the only realistic option would be hydrogen bombs, and lots of them. Vanderbilt estimates it would take about 250 megatons' worth of energy to divert an object like Comet Siding Spring. At 1 to 5 megatons per bomb, that would mean 50 to 250 bombs from the nuclear powers' stockpile. 

    "Whether we can effectively apply that energy to successfully divert the comet, we just don’t know," Vanderbilt wrote. "The problem has been studied a fair amount, and the answers vary. Nobody’s actually tested it. We would, under the circumstances, have little choice but to try."

    For the time being, Comet Siding Spring is shaping up as a huge near-miss: NASA's Jet Propulsion Laboratory's latest estimate has it missing Mars by about 31,000 miles (50,000 kilometers) — and at that distance, not even the debris flying off the comet is expected to affect the Red Planet or the probes flying around it. It helps that the comet's tail will be pointing away from the planet, as explained in this blog posting by the Planetary Society's Emily Lakdawalla.

    The comet would make an impressive sight if you were watching it from Mars (magnitude zero or brighter), and NASA's rovers will likely be doing just that. But it isn't expected to reach naked-eye brightness for earthly observers. Chances are that Comet Siding Spring will make its biggest impact as another reminder that we have to address the perils posed by cosmic threats sooner or later.

    Considering what's happened over the past month, how many more reminders do we need?

    More about cosmic threats:

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • How to get the most out of Comet PanSTARRS while it's at its peak

    Copyright 2013 John Sarkissian

    John Sarkissian, operations scientist at the Parkes Radio Observatory in Australia, captured this view of Comet PanSTARRS hanging in the sky over the Parkes Radio Telescope on March 5. The telescope was made famous in a movie from 2000 titled "The Dish." Sarkissian told SpaceWeather.com that the comet picture is a "5-second exposure taken through my Canon 400D digital camera set on ISO 1600."

    By Alan Boyle, Science Editor, NBC News


    You'll be hearing a lot about Comet PanSTARRS, also known as C/2011 L4, now that it's become visible in the Northern Hemisphere — but if you're not properly prepared, the experience can be underwhelming. You have to know where and when to look, and with what. Fortunately, there are lots of resources to draw upon.

    First, some quick facts: Comet PanSTARRS is thought to come from the Oort Cloud on the solar system's edge, and is making its first round through the inner solar system. It was discovered in 2011 by the Pan-STARRS Telescope team, but it didn't attract wide attention until last year, when astronomers noticed a brightening trend that promised to produce a sight visible to the naked eye. The comet is expected to shine brighter than the stars of the Big Dipper (magnitude +2 to +1) over the weekend.

    The challenge is that during this time of peak brightness, the comet will be visible quite low near the western horizon, just after sunset.

    "Look too early and the sky will be too bright," NASA postdoctoral fellow Rachel Stevenson said in a PanSTARRS preview provided by the Jet Propulsion Laboratory. "Look too late, the comet will be too low and obstructed by the horizon. This comet has a relatively small window."

    The farther north you are, the closer to the horizon you'll have to look. Those aren't exactly ideal conditions, especially if you have an obstructed view to the west, or if there are clouds on the horizon, or if there's significant haze in the air. The best viewing spots should be at higher elevations, far from haze and the glare of city lights, where the skies can get as dark as possible as soon as possible after sunset.

    Depending on your location in the Northern Hemisphere, you may not be able to get a good look at the comet until next week. But even if you miss seeing it on Thursday or Friday, it's worth checking out a variety of spots over the next few days to get ready for the peak experience on March 12 and 13. That's when Comet PanSTARRS is due to make a pretty appearance close to the crescent moon.

    Although the comet has become visible to the naked eye, you'll want to pull out the binoculars to make out the comet's tail. You might notice two elements to the tail, pointing in slightly different directions: One element is made up of glowing ionized gas, while the other is made up of dust that reflects the light of the sun.

    PanSTARRS is due to make its closest approach to the sun on Sunday, coming within 28 million miles (45 million kilometers). On each evening after that, the comet's position will be slightly more elevated from the horizon, and shift slightly to the north. It'll also become dimmer. By mid-April, the comet will no longer be visible to the naked eye, even under the best circumstances.

    Rufus Canty

    Rufus Canty posted this picture of Comet PanSTARRS to the Cosmic Log Facebook page on Tuesday. "From Puerto Rico, looks awesome," Canty wrote.

    This PanSTARRS time-lapse video from Stuart Thomson on Vimeo lasts only seven seconds, but it's a realistic look at viewing conditions in Werribee, a suburb of Melbourne, Australia. Watch it in full-screen HD.

