Posted on by Nancy Atkinson

Guest Post: Comet Kerfuffle

An image generated from Starry Night software of how Comet ISON may look on November 22, 2013 from the UK.

Editor’s note: This guest post was written by Stuart Atkinson, a space and astronomy enthusiast who blogs at Cumbrian Sky, Road to Endeavour, which follows the Opportunity rover, and The Gale Gazette which discusses imagery from the Curiosity rover.

Unless you’ve been cut off from the internet today you’ll have heard about The Comet. No, not Comet PANSTARRS, which is due to shine in the sky next March, perhaps rivalling the fondly-remembered Comet Hale Bopp from 1996, but another comet. Comet 2012/S1, or “Comet ISON” to give it its full name. It’s everywhere you look on Twitter, Facebook, Google Plus. Why? Because initial calculations of its orbit show it will pass ridiculously close to the Sun next November, skimming the solar surface at a height of just under two million kilometres. And that means it might shine jaw-droppingly bright in the sky at that time, before it heads back off into deep space again.

So, of course, adding two and two to get fifty, there are lots of people getting more excited about this comet than a dog in a lamp post factory. If you were to believe some of the comments being written about it, it is absolutely nailed-on guaranteed to shine like a welding torch in the sky next November, blazing at magnitude -16, with a tail stretching across the sky like a WW2 searchbeam.

Can we all just calm down, please?

Although Comet ISON looks promising, very promising in fact, it’s very early days. It needs to be observed a lot more before we know exactly what’s in store for us, and even then what it will actually look like in the sky is impossible to predict this far ahead. You see, comets are notoriously unreliable, and love nothing better than getting astronomers on Earth all fired up with the promise of a dazzling nocturnal display before fizzling out and being so faint they need binoculars to see them. Hardly surprising, seeing as comets are essentially great big chunks of dirty ice, and we only see them because they’re melting and falling to pieces as they race around the Sun. You can’t predict how that will work out now, can you?

There’s a whole spectrum of possibilities here. At one end of that spectrum, ISON will live up to the most breathless predictions and blaze in the sky like a science fiction movie special effect. Its tail will span half the sky, becoming visible as soon as the Sun has set, and we will stand on our hillsides and in our gardens looking at it and slowly shaking our heads in wonder before we remember we’ve actually got a camera set up, and start taking pictures of it.

At the other end of the spectrum, ISON will play us all for fools, and even before its close solar flyby it will break up without developing a searchbeam tail, and we’ll all stand on our hillsides and in our gardens looking at it through binoculars and shaking our fists at it angrily, cursing its icy crust.

I think we should cross our fingers for something between the two. We should hope that ISON stays in one piece, survives its close encounter with the Sun, and shines in the twilight sky next November like another Lovejoy or McNaught. I’ll be happy with that, to be honest. Because I’m a citizen of the northern hemisphere my only views of Lovejoy were on my computer monitor, as I drooled over the images of it taken by astronomers and skywatchers in Australia and New Zealand and across the southern hemisphere. I caught a fleeting glimpse of McNaught from here in Kendal – standing in the ruins of the castle that stands above my town, I saw the comet through binoculars through a brief gap in the clouds, as I stood in the rain – but again I ‘saw’ it online rather than with my own eyes, cursing (good naturedly) all those people south of the equator who were seeing the real thing shining in their sky…

An image generated from Starry Night software of how Comet ISON may look on November 29, 2013 from the UK.

(I have to be honest here: having missed the last two Great Comets because of my latitude, when I fired up STARRY NIGHT earlier today, and stepped forward in time to next November, I experienced a rather ungentlemanly “Ha! Our turn!” moment of pure smugness as I saw that ISON’s path will carry it through my sky..!)

The best thing we can do, seriously, is just cross our fingers. Hope for the best, but prepare for…something less than that.

