New study sheds new light on planet formation

July 4, 2012, University of Georgia
This illustration is an 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. Credit: Gemini Observatory/AURA artwork by Lynette Cook.

A study published in the July 5 edition of the journal Nature is challenging scientists' understanding of planet formation, suggesting that planets might form much faster than previously thought or, alternatively, that stars harboring planets could be far more numerous.

The study—a collaboration between scientists at the University of Georgia; the University of California, San Diego; the University of California, Los Angeles; California State Polytechnic University and the Australian National University—began with a curious and unexpected finding: Within three years, the cloud of dust circling a young star in the Scorpius-Centaurus stellar nursery simply disappeared.

"The most commonly accepted time scale for the removal of this much dust is in the hundreds of thousands of years, sometimes millions," said study co-author Inseok Song, assistant professor of physics and astronomy in the UGA Franklin College of Arts and Sciences. "What we saw was far more rapid and has never been observed or even predicted. It tells us that we have a lot more to learn about planet formation."

Lead author Carl Melis, a postdoctoral fellow at UC San Diego, 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."

The scientists first identified their star of interest by examining data from the Infrared Astronomical Satellite, or IRAS, which surveyed more than 96 percent of the sky in 1983. The star, known as TYC 8241 2652 1, was surrounded by a cloud of dust that was identifiable by its distinctive radiation of infrared energy. Like a skillet absorbing heat and then radiating it, the dust cloud was absorbing energy from the central star and radiating it in the infrared range. This warm dust is thought to be the raw material from which planets form, but scientists don't have a clear understanding of how long the process takes.

The scientists observed the same star in 2008 using a mid-infrared imager at the Gemini South Observatory in Chile and again with the same ground-based telescope in 2009. The 2008 observation revealed an infrared emission pattern similar to the 1983 measurement, but something surprising happened in 2009: The infrared emission dropped by nearly two-thirds. NASA's Wide-field Infrared Survey Explorer, or WISE, looked at the same star again in 2010, and the scientists found that the dust had mostly disappeared. The scientists confirmed their findings using two additional telescopes, the Japanese AKARI telescope and the European Space Agency's Photodetector Array Camera and Spectrometer, or PACS, at the Herschel Space Observatory, and the pattern held.

This illustration is an artist’s conceptualization of the dusty TYC 8241 2652 system as it might appear now based on observations by the Gemini Observatory and other ground and space-based observatories. Credit: Gemini Observatory/AURA artwork by Lynette Cook.
"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," said co-author Ben Zuckerman of UC Los Angeles, who has been investigating circumstellar disks since the 1980s.

The researchers explored several different explanations for how such a large quantity of dust could disappear so rapidly, and each of their explanations challenges conventional thinking about planet formation.

Runaway accretion. The most commonly held theory of planet formation is that minute particles of dust left over after a star forms clump onto each other, first through weak electrostatic interactions and later through gravitational forces. The aggregated dust particles eventually grow to become pebble-sized and then car- to house-sized objects. Ultimately, they become planets. The timescale at which this accretion occurs has been theorized and modeled mathematically, and Song said it is commonly thought to occur over hundreds of thousands of years, a time period that spans civilizations on Earth but is an astronomical blink of an eye.

"If what we observed is related to runaway growth, then our finding suggests that planet formation is very fast and very efficient," Song said. "The implication is that if the conditions are right around a star, planet formation can be nearly instantaneous from astronomical perspective."

The star that the scientists observed is 450 light years away, however, which means any planet formed would not be visible with today's technology.

Song added that a slightly different version of the "runaway accretion" theory suggests that dust grains accrete onto the central star in a very short timescale, implying that the star effectively eliminates planet-building material. If such events occur frequently, is much less likely than previously thought.

Collisional avalanche. Another explanation for the sudden disappearance of the dust is that it was expelled from the sun's orbit. Song explained that the particles are so small—a hundred times smaller than a grain of sand—that the constant stream of photons emanating from the sun could push them away and into each other, like pinballs, until they leave the suns' orbit.

Because large clouds of dust can be formed when orbiting planets crash into each other, astronomers have often viewed the presence of such clouds as indirect evidence of unseen planets. If clouds of dust are only fleeting, however, then many more stars than previously thought could harbor planets.

"People often calculate the percentage of stars that have a large amount of dust to get a reasonable estimate of the percentage of stars with planetary systems, but if the dust avalanche model is correct, we cannot do that anymore," Song said. "Many stars without any detectable dust may have mature planetary systems that are simply undetectable."

