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Fraser
2004-Jun-15, 04:37 PM
SUMMARY: Using a combination of ground and space-based telescopes, an international team of astronomers have measured the mass of an ultra-cool star and its companion brown dwarf. The star is located 40 light-years away, and contains only 8.5% the mass of the Sun. Its companion brown dwarf is even lighter; only 6% the mass of the Sun. They orbit one another at a distance of only 2.5 times the distance of the Earth and the Sun. Measuring these low mass objects is difficult because there's no relation between their size and brightness. But in a binary system like this, astronomers can determine their mass by measuring how the objects interact with each other.

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antoniseb
2004-Jun-15, 05:14 PM
We had a thread a few months ago debating what was the smallest possible star. We've had a few other threads debating whether Jupiter was almost a star or not. This story provides some solid evidence that Jupiter is less than one sixtieth part the mass of a minimum star, and confirms that the theory of stellar energy source [fusion] works at the very low end of the mass spectrum pretty much as theorized.

VanderL
2004-Jun-15, 06:20 PM
Very interesting story, I wonder what Hubble could show us. I'm curious how this star and brown dwarf look ( possibly they have sunspots and flares) and if there are any planets around. It seems unlikely, because any planets would have been visible in these images, I think.

Cheers.

antoniseb
2004-Jun-15, 07:07 PM
Originally posted by VanderL@Jun 15 2004, 06:20 PM
any planets would have been visible in these images
It seems likely that there'd be some sort of bodies orbiting this pair more distantly. There could easily be outer gas giants and KBO-type objects. I don't think they'd show up in these images, but Kuiper-Belt dust could be visible at much longer wavelengths, and be seen by the JWST once it is launched.

John L
2004-Jun-15, 07:11 PM
Originally posted by VanderL@Jun 15 2004, 01:20 PM
Very interesting story, I wonder what Hubble could show us. I'm curious how this star and brown dwarf look ( possibly they have sunspots and flares) and if there are any planets around. It seems unlikely, because any planets would have been visible in these images, I think.

Cheers.
The Hubble was used in this, and it was the lowest resolution telescope used IMO. The VLT, the Keck, and the Gemini North also took images, and the VLT's and the Keck's were the highest resolution.

Planetwatcher
2004-Jun-15, 08:04 PM
I may be wrong, but it seemed to me that a brown dwarf star does not have fussion but heat convection as the primary source of energy.
Making the smallest fussion star a red dwarf.

Neutron stars produce energy from the gravity compression, and pulsors from the rapid rotation of a neutron star, and white dwarfs from the combination of gravity compression and heat convection, if I got all this straight. :unsure:

antoniseb
2004-Jun-15, 08:57 PM
Originally posted by Planetwatcher@Jun 15 2004, 08:04 PM
Neutron stars produce energy from the gravity compression, and pulsors from the rapid rotation of a neutron star, and white dwarfs from the combination of gravity compression and heat convection, if I got all this straight.
Neutron stars and white dwarfs are cooling embers, that are slowly radiating away intense heat of formation. Both of these objects can gain heat if a second object is dumping material onto them. The way in which they radiate the energy can be quite different from each other, especially when recently formed, as the neutron star rotates VERY rapidly, and typically has a very intense magnetic field that traps ions and accelerates them as they move away from the core.