And yet…

Comets are magical, aren’t they? They bring out the dreamer, the optimist and the romantic in all of us. And although I’m fighting it, my head is full of images as I write this, memories of the comets I have seen before, and wondering what ISON will bring. I remember my first sighting of Halley’s Comet, on Guy Fawkes Night 1985. It was just a smudge of a blur in my binoculars, as I stood on the sports playing field near my home, breathing in the smell of bonfires and fireworks in the darkness; I remember standing in the deep, dark Cumbrian countryside, in the gravelled gateway of a farm field, and tracing out the ridiculous extent of Comet Hyakyutake’s pale green tail across the star-spattered sky; and I remember standing in the centre of the ancient Castlerigg stone circle outside Kewsick and, in perfect silence, and feeling a real connection to the watching Comet Hale-Bopp shining above the fells, its twin tails looking like they had been sprayed across the heavens by some cosmic grafitti artist…

What memories will I have after Comet ISON has flown past the Sun, I wonder…

It’s tempting to look at the elements of this comet, and to simulate its apparition using planetarium software, and to get excited. But really, let’s take it easy. I mean, we’ve been here before. Some comets in the past have promised the Earth (mentioning no names… *cough* Kohoutek *cough* ) only to pass by without any real fanfare or fuss, leaving astronomers with a lot of egg on their faces.

So, everyone, take a deep breath, and look at the calendar. ISON is going to be in the sky next November. NEXT November. That’s over a year away. Anything could happen before then.

And yet…

By Stuart Atkinson

Posted on by Nancy Atkinson

New ‘Sun-Skirting’ Comet Could Provide Dazzling Display in 2013

2013 is looking to be a promising year for potential naked-eye comets, as a new comet has been discovered that will likely skirt close to the Sun, and could provide a stunning display late next year. The comet, named Comet C/2012 S1 (ISON), as it was discovered by a Russian team at the International Scientific Optical Network (ISON), is currently about the distance of Jupiter’s orbit. But it is projected to come within less than 2 million km from the Sun at perihelion by November 28, 2013. Ernesto Guido and Giovanni Sostero from the Remanzacco Observatory in Italy, along with their colleague Nick Howes from the UK have imaged the comet with the RAS telescope in New Mexico, and say, “According to its orbit, this comet might become a naked-eye object in the period November 2013 – January 2014. And it might reach a negative magnitude at the end of November 2013.”

This new comet joins Comet C/2011 L4 PanSTARRS, which is projected to come within 45 million kilometers (28 million miles) of the Sun on March 9, 2013, which is close enough for quite a bit of cometary ice to vaporize and form a bright coma and tail. Comet PanSTARRS will be visible at perihelion to southern hemisphere, while Comet ISON should be visible to mid-latitude northern hemisphere skywatchers, according to the Remanzacco team.

Orbit diagram from JPL’s Small Body Database of Comet ISON, as of Sept. 25, 2012. Credit: JPL

Right now, Comet ISON is at magnitude +18, and only larger telescopes can see it. How bright will the comet get, and could it even be visible during daytime? That’s the big question which only time will answer. Just 2 million km distant from the Sun is incredibly close, and if the comet stays intact, some estimates say it could reach a brilliant negative magnitude of between -11 and -16. Comparatively, the full Moon is about magnitude -12.7.

But this will happen only if the comet will stay together. Comets can be fairly unpredictable, and other comets that have come that close to the Sun — such as Comet Elenin in 2011, Comet LINEAR in 1999 and Comet Kohoutek in 1973 — failed to live up to expectations of brightness and visibility.

But other comets have survived, like Comet Lovejoy earlier this year, which came two times closer, and Comet McNaught in 2007 which became visible even in daylight when it reached magnitude -5.5. It was not as close to the Sun as Comet ISON will be, however, as McNaught was about 24 million km away.

The discovery of C/2012 S1 (ISON) was made by Vitali Nevski, of Vitebsk, Belarus, and Artyom Novichonok, of Kondopoga, Russia with a 0.4-meter reflecting telescope near Kislovodsk, Russia.

You can see the ephermides of the Comet ISON here, from the Minor Planet Center.

The a Remanzacco Observatory team has more images, including an animation of Comet ISON on their website.

You can see the full visibility calculations of Comet ISON done by Daniel Fischer here.

Posted on by Nancy Atkinson

Comet Pan-STARRS: How Bright Will it Get?

