what a forming planet looks like

How long can you wait around while this happens?

I ask, cuz as far as I know, planets take billions of years to form from the stuff of which they're made. I mean, it isn't gonna be, "Look ma. See that accretion disk? Look again. Now there's a proto-planet in it!"

I would think you see first: a disk of "stuff" similar to the rings of Saturn, orbiting a star. Then, some billions of years later, you see a blob of that stuff and some big gaps in the disk. Then some more billions of years later, you see mostly a ball of stuff and almost no disk. Then some more billions of years later, you might see some kind of volcanism, maybe some atmosphere, clouds (think Venus). Then some even more billions of years later, you MIGHT, if you're lucky, see life. You know, life. Like pond scum.

So, I ask again. How long can you afford to wait?

Click on this link.
It will make you happy.

The Lonely One said:

Okay google image keeps giving me artist renditions, which all seem suspect. I want accuracy here.

I need to know what a forming planet looks like (one with similar composition to Earth, a terrestrial planet but much larger, with an accretion disk). At what point does the disk exist during the planet's evolution (this is key) and is there anything fun like volcanic activity visible from space or storms or anything of the like?

Curious.

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Have to be careful talking about accretion disks, they call the big disk of material in which a new star is formed a planetary accretion disk, which seems mis-named to me. By the context of your quesiton, when you say accretion disk, I think you mean a disk of material that is collapsing into a planet?

I don't think such an accretion disk would last long (in geologic time, anyway) once a planet has gained sufficient mass. The material in it will be colliding a lot as it orbits the new planet, degrading orbits. It will get sucked in within a few thousand years. The protoplanet will be very hot. It will be cloud covered, until it cools enough for water to condense into seas, and to start fixing atmospheric elements into various mineral deposits.

The planet will get hit regularly, for quite a while, as its orbit intersects rocks large and small, that are orbiting the central star in eccentric orbits. It will take millions and millions of years to really clear out space around the star, and for things to settle down. Lock at how pockmarked the moon is. Until then, the planet will stay hot, newly formed crust constantly broken up by fresh impacts. However, it won't generally be visible, because of the cloud cover (think Venus).

Spumes of ejecta will appear above the cloud cover when it gets hit by a large enough rock. Volcanos too will put in appearances, but mostly you'll see clouds, for a long time.

MargueriteMing said:

... but mostly you'll see clouds, for a long time.

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Right.
Like Venus.
Asimov's Foundation series spans millenia, rather long for a story, but a blink of an eye compared to the time it takes planets to form.

the early bombardment of earth would have made the planet a molten mass. the earth suffered extreme collitions with meteoroids and planetesimals that would have made the K-T impact look mild. the moon was formed when a mars sized planet collided with earth. this melted both planets and threw off the material that formed the moon.
after the early bombardment of earth, once the solar system settled down from its violent infancy, the earth would have remained molten for millions of years untill a crust of solidified rock formed at the surface. but still the inner material, as it is today, would have remained molten and would have spilled out regularly reforming the surface and making the atmosphere toxic. (the sky would not have been blue, think of venus today, pink.)


earth around 4.5billion years old.
0.5billion years of life on earth.

0.065billion since the dinoosaurs became extinct
0.0003billion since the first upright ape.
0.00004 billion years since the first human.

for the longest time the earth would have looked like hell, all hot rocks and burning skys.

jerry phoenix said:

the early bombardment of earth would have made the planet a molten mass. the earth suffered extreme collitions with meteoroids and planetesimals that would have made the K-T impact look mild. the moon was formed when a mars sized planet collided with earth. this melted both planets and threw off the material that formed the moon.

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Well, this is a theory. Carefully crafted computer models support the possibility, but nobody was there to witness it, so we can't say for sure how it happened. There are other possibilities.

For instance, there are about 7 dwarf "galaxies" in orbit about the MW, which pass through the disk of the MW periodically. This is probably why the MW has spiral arms, instead of a more balanced distribution of material. If in the past a star from one of those clusters passed near us, might we have captured a small planet from one?

We just don't know enough yet, even about or own neighborhood, to wind the clock back with any accuracy at all. When we have all 400 billion or so stars in the MW and her satellite "galaxies" mapped exactly, so we can wind all their orbits back exactly, then we can talk more exactly about what passed near us.

.

MargueriteMing said:

For instance, there are about 7 dwarf "galaxies" in orbit about the MW, which pass through the disk of the MW periodically. This is probably why the MW has spiral arms, instead of a more balanced distribution of material.