Next steps. Like many important discoveries, the scientists' finding raises more questions than it answers. Song said his colleagues now aim to compare measurements from 1983 with data from modern telescopes to systematically search for other stars that have rapidly depleted—or replenished—their dust clouds. The goal is to understand the frequency with which these processes occur and, ultimately, to advance understanding of how planets form.

"Many astronomers may feel uncomfortable with the suggested explanations for the disappearance of the because each of them has non-traditional implications," Song said, "but my hope that this line of research can bring us closer to a true understanding of how form."

Explore further: Astronomers discover a rare stellar disk of quartz dust

More information: Nature, July 4, pp 74-76.

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1.6 / 5 (12) Jul 04, 2012
Well, if those are the assumptions scientists have used, their calculations have been wrong.

An easy, 9th to 12th grade level physics calculation shows that such a collapse can occur with a 1M star, without the need for planets, in as little as 60 years for all of the matter within 40 astronomical units of the host star..

With the formation of planets as local mass/gravity maximums, and additional surface area footprint sweeping out the area of said orbits, it is reasonable to assume that the collapse could occur in a fraction of the 60 year, particularly in some optimal area in the middle of the range of the star.

A planet passing close to a dust cloud or asteroid belt will have a much greater gravitational influence on it than does the host star, even though the planet has much less mass than the host star, due to the inverse squared relationship of distance and gravity.

planets would accelerate the rate of collapse even if total system mass is the same either way...
4.8 / 5 (17) Jul 04, 2012
Well, if those are the assumptions scientists have used, their calculations have been wrong.

It's obvious that you didn't even bother to read the paper in question ("Rapid disappearance of a warm, dusty circumstellar disk", Nature (487): 74-76, 2012), let alone the other articles from which its results are based (E. Waxman and B. T. Draine, "Dust sublimation by gamma-ray bursts and its implications", Astrophys. J., (537): 796-802, 2000; A. Grigorieva, et al., "Collisional dust avalanches in debris discs", Astron. Astrophys., (130): 537-549, 2007; and B. Metzger, et al., "Global models of runaway accretion in white dwarf debris disks", Mon. Not. R. Astron. Soc. (423): 505-528, 2012). Of course, if you did and are deluded enough to believe that you are correct/that these well-established models are wrong, feel free to contact the editors of Nature and the other journals I listed: I'm sure they'll reiterate that your own "calculations" have little merit.
1 / 5 (4) Jul 04, 2012
"What we saw was far more rapid and has never been observed or even predicted. It tells us that we have a lot more to learn about planet formation."
It's well known already, try to read for example this ten years old article. It's example of so called sensationalism, which is pretending, that the results of research are more significant/fundamental/original, then they really are. Which I could understand, if it wouldn't often connected with the ignorance of the original findings and their authors. The scientific priority of the original idea or finding should be always respected.
5 / 5 (11) Jul 04, 2012
Oh, and one more thing. I actually did independently verify the results of C. Melis, et al.

For instance, taking the TYC 8241 2652 1 disc Poynting-Robertson drag into account and assuming that the underlying physical mechanisms are similar between it and metal-rich white dwarfs (R. R. Rafikov, "Runaway accretion of metals from compact discs of debris on to white dwarfs", Mon. Not. R. Astron. Soc. (416): 55-59, 2011), runaway accretion rates are sufficient to explain the disappearance of grains with size from 100m-1mm on a timescale of a few years. (In the event that the disc is hot and gaseous and assuming a constant accretion rate over the duration of the disc dissolution, a gas:dust ratio of 10, and 10^23g of 1mm-sized dust grains corresponding to a conventional distribution (S. J. Kenyon, et al., "Prospects for detection of catastrophic collisions in debris disks", Astron. J. (130): 269-279, 2005), the accretion rate is ~10^-8 to 10^-9 M solar yr^-1.)
1.4 / 5 (9) Jul 04, 2012
Re: "Many astronomers may feel uncomfortable with the suggested explanations for the disappearance of the dust because each of them has non-traditional implications"

And yet, we can be sure that the researchers will continue to refuse to question the underlying assumptions which got them to this point. They will continue to infer within the box of the gravitational scientific framework, while ignoring the ease with which laboratory plasmas conducting electrical currents are known to regularly and very rapidly accrete matter into balls called spherules (aka "blueberries").

From http://www.thunde...apter-6/

"Plasmas often contain a high proportion of charged dust grains, which will also be drawn into the filament. Viscous drag between the charged particles and neutral atoms will tend to draw the neutral atoms towards the filament as well."
1.6 / 5 (7) Jul 04, 2012

"Therefore, current filaments in space will tend accumulate matter in them as a result of the misalignment of the electric field causing the current and the total magnetic field.

