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Fraser
2006-Nov-15, 01:55 AM
Astronomers have turned up 20 new star systems in our corner of the Milky Way. The discoveries were made by the Research Consortium on Nearby Stars (RECONS) using the parallax method. The angles to various stars were measured at different times in the year - when the Earth is on opposite sides of the Sun. The closer a star is, the more its position will shift in the sky. This new batch of stars included the 23rd and 24th closest stars to the Earth.

Read the full blog entry (http://www.universetoday.com/2006/11/14/new-stellar-neighbours-found/)

Blob
2006-Nov-15, 12:55 PM
Title: The Solar Neighbourhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
Authors: Todd J. Henry, Wei-Chun Jao, John P. Subasavage, Thomas D. Beaulieu, Philip A. Ianna, Edgardo Costa, Rene A. Mendez

Astrometric measurements for 25 red dwarf systems are presented, including the first definitive trigonometric parallaxes for 20 systems within 10 pc of the Sun, the horizon of the RECONS sample. The three nearest systems that had no previous trigonometric parallaxes (other than perhaps rough preliminary efforts) are SO 0253+1652 (3.84 0.04 pc, the 23rd nearest system), SCR 1845-6357 AB (3.85 0.02 pc, 24th), and LHS 1723 (5.32 0.04 pc, 56th). In total, seven of the systems reported here rank among the nearest 100 stellar systems. Supporting photometric and spectroscopic observations have been made to provide full characterization of the systems, including complete VRIJHK photometry and spectral types. A study of the variability of 27 targets reveals six obvious variable stars, including GJ 1207, for which we observed a flare event in the V band that caused it to brighten by 1.7 mag.
Improved parallaxes for GJ 54 AB and GJ 1061, both important members of the 10 pc sample, are also reported. Definitive parallaxes for GJ 1001 A, GJ 633, and GJ 2130 ABC, all of which have been reported to be within 10 pc, indicate that they are beyond 10 pc. From the analysis of systems with (previously) high trigonometric parallax errors, we conclude that parallaxes with errors in excess of 10 mas are insufficiently reliable for inclusion in the RECONS sample. The cumulative total of new additions to the 10 pc sample since 2000 is now 34 systems -- 28 by the RECONS team and six by other groups. This total represents a net increase of 16% in the number of stellar systems reliably known to be nearer than 10 pc.

Read more (http://arxiv.org/PS_cache/astro-ph/pdf/0608/0608230.pdf) (67kb, PDF)

bobi596
2006-Nov-15, 02:57 PM
I wish I were there at the Andes observatory (or others).

John Mendenhall
2006-Nov-15, 03:55 PM
I wish I were there at the Andes observatory (or others).

Curiously enough, if the observatory is high enough, the lack of oxygen causes problems for human vision. Sky and Telescope had an article about this a few years back, with reports from people at high altitude observatories and their distress at knowing the seeing was near perfect and not being able to see much because their retinas were oxygen deprived.

jhwegener
2006-Nov-15, 04:47 PM
If such stellar systems can "escape" our view fo so long, we may speculate there may be closer systems than the closest known for the moment (closer than about 4 l.y.). Especially very dim stars or "stellar like objects". It is after all only recently astronomers discovered extrasolar planets, and Trans Neptune Objects bigger than Pluto.

antoniseb
2006-Nov-15, 06:23 PM
we may speculate there may be closer systems than the closest known for the moment (closer than about 4 l.y.)

Yes, we observe young brown dwarfs (say less than 30 million years old) from their IR output, but the same process that creates the new ones is likely to have created Brown Dwarfs five to ten billion years ago during the peak of star forming in our galaxy, and may well have created some in our own stellar nursery. Current estimates for the numbers of these things suggest that there is less than an even chance of one being closer to us than four light years, but our knowledge in this is not complete. There could be an old Brown Dwarf within a light year, and it would take some incredible luck for us to have discovered it.

hiro
2006-Nov-15, 07:17 PM
This reminds me about the nemesis theory.

John Mendenhall
2006-Nov-15, 10:45 PM
This reminds me about the nemesis theory.

Yes, it sure does. Would an all-sky IR survey be worthwhile? Or has it been done already?

antoniseb
2006-Nov-15, 11:21 PM
You'd be looking for an infrared source that doesn't appear at visible wavelengths, and has a high proper motion & parallax. This would probably require two full sky mid-IR surveys taken six months apart, with a resolution of better than 1 arcsecond.

John Mendenhall
2006-Nov-16, 05:48 PM
You'd be looking for an infrared source that doesn't appear at visible wavelengths, and has a high proper motion & parallax. This would probably require two full sky mid-IR surveys taken six months apart, with a resolution of better than 1 arcsecond.

Yes, send grant money!

Just kidding, I'm sure every facility would insist on academic credentials in Physics or Astronomy. But for someone with a fresh degree this might be good project.

antoniseb
2006-Nov-16, 06:19 PM
I'm not sure even the JWST will have the resolution at the right wavelengths to pick up parallax at one light year in the mid-infrared. Even if it could, you'd need to get pretty lucky to aim it at the right area of the sky to find this thing.