Comments on: Brown dwarf T party

By: Adam Solomon

Adam Solomon — Mon, 16 Oct 2006 17:56:59 +0000

To answer some questions that have come up before, a brown dwarf in solar orbit at the hypothesized Nemesis distance wouldn’t need to be QUITE that dim (M ~ 42) to have gone undetected. A couple of years ago a fairly detailed study came out analyzing the limits of the telescopes that would likely have found such an object by now, and all that does is put a mass limit of about 40 Jupiter masses on it, although I’m not quite sure what magnitude that corresponds to at solar age (in all likelihood it would be a T dwarf, I know people who have conducted studies ruling out most likelihoods of finding an L dwarf Nemesis), but I doubt its anywhere near 42 (probably late teens).

The reason we might not have detected Nemesis when we can find all these other brown dwarfs is twofold. First, we’re still nowhere near finding all the T dwarfs that are right in front of our eyes. Brown dwarfs are usually found by combing through data from all-sky surveys, but T dwarfs are very faint and their colors make them look like other objects (galaxies, stars, etc.), so finding them is very much “diving into the muck.” The other problem is that Nemesis, given its proximity and its orbit around the Sun, would be moving so quickly that it could feasibly have avoided detection in the all-sky surveys.

Oh, and try Oh, Be A Fine Girl, Kiss Me Lovingly Tonight

By: Mungascr

Mungascr — Fri, 22 Sep 2006 14:34:24 +0000

That a brown dwarf could have such an influence on the exo-Saturn’s orbit making it eccentric from thatfaraway is indeed pretty amazing.

So much so that it makes me rather skeptical its actually happenening. Granted the brown dwarf is quite massive with a hefty gravitational tug but from my undestanding an object at Pluto’s distance affecting something at Mercury’s so strongly just seems highly unlikely unless its a black hole or neutron star which it clearly ain’t!

Have they ruled out other closer-in planets or possible reasons for the exo-Saturn’s orbit? Are they sure?

By: Mungascr

Mungascr — Fri, 22 Sep 2006 14:27:03 +0000

Spectral types R, N, S are rediant or supergiant ones usuallysyyubsumed under the M category.

There’s also a W class for Wolf-Rayet stars at the opposite end of the spectral class spectrum (try saying that five tuimes quicklyafter drinking afew shots of tequila! … ) which is sometimes included as type O.

Maybe the all-encompassing mennonic could be :

Whoa! Oh Be A Fine Girl Kiss Me Right Now – Sex Later Tonight?!

One point BA – I thought G type stars were 4 % of thestellar population not 10 %?

Got this from a Ken Croswell article on Alpha Centauri in Astronomy magazine (April 1991 issue) which had a pyramid graphically illustrating the breakdown of star type /numbers as follows :

70 % red dwarfs

10 % white dwarfs

15 % orange dwarfs

4% yellow dwarfs

1 % F class dwarfs & main-sequence white Sirian A type stars

and finally less than 1 % all other star types…

Now this was before the L & T type brown dwarfs were added so its a bit out of date but other than that – is it that wrong? Have we found that many more G-type stars since?? Has that idea been revised? Or did the BA (cough,cough, ahem) get it a trifle wrong? What _are_ the approximate relative percentages?

BA? Anyone?

By: Bryan

Bryan — Fri, 22 Sep 2006 04:05:26 +0000

That’s why I’m surprised he didn’t bring it up again. It seems that the astronomers that discovered it are classifying it absolutely as a brown dwarf, and I’m wondering what was behind that decision.

By: Tim G

Tim G — Thu, 21 Sep 2006 07:46:43 +0000

Bryan, he talked about the upper limit to a planet a couple of weeks ago.

By: Bryan

Bryan — Thu, 21 Sep 2006 00:32:05 +0000

So if there is an object with 20 times jupiter’s mass not fusing hydrogen that orbits a star that is fusing hydrogen, and other planets are already in the system. What defines the object as a brown dwarf, and not as a planet- the distance between the dwarf and the other star? After all of the Pluto stuff the lower limit for planets is set, but where is the upper mass limit? I’m surprised you didn’t comment on that.

By: Thomas Siefert

Thomas Siefert — Wed, 20 Sep 2006 20:06:58 +0000

Navneeth,