Remembering that pinches can occur if any misalignment of I and B occurs, any matter that has been drawn into the filament will also be compressed if a misalignment of I and B occurs. If the pinch force is large enough, it can fragment the filament into discrete spherical or toroidal plasmoids along the axis of the current. Any matter in the pinch zone would then become compressed into the same form.

Because the electromechanical forces are vastly stronger than gravity, this mechanism offers a means by which diffuse matter can be accumulated and compressed in a much more efficient way than gravitational compression of diffuse clouds of fine dust particles."


In other words, when the MHD models are fixed to permit the formation of E-fields, electricity over plasmas can solve this problem.
1 / 5 (2) Jul 04, 2012

I used the gravitational acceleration formula and the distance formula for acceleration, and worked backwards to obtain time, given the mass of the host star.

At any rate, it certainly only comes to a few billion SECONDS, not millions or hundreds of thousands of years.

Note: I didn't invent distance or gravitational acceleration formulas. I just plugged real world values into them and got the outputs.
4.7 / 5 (7) Jul 04, 2012
The devil will be in the observational details, the disks are best seen top down, while the resulting planets are best seen by wobble or transit from sideways. That said, the Kepler and Corot data is sufficient to conclude that planet formation rates are high, and gravitational microlensing statistics says the same for expelled wandering exoplanets.
As for science denialists suggesting that they know the field of planet formation is wrong - it was already in a dynamic state after the Corot & Kepler finds of diversity that older models couldn't predict. So they question models, they don't do "assumptions" that are never tested. We will see what it lands in, this was _one_ observation, hardly putting stress on the models yet. It needs to be repeated, for one.

And so hilarious: plasmas isn't even on the table to explain gravitational systems like planet systems. Pattern search isn't science, science is prediction and testing.
1 / 5 (4) Jul 04, 2012
Conventional ideas for this sudden change run into qualities that standard models of stellar behavior hold to. The great extent of the effect; the relative unpredictable and spotty behavior of random interactions of particles, such as, say collisions or accretion; the relative weakness of gravity which could cause accrestions of collisions. An alternative getting around the randomness and great size of the problem is a stellar explosion or outgassing, which, emanating from a single point, is not random, a single expanding wave, and, for a powerful enough event, is not hampered by a weak force. But no such event seems to have been recorded. There is, though, at least one alternative which involves influence that is not so random, can be wide ranging and can employ enough power to get the job done in so short a time. Maybe we are witnessing an alien race that came upon the star and decided to remove the dust and use the system for their own purposes.
2.3 / 5 (6) Jul 05, 2012
Re: "Hannes, please stop posting your ideas until you can actually demonstrate them. I work with plasmas and you are wrong about what you are saying. Once you see a plasma system truly operate and run some tests for yourself you will no longer write the complete crap you just wrote. You are making the EU side look really bad."

If physorg was a place which wanted to encourage and enable its readers to ignore those people with whom they disagree with, they would implement a Slashdot-like rating system where we could vote people down who diverge from conventional wisdom.

If you have a problem seeing people talk about theories which you don't agree with, I would argue (1) that science is probably not your thing, to begin with. You are looking for a society to belong to. But, (2) you might want to spend your time at a forum where the moderators will accommodate your sensitivities.

By the way, how in the world am I "making the EU side look really bad" by quoting EU materials?
2.3 / 5 (6) Jul 05, 2012
Re: "As for science denialists"

In theory, science is supposed to be big enough to accommodate disagreements -- especially when it comes to such uncertain topics as the formation of planets.

Re: "this was _one_ observation, hardly putting stress on the models yet."

Only a specialist would view falsification in terms of scientific domains. It's the scientific framework which is being judged here, and when it comes to evaluating that, we must take a holistic perspective of ALL of the disciplines which are based upon that framework.

When questioning assumptions might lead to the conclusion that the experts are no longer the experts, then the experts will (consciously or subconsciously) avoid questioning assumptions, and collectively defend themselves from criticisms from outsiders (which they will view as hostile attacks).

If we only teach and investigate one framework, should we really be surprised when bias creeps in? The monolithic approach to cosmology is a dangerous approach.
1.7 / 5 (6) Jul 05, 2012
Re: "Pattern search isn't science, science is prediction and testing."

Interdisciplinary synthesis is indeed integral to science -- particularly at the level of theory-making.

