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Unmanned Spaceflight.com _ Telescopic Observations _ Planet-Forming Disk Vanishes In Less Than Two Years

Posted by: Mongo Jul 4 2012, 07:21 PM

http://news.sciencemag.org/sciencenow/2012/07/poof-planet-forming-disk-vanishe.html

QUOTE

Some 460 light-years away in the constellation Centaurus, a thick disk of dust swirled around a young star named TYC 8241 2652 1, where rocky planets like our own were arising. Then, in less than 2 years, the disk just vanished. That's the unprecedented observation astronomers report in a new study, out today. Even more intriguing: The same thing may have happened in our own solar system.

Born about 10 million years ago, the TYC 8241 2652 1 system was chugging along just fine before 2009. Its so-called circumstellar disk glowed at the infrared wavelength of 10 microns, indicating it was warm and lay close to a star—in the same sort of region that, in our own sun's neighborhood, gave rise to the terrestrial planets Mercury, Venus, Earth, and Mars. The infrared data reveal that the dust was about 180°C and located as close to its star as Mercury is to the sun.

By January 2010, however, nearly all infrared light from the dusty disk had vanished. "We had never seen anything like this before," says astronomer Carl Melis of the University of California, San Diego. "We were all scratching our heads and wondering what the hell did we do wrong?" But subsequent observations with both infrared satellites and ground-based telescopes confirmed the surprising discovery, he says: "The disk was gone."

Nature letter (behind paywall) http://www.nature.com/nature/journal/v487/n7405/full/nature11210.html

Posted by: JRehling Jul 5 2012, 04:55 PM

Two things are striking there:

1) That such a thing can happen at all.
2) That we were unbelievably lucky enough to witness an example of it happening.

Even if this happened to every star, how many would you have to be watching to expect to get a before-and-after of one of them in our lifetimes? There's a formal answer to that seemingly rhetorical question, and I'd like to see the math.

I wonder if the "dust" was actually ice. It's pretty easy to imagine a trillion grains of ice vanishing in a short time frame. Rock, that's trickier.

Posted by: Hungry4info Jul 5 2012, 06:34 PM

Could this have been an impact on some planetary or asteroid body further from the star? In the two years since, the dust may have cooled beyond detectability?

Posted by: Gsnorgathon Jul 6 2012, 01:17 AM

Inmigrating Jovian? I'd be interested to know if anyone's looked for planets around this star.

Posted by: Vultur Jul 7 2012, 06:59 PM

QUOTE (JRehling @ Jul 5 2012, 05:55 PM)

I would think it would depend on the star's lifetime ... if it happened exactly once per star, and we assume that our time-of-observation is randomly placed within the star's lifetime (which probably isn't truly accurate - there are many more M dwarfs than anything else, and AIUI their lifespans are so long that all low-mass M dwarfs are 'young' since the universe is only c. 14 billion years old), then - for each star - the probability of observing it in the time during which we observe the star would be (time of observation)/(star's lifetime), wouldn't it?

Posted by: brellis Jul 7 2012, 08:29 PM

Two questions: why do they think the system is 10 million yrs old? and what if the ring disappeared because the star tilted edge on to our p.o.v.?

Posted by: Explorer1 Jul 8 2012, 01:05 AM

Then the dust would obscure its light, easily detectable from here. How would an entire dust cloud tilt in unison in the first place? They should be stationary from whatever angle they formed at (like Uranus's rings being as titled as their planet).

Posted by: Hungry4info Jul 8 2012, 04:46 AM

He's probably thinking of the proper motion of the star bringing us into the plane of the disk (similar to how Saturn's rings "disappear" every few years).
But the timescales involved with this would be enormous and as Explorer1 said, the star would noticably dim.

Besides I don't think circumstellar disks are nearly as thin as planetary disks.

Posted by: JRehling Jul 13 2012, 05:54 PM

Vultur, your math is right, but the key question is how many stars we are observing. The odds of seeing any particular star's once-in-a-lifetime event is essentially zero. The odds of seeing one if we observe millions of stars starts to become credible (with caveats).

So without saying any more than that about the specifics of this event, if we are not similarly tracking millions of stars, then this is probably not a once-in-a-star's-lifetime event.

If we imagine that each Mars-sized planetesimal arises from the collision of 10 Luna-sized planetesimals, and each Earth-sized planet arises from the collision of 10 Marses, then for a system to acquire the quartet of terrestrial planets that our solar system has would involve about 500 collisions. Forming the cores of the gas giants would involve far more, putting the number into the thousands. And many other collisions would take place on the sub-Luna level. So I suspect that is more likely the kind of event we're seeing rather than the one and only disappearance of the only dusty disc this star will ever have.