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Space Science

Nine More Extrasolar Planets Discovered 11

Posted by Hemos
from the more-to-colonize dept.
Complete Bastard writes: "Several news sites including BBC and Reuters are running a story about the discovery of an additional nine extrasolar planets, to be announced at a meeting of the International Astronomical Union (IAU). It will be further announced that astronomers have discovered two Saturn sized planets orbiting the star HD 83443. There is more to the BBC article, which can be found here."
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Nine More Extrasolar Planets Discovered

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  • by JetJaguar (1539) on Monday August 07, 2000 @01:44PM (#873750)

    Well, you're basically on the right track, but...

    I'm not sure what you are trying to get at concerning binary star formation. I've seen computer models that do a pretty good job of forming binary systems. There's still a lot of open questions, but the spinning cloud model does look as though it can create close binary systems. Obviously this doesn't solve the problem of how planets might form in a multiple-star system, but to my knowledge, I don't believe any of the recently discovered planets have been in binary systems (with the exception of the binary pulsar planet which was later retracted).

    Second, the issue of Jupiter sized planets near their stars is a bit surprising, but I don't think it's a big enough surprise to shatter our formation theories. Gravity is the ultimate factor that determines what gasses can be captured, not the amount of heat that is pumped into it.

    For example, what if, in our own solar system, planets started forming a little later in the formation process than in these other systems. That means the sun would have more time to blow off the gas (and other volatiles) in the inner solar system, leaving only enough material for the rocky planets. Conversely, in these other solar systems, the planets may have started accreting much earlier in the process allowing them to sweep up more of the lighter elements (and become much more massive in the process) before their central star grew hot enough to start clearing out the inner solar system. Given the state of our current understanding, I there's good reason to believe that both these scenarios are possible.

    Lastly, I don't think that planets forming out of an accretion disc necessarily requires that the orbit of the resulting planet have a low eccentricity. We don't know enough about the accretion process to say what the orbit of the planet will look like...other than the fact that it does need to orbit in the right direction.

    That's not to say that there are no explanations about why the planets in our solar system have nearly circular orbits, but some of the explanations do depend on the particulars of our solar system (having a gas giant at 5 AU).

    Also, don't forget that we are dealing with some very big selection effects in these discoveries as well. A Jupiter sized planet at 5 AU is going to be harder to detect because it simply takes longer for the planet's influence to be detected, that long orbital period makes things much more difficult.

  • This brings the total number of extrasolar planets to 50.
    I presume that you mean KNOWN extrasolar planets. It would be quite amazing if there were exactly 50 extrasolar planets. :-)
  • That's true, didn't seem that long ago that scientists were saying that there was no way we could detect extrasolar planets because our instruments weren't sensitive enough. Now not only are we detecting them, there is talk of building optical interferometers and such to *image* them.

    Pretty soon it'll be a big deal if a star is discovered that *doesn't* have any planets. :)
  • What I find interesting is with all the gas planets out there they probably have many moons like our solar system's gas planets. Now for the gas planets that are orbiting the stars in the "green zone" there may be more possibilites for habitable moons than their may be for habitable planets. Just a thought...

  • Now for the gas planets that are orbiting the stars in the "green zone" there may be more possibilites for habitable moons than their may be for habitable planets.
    Isn't this "green zone" based on just one data point, Earth (actually, just the surface of Earth)? We shouldn't rule out other planets as habitable just because they don't resemble the surface of Earth. After all, we have iron-breathing bacteria one mile deep inside the Earth's crust. No need for oxygen; no need for liquid water.
  • Here are some articles that illustrate how life on Earth discredits the criterea for designating a planet of being capable of supporting life:
  • With the number of Gas Giants that are being found "out there" it seems that it's just a matter of time before the instruments get sensitive enough to measure small (probably rocky) planets...

    Any volunteers to visit them?
  • by skwang (174902) on Monday August 07, 2000 @07:59AM (#873757)

    It seems that there is a lot of hype with the discoveries of all these planets. Many of the comments about the prvious article on the finding of the Jupiter sized planet around Epsilon Eridani all seems to assume that we are close to finding the answers about planets and we can start searching for "earth-like planets" and that we will understand everything about extrasolar planets. In fact nothing could be further from the truth.

    First of all, I am studying to receive my degree in Astronomy, so if any Astronomers out there want to correct me, please feel free to do so.

    Let's take a quick look around our solar system:

    The Earth and other inner planets are about 0-2 AU (1 AU = radius of Earth to Sun). Mars, the futhest inner planet is about 1.5 AU from the Sun.

