They are called brown dwarves because they have insufficient mass to trigger fusion in the core. They emit energy due to gravitational contraction and compression of the core. As soon as this runs out they go dark. It is a very low frequency form of energy output. Jupiter does some of this also because it emits slightly more energy than it would if it was all from solar reflection. Kent Gittings
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Peifer, William [OCDUS] Sent: Tuesday, January 08, 2002 12:41 PM To: '[EMAIL PROTECTED]' Cc: 'aimcompute' Subject: RE: Extra-solar Planet Imaged Optically Tom C. wrote: > Thought some may enjoy this. Apparently a ground based telescope > has optically resolved a brown dwarf orbiting another star. http://www.cnn.com/2002/TECH/space/01/07/brown.dwarf/index.html Hi Tom, Yeah, that's pretty cool. If I did my arithmetic correctly, that's an apparent separation of about one fourth of one milliarcsecond. Even with monster, multi-meter-class ground-based telescopes, resolution at visible wavelengths -- without adaptive optics -- is limited to about one half of an ~arcsecond~ (i.e., 500 milliarcseconds, or about 2000 times less resolution than these fellows obtained) because of atmospheric turbulence. Adaptive optics are pretty amazing. Telescopes like the Keck can obtain theoretical resolutions on the order of 10 milliarcseconds in the visible, and even better in the infrared. (Sounds like these fellows were going a step further and doing infrared interferometry, which would boost resolution even further.) I just wish these "science journalists" would learn the difference between brown dwarfs and planets. Methinks they're giving the impression to the general public that all these "planets" are just like Earth, which of course is not the case at all. Not sure where the dividing line is between carbon stars and brown dwarfs -- IIRC, carbon stars use heavy atoms to fuel nuclear fusion reactions, but I don't know if brown dwarfs can do this. They emit in the infrared, but I'm not sure what powers this process. Heavy-element fusion?? If you want to see something really neat, look at the January 2001 (last year's) issue of Sky & Telescope. I was just looking at this back issue last night. There's a brief note in the front about some amateurs using a small scope (14" Schmidt-Cass, I think), a CCD, and some photometric software to get a light curve for some star with a known short-period extrasolar planet. From our vantage point here on Earth, this planet transits across the face of its star every few days, causing a very small (0.02 magnitude) drop in the star's apparent intensity. They measured the intensity of the star during one of these planet transits, and sure enough, they could actually observe the intensity variation as the planet blocked some of the star's light from our view. Pretty good for off-the-shelf amateur equipment! All this is giving me an itch to point one of my Pentaxen skyward, but I'm afraid all I'll get this week will be clouds. Aarrrgh!! At least they're 18% gray.... :-) Bill Peifer Rochester, NY - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org . ********************************************************************** This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses. www.mimesweeper.com ********************************************************************** - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