    NASA

    This chart shows the position of Comet PanSTARRS on several nights in March, as well as the position of the crescent moon on March 12, which is arguably the best day for comet-watching.

    When PanSTARRS fades from the spotlight, don't put your binoculars back in the attic: Another starry messenger from the outer solar system, known as Comet ISON, is due to make its appearance in November. Some skywatchers have dubbed ISON the "Comet of the Century" because the most optimistic projections suggest it could shine as brightly as the full moon. It's way too early to make firm predictions, but it's a good bet that the comet-watching skills you develop while looking for PanSTARRS will come in handy when it's ISON's turn.

    Got comet pictures? Share them via NBC News' FirstPerson photo upload site and we'll pass them along in a future posting.

    Now for those resources:

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • The outlook brightens for Comet PanSTARRS as sky show shifts

    Minoru Yoneto

    Minoru Yoneto captured this picture of Comet PanSTARRS shining over Queenstown, New Zealand, on March 2. The comet's tail has two components, consisting of glowing gas and shining dust. Yoneto told SpaceWeather.com that "it's a splendid appearance."

    By Alan Boyle, Science Editor, NBC News


    Observers in the Southern Hemisphere have been watching Comet PanSTARRS for weeks, but the Northern Hemisphere is due to get its first looks at one of the year's most eagerly anticipated sky extravaganzas this week. And there's good news for northerners: The up-and-down expectations for the cometary show are trending upward again.

    "In the Southern Hemisphere we have a few days to enjoy it," Argentine photographer Victor Gabriel Bibe, one of many observers who have been tracking the comet's brightening glow, said in an email.

    On Tuesday, PanSTARRS makes its closest approach to Earth. On Thursday or so, it should start becoming visible to Northern Hemisphere observers in the western sky, low to the horizon just after sunset. The best photo ops will come March 12 and 13, when PanSTARRS pairs up with the crescent moon.

    The brightness of an astronomical object is measured by magnitude, with lower numbers denoting brighter objects. Magnitude +6 is about the limit for naked-eye observations under prime conditions. Magnitude +2 is equivalent to the brightness of Polaris, the North Star. Early on, astronomers said PanSTARRS could get to magnitude zero, putting it in a league with some of the brightest stars in the sky. More recently, they noted that the comet wasn't brightening as quickly as they originally thought and revised the forecast to around +2. Now, the consensus is that it could get to +1 or brighter — maybe not dazzling, but definitely not bad.

    "As long as it continues its behavior for a few days, it looks like the Northern Hemisphere — even us city-dwellers — might get a pretty good view of this thing," said Karl Battams of the Naval Research Laboratory in Washington.

    The comet was discovered in June 2011 by the Panoramic Survey Telescope and Rapid Response System, or Pan-STARRS, in Hawaii — which helps explain the genesis of its official name, Comet C/2011 L4 (PanSTARRS). The "C" means that the comet is considered a non-periodic newbie, coming in for the first time from the Oort Cloud on the solar system's edge. The "L4" means it was the fourth comet discovered during the first half of June.

    Victor Gabriel Bibe

    Comet PanSTARRS shines above a mountain range in Tierra del Fuego, Argentina. The picture was taken by Ushuaia photographer Victor Gabriel Bibe. For more of Bibe's pictures, check out El Cielo de Tierra del Fuego.

    Dieter Willasch

    Dieter Willasch snapped this picture of Comet PanSTARRS on March 2 from Somerset West in South Africa. Visit Astro-Cabinet for more images by Willasch.

    NASA

    This chart shows Comet PanSTARRS' location in the Northern Hemisphere evening sky after sunset for several dates during prime time. The position of the crescent moon is shown for March 12. Watch a NASA video about Comet PanSTARRS.

    Even though PanSTARRS is still a few days away from Northern Hemisphere visibility, you can take advantage of these tips to maximize your comet-viewing experience:

    • Scope out a spot with good western exposure and a minimum of trees, buildings or hills to spoil the view. PanSTARRS won't get very high in the sky, so you'll want to scan the horizon as soon as the sun goes down. But not before! It'd be a tragedy to damage your eyes for the sake of a comet.
    • The farther you are from city lights and cloudy weather, the better you'll be able to see the comet. "I was very lucky to observe the comet, because in the area where I live, the weather is very unstable and the sky is always cloudy. Every time the sky clears, I attempt to observe," Bibe said.
    • Although the comet is visible to the unaided eye, binoculars will enhance the view — particularly when it comes to seeing the tail. "To the naked eye, this comet has a stellar aspect. But with 10x50 binoculars you can see the tail clearly," Bibe said.
    • Once it's visible in the Northern Hemisphere, the comet will rise higher in the sky on each succeeding night. If PanSTARRS follows the expected trend, the viewing should be best between March 10, when it makes its closest approach to the sun, and March 13 or so. After about that time, the glare of the waxing moon could take some of the shine off the comet. PanSTARRS is projected to fade from naked-eye visibility in April.

