Want to make planets? Better hurry
May 24, 2011 By Jon Voisey, Universe Today
Artist's impression of planetary formation. Credit: NASA
Currently, astronomers have two competing models for planetary formation. In one, the planets form in a single, monolithic collapse. In the second, the core forms first and then slowly accretes gas and dust. However, in both situations, the process must be complete before the radiation pressure from the star blows away the gas and dust. While this much is certain, the exact time frames have remained another matter of debate. It is expected that this amount should be somewhere in the millions of years, but low end estimates place it at only a few million, whereas upper limits have been around 10 million. A new paper explores IC 348, a 2-3 million year old cluster with many protostars with dense disks to determine just how much mass is left to be made into planets.
The presence of dusty disks is frequently not directly observed in the visible portion of the spectra. Instead, astronomers detect these disks from their infrared signatures. However, the dust is often very opaque at these wavelengths and astronomers are unable to see through it to get a good understanding of many of the features in which they’re interested. As such, astronomers turn to radio observations, to which disks are partially transparent to build a full understanding. Unfortunately, the disks glow very little in this regime, forcing astronomers to use large arrays to study their features. The new study uses data from the Submillimeter Array located atop Mauna Kea in Hawaii.
To understand how the disks evolved over time, the new study aimed to compare the amount of gas and dust left in IC 348′s disc to younger ones in star forming regions in Taurus, Ophiuchus, and Orion which all had ages of roughly 1 million years. For IC 348, the team found 9 protoplanetary disks with masses from 2-6 times the mass of Jupiter. This is significantly lower than the range of masses in the Taurus and Ophiuchus star forming regions which had protoplanetary clouds ranging to over 100 Jupiter masses.
If planets are forming in IC 348 at the same frequency in which they form in systems astronomers have observed elsewhere, this would seem to suggest that the gravitational collapse model is more likely to be correct since it doesn’t leave a large window in which forming planets could accrete. If the core accretion model is correct, then planetary formation must have begun very quickly.
While this case don’t set any firm pronouncements on which model of planetary formation is dominant, such 2-3 million year old systems could provide an important test bed to explore the rate of depletion of these reservoirs.
Source: Universe Today
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May 24, 2011
Rank: 1.1 / 5 (18)
Planets were initially big blobs of water. Then with sudden catastrophic compression as well as element transformation, the cores and other different layers of the planet gets formed. This would happen in the space of minutes or hours at the most, not millions of years.
Simple logic applied at the mechanical/physical make-up of our own planet would dictate that one doesn't have a lot of time to get the planet into the layered composition and shape it is currently in. It's an all or nothing operation that needs to happen really, really fast.
Sure, you can call me nuts but this idea does present a different option to those proposed above. And since those are also just theories, this one is equally valid.
In addition, if one could line up the electron spin of the water molecules just before the collapse/compression/transformation, one would be left with the decaying magnetic field we observe in most planets today. The other two models have no way to explain fields.
May 24, 2011
Rank: 4.5 / 5 (8)
Not really. The models above are backed up by math, yours is not.
I have a question though. Can anybody tell me whether the protoplanetary disk is just gas, or if we assume that it contains chunks of stuff like asteroids and comets?
Here's another thought. What if there's more than one mechanism? Do gas giants form the same way that rocky planets do?
Or this one. Which forms first, the planets or the star, or do they both form at the same time? Could the planets actually be forming long before the star is anywhere near critical mass? Personally I don't think the fact that a new star blows its gas envelope away quickly after reaching critical mass has any bearing on which theory is correct. Planets being smaller, it seems logical to assume that if they accrete then they would be formed before the star becomes a star.
May 24, 2011
Rank: 4.6 / 5 (9)
Yeah, no. What makes theories valid is groups of corroborating evidence.
For instance, what leads you to belive there is "sudden catastrophic compression as well as element transformation"? If it's just the fact that it's necessary for your "theory" to make sense than that is not valid.
May 24, 2011
Rank: 1.3 / 5 (13)
So just how did they start out before they got backed up by maths?
Similar question to the above. For any theory to make sense the postulates have to make sense first - otherwise how are you going to pursue your outcomes?