Re: "And so hilarious: plasmas isn't even on the table to explain gravitational systems like planet systems."

You guys crack me up. You insist that you're working with a gravitational system, even though you still can't pin down G's value, and even though galaxies completely and dramatically refuse to abide by it.

New Scientist, 22 September 2002:

Newton's constant, which describes the strength of the gravitational pull that bodies exert on each other, is the most poorly determined of the constants of nature. The two most accurate measurements have experimental errors of 1 part in 10,000, yet their values differ by 10 times that amount. So physicists are left with no idea of its absolute value.
1.7 / 5 (6) Jul 05, 2012
From the same article, titled "Earth's magnetic field 'boosts gravity'":

"Studies of the Sun also support the theory. To make mathematical models of the star's interior tally with experimental data, physicists have to use a lower value of G than is traditionally agreed. Mbelek says his calculations predict that electromagnetism would not boost gravity as much at higher temperatures, so you would expect G to be lower inside the Sun."

An alternative explanation for our solar system's stability is not difficult to devise, based upon a very simple feedback system of planets interacting at conjunction:


So, yes, plasmas are on the table. You simply confined your investigation to a box which excluded any possibility of an inference using plasmas.
1.7 / 5 (6) Jul 05, 2012
From http://scienceblo...-nothin/

"Theres a minor scandal in fundamental physics that doesnt get talked about much, and it has to do with the very first fundamental force discovered, gravity. The scandal is the value of Newtons gravitational constant G ... To make matters worse, recent measurements of G dont necessarily agree with each other ... Their value is 6.672 34 ± 0.000 14 x 10-11 m3 kg-1 s-2, which has nice small error bars only the Eöt-Wash result is better in that regard but is way, way off from the other values. Like, ten times the uncertainty off from the other values. Theres no obvious reason why this would be the case, though. If anything, the experiment is simpler in concept than any of the others, so you would expect it to be easier to understand. There arent any really glaring flaws in the procedure, though (it never wouldve been accepted otherwise), so this presents a problem."
1.7 / 5 (6) Jul 05, 2012
From http://www.nature...30a.html

"But the relentless honing of G may have hit a stumbling block. Two recent experiments are in striking disagreement with earlier findings, and the overall uncertainty in the value of the constant may be set to increase ...

Metrologists had expected much smaller disagreements among the results ...

Stephan Schlamminger of the University of Washington, who measured G while at the University of Zurich in Switzerland and reported4 a result consistent with that of Gundlach and Merkowitz, says he cannot explain the inconsistency ...

Faller says the fear of being wrong can cause investigators to wait many years before publishing results that don't agree with previous measurements. He and Parks ran their experiment in 2004, and have spent the time since then searching for effects they might have missed. But he's sure their measurement is sound: "I feel like I've checked everything and I have to wash my hands." "
4.3 / 5 (9) Jul 05, 2012
@ HannesAlfven:

"If you have a problem seeing people talk about theories".

But they _aren't_ theories, they are crank pattern search: nothing is presented that can be tested.

Most people go here for the science, not to have to read cranks reject it (hence denialists) and then besmudge it by replacing it with crank 'theories'. I am sure a crank can set up a crank site and start cranking, speech and religion is free and you can have your own belief. But you can't own your own scientific facts and theories.

'Nuff said, it is hard enough to distinguish between trolls and cranks, and you are trolling accepted science. "Never feed the trolls" applies.
1.7 / 5 (6) Jul 05, 2012
Re: "But they _aren't_ theories, they are crank pattern search: nothing is presented that can be tested."

This couldn't be further from the truth, but it will surely seem that way for people who refuse to learn the framework. All you had to do was Google "electric universe predictions". It's the 2nd link.

The problem is that you're simply not interested in elaborating ideas which fail to validate the textbook theories. You will only find what you look for (especially when it comes to electron drifts!), and you will only understand that which you permit yourself to read and learn about. Not only are electrical cosmology papers peer-reviewed, they are published by the world's largest scientific institution - IEEE - within Transactions on Plasma Science. And the ideas are grounded in the work of a Nobel laureate, Hannes Alfven, who struggled to convince conventional astrophysicists to properly apply the MHD models which he helped originate (and for which he received the Nobel).
2.1 / 5 (7) Jul 05, 2012
Re: "Most people go here for the science"

There is nothing at all unscientific about supposing that we can understand cosmic plasmas by observing laboratory plasmas. Instead, it is the sweeping assumption that plasmas can be modeled as superconductors, with "fossil" frozen-in magnetic fields which is pseudo-scientific. To refuse to question these assumptions is no different than codifying them into physical law. And when we fail to even discuss the ramifications of these assumptions possibly being wrong, we ignore literally thousands of alternative, competing inferences.