    After PanSTARRS: ISON
    PanSTARRS is the first of two comets expected to take the spotlight this year. The other one is Comet ISON, which has the potential to get much, much brighter than PanSTARRS in November. Some experts are hoping it will equal the brightness of the full moon, although Battams says it's way too early to make firm predictions.

    To prepare for ISON's arrival, Battams and other researchers are helping NASA organize a comet observing campaign. "We just want to make sure that all the major observatories are aware of this," Battams said.

    ISON is expected to pass as close to the sun's surface as 684,000 miles (1.1 million kilometers), which could produce a dramatic brightening of the comet when it swings back out of the inner solar system. It could produce scientific insights as well.

    "Sungrazing comets are unique objects that experience the most extreme thermal and gravitation forces our solar system has to offer them," the campaign's Web page says. "However, rarely do we get to see these objects more than a few hours before their demise. Comet ISON offers us the rare opportunity to study a sungrazer in great detail, for an extended period, and place it in the context of other comets."

    For updates on the year of the comets, check in with the "Waiting for ISON" blog as well as SpaceWeather.com and the Remanzacco Observatory website, and follow @ISONUpdates on Twitter.

    Got comet pictures? Share them via NBC News' FirstPerson photo upload site and we'll pass them along in a future posting.

    More about comets:

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • Comet just might hit Mars in 2014

    Chris Smith / NASA file

    An artist's conception shows a comet streaking through Martian skies.

    By Nancy Atkinson
    Universe Today

    There is an outside chance that a newly discovered comet might be on a collision course with Mars. Astronomers are still determining the trajectory of the comet, named C/2013 A1 (Siding Spring), but at the very least, it is going to come fairly close to the Red Planet in October of 2014.

    "Even if it doesn’t impact, it will look pretty good from Earth, and spectacular from Mars, probably a magnitude -4 comet as seen from Mars' surface," Australian amateur astronomer Ian Musgrave wrote.

    The comet was discovered in the beginning of 2013 by comet-hunter Robert McNaught at the Siding Spring Observatory in New South Wales, Australia. According to a discussion on the IceInSpace amateur astronomy forum, when the discovery was initially made, astronomers at the Catalina Sky Survey in Arizona looked back over their observations to find "pre-recovery" images of the comet dating back to Dec. 8, 2012. These observations placed the orbital trajectory of comet C/2013 A1 right through Mars orbit on Oct. 19, 2014.

    However, after 74 days of observations, comet specialist Leonid Elenin notes that current calculations put the closest approach of the comet at a distance of 67,853 miles (109,200 kilometers), or 0.00073 AU from Mars in October 2014. That close pass has many wondering if any of the Mars orbiters might be able to acquire high-resolution images of the comet as it passes by.

    But as Ian O’Neill from Discovery Space points out, since the comet has only been observed for 74 days (so far), so it’s difficult for astronomers to forecast precisely where the comet will be 20 months from now. "Comet C/2013 A1 may fly past at a very safe distance of 0.008 AU (650,000 miles)," O'Neill wrote, "but to the other extreme, its orbital pass could put Mars directly in its path. At time of Mars close approach (or impact), the comet will be barreling along at a breakneck speed of 35 miles per second (126,000 miles per hour)."

    Elenin said that since C/2013 A1 is a hyperbolic comet and moves in a retrograde orbit, its velocity with respect to the planet will be very high, approximately 56 kilometers per second (126,000 mph). "With the current estimate of the absolute magnitude of the nucleus M2 = 10.3, which might indicate the diameter up to 50 kilometers [30 miles], the energy of impact might reach the equivalent of staggering 2×10^10 megatons!"

    While the massive Comet Shoemaker–Levy 9 (9.3 miles or 15 kilometers in diameter) that crashed into Jupiter in 1994 was spectacular as seen from Earth orbit by the Hubble Space Telescope, the sight of C/2013 A1 slamming into Mars would be off the charts.

    Astronomers are certainly keeping an eye on this comet, and they will refine their measurements as more data comes in. You can see the orbital parameters available so far at JPL’s Solar System Dynamics website.

    More about comets:

    This report originally appeared on the Universe Today website as "Is a Comet on a Collision Course With Mars?" Copyright 2013 Universe Today. Reprinted with permission.

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