Discussion: Baby Planet Puzzles Astronomers

[Fraser]

SUMMARY: In June, researchers from the University of Rochester discovered a planet around a star so young that it shouldn't exist according to existing theories of planetary formation. Further observations have backed up the discovery; there's definitely a planet there which is only 100,000 to 500,000 years old. This is much too young for either of the established theories of planetary formation. In the "core accretion" model, larger and larger chunks of rock smash together for 10 million years until a large planet is formed. In the "gravitational instability" model, a cloud of material pulls together into a planet by its own gravity; this is faster, but still not fast enough to explain how the planet got there.

What do you think about this story? Post your comments below.

[antoniseb]

Another theory is that some larger planets begin forming at the same time as the star. When the star reaches a certain point in its development, it starves these proto-planets of new ISM material to accrete. They will then being absorbing material from the accretion disk. This process will bring the planet's orbit into the plane of the disk and circularize it. That may be what we are seeing here.

[Duane]

Or perhaps we are seeing a that it is not one process, but a mixing of several. Back to the models boys and girls!

[lswinford]

I think that the planets begin to form first. The larger accretion of material, that center of gravity for the disk, builds up bigger and bigger in the meanwhile, and then later flames into a star, takes the real time.

[StarLab]

Actually, while I never thought about it that way before, Ford's idea makes sense. Hmm.. :blink:

[galaxygirl]

Is it possible that the planet was a rogue planet which was pulled into an orbit of that star?

[Duane]

I don't think so GG, because there is a pretty extensive disc around the star, except for the area where this planet has cleaned it out.

[PK]

yes that's it I recall it explained some time back, but it wasn't this planet it was the possiblity of another. It got blasted out from one sol system due to a supernova and then it became a lost rogue planet, then as suns move through space it became captured by another Star and thus existed around a very young star

[om@umr.edu]

This is an interesting story.

It illustrates a common problem in science.

It is probably correct to assume that rocky planets like Earth, Mars, Venus and Mercury formed by accreting together meteorite-like chunks of material.

That is why the upper mantle is extensively reworked but the lower mantle is relatively primitive.

Radioactive parent/daughter measurements show that planet Earth formed quickly and degassed its upper mantle to produce its crust, atmosphere, and oceans. The gaseous decay products of extinct I-129 and Pu-244 accumulated in the upper mantle, together with those of longer lived K-40, U-235 and U-238.

However, giant gaseous planets like Neptune, Uranus, Saturn and Jupiter cannot form that way. There are no meteorites made of the highly volatile material in those planets.

They probably formed by gravitational collection of highly volatile elements and compounds like H, He, N and methane. This process may, or may not, have required solids to form first and then accrete together.

Many volatile compounds freeze at the low temperatures in the outer solar system today, but the early solar system was hot - continually heated from short-lived radioactive elements made in the supernova that gave birth to the solar system.

Finally, it is noteworthy that the Rochester team are only "backing up the original conclusions, saying they've confirmed that the hole formed in the star's dusty disk could very well have been formed by a new planet."

With kind regards,

Oliver
http://www.umr.edu/~om

[Ola D.]

Here's a brief article that is somehow related to the story discussed here..

Astronomers Discover Planet Building is Big Mess

-- Ola

[STELLY]

It makes perfect sense to me that planets and stars start forming at the same time, which would make Jupiter a Failed Brown Dwarf that was robbed of its chance to get bigger by the ignition of our sun. I totally agree with a combination of the core accretion model and the combination of the same time model. It has really never made sense to me that only stars would start forming and planets would not in the early solar systems and nebulas. Gravity would "clump" together all ranges of sizes of for lack of a better word "clumps" witch would then Interact with the bigger "clumps" and start spiraling in material into "Super clumps" witch would then someday turn into a Star and Protoplanetary Disc with some protoplanets or “clumps” already set in motion by gravity from day one with others on the way with the current core accretion model of planetary formation

[antoniseb]

Originally posted by om@umr.edu@Nov 13 2004, 01:55 PM
Many volatile compounds freeze at the low temperatures in the outer solar system today, but the early solar system was hot - continually heated from short-lived radioactive elements made in the supernova that gave birth to the solar system.

Thanks for a nice outline of planet formation.

I have a few minor quibbles with what you've written. One is the paragraph above. It is safe to say that THE PLANETS in the early solar system were hot, both from impacts and from radioactive decay, but most of the particles in the disk that eventually accreted in to larger object cooled very rapidly. They had a lot of surface area for the given mass, and could radiate heat in minutes, not millions of years. When we make infrared images of the dusty disks around new stars, this model is confirmed. Except very near the star, these disks are cold enough to freeze methane.