Comet PanSTARRS on September 4, 2012 as seen from Puerto Rico. Credit: Efrain Morales/Jaicoa Observatory.

Early next year, a comet will come fairly close to Earth and the Sun — traveling within the orbit of Mercury — and it has the potential to be visible to the naked eye. Amateur and professional astronomers alike have been keeping watch on Comet C/2011 L4 PanSTARRS (or PanSTARRS for short), trying to ascertain just how bright this comet may become. It will come within 45 million kilometers (28 million miles) of the Sun on March 9, 2013, which is close enough for quite a bit of cometary ice to vaporize and form a bright coma and tail.

But just how bright, no one can say for sure. Comets have been known to be very unpredictable (remember the breakup of Comet Elenin?) but some estimates have said this comet could become a naked-eye object, as bright as Vega or Arcturus next March.

Right now it is at about Magnitude 12, and skywatchers in the southern hemisphere observers will have a great view as this comet gets closer and brighter, as it will remain high in the sky. But right now, skywatchers in the northern latitudes are saying farewell to Comet PANSTARRS, as it becomes low on the horizon. Astrophotographer Efrain Morales from Puerto Rico took the image above on September 4th, 2012 at 00:31 UTC. “It was very difficult to image due to the forest tree tops and sunset light but I was able to capture it at high magnification,” Efrain told us. (He used an LX200ACF 12 inch, OTA, CGE mount, F10, ST402xmi Ccd, Astronomik Ir/UV filter at 2 minutes. )

Observers in the mid-northern latitudes won’t be able to see the comet again until after its perihelion, unfortunately. And after that, we may never see Comet PanSTARRS again.

The discovery of the comet was made in June 2011 with the 1.8 meter (70.7 inch) Panoramic Survey Telescope & Rapid Response System or Pan-STARRS telescope on Mount Haleakala. PanSTARRS is looking to image the entire sky several times a month to hunt for Earth-approaching comets and asteroids that could pose a danger to our planet.

Richard Wainscoat and graduate student Marco Micheli confirmed the object was a comet using the Canada-France-Hawaii Telescope on Mauna Kea.

“The comet has an orbit that is close to parabolic,” Wainscoat said, “meaning that this may be the first time it will ever come close to the Sun, and that it may never return.”

Astronomers at the PanSTARRS telescope say that making brightness predictions for new comets is difficult because astronomers do not know how much ice they contain. Because sublimation of ice (conversion from solid to gas) is the source of cometary activity and a major contributor to a comet’s overall eventual brightness, this means that more accurate brightness predictions will not be possible until the comet becomes more active as it approaches the sun and astronomers get a better idea of how icy it is.

It will be an adventure to follow the comet’s close approach, and we hope our readers and astrophotographers in the southern hemisphere will keep us posted!

See our previous article about this comet.

Posted on by Nancy Atkinson

Asteroid Lutetia Flyby Animation

All asteroids and comets visited by spacecraft as of November 2010 Credits: Montage by Emily Lakdawalla. Ida, Dactyl, Braille, Annefrank, Gaspra, Borrelly: NASA / JPL / Ted Stryk. Steins: ESA / OSIRIS team. Eros: NASA / JHUAPL. Itokawa: ISAS / JAXA / Emily Lakdawalla. Mathilde: NASA / JHUAPL / Ted Stryk. Lutetia: ESA / OSIRIS team / Emily Lakdawalla. Halley: Russian Academy of Sciences / Ted Stryk. Tempel 1, Hartley 2: NASA / JPL / UMD. Wild 2: NASA / JPL.

In today’s Weekly Space Hangout, Emily Lakdawalla from the Planetary Society mentioned an animation of recently released images from the Rosetta mission’s flyby of asteroid Lutetia. It was put together and processed by Ian Regan, and Emily suggested you play this on a hand-held device (like a smart phone) in a dark room and move it around like you yourself are maneuvering the flyby! Try it — it is a very cool effect!

And while you’re at it, you also need to check out Emily’s montage poster of asteroids and comets, below:


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Check out more pretty images of Lutetia by Emily at the Planetary Blog.

