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Fraser
2005-Jan-20, 05:55 PM
SUMMARY: Astronomers have used the European Southern Observatory's Very Large Telescope (VLT) to watch a small, faint companion as it orbits around a larger star. By measuring its orbit, the astronomers have been able to estimate that its mass is 93 times that of Jupiter. This is much less than a normal star, but twice as heavy as predicted by theory. If these brown dwarfs and free floating extrasolar planets are heavier than expected, then astronomers have been overestimating the number of them in the Universe.

View full article (http://www.universetoday.com/am/publish/small_stars_heavier.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Jan-20, 10:17 PM
More than a hundred Jupiter Masses, 88 to 98 Jupiter masses. I guess either way we're talking about more than what is predicted for the mass, based on temperature and luminosity.

Still I wonder to what degree this system being only about 50 million years old has to do with all this, or for that matter whether the "Brown Dwarf" being this heavy puts it in a special category of pre-main-sequence low mass red dwarf that might have that lower surface temperature.

So far, we haven't gotten enough photons from it to determine a Lithium abundance, or any other such test. It will be interesting to follow this story, and see what the masses of the next Brown Dwarfs look like.

GOURDHEAD
2005-Jan-20, 10:33 PM
If these brown dwarfs and free floating extrasolar planets are heavier than expected, then astronomers have been overestimating the number of them in the Universe. This is an odd statement considering the matter deficit. Instead of assuming fewer of these items why not reduce the amount of missing matter? How shall we decide what to do?

antoniseb
2005-Jan-20, 10:39 PM
Originally posted by GOURDHEAD@Jan 20 2005, 10:33 PM
This is an odd statement considering the matter deficit.
The total mass of Brown Dwarfs is expected to be less than one percent the normal matter in the galaxy. Thus doubling the amount of mass taken up in Brown Dwarfs doesn't really solve the missing mass problem. It's four or five orders of magnitude to tiny. The real issue being addressed is that IF this observation is accurate, than the theory about how low mass stars work needs tweaking.

Greg
2005-Jan-22, 06:14 AM
I think the conclusion made in the summary means that if the amount of solid matter is known and brown dwarfs are more massive than expected, then that must mean there must be fewer of them out there (which are larger than expected). I do not agree with this conclusion in principle. Brown dwarves until very recently could not be seen at all and they at one time constituted the main component of missing mass in the universe aka "dark matter as MACHOS" WIMPS are now considered the main constituent of missing/unobservable/dark matter. So the only conclusion I would draw is that brown dwarves can be more massive than some theories predict and in fact there are probably more of them out there as a result. OF course this would not be nearly enough to alter the current assumptions about the nature of dark matter being predominantly WIMPS.