Gemini: Planet-Forming Disk Goes Out of Business

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Gemini: Planet-Forming Disk Goes Out of Business

Post by bystander » Thu Jul 05, 2012 8:51 pm

Going Out Of Business: Planet-Forming Disk Turns Off Lights, Locks Doors ...
Gemini Observatory | 2012 July 04
Click to view full size image 1 or image 2
Artist's conceptualization of the dusty TYC 8241 2652 system as it might
have appeared several years ago when it was emitting large amounts of
excess infrared radiation and (mouse over) as it might appear now after
most of the surrounding dust has disappeared - based on observations by
the Gemini Observatory and other ground and space-based observatories.
(Credit: Gemini Observatory/AURA artwork by Lynette Cook)

That surprise you feel when your favorite store turns off its lights, locks up its doors, and suddenly, for no apparent reason, goes out of business? That's just how astronomers felt recently when a dusty disk of rocky debris around a nearby star abruptly shut down and by all appearances went out of business.

The star -- designated TYC 8241 2652 and a young analog of our Sun -- only a few years ago displayed all of the characteristics of hosting a solar system in the making. Now, it has transformed completely: very little of the warm dusty material thought to originate from collisions of rocky planets is apparent - it's a mystery that has astronomers baffled.

Carl Melis of the University of California, San Diego, led the discovery team, whose report is published in the July 5th issue of the journal Nature. He said, "It's like the classic magician's trick: now you see it, now you don't. Only in this case we're talking about enough dust to fill an inner solar system and it really is gone!"

Co-author Ben Zuckerman of the University of California Los Angeles, observed, "It's as if you took a conventional picture of the planet Saturn today and then came back two years later and found that its rings had disappeared."

The dusty disk at TYC 8241 2652 was first seen by the NASA Infrared Astronomical Satellite (IRAS) in 1983, and remained brightly glowing for 25 years. Like Earth, warm dust absorbs the energy of visible starlight (sunlight) and reradiates that heat energy as infrared radiation. An infrared image obtained at the Gemini telescope in Chile on May 1, 2012 - just as the paper was being accepted by Nature - confirmed that the warm dust has now been gone for 2.5 years.

"A perplexing thing about this discovery is that we don't have a really satisfactory explanation to address what happened around this star. The disappearing act appears to be independent of the star itself, as there is no evidence to suggest that the star zapped the dust with some sort of mega-flare or any other violent event," said Melis.

Zuckerman, who has been investigating circumstellar disks (debris disks around stars) since the 1980s, noted that "the dust disappearance at TYC 8241 2652 was so bizarre and so quick, initially I figured that our observations must simply be in error in some strange way."

Norm Murray, Director of the Canadian Institute for Theoretical Astrophysics, who was not part of the research group, said, "The history of astronomy has shown that events that are not predicted and hard to explain can be game-changers".

The lack of an existing model for what is going on around this star is forcing astronomers to rethink what happens within young solar systems in the making.

"Although we've identified a couple of mechanisms that are potentially viable, none are really compelling," said Melis. "In one case, gas produced in the impact that released the dust helps to quickly drag the dust particles into the star and thus to their doom. In another possibility, collisions of large rocks left over from an original major impact provide a fresh infusion of dust particles into the disk which then instigate a runaway process where small grains chip into oblivion both themselves and also larger grains."

Major dusty regions such as the asteroid belt and another located out beyond the orbit of Neptune are known to exist in our own solar system. Nearly 30 years ago, NASA's Infrared Astronomical Satellite (IRAS) first discovered similar regions orbiting other stars. Now hundreds of stars similar to our Sun are known to emit an excess of infrared radiation that is usually attributed to dusty materials orbiting the star in what are called debris disks. It is believed that this material results from planetary system formation and is due to collisions and reprocessing of objects like the comets and asteroids that are part of our own solar system. But nothing like the disappearing dust disk at TYC 8241 2652 had ever been seen during these three decades.

The result is based upon multiple sets of observations of TYC 8241 2652 obtained with the Thermal-Region Camera Spectrograph (T-ReCS) on the Gemini South telescope in Chile, the IRAS satellite, the Wide-field Infrared Survey Explorer (WISE) satellite, NASA's Infrared Telescope on Mauna Kea in Hawai`i, the Herschel Space Telescope of the European Space Agency, and AKARI (a Japanese/ESA infrared satellite).