Posted on by Nancy Atkinson

Frantic Comet Massacre Taking Place at Fomalhaut

Herschel's far-infrared observations of Fomalhaut and its disk. Credit: ESA

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There may be some frantic activity going on in the narrow, dusty disk surrounding a nearby star named Fomalhaut. Scientists have been trying to understand the makeup of the disk, and new observations by the Herschel Space Observatory reveals the disk may come from cometary collisions. But in order to create the amount of dust and debris seen around Fomalhaut, there would have to be collisions destroying thousands of icy comets every day.

“I was really surprised,” said Bram Acke, who led a team on the Herschel observations. “To me this was an extremely large number.”

Fomalhaut is a young star, just a few hundred million years old, about 25.1 light years away and twice as massive as the Sun. It is the brightest star in the constellation Piscis Austrinus and one of the brightest stars in our sky, visible in the southern sky in the northern hemisphere in fall and early winter evenings.

Fomalhaut’s toroidal dust belt was discovered in the 1980s by the IRAS satellite. It’s been viewed several times by the Hubble Space Telescope, but Herschel’s new images of the belt show it in much more detail at far-infrared wavelengths than ever before.

The narrow and asymmetrical properties of the disk are thought to be due to the gravity of a possible planet in orbit around the star, but the existence of the planet is still under study.

Hubble's view showing a possible exoplanet Fomalhaut b (NASA/HST)

Acke, from the University of Leuven in Belgium, and his team colleagues analyzed the Herschel observations and found the dust temperatures in the belt to be between –230 and –170 degrees C, and because Fomalhaut is slightly off-center and closer to the southern side of the belt, the southern side is warmer and brighter than the northern side.

Those observations collected starlight scattering off the grains in the belt and showed it to be very faint at Hubble’s visible wavelengths, suggesting that the dust particles are relatively large. But that appears to be incompatible with the temperature of the belt as measured by Herschel in the far-infrared.

While observations with Hubble suggested the grains in the dust disk would be relatively large, the Herschel data show that the dust in the belt has the thermal properties of small solid particles, with sizes of only a few millionths of a meter across. HST observations suggested solid grains more than ten times larger.

To resolve the paradox, Acke and colleagues suggest that the dust grains must be large fluffy aggregates, similar to dust particles released from comets in our own Solar System. These would have both the correct thermal and scattering properties.

However, this leads to another problem.

The bright starlight from Fomalhaut should blow small dust particles out of the belt very rapidly, yet such grains appear to remain abundant there.

So, the only way to explain the contradiction is to resupply the belt through continuous collisions between larger objects in orbit around Fomalhaut, creating new dust.

This isn’t the first time that evidence of cometary collisions have been seen around another star. Last year, astronomers using the Spitzer Space Telescope detected activity resembling a ‘heavy bombardment’ type of event where icy bodies from the outer solar system are possibly pummeling rocky worlds closer to the star.

At Fomalhaut, however, to sustain the belt, the rate of collisions must be remarkable: each day, the equivalent of either two 10 km-sized comets or 2,000 1 km-sized comets must be completely crushed into small, fluffy dust particles.

In order to keep the collision rate so high, scientists say there must be between 260 billion and 83 trillion comets in the belt, depending on their size. This is not unfathomable, the team says, as our own Solar System has a similar number of comets in its Oort Cloud, which formed from objects scattered from a disc surrounding the Sun when it was as young as Fomalhaut.

“These beautiful Herschel images have provided the crucial information needed to model the nature of the dust belt around Fomalhaut,” said Göran Pilbratt, ESA Herschel Project Scientist.

Source: ESA

Posted on by Nancy Atkinson

Milky Way’s Supermassive Black Hole is Feasting on Asteroids

Mysterious X-ray flares caught by Chandra may be asteroids falling into the Milky Way's giant black hole. Credit: X-ray: NASA/CXC/MIT/F. Baganoff et al.; Illustrations: NASA/CXC/M.Weiss

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For the past several years, the Chandra telescope has detected X-ray flares occurring about once a day from the supermassive black hole at the center of the Milky Way Galaxy. These flares last a few hours with brightness ranging from a few times to nearly one hundred times that of the black hole’s regular output. What could be causing these unusual, mysterious flares? Scientists have determined that the black hole could be feasting hungrily on asteroids that come too close and vaporizing them, creating the flares. Basically, the black hole is eating asteroids and then belching out X-ray gas.

