Astronomers Discover Third-Closest Star System To Earth

The Bad Astronomer writes "Astronomers have found the third-closest star system to the Earth: called WISE 1049-5319, it's a binary brown dwarf system just 6.5 light years away. Brown dwarfs are faint, low mass objects 13 — 75 times the mass of Jupiter, and are so dim they are very difficult to detect. These newly-found nearby objects were seen in observations from 1978 but went unnoticed at the time, but since that date the large apparent motion of the binary made their proximity obvious. Only two star systems are closer: Alpha Centauri (4.3 light years) and Barnard's star (6 light years)."

If brown dwarfs can't sustain fusion

[mozumder]

then why are they considered stars?

And where's the mass of the universe?

[sshambar]

Can someone explain to me how discovering the THIRD closes system to ours in 2013 doesn't suggest that all the Dark Matter(tm) that's out there just isn't a mass of brown dwarfs that we can't see, and not a whole new class of matter?

Re:If brown dwarfs can't sustain fusion

[MyLongNickName]

I'm not sure why this is modded down. A brown dwarf never achieves sustained fusion and is not considered a full-fledged star, so i am also confused to why it is considered a star system.

Re:If brown dwarfs can't sustain fusion

[MightyYar]

It's subject to some debate. Basically, mostly the differentiation between a gas giant and a small brown dwarf comes down to how it formed and the physics going on inside.

Re:And where's the mass of the universe?

[Charliemopps]

Because dark matter isn't dark because it doesn't give off light. It's dark because it doesn't even interact with normal matter in any other way than gravitation. We can see the effects of its mass, but it does not occlude stars behind it, the light and radio waves passes right through as if it didn't exist.

new dark matter results any day now

[peter303]

That very expensive special detector on the Space Station is reputed to announce interesting results any day now. Detecting certain classes of dark matter was one of its capabilities.

Congress had to fund a special extra shuttle launch to get this into orbit. Furtmore, the physicists decided to swap in a new set of magnets last minute, postponing it over a year.

very interesting

[kilodelta]

And I still maintain if we had funded NASA like we funded them in the 1960's and early 1970's we'd be at Alpha Centauri or Barnard's Star by now. But instead we'd prefer to fund military misadventure. However look at the private interest in mining asteroids - that will be cool!

Re:If brown dwarfs can't sustain fusion

[jc42]

I think if it is the center of a planetary system, then it is a star.

This is a nice example of why you need to be careful in how you define things. With the above definition, our own sun isn't a "star" (most of the time).

Isaac Newton was one of the people who pointed this out. The objects in our solar system actually orbit the barycenter of the system, the technical name for what is often called the center of mass (or more weirdly, the center of gravity). Because most of the solar system's mass outside the sun is Jupiter, and because Jupiter is far enough away from the sun, the barycenter of the solar system is usually outside the sun. Not far outside, true, but outside the visible "surface" of the sun. It's only inside the sun when most of the other big planets are on the other side from Jupiter.

So, technically speaking, Earth and the other planets don't actually orbit the sun; they orbit the barycenter, which is (usually) outside the sun. The sun itself also orbits the same barycenter, in a very close orbit. And a few humorous remarks have been made based on the fact that Newton actually demonstrated that the Earth doesn't revolve around the sun.

We probably need a better definition of the term "star" than "has planets". That also causes a different problem: It's a circular definition, since the common definition of a "planet" includes orbiting a star. So one might decide that Jupiter is a star, and at least its four major moons instantly become planets, which then is used in the definition of "star" to prove that Jupiter is indeed a star.

There's a lot of humor in the way such terms are being defined by various (mostly non-astronomical) parties. Maybe we should go back to the definition that a star is an astronomical thing that undergoes sustained nuclear fusion. Ya think that'd work?

(We do have to carefully word it so that the experimental fusion projects in Earthly labs don't qualify as stars. ;-)