TYC 8241 2652 lies in the direction of the constellation of Centaurus. Observations by Australian co-authors Simon Murphy and Michael Bessell with the Australian National University's 2.3-meter telescope established that the star is roughly 10 million years old and 450 light years distant.

Study in Nature sheds new light on planet formation
University of Georgia | 2012 July 04

Astronomers discover Houdini-like vanishing act in space
University of California, Los Angeles | 2012 July 05

Fetal Solar System Aborted
Discovery News | Irene Klotz | 2012 July 04

The Case of the Disappearing Dust
Universe Today | Jason Major | 2012 July 05

The Mysterious Case of the Disappearing Dust
NASA JPL-Caltech | 2012 July 05

Rapid disappearance of a warm, dusty circumstellar disk - Carl Melis et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by neufer » Thu Jul 05, 2012 9:15 pm


"A perplexing thing about this discovery is that we don't have a really satisfactory explanation to address what happened around this star. The disappearing act appears to be independent of the star itself, as there is no evidence to suggest that the star zapped the dust with some sort of mega-flare or any other violent event," said Melis.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by geckzilla » Thu Jul 05, 2012 9:58 pm

Is it not possible for the disc of dust to have rotated to the point that we aren't looking at its edge but through the hole in the middle? Or maybe it was never shaped like a disc like the illustration.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Chris Peterson » Thu Jul 05, 2012 10:16 pm

geckzilla wrote:Is it not possible for the disc of dust to have rotated to the point that we aren't looking at its edge but through the hole in the middle?
I'm not sure if the angle we're viewing this system is even known. I think the data comes from looking at the intensity of IR radiation in the 1-100 um range. I don't think that would change much with orientation. That said, what could change the orientation of a dust disc the size of a solar system? That would probably be an even more remarkable thing than the disappearance of the IR heat signature itself.
Or maybe it was never shaped like a disc like the illustration.
Do you have some other shape in mind? How would that make the IR signal go away, either now or periodically?
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by geckzilla » Thu Jul 05, 2012 10:18 pm

Oh, so it would be detected even if the light weren't shining through the dust? Then I guess it wouldn't matter what shape it was in.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Chris Peterson » Thu Jul 05, 2012 10:41 pm

geckzilla wrote:Oh, so it would be detected even if the light weren't shining through the dust? Then I guess it wouldn't matter what shape it was in.
My understanding is that the dust is absorbing energy from the star, and re-radiating it in IR. A hot star doesn't produce much IR, so when it is observed it's assumed to be from dust. There are only a handful of stars that have actually had dust rings imaged in the sense of being spatially resolved. I think in this case it's just a spectrum that is being observed, and there's been a big drop in intensity at IR wavelengths. That's what everybody is scratching their heads about, because that much (assumed) mass shouldn't be able to dissipate quickly, or cool quickly.

I suppose you could imagine cases where shape would matter. If it were a very thin disc, the foreground dust might obscure much of the signal from the rest when edge-on, making a small signal. But then you have to figure out how the orientation could shift so quickly. An isolated hot blob orbiting the star (like a proto binary component) might get eclipsed by something. But what? That would probably produce some interesting absorption lines... not sure if anybody has looked. It's a safe bet that a lot of instruments are going to be focused on this object over the near term, trying to figure it out.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by geckzilla » Thu Jul 05, 2012 10:53 pm

I was thinking of something like the "vanishing" rings of Saturn. And I don't know what other shapes are possible, I just thought that since nothing else in the universe is perfectly shaped all the time that I shouldn't assume a dust disc would be either. Anyway, as usual, I misunderstood the fundamentals.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by neufer » Thu Jul 05, 2012 11:04 pm

geckzilla wrote:
I was thinking of something like the "vanishing" rings of Saturn.
The rings of Saturn "vanish" because the observer's position relative to Saturn changes over time.

However, our position relative to TYC 8241 2652 is not changing.