If confirmed, this result would mean that there is a huge, bustling cloud around the black hole containing hundreds of trillions of asteroids and comets.

“People have had doubts about whether asteroids could form at all in the harsh environment near a supermassive black hole,” said Kastytis Zubovas of the University of Leicester in the United Kingdom, and lead author of a new paper. “It’s exciting because our study suggests that a huge number of them are needed to produce these flares.”

The scientists say this really isn’t as far-fetched as it may sound, as it mirrors an event that regularly takes place in our Solar System: About every three days a comet is destroyed when it flies into the hot atmosphere of the Sun. Despite the significant differences in the two environments, the destruction rate of comets and asteroids by the Sun and the black hole at the center of our galaxy, called Sagittarius A*, or “Sgr A*” for short, may be similar.

These asteroids and comets have likely been ripped from their parent stars, and to create the flare the asteroids or comets have to be fairly large, at least 19 km (12 miles) wide.

The astronomers propose this scenario: An asteroid undergoes a close encounter with another object, such as a star or planet, and is thrown into an orbit headed towards Sgr A*. If the asteroid passes within about 100 million miles of the black hole, roughly the distance between the Earth and the Sun, it would be torn into pieces by the tidal forces from the black hole. These fragments then would be vaporized by friction as they pass through the hot, thin gas flowing onto Sgr A*, similar to a meteor heating up and glowing as it falls through Earth’s atmosphere. A flare is produced and the remains of the asteroid are swallowed eventually by the black hole.

“An asteroid’s orbit can change if it ventures too close to a star or planet near Sgr A*,” said co-author Sergei Nayakshin, also of the University of Leicester. “If it’s thrown toward the black hole, it’s doomed.”

The team says these results reasonably agree with models estimating of how many asteroids are likely to be in this region, assuming that the number around stars near Earth is similar to the number surrounding stars near the center of the Milky Way.

“As a reality check, we worked out that a few trillion asteroids should have been removed by the black hole over the 10-billion-year lifetime of the galaxy,” said co-author Sera Markoff of the University of Amsterdam in the Netherlands. “Only a small fraction of the total would have been consumed, so the supply of asteroids would hardly be depleted.”

This scenario would not be limited to asteroids and comets, however. Planets thrown into orbits too close to Sgr A* also could also be disrupted by tidal forces, although planets in the region are less common. And of course, if a planet was consumed, it would create an even larger flare; and this may have occurred about a century ago when Sgr A* brightened by about a factor of a million. Chandra and other X-ray missions have seen evidence of an X-ray “light echo” reflecting off nearby clouds, providing a measure of the brightness and timing of the flare.

“This would be a sudden end to the planet’s life, a much more dramatic fate than the planets in our solar system ever will experience,” Zubovas said.

Very long observations of Sgr A* will be made with Chandra later in 2012 that will give valuable new information about the frequency and brightness of flares and should help to test the model proposed here to explain them. The team said this work could improve understanding about the formation of asteroids and planets in the harsh environment of Sgr A*.

Paper: “Sgr A* flares: tidal disruption of asteroids and planets?”; K. Zubovas, S. Nayakshin, S. Markoff”

Sources: Chandra, RAS

Posted on by Nancy Atkinson

Beautiful Conjunction: Comet Garradd Meets M92

This lovely image of Comet Garradd (C/2009 PI) as it passes by the globular cluster M92 in the constellation Hercules, was taken remotely from the Tzek Maun Observatory in New Mexico by our friends Giovanni Sostero, Ernest Guido and Nick Howes. While the two objects look like they are right next to each other, M92 is over 25,000 light-years away while Comet Garradd is 12.5 light-minutes away from Earth! The comet looks almost like a bird or winged starship in flight with the dust tail and ion tail shooting off on either side. Comet Garradd is still on show in the northern hemisphere, although you’ll at least need binoculars to see it. The comet is around magnitude 7 now, and is heading north, so over the course of the next few weeks, it should become a little easier to see. For now, you need to get up early to see it, (around 5:30 to 6:30 am), but by the end of the month it should be visible all night long.

