PC Pals Forum
General Discussion => Science & Nature => Topic started by: Simon on November 11, 2009, 22:07
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Astronomers may have found a way to identify those Sun-like stars most likely to harbour orbiting planets.
A survey of stars known to possess planets shows the vast majority to be severely depleted in lithium.
(https://www.pc-pals.com/smf/proxy.php?request=http%3A%2F%2Fnewsimg.bbc.co.uk%2Fmedia%2Fimages%2F46708000%2Fjpg%2F_46708100_li-exoplanets-final.jpg&hash=7bd5d9ed0bd8eb6a455ea3bc3558a0e95de0fa36)
http://news.bbc.co.uk/1/hi/sci/tech/8354522.stm
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That's quite a major breakthrough. Most stars should contain similar amounts of lithium because it was mainly produced at the time of the Big Bang. Almost all of the other elements (apart from hydrogen and helium) are actually synthesised by nuclear reactions inside stars so this is a cracking method of locating exoplanets! Sam's speciality! 8-)
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Our future lies in his hands! 8-)
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Depends what they are holding right now Simon. :laugh:
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:laugh: :laugh:
Lithium.. hmmm, I've used the Lithium test to determine if an object was an L or T type star (i.e. a brown dwarf) - the presence in one shows certain physics occuring... will have to look this up in more detail... though these days my life is taken over by statistics.
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I thought you wrote Litmus test for a moment. ;D
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hahahahahaha.
I have done a Litmus test and had the fun of teaching that last year.. but nope nothing that fun! (http://en.wikipedia.org/wiki/Brown_dwarf ; http://www.iop.org/EJ/abstract/1538-3881/118/2/1005)
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ABSTRACT. We present high-, mid-, and low-resolution spectroscopy of the field brown dwarf candidate PC 0025+0447 (M9.5) spanning a 4 yr baseline (1994–1998). The strength of the emission lines and the amount of optical veiling are very variable. Our spectra taken at an epoch of low veiling allow us to detect the lithium resonance line, which was not detected when the veiling was high. The presence of lithium proves that PC 0025+0447 is a substellar object less massive than ~0.06 Modot and younger than ~1 Gyr. We also present mid-resolution spectra of three brown dwarf candidates in star-forming regions, namely ρ Oph 162349.8-242601 (M8.5), V410 Tau X3 (M6.5), and V410 Tau X6 (M6). Lithium is detected in all of them, supporting their very young age. Of these three objects, only the one in ρ Oph is sufficiently cool to warrant an unambiguous substellar status. The spectroscopic characteristics that PC 0025+0447 and ρ Oph 162349.8-242601 have in common are moderately strong Li I lines (pseudo–equivalent width ~ 1 Å), persistent Hα emission with equivalent width greater than 50 Å, and weaker K I and Na I lines than field dwarfs of the same spectral type.
I knew that. :D
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:believe:
hehe - ok that wasn't the best of links to put up, might have made some sense to Clive at the least...
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The wiki link seemed not to work too well. :dunno:
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The wiki link seemed not to work too well. :dunno:
tis cause I put a ";" at the end as a separator... woops, fixed now... still it tells you all about brown dwarfs... hopefully more comprehensible than the paper.
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Are they actually any relation to Red Dwarf, as in the TV show?
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No, not at all :-D
Those there are types of stars called Red Dwarf - just means a small red star... :dunno:
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Brown dwarfs are stars that are too small to allow nuclear reactions to take place. They are so dim that they can only be seen in infrared light. There are probably lots of them but being so small and dim they are hard to find.
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they have pockets of fusion - and quite a few of them are pretty strong radio sources (thus my interest) - which was rather unexpected.