New multiplanet star system found

[MeteorWayne]

University of Texas at Austin astronomers William Cochran and Michael Endl, working with graduate students Robert Wittenmyer and Jacob Bean, have used the 9.2-meter Hobby-Eberly Telescope (HET) at McDonald Observatory to discover a system of two Jupiter-like planets orbiting a star whose composition might seem to rule out planet formation. This NASA-funded study has implications for theories of planet formation.<br /><br />Cochran and Endl have been monitoring the star, HD 155358, since 2001 using the High Resolution Spectrograph on HET. Their measurements of its radial velocity, or motion toward and away from Earth, show that the star has a wobble in its motion, which is caused by unseen companions tugging on the star.<br /><br />HD 155358 is slightly hotter than the Sun, but a bit less massive. Most important, it only contains 20 percent as much of the chemical elements called metals — elements heavier than hydrogen or helium — as the Sun. Along with one other star (called HD 47536), it contains the fewest metals of any star found to harbor planets.<br /><br />Bean specializes in studying the metal contents of stars. His in-depth studies of the star's spectrum revealed its metal-poor nature, and allowed him to deduce the star's age of roughly 10 billion years.<br /><br />One planet has an orbital period of 195 days and, at a minimum, is 90 percent as massive as Jupiter. It orbits HD 155358 at a distance of 0.6 AU. (An astronomical unit, or AU, is the Earth-Sun distance of 150 million km, or 93 million miles.) The other planet orbits HD 155358 in 530 days, with a minimum mass half that of Jupiter, at a distance of 1.2 AU.<br /><br /><br /> link <br /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[heyscottie]

Interesting ... but it seems like planetary formation could occur out of clouds that are mostly hydrogen just as they can out of metal-rich clouds. Of course, we wouldn't get rocky planets, but gas giants seem reasonable to me.<br /><br />Is there some reason why planetary formation theories have seemed to rule out low-metal solar systems up to this point?

 

[MeteorWayne]

If you read the article, it has to do with the cooling effect that the metals provide. It allows things to condense faster, since without the cooling, pure H-He has a hard time condensing. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[MeteorWayne]

Again, from the article, there is another method involving instabilities within the protostellar disk.<br />Both theories can work, and likely reality will be a mix of the two.<br /><br />No paradigm shift is yet required. That doesn't mean that future data won't require one <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[space_coops]

Hmmm, interesting. This is great news because if we know that planets out there are orbiting stars whose composition might seem to rule out planet formation, then it opens up so much more possibilities of Earth like planets. And at the end of the day thats what we all want to hear, that life exists outside our own planet.

 

[3488]

Thank you very much MeteorWayne.<br /><br />This is further proof of the robustness of the planetary formation process.<br /><br />The planets are almost certainly gas giants like Jupiter & Saturn.<br /><br /> HD 155358.<br /><br /> HD 155358 in Hercules further data.<br /><br /> HD 155358 Planetary discovery in Texas, USA.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[robnissen]

Yes, but. It would seem unlikely to me that metal poor stars would likely be the home to many rocky planets. But while the odds are still poor, they are higher than before the discovery of this system.