If you prefer to talk about things where everybody agrees, then you might consider discussing a subject which is not controversial. But, unfortunately, topics like planetary formation remain highly controversial subjects. If we are to think critically about these subjects, then we are bound to keeping an open mind to the alternatives.

There are no shortcuts to critical thinking. Critical thinking != crackpot.
3.7 / 5 (3) Jul 05, 2012
There are no shortcuts to critical thinking. Critical thinking != crackpot.

That's true, but ironic when uttered by someone who suffers from the Dunning-Kruger effect!
5 / 5 (2) Jul 07, 2012
Since this is (so far) a unique observation, low probability scenarios need to be considered. To put just one on the table, a "rogue" planet could have passed near the star. Your choice of masses, but my choice would be a planet that picks up enough dust from the cloud to be captured by the star.

On the other hand, maybe that scenario is more common than we expect today. A large number of free orbiting proto-planets could be part of star-forming dust clouds. Even though it might take a hundred million years (on average) for a young star to be visited by one of these objects. Each star could see several visits during its planet forming period.

Evidence? The best existing evidence is the late heavy bombardment (LHB) that occurred about 0.8 Gyr after the origin of the solar system. (There are lots of arguments about the LHB, including timing and cause. But it has become clear that something happened about then to stir up the solar system.)
1 / 5 (3) Jul 09, 2012
HannesAlfven is right. Unfortunately, (assuming the scalability of laboratory plasma & electromagnetic phenomena is correct, which it sure seems to be) he's describing an accurate and stunningly beautiful scenario to the willfully blind.
not rated yet Jul 09, 2012
There are four people who downvote every comment of HannesAlfven but don't show any interest in disputing his scientific statements.
I'd be interested in someone's opinion to HannesAlfven's statements
Newton's constant, which describes the strength of the gravitational pull that bodies exert on each other, is the most poorly determined of the constants of nature.

Stephan Schlamminger of the University of Washington, who measured G while at the University of Zurich in Switzerland and reported a result consistent with that of Gundlach and Merkowitz, says he cannot explain the inconsistency ...

Why are some people more keen on distributing four-letter words than explaining physical discrepancies to me?
This behaviour is of no merit.

it's his "all of science is a conspiracy and refuses to admit plasmas are relevent" state of mind that gets him 1's from me.
1 / 5 (1) Jul 09, 2012
frajo and Shelgeyr, thank you for your reasonable and rational responses! jsdarkdestruction, I think he's just hoping we will give equal weight to any explanation on its own merits, as opposed to its tally of proponents. Scientific fact is not voted on, it is demonstrated. And it stands to reason that any newer explanation will have fewer proponents just because it is newer. So of course the majority of folks are going to propound a non-EU viewpoint - which *would* give an EU person a certain surrounded feeling. And what could be more natural than for proponents of a non-EU viewpoint to be unwilling to give a very big place to plasma in a gravity-based astrophysics? Do you see how understandable his attitude is? And isn't that a nicer way to approach him? Let's shake hands and be friends! :)
not rated yet Jul 09, 2012
no, i dont see how. look at a2g or whatever that guys name is, he's a eu guy but you dont see him going off on rants about how its a conspiracy to hold back eu all the time. if hannes acted like that i'd be alot more willing to give him some serious consideration. until then he's just a crackpot. you and i can shake hands and be friends though.
5 / 5 (3) Jul 09, 2012
And what could be more natural than for proponents of a non-EU viewpoint to be unwilling to give a very big place to plasma in a gravity-based astrophysics? Do you see how understandable his attitude is?
That's the problem. Astrophysics does pay attention to plasma. It's the EU people that have this crazy notion that it's ignored. They're pretty easy to dismiss when it so obvious how unfamiliar with science they actually are.
1 / 5 (1) Jul 09, 2012
If plasma was not being ignored, why do astrophysicists continue to use a fluid dynamics model and talk about a solar "wind" and "sleeting particles" instead of plasma phenomena, magnetic "reconnection" of field lines (which are helpful abstractions that live only in our heads), and magnetism in space without accompanying current, etc? The last item really brings it into relief: magnetism and current are two sides of the same coin - how can you have magnetic phenomena without current? Yet magnetism is often mentioned, but current virtually never. Progress is happening, though. There seem to be more plasma-related concepts entering the discussions as time goes by. So this is a developing situation - not a static deadlock or anything.

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