My other quibble is in the statement as though it were fact that the lower mantle is primative. We have no samples from the lower mantle. We can't know the isotope ratios, or chemical mixing that has gone on there. Seismic data doesn't tell us it hasn't been reworked.

[Duane]

Seismic data doesn't tell us it hasn't been reworked.

In fact, seismic studies of s and p-wave propagation through the mantle and core has revealed areas of upwelling called "superplumes" that come from the base of the lower mantle at the core and rise all the way up to the lithosphere (see here for example). The process also inolves the sinking of cooled magma in other spots back to the base--in other words the mantle recycles.

I have posted sites to this in the past, which Dr Manuel again ignores.

For more information, check out Prof Barbara Romanowcz's studies at U of C Berkley, or by Jeroen Ritsema and Hendrik van Heijst of the California Institute of Technology, or by Jerry X. Mitrovica of the University of Toronto, or by Cynthia Ebinger of the University of London, or Royal Holloway, in Egham or Stanford University's Norman Sleep, or a host of others.

Get it straight people--the mantle is not only melted throughout, it recycles. Furthermore, the lower mantle is not primitive--it can't be, because it recycles! Dr Manuel can wish it to be different all he wants, the observations prove it to be true.

[damienpaul]

and more, and i mean a tremendous amount more about mantle plumes can be found here

[om@umr.edu]

Sorry folks, but there is overwhelming evidence the lower mantle is primitive.

It has even retained primordial (not radiogenic) He-3.

That primordial He-3 is still leaking out today, through the depleted upper mantle, and appearing at the Earth's surface in Mid-Ocean Ridge Basalts (MORB).

This old ball of dirt we call Earth accreted in layers, beginning with the formation of its iron core by accreting material like that in iron meteorites.

That doesn't fit textbook stories, but that's the way it happened.

You can see the experimental data and find references for the measurements in: "The Noble Gas Record of the Terrestrial Planets"

http://web.umr.edu/~om/archive/NobleGas.pdf

With kind regards,

Oliver
http://www.umr.edu/~om

[damienpaul]

so that website and my many years of geological study (yes i am a geologist by profession as well as a teacher) incorrect...(btw, we never used textbooks, mongrel things to carry into the field)

I had to do a lot of geophysical and seismological work and what duane says has come up again and again in our experiments and observations...certainly a fascinating field though.

I remember when we landed by helicopteron White Island volcano in NZ, for a side trip - AWESOME

I am still involved in seismology but at a less significant way and have not been to white island for a long time

[damienpaul]

Hey wait a sec, how do you know that there is He-3 in the bottom of the mantle????? I mean know for certain????? Then again, I have seismological data that we collected, no chemical data... although if we did - it'd have to come out of a volcano, cause i aint digging no stinkin' hole to the bottom of the stinkin' mantle!!!!

[om@umr.edu]

Originally posted by STELLY@Nov 13 2004, 03:31 PM
It makes perfect sense to me that planets and stars start forming at the same time.

I agree, Stelly.

And welcome to UT!

Many scientists do not want to consider that the Sun, like the planets, formed over a period of time by accretion.

If that happened, heavier elements would sink and accumulate in the interior of the Sun.

The standard solar model wants the inside composition of the Sun to be the same as its surface.

The standard solar model thus assumes that the Sun formed without accretion of material.

See the ApJ paper by Dar and Shaviv, reference #33 in this paper:
http://web.umr.edu/~om/abstracts/ACM-2002.pdf

With kind regards,

Oliver
http://www.umr.edu/~om

[(Q)]

If that happened, heavier elements would sink and accumulate in the interior of the Sun.

What process or mechanism makes the elements "sink" to the interior?

[damienpaul]

Dr. M. can you please explain to me about the He-3 in the mantle, i am very curious - is it from volcanological data? (I did read your article, I have trouble reading, on screen responses seem to work best for me )

[om@umr.edu]

Originally posted by antoniseb@Nov 13 2004, 04:38 PM
I have a few minor quibbles with what you've written.

One is the paragraph . . . most of the particles in the disk that eventually accreted in to larger object cooled very rapidly.

My other quibble is in the statement as though it were fact that the lower mantle is primitive.

Right, Anton.

1. The surface/volume ratio decreases as the early condensates accrete together to form larger bodies. E.g., pueudo-meteorites -> asteroids -> planets

Geochemical measurements on planet Earth show that accretion occurred and the upper mantle melted to form the crust, the atmosphere, and the oceans before extinct I-129 and Pu-244 had decayed away.

2. The lower mantle has retained primordial He-3, Neon, and is more primitive than the upper mantle. There is no way iron could have moved through the lower mantle to form the Earth's core.