So is something causing the disk to precess?
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Chris Peterson » Thu Jul 05, 2012 11:11 pm

neufer wrote:However, our position relative to TYC 8241 2652 is not changing.
...very fast.
So is something causing the disk to precess?
In principle the system could be precessing, but is it possible it could precess so quickly? Perhaps there could be a sudden drop in signal if the disc was very close to edge-on, and has precessed to fully edge-on over just a few years. Of course, if that explanation holds true, the signal will soon increase again.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by geckzilla » Fri Jul 06, 2012 12:10 am

Could it be warped?
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Chris Peterson » Fri Jul 06, 2012 5:15 am

geckzilla wrote:Could it be warped?
It depends on its density. If the dust is fairly low density, such that each particle is essentially in its own orbit and doesn't interact strongly with any other material, it could be a cloud of almost any shape, including an oval disc or a warped disc. But if the density is higher, so that there is angular momentum being transferred by gravitational, electromagnetic, or fluid dynamic mechanisms, it would only be stable as a flat, round disc. Of course, it could be temporarily perturbed into a warped structure, say by a collision with a dense gas cloud.
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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by MalcolmP » Fri Jul 06, 2012 10:35 am

Something that absorbs IR, but not the visible light of the star, got between us and it ? A cloud of gas perhaps, is there such a gas that would be sufficiently transparent to the visible light but not IR ? And it would need to be far enough away from the star for it not to be hot itself !
But that must be a non-runner else they would have postulated it themselves :(

'tis strange though, not normal for planetary and star sized quantities of stuff to change so quickly.
Maybe it is an "ooops" thing, like those neutrinos that wernt goingt quicker than light after all.
How many independent obs were made originally, was it just IRAS ?
The big list of instruments at the bottom of the report have all been observing it in the past ? or are they all just being used to confirm it is nolonger there iyswim
If they all have been looking at it over a number of years then there would be some decrease with time to be plotted, no mention of that in the report :(

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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Ann » Fri Jul 06, 2012 11:40 am

Chris wrote:

My understanding is that the dust is absorbing energy from the star, and re-radiating it in IR. A hot star doesn't produce much IR, so when it is observed it's assumed to be from dust. There are only a handful of stars that have actually had dust rings imaged in the sense of being spatially resolved. I think in this case it's just a spectrum that is being observed, and there's been a big drop in intensity at IR wavelengths. That's what everybody is scratching their heads about, because that much (assumed) mass shouldn't be able to dissipate quickly, or cool quickly.
Is it at all possible that the IR light came directly from the star, not from a dust disk surrounding it?

Stars occasionally undergo IR outbursts. A very famous (and unexplained) example is the tremendous IR-brilliant "sudden supergiant" V838 Monocerotis. Clearly the "vanishing dust disk" in the case of TYC 8241 2652 can't be explained by the gradual fading of an outburst similar to V838 Mon.

But what about a mechanism similar to the ones driving the IR behaviour of stars like R Corona Borealis?
http://en.wikipedia.org/wiki/R_Coronae_Borealis wrote:

R Coronae Borealis is a yellow supergiant star, and is the prototype of the RCB class of variable stars, which fade by several magnitudes at irregular intervals. R Coronae Borealis itself normally shines at approximately magnitude 6, just about visible to the naked eye, in the constellation of Corona Borealis, but at intervals of several months to many years fades to as faint as magnitude 14. Over successive months it gradually returns to its normal brightness, giving it the nickname "Fade-Out star," or "Reverse Nova".
Apparently R Corona Borealis returns to normal brightness within a few months. Clearly the young star observed by Gemini isn't a supergiant star. Isn't it still possible, nevertheless, that the sudden disappearance of the presumed dusk disk surrounding the star might be, instead, the gradual clearing of the "soot" that had been deposited in the stellar atmosphere during a previous outburst?

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Re: Gemini: Planet-Forming Disk Goes Out of Business

Post by Chris Peterson » Fri Jul 06, 2012 3:09 pm

Ann wrote:Is it at all possible that the IR light came directly from the star, not from a dust disk surrounding it?
When it comes to matters astronomical, I would be very reluctant to brand anything as impossible!
But what about a mechanism similar to the ones driving the IR behaviour of stars like R Corona Borealis?
From the little bit of technical information I've found online (not much), it seems like the observation reflects a decrease in the intensity of what otherwise presents as a pretty ordinary blackbody spectrum. If so, that means there is no change in temperature, just brightness. I don't know what stellar mechanism could do that, either directly (something in the star itself) or indirectly (a change in radiation output affecting a surrounding dust disc). And it's all the more mysterious given that I haven't seen any reports of a change in the visible light intensity of the star.

I did find another paper by the author of this one (Moerchen) that describes a system (HR 4796A) which shows asymmetric heating of its dust ring. That leads me back to the idea of a hot spot rotating to the foreground of an edge-on disc, or rotating back and being shadowed. I don't know if that's possible. But some kind of eclipsing mechanism seems more likely to me than the dust going away.
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