APOD: The Protoplanetary Disk of HL Tauri... (2014 Nov 10)

[Craine]

Perhaps, at one time, there was indeed a major terrestrial planet between Mars and Jupiter at the position of the asteroid belt.

Sorry, but this has been disproven a while ago. The combined mass of the asteroids in the belt is far too small. Far smaller then the mass of Earths moon. Even calculating in Jupiter's Greeks and Trojans and any mass that likely would have escaped would still fall far short of becoming anything approaching planet size.

[Chris Peterson]

Will humans ever be able to terraform proto solar systems?

No. The technology might be developed (although I expect humans will be extinct long before that could happen), but the ability to get to other stars won't happen, and even if it did, why would we terraform a proto system when it would be much easier to either find a planet already like the Earth, or close enough that it could be terraformed?

[Chris Peterson]

An issue troubling the scientific community has been the asteroid belt of the Solar System.

That's the part of the scientific community I'm part of, and it isn't a particularly troubling issue. While there are many unknowns about the formation of the solar system (and planetary systems in general), the asteroid belt is broadly understood as a region of gravitational resonances that originally (and in a different place) prevented material from forming planetesimals, and which currently has its structure maintained by those resonances. The presence of a few larger bodies is not problematic.

[Chris Peterson]

I've been wondering where the dust torus that so frequently appears in pre-planetary nebulas comes from. I've been under the impression that the star itself somehow creates the dust but I'm very confused on the matter.

The dust does not come from the protostar. It is present in the molecular cloud that collapsed (or is collapsing) into the protostar. Molecular clouds are primarily hydrogen, along with some helium and a bit of oxygen, and heavier elements in the form of dust (less than 1% by mass). Models suggest that this very small amount of dust is important for the gravitational collapse process, however. And it's the source of all the material that ends up in the dust torus and later the planets.

I wonder if these stellar disks sometimes never coalesce into planets. Like maybe a binary star could have the dust disk but it never forms a planet because of the second star? Just some random conjecture.

We see so many different variations in the protoplanetary systems so far observed that I'd think it very likely that initial conditions could exist (such as your binary star example) that might prevent planets from forming.

[dmullins@lcogt.net]

There was a time when "NO other planets" existed, and not all that long ago, (even the 1970's)....except in Science Fiction stories...and in our own Solar System. This is one of the limitations of the Scientific Method...because if you cannot observe it...it does not exist....and that causes an erroneous belief.

Just because you have not observed something, does not mean it does not exist. It means, you have not observed it yet....every time humans have improved their technology, and instruments, we get more clear data...more details, and more refined images, and data, and out of that our knowledge increases. I eagerly await the next advances....so we can see, the OTHER things "that do not exist"....

Oh, come on. This is not a problem with the scientific method. If anyone was telling you they were sure there are no planets around other stars out there, you were not listening to any credible scientist.

I remember, as a kid, in the 1970s, my dad going through the calculations as to whether or not there were other planets, or not. At that time, it was, "if one tenth of one percent of all the stars in the galaxy..."

[Chris Peterson]

There was a time when "NO other planets" existed, and not all that long ago, (even the 1970's)....except in Science Fiction stories...and in our own Solar System. This is one of the limitations of the Scientific Method...because if you cannot observe it...it does not exist....and that causes an erroneous belief.

Science never said other planets didn't exist. What it said is that no other planets had been observed. Big difference. For a very long time most scientists have argued that other planets probably existed, even though they admitted that this was purely based on perceived probabilities given the very large number of stars in the Universe.

The scientific method does not require that something be observed in order to be treated as real.

[Bellerophon]

The disk has some interesting features. Notice the wide dark ring about twice the distance out from the second of the two inner dark rings. It has a broken lighter band in the middle. I see four darker areas, one pair 180 degrees apart at upper left and lower right, and a less distinct opposing pair about 60 degrees counterclockwise. The second pair could be at something like Lagrangian points created by the large masses at the first pair. Any astronomers here willing to give us a more intelligent explanation of the features we see? (I'm not up to it--three body problems kicked my butt in college.)

[DavidGovett]

That's all, folks!

[Craine]

The disk has some interesting features. Notice the wide dark ring about twice the distance out from the second of the two inner dark rings. It has a broken lighter band in the middle. I see four darker areas, one pair 180 degrees apart at upper left and lower right, and a less distinct opposing pair about 60 degrees counterclockwise. The second pair could be at something like Lagrangian points created by the large masses at the first pair. Any astronomers here willing to give us a more intelligent explanation of the features we see? (I'm not up to it--three body problems kicked my butt in college.)

