View Full Version : Brown Dwarf Detected Very Close to Star

2002-Jan-07, 07:28 PM
FYI - CNN article for 01/07/02. The object (http://www.cnn.com/2002/TECH/space/01/07/brown.dwarf/index.html) is 58 light-years away in the constellation Sagitta, and is closer to it's companion star than Uranus is to our sun. The star's name is "15Sge."

2002-Jan-07, 07:43 PM
Interesting article. It doesn't say what technique they used. At first I thought opticle interferomitry but then they said the astonomers had used a scope in Chili and also the Kecks?!? Whatever that means.

Donnie B.
2002-Jan-07, 07:54 PM
Russ, Russ! How could you not know about the Keck telescopes? They're only the most powerful ground-based telescopes!

Now, as to how they detected the brown dwarf, I'd say it was interferometry, though I wasn't aware that they had started doing VLBI in the optical band. Still, it's the only way telescopes in Chile and Hawaii could be used "simultaneously".

2002-Jan-07, 07:58 PM
Well, given that the last paragraph of the linked CNN.COM story says:

"Only by using adaptive optics to produce very sharp images could we have found this companion. It is too faint and too close to its parent star to be seen otherwise," said Liu, who presented the images at a meeting of the American Astronomical Society.

I'd guess that they used adaptive optics to find the object . . . Of course, that's just a guess.


2002-Jan-07, 09:06 PM
There are quite a few "adaptive optics" websites around, but one has to dig a bit deeper for any technical explanations as to how the method works.

The site for the University of California's Center for Adaptive Optics (http://cfao.ucolick.org/) has a rather blunt but lucid motto: "Removing the blurring of images caused by changing distortions in optical systems." (Bad poetry but good science!)

The University of Arizona in Tucson has a very impressive Center for Astronomical Adaptive Optics (http://caao.as.arizona.edu/).

If anyone works in this field or knows of folks who do, some of us old fashioned outdoor, winter freezing, averted vision, dusty eyepiece squinters (i.e. amateur astronomers) would appreciate a brief description of this sophisticated technique.

<font size=-1>[ This Message was edited by: Chip on 2002-01-07 16:09 ]</font>

2002-Jan-07, 09:35 PM
Well, I don't work in the field, but my understanding is that it involves the main mirror of the telescope consisting of hundreds (thousands? millions?) of tiny mirrors which are all mounted on motors and can be turned independently.

They then use a laser beam to create an artificial "star" in the sky. By continuously adjusting the mirrors to keep the laser-created star sharp and in focus, the 'scope compensates for the atmospheric distortion and produces a clean, focussed image of the sky.

Or something like that, anyway.

The Bad Astronomer
2002-Jan-07, 10:30 PM
Try here (http://www.badastronomy.com/bitesize/vlt.html) /phpBB/images/smiles/icon_wink.gif

2002-Jan-08, 06:29 AM
On 2002-01-07 17:30, The Bad Astronomer wrote:
Try here (http://www.badastronomy.com/bitesize/vlt.html) /phpBB/images/smiles/icon_wink.gif

Thanks Mr. BA! (I should always remember to check around your website first before asking some questons.)
This is actually an interesting sophisticated development! (I think it will be a while before Mead or Celestron introduces some form of adaptive optics in their smaller telescopes.) /phpBB/images/smiles/icon_wink.gif

2002-Jan-08, 01:26 PM
Washington Post article (from today's paper) about using adaptive optics to image extra-solar planets:


Though I wonder about the caption on the illustration: "The star appears smaller in comparison because it is farther from Earth."
Um, it's not that much farther.

2002-Jan-08, 01:51 PM
Here's the original press release from the Gemini Observatory: