First confirmed image of extrasolar planet. A couple of questions.

I just came across this article which says, in part, that this image has been confirmed as a planet orbiting another star. I haven't kept up with the latest findings in this area so I have a couple of questions.Firstly, is this indeed the first image, or just the first confirmed image? That is, have there been other candidates for images of extrasolar planets which we've just never been able to verify? The way I read the article, this particular picture was taken in September last year, and has only now been confirmed after observing it for the duration. Were there other "possibles" that came along before this one?To be clear, I know that we've been finding planets for some time now by observing the stars. I am speaking specifically of direct images of the planets themselves.Secondly, I have a question about one of the details I read. Now, I've heard two different stories and I don't know which one is correct.The first is that, as a planet, Jupiter is more or less as big as it could be, that if it had amassed much more during its formation it would have become a second sun. The second is that it would actually take much, much more than the current mass of Jupiter (something like 70 or 80 times more) for it to become a star.Now, obviously, at least one of these is wrong. Can somebody clear this up for me?And if the first is true, then how is it that this planet can be five times that of Jupiter and not be a star itself? Looking back, I see that the article actually uses the words, "...about five times the size of Jupiter..." so that may be my answer right there.Still, it's quite interesting, none the less. And I'm always eager to be cured of my ignorance.Admin, please feel free to move this wherever you wish. I suppose the obvious forum would be cosmology, but then it's not really intended to be a long discussion or debate. So it's all good. I'll be happy with whatever you do.

Thread moved here from the Proposed New Topics forum.

I'm somewhat confused as well. The picture included with the article you posted is similar to one from an earlier and unconfirmed report found here but there was an announcement yesterday about confirmed sightings reported in this article.The former article refers to an object that may be circling a brown dwarf "2M1207" while the later is said to orbit a star similar to the sun called GQ Lupi.The article you posted has the picture from the earlier article but seems to be refering to the recent announcement.

---

Aslan is not a Tame Lion

The first photo (of 2M1207b dated 10th Sep) was the first one taken of an exosolar planet, but they couldn't comfirm that's what it was:The second photo (the planet at GQ Lupi, 1st Apr) was taken afterwards, but was a definite planet:The last article is comfirming that 2M1207b was indeed a planet.IIRC, it's about 50 jupiter masses to become a star, but
a) I'm probably wrong,
b) It probably depents on the composition, and
c) Eta C. will know off the top off his head...

---

Mat 27:5 And he went and hanged himself
Luk 10:37 Go, and do thou likewise.

The mass where a planet becomes a brown dwarf is composition dependent.The mass is somewhere in the 10-40 Jupiter mass area. (The mass where a brown dwarf becomes a star is 50-80 Jupiter masses) This uncertainty is very sensitive to the equation of state used in the computer models and as such is sensitive to the composition of the material.From an observational perspective the appearance of an object is very sensitive to the atmospheric composition and thus the theoretical models atmospheric treatment is an important factor.Note - there are many confirmed extra solar planets but what they are talking about here is the direct imaging. The vast majority of the planets will never be directly imaged since they are too close to the parent star. That doesn't mean they are not confirmed.This message has been edited by Eta_Carinae, 05-02-2005 11:09 AM

Ah, I was hoping to hear from you, Eta. This isn't particularly on topic, but I had a question some time ago about the composition of Jupiter. I understand that it has no solid surface but, on further consideration, I started to wonder if it even has what we would consider a "surface" at all.What I mean is that, on the Earth, if you come down through the atmosphere to an oceanic surface there is a sudden change in density. That is, there is a definite, identifiable surface.Is Jupiter believed to be the same, in this regard? Does it have a gaseous atmosphere which sits over a liquid surface, as on the Earth? Or is Jupiter's composition more of a continuum? Does it begin, far out, with a thin, gaseous atmosphere whose density gradually increases the deeper you go until, eventually, it is what we would consider a liquid, yet without having any clearly definable "surface" where gas ends and liquid begins, so to speak?The way I believe I phrased this before was, if you were to fly a ship straight down through Jupiter's atmosphere, would there be, at some point, a definite "splash," or would there just be a gradually increasing resistance to your descent? Yes, just to be clear, I wasn't suggesting that the existence of extrasolar planets isn't confirmed until they've been photographed. What I meant was specifically images which have been confirmed to indeed be images of extrasolar planets. I realize that the non-imaged planets are confirmed to exist. I was just wondering if there have been any other images of extrasolar planets, whether confirmed or unconfirmed (as imaged planets).I knew they'd come along, I just wasn't expecting them so soon. I haven't looked into the latest in this area for some time and, the last I heard, it was still not possible to capture the planets themselves. But things have obviously come along since then. Guess I underestimated you guys.

At some point, the electromagnetic force is overcome by pressure and electrons are shared amongst the hydrogen atoms. Hydrogen is effectively a metal (read some of the stuff by Salpeter for a mathematical clarification of the equations of state). Thus Jupiter has a "surface" composed of metallic hydrogen due to the immense pressure in the interior. However, the density change is probably not as sudden as on Earth. I'll have to look at my old notes.The less massive gas planets, like Uranus and Neptune, probably do have rocky surfaces overlain by atmosphere.

I've heard of this metallic hydrogen before. Do you think it could be stable on earths surface (like diamond is)? It'd be cool to have a solid metal that floats

Well, to get up to the pressures required for metallic H, we'd need a very strong press. Currently shock systems are the best way of getting high pressures, but they also have the unfortunate effect of rapidly heating the material, and I don't think anyone has gone up to the pressure necessary for producing metallic H2. Oh well.

I thought the metallic hydrogen was located beneath the surface? That is to say, the volume between the core and the surface. Or is that what you meant? I seem to recall reading or hearing that...somewhere. I don't remember where, though. It may well be mistaken. Indeed. What I'm really wondering is whether or not there is any detectable "jump" in density at all. Or is the density increase, down through the planet, essentially a smooth transition with no real jumps from one level to another? Rather than there being distinct "layers," like on the Earth, is there, in a manner of speaking, one single layer that goes all the way down, never "leaping" to a greater density (a separate layer of density) but merely displaying a steady "thickening" (a progression through all layers with no jumps in between), with ever greater depth?Ugh, I'm not sure how clear I was there. Did that make sense? Really? I thought that all the Jovian planets were essentially large balls of gas and liquid. Is it really believed that Uranus and Neptune have rocky surfaces? I can't say I've ever heard that before. Man, now I'm confused. I'll have to take a look and see if I can find anything on this.Eta, are you around? What say you?

I think that there may be a "rocky" or metallic (Fe, Ni, not H) core to Jupiter, but by far away the majority of the solid material is metallic H and He. I don't think there's anything covering the metallic H and He. My "Planetary Scientist's Companion" (Lodders and Fegley 1998) has "rocks" at the core of Uranus and Neptune. This is based on the higher density of these planets compared to Jupiter and the non-solar abundances of the elements. However, these are still open questions in planetary science (although not actively researched, as there aren't any missions heading out that way anytime too soon).I'll have to get back to you on the other points/questions- I've had a class in this, but it was my least favorite among the planetary science classes.

Just to be clear, if you're talking about solid cores in these planets then I understand. I'm not sure I understand what you mean by nothing "covering the metallic H and He." If I'm reading you correctly, the metallic Hydrogen and Helium we are talking about is solidified, right? If so then is it not covered by Jupiter's atmosphere? Or are you just saying that there is nothing else solid covering the metallic core?Sorry about this. I'm not trying to be a pest, I'm just having trouble following your train of thought. Again, if we are talking about planetary cores then I follow you.I think one of the problems with this is that, by its very nature, it's easy to confuse what we're talking about. If we are discussing a gas giant with no solid surface and an atmosphere that becomes gradually denser the deeper you go, it's difficult enough just to define what we mean by the word "surface." To be honest, I really don't see how it can have any clear meaning, in this scenario. Even on a "water-world," it would have an unambiguous meaning. There may be no solid surface but there is still a clearly definable surface.However, on a planet with an "atmospheric continuum," there is no clear-cut meaning; nowhere you can draw a line between everything "above the surface" and everything "below the surface." Instead, "above" and "below" blend into each other and become one big shade of grey.But if a planet has this nature yet contains a solid core, would there be any merit in arguing that the core itself is the planet's surface, and the rest is just its surrounding atmosphere? Of course, in the case of a planet as large as Jupiter, it would be an atmosphere of unimaginably great altitude (I don't know the figures but I would guess tens of thousands of kilometers from its "solid surface" to "space"), but would this be accurate, none the less? Would it reflect the true reality of the system or am I just playing games with the way we define these things? No problem, please take your time. Thanks for your help so far.

Solid, or maybe molten, or maybe something else altogether. I'm not sure what most minerals do at 8000K and 8 Mbar. I don't think we have the phase diagram that well constrained. You're right, but the impression I got from your post 10 was whether metallic H was beneath another solid surface. Many scientists have similar problems. Jupiter's radius is defined as the distance from the center of the planet to the point at which the pressure becomes 1 bar, and similarly for Saturn. The "surface" of both planets is hard to define, mainly because our own knowledge of the chemical phases of elements at these pressures and temperatures is very limited. It's extremely difficult to do experiments of that nature, and the funding is definitely not there. They may be solid, molten, or perhaps in some unusual gas-liquid state.I would probably agree with you to some extent about the planet's surface being defined as the solid body portion of a planet, especially for the rocky planets. Rocky planets essentially have the same "radius" and "surface", but gas giants do not. The gas giant planets have a significant portion of their total mass in their atmosphere (on the order of a few percent), so we typically use the radius of a planet when discussing its physical features. The atmosphere is also the only thing we can visually observe.Gah. Good questions.

Hi Matt. Ah! Yes, I believe I can see where I gave that impression. I said... That wasn't very clear. My apologies.At this point, I was still taking it for granted that the planet's "surface" was considered to be somewhere in the upper layers of its atmosphere; for all intents and purposes, the planet's "surface" would be what we see when we look at it from space.That's what I meant when I said "...the volume between the core and the surface." I was assuming that if there were any solid mass in the planet, it would be contained within the core. I was thinking that, perhaps, the Hydrogen may sit above the core but, at this point, I was imagining it as liquid metallic Hydrogen. Perhaps a Mercury-like substance?So, in essence, I was thinking: Solid core, covered by liquid metallic Hydrogen, covered by other atmospheric substances decreasing in density as you approach the planet's "surface." Or to use an analogy, I was thinking that the region of metallic Hydrogen may be Jupiter's equivalent of the Earth's mantle. In this analogy, the atmosphere above the Hydrogen would represent Jupiter's "crust."Urk! Hopefully that was clearer than before. Yes, I was thinking along these lines. But it was from the perspective that if there does exist a true atmospheric continuum on these planets then the "grey area" between what we would consider "obviously gas" and what we would consider "obviously liquid" would likely be a kind of superposition between the two; both gas-like and liquid-like. Hence the difficulty in establishing any clearly definable surface. Well, in the case of the terrestrial planets, I just took this for granted. For example, all we can see when we look at Venus is its thick layers of clouds, but I don't think of this as its "surface." I reserve that title for the solid, rocky mass beneath the clouds. I suppose this is kind of arbitrary. After all, one might well argue that the atmosphere is every bit as much a part of the planet as is the solid mass, but this is just the way I've always thought of it.I think it gets a little more contentious, though, when dealing with the Jovian planets. And even more so if there is no solid core to speak of. Then what? Where, exactly, is the "surface" of a large, fluidic ball which begins with a few stray particles at its outermost edge, and grows denser at a constant rate as you approach its centre? That's harder to agree on. The only kind I ask.But seriously, thank you. I do have a habit of coming up with questions that are difficult to give a simple, concise answer. It's not that there are no answers to them, it's just that I have a tendency to be the most fascinated by concepts that I have the least chance of understanding.You seem quite knowledgeable of this. If you're interested you might want to check out other questions I've had. There are two main threads that I've started in an attempt to understand things better: Relative Motion (A Thought Experiment) and Dimensional Discourse. Please feel free to check these out if you wish. Perhaps you can help me in my unending quest to cure my ignorance.