I am not sure it matters this early in the development of a system. When planets form they gather mass as well as kick mass around in that system. And there will be a lot of jostling and migrating of orbits before any remaining planets settle in some kind of resonance pattern. Whatever orbits you may see now are almost certainly not what they end up being in another 100 million years or so.

[andy5913]

There seem to be radial bands similar to the ones observed in Saturn's rings.

[BobStein-VisiBone]

Will humans ever be able to terraform proto solar systems?

The proto part seems foolhardy. Wouldn't that be like building homes in an active volcano's lava path? Or beach houses in an era of rising sea level? Oh wait.

[geckzilla]

I've been wondering where the dust torus that so frequently appears in pre-planetary nebulas comes from. I've been under the impression that the star itself somehow creates the dust but I'm very confused on the matter.

The dust does not come from the protostar. It is present in the molecular cloud that collapsed (or is collapsing) into the protostar. Molecular clouds are primarily hydrogen, along with some helium and a bit of oxygen, and heavier elements in the form of dust (less than 1% by mass). Models suggest that this very small amount of dust is important for the gravitational collapse process, however. And it's the source of all the material that ends up in the dust torus and later the planets.

Just for clarification I was kind of straying away from the protoplanetary to much later in an AGB star's life when it supposedly becomes a pre-planetary nebula. Coincidentally, Dave Jones was using the Astrotweeps account last night and I exchanged a few messages back and forth with him. I was afraid I simply had not read enough but according to him the dust toroids are a bit of a mystery. The dust is expected but why is it where it is and why is it in that shape? I'm still confused as to whether it is more likely that the dust originates from within the star or from around the star. He pointed me to this paper which shows that one possibility is the companion star shredding in order to form an accretion disk (Figure 3).

Note: I may have confused post-AGB and AGB in this post. Seems like a stupid mistake but I can't figure out which to write.

[Chris Peterson]

Just for clarification I was kind of straying away from the protoplanetary to much later in an AGB star's life when it supposedly becomes a pre-planetary nebula. Coincidentally, Dave Jones was using the Astrotweeps account last night and I exchanged a few messages back and forth with him. I was afraid I simply had not read enough but according to him the dust toroids are a bit of a mystery. The dust is expected but why is it where it is and why is it in that shape? I'm still confused as to whether it is more likely that the dust originates from within the star or from around the star. He pointed me to this paper which shows that one possibility is the companion star shredding in order to form an accretion disk (Figure 3).

Note: I may have confused post-AGB and AGB in this post. Seems like a stupid mistake but I can't figure out which to write.

There may be some confusion here. A protoplanetary nebula (which is the same as a preplanetary nebula) is something seen in a highly evolved star, transitioning between the asymptotic giant branch and a planetary nebula. That's what the referenced paper is talking about. Today's APOD is showing a protoplanetary disk, which is a completely separate thing. It occurs around a protostar (which hasn't started fusing yet) or a pre-main-sequence star (as in today's image). The dust in this case is coming from the presolar nebula, and its formation into a disk or toroidal structure isn't particularly mysterious.

[geckzilla]

I'm well aware of that potential confusion. That's why I use "pre" instead of "proto" for the prefix when referring to planetary nebulas. It makes it a little harder to confuse it with protoplanetary disks. But I was wondering if there was any possible connection between the two.

[chuckster]

Isn't this image kind of unprecedented ? I've seen tiny, fuzzy photos described as possible nascent star systems before, but, at 450 light years distant, and using a ground-based observatory, this is an image of amazing detail. Does the Hubble have the instruments to capture a similar image from space ?

As for that $10 bet, it's hard to see human futures through all the haze and intervening dust, also. Not the least because we sure look to be on track for turning over the Earth to the raccoons and cockroaches, etc. As far as influencing planetary system formation, that might be an endeavor for the future times when the universe is starting to thin out from millenia of expansion.
Causing gas clouds to gravitationally collapse, that might not otherwise do so naturally, might become an option for beings looking to stave off the darkening of their skies, or maybe they just walked through a portal into the next "brane" over, and carried on in style over there, under completely different physical laws !

