Watching the population of nearby stars grow is a chastening exercise. It reminds us that even in our own stellar neighborhood, there is much we have to learn. Consider that since the year 2000, the population of known stars within 10 parsecs (roughly 33 light years) of the Sun has grown by 16 percent. That includes 20 new stars identified recently by the Research Consortium on Nearby Stars (RECONS), whose list of the 100 nearest star systems can be found here.
As you might have guessed, all twenty of the new objects are red dwarfs, and if you look throughout that 10-parsec volume, 239 of the 348 stars within it (other than our own star) are red dwarfs. That tallies nicely with earlier estimates that red dwarfs make up about 70 percent of the stars in the Milky Way, and points to the obvious fact that when you look up into the night sky, you’re getting an unbalanced look at what’s around us. None of the new stars are remotely visible with the naked eye.
Image: The binary red dwarf represented in this artist’s concept is SCR 0630-7643 AB, a system discovered and measured by the RECONS survey. The measured separation of the two stars is 0.90 arcseconds; at a distance from Earth of 8.8 parsecs (28.7 light-years) as obtained by RECONS, this equates to 7.9 Astronomical Units between the two, a bit less than the distance between the Sun and planet Saturn. The orbital period of the red dwarfs is roughly 50 years. Credit: Zina Deretsky/National Science Foundation.
RECONS has been working with telescopes at Cerro Tololo Inter-American Observatory (CTIO) in Chile to make observations using parallax, measuring the change in apparent motion of a nearby star as the Earth revolves around the Sun. That’s a method useful only for relatively nearby objects, of course, but I was surprised to learn that if you extend parallax measurements over several years, you can reach an accuracy of better than 10 percent out to 300 light years.
But what I like best about this announcement is a quote from RECONS Project Director Todd Henry (Georgia State University): “We expect to announce more systems within 10 parsecs in the future. The pool of nearby stars without accurate parallaxes is nowhere near drained.” Thus the essential cataloguing continues. RECONS is all about finding not just red dwarfs but brown dwarfs as well in the vicinity of the Sun. In terms of stellar classifications, that means type M (red dwarfs) and types L and T, covering the known range of brown dwarfs.
It goes without saying that close-by stellar systems make interesting hunting grounds for exoplanets; fine-tuning the target list is crucial to the success of future space-based searches. The paper is Henry et al., “The Solar Neighborhood. XVII. Parallax Results from the CTIOPI 0.9 m Program: 20 New Members of the RECONS 10 Parsec Sample,” Astronomical Journal 132:2360-2371 (December, 2006), with abstract available online.
that is really great news – it means that we now have more “close” stars from which to chose to visit!? but just in general it is always good to obtain more information anyhow. more reason to look for stardrives also… as if anyone here needed them! i will continue to think about it i hope so will everyone else! this would be a cool heading under which to discuss this come to think of it ! hope i’ll read plenty over the next few days :) your friend george
It’s so surprising to me sometimes that with everything astronomy is capable of knowing how little is actually known for sure.
you know anthony that seems to be the cae for so many things i agree! george
And let us not assume that every dim stellarish object
glowing in the infrared is of natural origin.
As has been touted as of late, conducting SETI at bright
and very visible yellow suns may not be the best place to
search for advanced civilizations.
The representation of stars you see when you look up is even worse. The dimmest stars are something like 10,000 times dimmer than the Sun. The brightest stars are something like 10,000 times brighter than the Sun. So, one of these behemoths out at 1000 light years is as bright as the Sun is at 10 light years. So Sirius, only a little brighter than the Sun at around 10 light years is only a little brighter than Deneb, which is so far that parallax doesn’t accurately tell us how far it is, but which may be over 3,000 light years out.
Nearby stars are cool. And therefore hard to find.
When Bessel was trying to do parallax in the early 1800’s, he wasn’t the first to try. Most people figured that the bright stars were closer, and since that’s wrong, they failed. Bessel did data reduction on data other astronomers had taken over a 300 year period. Part of what he found was some 30 odd stars with lots of apparent motion. These, he figured, were nearby. And yet, his first success was on a star some 13 light years out. It is totally amazing that he was able to detect parallax that far out with what he had or could cobble together.
I have a 19 CD set of images of the entire sky down to 19th magnitude. I don’t think this is dim enough to have any of these new stars represented.