You can see another image of Garradd on today’s APOD (but personally I really like the one right here!)

Posted on by Nancy Atkinson

Can We Land On a Comet?

An artist concept of the Philae lander on comet 67P/Churyumov-Gerasimenko. Credit: Astrium - E. Viktor/ESA

The Rosetta mission will do something never before attempted: land on a comet. The spacecraft is now on its way to intercept comet 67P/Churyumov-Gerasimenko in January 2014 and land a probe on it for what promises to be an amazing view. But what we know of comets so far comes from a few flyby missions. So, with surface composition and conditions largely a mystery, so how did engineers prepare to land on something that could be either solid ice or rock, or a powdery snow or regolith – or something in between?

They had to design the Philae lander so it could land equally well on any surface. In the tiny gravitational field of a comet, landing on hard icy surface might cause Philae to bounce off again. Alternatively, hitting a soft snowy one could result in it sinking. To cope with either possibility, Philae will touch as softly as possible. In fact, engineers have likened it more to docking in space.

Philae will fire harpoons to secure itself to the comet; additionally, the landing gear is equipped with large pads to spread its weight across a broad area (kind of like snowshoes.)

While landing on a comet will certainly be nail-biting, having a front row seat for when the comet gets closer to the Sun is the most highly anticipated part of the mission.

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“In some ways, a flyby is just a tantalizing glimpse of a comet at one stage in its evolution,” says Claudia Alexander, project scientist for the U.S. Rosetta Project at JPL. “Rosetta is different. It will orbit 67P for 17 months. We’ll see this comet evolve right before our eyes as we accompany it toward the Sun and back out again.”

We’ll be able to watch as it becomes “something poetic and beautiful, trailing a vast tail,” said Alexander. For once, we’ll be able to watch the surface of a comet transform in front of our eyes instead of relying on artist concept drawings! Additionally, the Rosetta spacecraft up above will be busy mapping the comet’s surface and magnetic field, monitoring the comet’s erupting jets and geysers, measuring outflow rates, and much more. Together, the orbiter and lander will build up the first 3-D picture of the layers and pockets under the surface of a comet.

Comets are considered a gold mine for astronomers who want to know what conditions were like back in the early days of our Solar System. And the data and images from this mission promises to be some of the most stunning we’ve yet seen.

Find out more about the Rosetta mission in the accompanying video, or see the ESA Rosetta website.

Source: Science@NASA

Posted on by Nancy Atkinson

5 Hours of Beautiful Comet Lovejoy in 30 Seconds

Colin Legg from Esperance, Australia has been documenting Comet Lovejoy’s holiday gift to the southern hemisphere, and this is his latest — and possibly last — timelapse, as the comet has started to fade. This one covers almost 5 hours of Legg’s Comet Lovejoy views as seen during the early morning hours of December 27, 2011. “I used a tracking device to track in azimuth only to maximize coverage,” Legg said. “If you look closely at the head in the 2nd half you can see it moving against the stars.”

Posted on by Nancy Atkinson

Stunning! Comet Lovejoy Photographed from the Space Station

Comet Lovejoy is visible near Earth’s horizon in this nighttime image photographed by NASA astronaut Dan Burbank, Expedition 30 commander, onboard the International Space Station on Dec. 21, 2011. Credit: NASA

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*Now updated with video!*

We can’t get enough of Comet Lovejoy! But this latest image is off the charts for its beauty and it’s jaw-dropping to contemplate it was taken from space. Dan Burbank, Expedition 30 commander onboard the International Space Station took this image of Comet Lovejoy on Dec. 21, 2011. See more of Burbank’s shots of Lovejoy here.

NASA now has a timelapse video of Burbank’s observations of Comet Lovejoy: