Brown Dwarf Companion to Epsilon Indi

silent lurker writes "A team of European astronomers has discovered a Brown Dwarf object (a 'failed' star) less than 12 light-years from the Sun. It is the nearest yet known. Now designated Epsilon Indi B, it is a companion to a well-known bright star in the southern sky, Epsilon Indi (now "Epsilon Indi A"), previously thought to be single. The binary system is one of the twenty nearest stellar systems to the Sun. ...and astronomers believe there might be as many as 12x as many brown dwarf stars as there are visible ones! Hmmmm... Lots o' juicy fodder for SF content creators, dontcha think? ...not to mention astronomers themselves. See press release from European Southern Observatory. Another item is from Science Daily."

Comments

Astrophysics 101

[barakn]

Some back-of-the-envelope calculations using some crude rules-of-thumb: Stars roughly follow a mass-luminosity relationship. L / Lsun=(M / Msun)^2.3 (for M.5*Msun). An estimate for this object indicates it should be .0007 times as luminous as the sun. Actually, due to the lack of fusion, it is only .00002 times as bright. Also, from Wien's displacement law (lamda_max*T = .290 cm K) and the object's estimated surface temperature of 1273 K, it's peak radiation occurs at a wavelength of 2280 nm, far into the infrared. The bulk of what little light brown dwarves emit is emitted in the infrared, making them practically invisible without a very expensive (and new) telescope. This has led to speculation that an unnoticed brown dwarf (the infamous Nemesis) could be orbiting our own sun!

Re:Astrophysics 101

[barakn]

UKIRT has had a series of upgrades starting in about 1990, including several generations of IR imagers, the addition of active optics, etc.. Thus the modern version of UKIRT is not 23 years old. Nor is 23 years particularly old compared to the ~400 years that telescopic observations have been made. If you read the fine print, you'll note that it took collaborative observations by 5 different telescopes to merely confirm that brown dwarfs vary in brightness (differently at different colors). While it might confirm they have weather, it certainly does not "determine what kind of weather patterns their atmospheres have." A confirmed observation of a brown dwarf was not made until 1995 (reference).

Re:Lots of brown dwarfs?

[CanSpice]

Actually, Jupiter and Saturn are too small to be considered brown dwarfs. The upper mass limit for brown dwarf is about 0.08 solar masses, or about 80 Jupiter masses. The lower limit is a little squishy, but most astronomers who study brown dwarfs would not include Jupiter in the brown dwarf category. The lower limit is probably something like 10 Jupiter masses.

Re:Lots of brown dwarfs?

[barakn]

7% of the exoplanets listed at this table are greater than 10 Jupiter masses. Deuterium burning occurs at 10-12 Jupiter masses and greater, but doesn't help us categorize objects that have burned up their deuterium. 2-3 Jupiter masses might be a good dividing line, as it marks the transition from the object's radius increasing with mass to the radius actually decreasing with mass (which I won't go into as it leads to discussions of things like electron degeneracy pressure). Other definitions of planets and brown dwarfs make a distinction between the method of formation of the object, but this makes the mass much less important than the object's history, which is much harder to deduce. For instance, Jupiter was long regarded as having formed from runaway accretion starting with a small rocky core, but recent computer models suggest it (and the other gas giants) formed directly from gravitational collapse, just like a star. Also consider the 55-78 Jupiter mass object found orbiting at a distance roughly equivalent to Saturn's orbit around a sun-like star, a distance much too close for many astronomers' comfort.

Re:Lots of brown dwarfs?

[iggymanz]

actually no, if G the gravitational constant, M the sum of the mass of earth & "Snerd's Turd [he just named the brown dwarf], w is 2*pi over orbital period, and r the distance between "Witch-tit World" and Snerd's Turd, we find that:

G*M = w^2 * r^3

which shows that if we decrease M, it can be compensated for to yield same orbital period by decreasing the distance between the two bodies.

Dr. Snerd says he is folding a wire coathanger and to please report to the Observatory for your knuckle pimp-sticking