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Nope. the collision with dwarf galaxies would distort the spiral arms (in fact there's evidence of that happening even now), but the arms themselves form from so-called "density waves" as part of the galactic rotation, and also get involved in all the "dark energy" stuff invoked to explain the rotational characteristics of spiral galaxies. Spiral galaxies are a common feature in galactic evolution. Our galaxy is, by the way, now known to be a barred spiral, with a core region expanded into a rotational "bar", a less common but well-known subgroup of spiral galactic geometries.

caw

I don't understand how the bar can exist for long. Don't orbital periods vary with distance from the center?

MargueriteMing said:

I don't understand how the bar can exist for long. Don't orbital periods vary with distance from the center?

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Actually, scientists don't understand that, either. In fact, the stars at the visible outer edges of galaxies rotate much faster than they should by the Keplerian orbital laws that govern our sun's planetary orbitals. The conclusion they've come to is that something unseen, lying outside the visible galactic planes, having great invisible mass and therefore exercising gravitational force, must be pulling galactic rotations. Ergo "dark matter", an astronomical euphemism for "we don't know what the hell is going on."

On an astronomical time-scale, most scientists think that galactic "bars" are a rather transitory manifestation of the "dark matter" influence, and may even come and go over many millions of years. I'm intending to hang around long enough to find out. A couple of good links:

http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/image/0501/ngc1300_hst_c30g90.jpg

http://www.sciencedaily.com/releases/2007/04/070403134630.htm

caw

blacbird said:

Actually, scientists don't understand that, either. In fact, the stars at the visible outer edges of galaxies rotate much faster than they should by the Keplerian orbital laws that govern our sun's planetary orbitals. The conclusion they've come to is that something unseen, lying outside the visible galactic planes, having great invisible mass and therefore exercising gravitational force, must be pulling galactic rotations. Ergo "dark matter", an astronomical euphemism for "we don't know what the hell is going on."

On an astronomical time-scale, most scientists think that galactic "bars" are a rather transitory manifestation of the "dark matter" influence, and may even come and go over many millions of years. I'm intending to hang around long enough to find out. A couple of good links:

http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/image/0501/ngc1300_hst_c30g90.jpg

http://www.sciencedaily.com/releases/2007/04/070403134630.htm

caw

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Are they correcting for time differential?

Unless you are looking at a galaxy from 90 degree north or south of the axis of rotation, the light reaching you was generated at different times from different parts of the galaxy.

For example:

Say you see a galaxy with a "bar", and one end of the bar is near you, but you are looking at the galaxy from 45 degrees above its ecliptic. If the galaxy is 100,000 LY across, then the light from the far side of the galaxy started more than 70,000 LY earlier ( cos 45 (.707) * 100k LY). The stars that you "see" as being there are actually 70,000 years ahead of there in their orbits. This would have to bend the bar, if you plotted their actual locations, relative to the near edge.

We have this problem with all astronomical observations: things are no longer where we see them. Since the data that we see was created at different times, our calculations are off when we try to understand why they are where they appear.

For a galaxy 100k LY across, viewing it at 5 degrees off its axis of rotation gives 10,000 year differential between the near and far edges. Half a degree off yields data from the far edge that is 1000 years earlier than the near edge.

What you see through the telescope is an optical illusion.

Since we are viewing our own galaxy edge on, the distortion is even more pronounced. We're about 25,000 LY from the core. A star on the far edge would be 125,000 LY from us. Where we see it is where it was 125,000 years ago, it has since moved quite a bit.

You need to be more specific on what stage of the planet-forming process it is at, there are several different points.

Hiding inside an accretion disc? I hope they have good shields/armor. ;-)

That looks like a solid image. Consider that the shade of the entire disc would be tinted by the base color of the star as the emitted light refracts through the dust and particles. The link from Smiling Ted has some real images of protoplanetary discs.

And here's a list of all known circumstellar disc types:

http://en.wikipedia.org/wiki/Circumstellar_disk

Also, it might be pertinent to consider: the distance across the disk visible in that photo is probably close to half a light year.

Now where'd I put that book of adages? Oh, here it is. (thumb, thumb thumb) Ah yes. Finding your pirate in there would be about as easy as "... finding a needle in a haystack."




ETA: Unless the pursuers were hot on the pirate's trail, in which case they could probably identify where he entered the disk and .... Well, as Luhn has reminded us many times, there ain't no way to hide in space. I think that once you're in that disk of "stuff" whatever it is (dust and little meteroids and suchlike) you'll find yourself in mostly vacant space. The image of our own asteroid belt as a cloud of floating rocks through which maneuvering a starship takes extreme piloting skill is just bunk.