[BDanielMayfield]

I'm well aware of that potential confusion. That's why I use "pre" instead of "proto" for the prefix when referring to planetary nebulas. It makes it a little harder to confuse it with protoplanetary disks. But I was wondering if there was any possible connection between the two.

"Any possible connection between the two" what, exactly, geck? Surely someone with all your experience processing "planetary" nebula data into images and reading these discussions knows that they are generated near the end of a star's 'life', whereas protoplanetary disks come about right near the star's beginning. In our system for example these periods will have ultimately been separated by, what, 9.5 billion years? The only "connection" here would be that they occur around the same star. But that isn't what your asking about, or what?

[geckzilla]

"Any possible connection between the two" what, exactly, geck? Surely someone with all your experience processing "planetary" nebula data into images and reading these discussions knows that they are generated near the end of a star's 'life', whereas protoplanetary disks come about right near the star's beginning. In our system for example these periods will have ultimately been separated by, what, 9.5 billion years? The only "connection" here would be that they occur around the same star. But that isn't what your asking about, or what?

I was actually asking exactly that: whether or not the protoplanetary disk could last that long under any circumstance.

[BDanielMayfield]

I was actually asking exactly that: whether or not the protoplanetary disk could last that long under any circumstance.

Hmm. Well, consider our system. What's left of our protoplanetary disk are (1) the planets and their moons, (2) the assorted rubble making up the asteroid belt, (3) the scattered disk Kuiper belt objects and (4) the band of dust centered on the average plain of our planetary system. Did I leave anything out?

Anyway, after billions of years there must be great erosion of any stellar system's original disk, I would think.

[Chris Peterson]

I was actually asking exactly that: whether or not the protoplanetary disk could last that long under any circumstance.

I don't see how. The disk is short lived. At the end, a new dust structure forms, possibly made up of some original material but mainly dust created in the star over its life. The early disk is accretionary; the later is some sort of ejected structure.

[MarkBour]

Fantastic image. Perhaps even an historic one? Can I ask, what causes the light that we see in the image? At the center, the star has already formed and is undergoing stellar fusion, correct? But the star itself is considerably smaller than even the innermost bright yellow circle, correct? Then what makes a yellow disk or ring in this image; what makes an orange ring or red ring further out? Are we seeing emissions from the dust around the star, re-emitting the radiation from the star? There are so many features in the rings that I expect it will be quite simple to watch the rotation of the disk. Is there any data already known about the rate of rotation?

[geckzilla]

I don't see how. The disk is short lived. At the end, a new dust structure forms, possibly made up of some original material but mainly dust created in the star over its life. The early disk is accretionary; the later is some sort of ejected structure.

Ok, away from accretion disks again ... How about the various ring systems in our solar system? How do they compare? Saturn's rings are obviously very robust while all other planets have much fainter ones. What keeps Saturn's going? They just started out like that and the other planets didn't? I don't find the idea that a star could have a long-lived ring system to be out of the question unless there is something about the star that blows away the rings. Hmm.

[moontrail]

Can somebody help put a scale to this photo?
The description just states it can resolve details as small as 40 light minutes. But 40 light minutes is ~720 million KM, or just shy of where Jupiter orbits.

Does that mean the innermost dark band is approximately where Jupiter would orbit?

Here is a picture that shows the solar system in comparison.

I find the proposed solar system comparison image confussing. Shouldn't be like this one?

[Nitpicker]

Can somebody help put a scale to this photo?
The description just states it can resolve details as small as 40 light minutes. But 40 light minutes is ~720 million KM, or just shy of where Jupiter orbits.

Does that mean the innermost dark band is approximately where Jupiter would orbit?

Here is a picture that shows the solar system in comparison.

I find the proposed solar system comparison image confussing. Shouldn't be like this one?

The caption for the image linked by Markus, suggests that the outermost orbit is Neptune's.

[Guest]

Agree about Neptune and not including Plato but planets orbits diameters relative proportion, sun size, highlighted planet suggesting to be Earth but being Mars...

[DavidLeodis]

In the item that is brought up from the 'unprecedented detail' link it states:-

"ALMA's new high-resolution capabilities were achieved by spacing the antennas up to 15 kilometers apart. This baseline at millimeter wavelengths enabled a resolution of 35 milliarcseconds, which is equivalent to a penny as seen from more than 110 kilometers away". Wow, that is amazing (well it is to me ).