Interestingly, large iron meteorites contain decay products of extinct elements and unmixed isotopes from nucleosynthesis reactions. I suspect the same would be found in the Earth's core, but there is way to access that material.

With kind regards,

Oliver
http://www.umr.edu/~om

[alainprice]

What process allows heavier elements to sink?

Buoyancy!!!

It's really only denser materials that can sink, not heavier ones.

[damienpaul]

and i am definitely ain't going to the stinkin' core to find out!!!!

[Duane]

Dr Manuel is simply wrong. His method does not account for the collision of the proto-earth with the Mars-sized body that formed the Earth, he ignores years of research into the seismic studies of the deep interior of this planet, and he dogmatically sticks to the method he employs of saying "I say it is true, for proof look at my work where I say it is true".

I also have training in geology and have studied reams of data arising from seismic waves initiated by surface and sub-surface explosions while searching for oil over most of northwestern Canada, including the arctic.

S-wave and P-wave studies of the deep interior identify not only deep-seated plumes rising from and sinking to the core/mantle boundry, they also identify an area of stiffness marking that boundry. The stiffness is the settling out of heavier material from the molten, differencitiated, recycling mantle.

The means by which the Earth and sun formed are completely different, as any nuclearphysicist or solar-physicist knows. Dr Manuel is a nuclear-chemist, not physicist, and his views of accretion, neutron degeneration, and every other aspect of nuclear physics is coloured by his perceptions of chemical reaction.

He is wrong about the Earth's formation, he is wrong about the Earth's makeup, he is wrong about the Sun's formation, and he is wrong about the makeup of the sun.

[Planetwatcher]

If that happened, heavier elements would sink and accumulate in the interior of the Sun.

I find that a little hard to swallow.
At such a phase of development, there is nothing to sink to. No real center of gravity to speak of. If there was, there would be no accredition.
This kind of reasoning can only come from a person who believes the Iron Sun theory.

But if the whole works were spinning, and especially if doing so rapidly, then the heavier elements would move toward the outer parts of the disk, where the planets would form, and the lighter elements would tend to move toward the center. Where gravity would attract them to each other, begin to heat up by friction, and eventually ignite a fussion reaction, thus giving birth to a protostar.

Meanwhile, the heavier elements farther out in the disk are also attracted by gravity, clumping together to eventually become planets.

But now how one could form so quickly,
Perhaps there were a lot of very big clumps to begin with which would have cut down the time of formation.

[Victoria]

So...antioseb says( if I get it :P ), planets form in the way of collection and not entirely in the form of material. Great Post.

[om@umr.edu]

Originally posted by damienpaul@Nov 13 2004, 06:19 PM
Hey wait a sec, how do you know that there is He-3 in the bottom of the mantle?????

Damienpaul.

We know the depleted upper mantle is rich in radiogenic isotopes.

Xe-129 from the decay of extinct I-129
He-4 from the decay of U and Th
Ar-40 from the decay of K-40
Xe-136 from the decay of extinct Pu-244

Accompanying those radiogenic isotopes in mid-ocean ridge basalts are primordial He-3 and traces of primordial Ne.

The reasons for attributing He-3 and Ne to gases leaking from the undepleted lower mantle are explained in detail in:

"The Noble Gas Record of the Terrestrial Planets"

http://web.umr.edu/~om/archive/NobleGas.pdf

With kind regards,

Oliver
http://www.umr.edu/~om

[damienpaul]

ah i see, yes the mid ocean ridges are indeed the logical place for detection, as are hotspots i'd assume (i could be wrong there).

So the way i see it, the way that He-3 gets to the surface is through the convection detected by seismic data that myself and my colleagues and Duane and his colleagues independently observed (as with countless multitudes no doubt).

this is very interesting indeed.

[antoniseb]

Originally posted by om@umr.edu@Nov 14 2004, 05:33 AM
We know the depleted upper mantle is rich in radiogenic isotopes.

This paper starts off with an assumption that I don't completely accept:

The Earth’s atmosphere was produced by exhaustive degassing of the upper mantle during the first 200My

I think it is very likely that the Earth started with a huge atmosphere picked up during the accretion process, and that most of that atmosphere has boiled away during the first billion years, especially during the moon-forming event. A comparison of the isotope abundances in the ISM, Jupiter, and the Photosphere of the sun support this model. I can't guess where your idea came from.

So this paper makes some odd interpretations of the meaning of the isotope ratio differences observed in the air, the oceans, and volcanic venting. On the very positive side, if you ignore the conclusions, there is a lot of very nice data collection here, making it worth plowing through the 40 or so pages. Thanks for putting it online.

[(Q)]

Oliver,

You have conveniently ignored my question, one of many that could make or break your pet theory.

What mechanism causes the heavier elements to 'sink?'