    The outer planets are (respectivly) 5, 9.5, 19, 30, and 40 AU from the Sun.

    All the orbits of the planets (except Mercury and Pluto) are almost perfectly circular. The eccentricity of the orbits (where 0 is a perfect circle) range from .004 - .09 (Mercurey is .2, Pluto is .25).

    These three facts are part of the theory of how our solar system formed, here is the short version. A large gas cloud collapes under gravity (Jean's Mass for those astronomers) and spins due to conservation of angular momentum. The spinning cloud's center begins fusion and the star is "born." The gas and other matter around the star forms into an acresion disk. When the disk cools, planetessials form which collide together to form planets. Inner (rocky) planets form within 2 AU because there is enough gravity to hold heavier elements and there is enough heat to let H and He escape (this is another discussion involving statisitcal mechanics). Outer planets form with gas and since there is not enough heat, H and He stay.

    Now there are a lot of other things that may have happened. For example, capturing Pluto to make it a planet, Jupiter acting as the vaccuum cleaner sweaping up dust and small objects. Jupiter and Mars acting together to "form" the astroid belt. But for the most part, this is the theory of how our Solar System formed.

    Of course with now other planets being discovered until recently, this is also how we though other solar systems would possible form elsewhere is the galaxy. However, the after discovereing about 50 some planets it looks like we have some major rethinking to do.

    ONE 90% or so of all stars in our galaxy are binary (or more) stars. Firstly, we don't have a good theory on how binary stars form. The spinning gas cloud theory I described above doesn't lend itself to form two stars. Secondly, how do you get planets with binary star systems? For those who know, N-body gravity problems are very difficult. With 3 bodies, two stars and one planet, the planet almost always flys out of the system!! Unless the two starts are very close together and the planet is orbiting far away, so that the two stars act as one. So, as we are discovereing new planets we run itno this problem that bianry stars don't seem like good "solar systems." I don't know the statistics, but I would like to know how many of these new planets are around binary systems.

    TWOMost of the new planets are Jupiter sized planets. There is nothing strange about this, our instruments can only measure a Jupiter sized planet's wobble. But what is interesting is that many Jupiter sized planets have not been found at 5-30 AU, but all over. There are some that are as close as .5 AU! Once again, I haven' seem the statistics, but I would like to see a correlation between the distance of thuse Jupiter size planets and the type of star they orbit.

    Jupiter size planets form because there is not enough heat for the H and He to escape the gravity
    This finding seems to counter our original theory of solar system formation.

    Some of the planets found have highly elliptical orbits. Without the statisitcs I cannot make any real guess on why but it does seem to refute the idea of the acresion disk forming planets, after all all of the planets in our system have near circular orbits (the .2 that mecury and pluto have isn't that ellipitcal either).

    I would guess to say that we (science) need to rethink our theories of solar system formation. We need to figure out how thost extrasolar planets formed and come up with models ofhow our system could form in such a "untypical" manner. Of course we need to make many more observations to verify that we are not normal. After all, we could just be finding the fringle systems and al most all other systems are just like ours.

    Then we can go out and find other "Earths."

  • The story was generated based on several presentations given at the General Assembly of the International Astronomical Union (IAU). The total number of new planets discovered is 10, including the double planet system of twin Saturn-sized planets.

    The information was actually released to the various news agencies last week, but was under strict embargo until early this morning.

    This brings the total number of extrasolar planets to 50.

    Here're the original source links to this story:

    And then coverage by news sources around the Internet:

    And of course, my own coverage on Universe Today.
    Planet Discoveries Coming Fast and Furious [universetoday.com] - August 7, 2000

    Fraser Cain

  • It seems like almost once a week we get news that a new planet has been found. I agree with the statement that NOT finding planets is news. I mean, we're in the middle of nowhere galaxtically speaking, and we've got 9 or so planets orbiting ol' sol. And 3 or 4 planets/moons that may have life? Maybe it's just me, but I would be just as surprised to find that we are the only intelligent life around as I would have been to have find there are no other planets.


    -----
    My karma is still less than my age.
  • It seems to me that searching for all these planets is a huge waste of money. Who is paying these scientists to look at wobbles of a star?? I say if the stars name can come directly from a license plate, then it isn't worth studying. I mean, the only proof of these existing are movements in stars detected by sensitive equipment. Well, if the equipment is so sensitive, then how do we know it's not detecting someone walking next to it and shaking the ground just enough for the telescope itself to move? It just seems like a waste to me.

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