Astrophysics, abstract
astro-ph/0703133
From: Charlie Finch [view email]
Date: Tue, 6 Mar 2007 22:54:14 GMT (107kb)
The Solar Nieghborhood. XVIII. Discovery of new proper motion stars with 0.40 arcsec yr^-1 > mu >= 0.18 arcsec yr^-1 between declinations -90 degrees and -47 degrees
Authors: Charlie T. Finch (1), Todd J. Henry (1), John P. Subasavage (1), Wei-Chun Jao (1), Nigel C. Hambly (2), ((1) Georgia State University, (2) Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh Royal Observatory, Blackford Hill, Edinburgh, Scotland, UK)
Comments: 30 pages, 8 figures (reduced quality), accepted 2 March 2007 for publication in Astronomical Journal
We report 1606 new proper motion systems in the southern sky (declinations -90 degrees to -47 degrees with 0.40 arcsec yr^-1 > mu >= 0.18 yr^-1. This effort is a continuation of the SuperCOSMOS-RECONS (SCR) proper motion search to lower proper motions than reported in Papers VIII, X, XII, and XV in this series. Distance estimates are presented for the new systems, assuming that all stars are on the main sequence. We find that 31 systems are within 25 pc, including two systems — SCR 0838-5855 and SCR 1826-6542 — we anticipate to be within 10 pc. These new discoveries constitute a more than ten-fold increase in new systems found in the same region of sky searched for systems with mu >= 0.40 arcsec yr^-1, suggesting a happy hunting ground for new nearby slower proper motion systems in the region just north (declinations -47 degrees to 0 degrees, much of which has not been rigorously searched during previous efforts.
http://arxiv.org/abs/astro-ph/0703133
Spectroscopic distances of 28 nearby star candidates
Authors: H. Jahreiss, H. Meusinger, R.-D. Scholz, B. Stecklum
(Submitted on 12 Mar 2008)
Abstract: 28 hitherto neglected candidates for the Catalogue of Nearby Stars (CNS) were investigated to verify their classification and to improve their distance estimates. All targets had at least a preliminary status of being nearby dwarf stars based on their large proper motions and relatively faint magnitudes. Better photometric and/or spectroscopic distances were required for selecting stars which are worth the effort of trigonometric parallax measurements.
Low-resolution spectra were obtained with NASPEC at the Tautenburg 2m telescope and with CAFOS at the Calar Alto 2.2m telescope. The spectral types of M-type stars were determined by direct comparison of the target’s spectra with those of comparison stars of known spectral types observed with the same instrument. The classification of earlier types was done based on comparison with published spectral libraries.
The majority were classified as M dwarfs including 11 stars within 25 pc. The fainter component of LDS 1365, previously thought to form a nearby common proper motion pair, is according to our results an unrelated high-velocity background star. For several other nearby common proper motion pairs our distance estimates of the fainter components are in good agreement with Hipparcos distances of the brighter components. (abridged)
Comments: 5 pages, 4 figures, accepted by Astron. Astrophys
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0803.1813v1 [astro-ph]
Submission history
From: Hartmut Jahreiss [view email]
[v1] Wed, 12 Mar 2008 16:58:22 GMT (53kb)
http://arxiv.org/abs/0803.1813
Towards a complete census of young stars in the solar neighbourhood with SkyMapper
Authors: Simon J. Murphy, Michael S. Bessell
(Submitted on 10 Jun 2008)
Abstract: In this contribution we outline plans for identifying and characterising numerous young, low-mass stars within 150 pc of the Sun using the new SkyMapper telescope and Southern Sky Survey.
We aim to learn more about the star formation history of the solar neighbourhood over the past 5-50 Myr, the dispersal processes involved, as well as testing pre-main sequence evolutionary models and the universality of the stellar Inital Mass Function. Searching for the dispersed halo of low-mass objects predicted to surround the Eta Chamaeleontis cluster will be one of the first goals of the project.
Comments: 5 pages, 2 figures. To appear in proceedings of the 8th Pacific Rim Conference on Stellar Astrophysics, Phuket, May 2008
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0806.1611v1 [astro-ph]
Submission history
From: Simon Murphy [view email]
[v1] Tue, 10 Jun 2008 10:22:46 GMT (63kb)
http://arxiv.org/abs/0806.1611