May 24, 2011
Rank: 5 / 5 (9)
Water? You have planet sized blobs? What causes the compression? Magic? Element transformation? Perhaps a giant linear accelerator? More magic?
Total nonsense as usual.
May 24, 2011
Rank: 5 / 5 (5)
You can't call it a theory until you can back it up, until then it's just a thesis.
May 24, 2011
Rank: 5 / 5 (2)
Perhaps there are some knots that collapse, and some later protoplanets acrete material, or maybe both happen simultaneously to a degree. Perhaps both processes together create planets very quickly as well. Tell me is there something wrong with this idea?
May 24, 2011
Rank: 1.3 / 5 (13)
May 24, 2011
Rank: 4.2 / 5 (5)
I'd say that they form at the same time but that planetary accretion stops shortly after ignition.
My reason would be that if it didn't stop then we should be seeing a lot more multi-sun systems (because many more planets would continue to accumulate to critical mass and turn into suns themselves)
Again just speculation: First generation solar systems would probably be only gas (since no heavier elements have been bred, yet). After that we should see a mix of gas and bigger debris as dust clouds are seeded/compressed by nearby (super)nova shockwaves.
The biggest mass concentration should accrete matter at the fastest rate. I'd guess sun and planets form at the same time. The sun just takes longer because it needs more mass.
May 25, 2011
Rank: 1.4 / 5 (9)
1. "The noble gas record of the terrestrial planets", Geochemical Journal 15, 247-267 (1981).
www.omatumr.com/a...eGas.pdf
2. "Terrestial-type xenon in meteoritic troilite", Nature 299, 807-810 (1982).
www.nature.com/na...7a0.html
3. "Solar abundances of the elements", Meteoritics 18, 209-222 (1983).
www.omatumr.com/a...nces.pdf
With kind regards,
Oliver K. Manuel
May 25, 2011
Rank: not rated yet
Here's a snippet to give you an idea: http://www.britan...position
May 25, 2011
Rank: not rated yet
yeah, of course a first generation system would be fairly homogenous and made of H.
In a later generation system though, the material should be what's left from a star exploding. I wouldn't expect all that material to be tiny little pieces. To use observations of Sol as a guide, I'd expect the explosion to have some characteristics similar to solar flares. Even as a star explodes, there would still be bands of intense magnetism which results in some prety large globs of stuff rather than just gas molecules or ions. I can easily imagine clumps of superheated liquid held together by gravity and electrostatic charge, which might later bump into and stick to others. I wouldn't expect to see anything cool enough to be a solid object for quite a while after the nova, or is my understanding of the heat wrong?
May 25, 2011
Rank: 5 / 5 (1)
May 25, 2011
Rank: 4 / 5 (4)
I never quite understood why there is speculation that planets don't form at the same time as the main star starts accreting materials from the dust and gases it effect gravitationally. Is there a necessitation of a orbit to form large massive bodies?
I always felt it was like a big game of Hungry Hippo. You try to capture as much out there you can grasp, but the first one full ends the game.
May 25, 2011
Rank: 5 / 5 (4)
A Bed Bugs or Cooties analogy would also have been acceptable.
;P
May 29, 2011
Rank: 1.2 / 5 (9)
The assertion that planets slowly formed from coagulating space debree is equally unverifiable as the assumption that initially all celestial bodies consisted of milk-chocolate.
May 29, 2011
Rank: 5 / 5 (4)
But we may be able to observe dust clouds in various stages of planet formation in the future. With a bit of luck we should be able to also catch a 'first light' event from a newly ignited sun.
Jun 06, 2011
Rank: 5 / 5 (2)
WTF? You know this how??? Why not just claim they were initially creme cheese? Makes about as much sense. Jeez, Kev... You're literally out in the deep end... even for YOU. Not even the Bible claims this.
Aren't you always complaining about science articles claiming things as absolute facts when they should be considered theories, then you go and make a bold face, blatant "matter of fact" statement like "Planets *WERE* initially big blobs of water."?!?!?!?
You didn't say planets MIGHT HAVE BEEN, or COULD HAVE BEEN, or I THINK MAYBE... NO, you said they WERE!
You're doing EXACTLY what you falsely accuse the science articles of doing.