In 1995, astronomers confirmed the discovery, for the first time, of a brown dwarf, a celestial body too small to be a star and too large to be a planet. Turns out that wasn’t all.
Researchers have now studied that brown dwarf in more depth and discovered that it is not one, but two. They are orbiting very close to each other, around a small star. This fact was documented in two new studies that used telescopes in Chile and Hawaii.
The two brown dwarfs are gravitationally tied to each other, something called a “binary system”, a widely observed arrangement between stars. Thus, the brown dwarf named Gliese 229B three decades ago is now known as Gliese 229Ba — with a mass 38 times greater than Jupiter, the largest planet in our solar system — and 229Bb, with a mass 34 times greater.
They are located 19 light-years from our solar system – something considered close on the cosmic scale –, in the constellation Lepus. A light year corresponds to the distance that light travels in one year, or 9.5 trillion kilometers.
Binary brown dwarfs are a rarity. These two orbit every 12 days and at a distance of just 16 times that between the Earth and the moon. Only other pair of known brown dwarfs orbit so close to each other.
Brown dwarfs are neither planets nor stars, but something in between these two stars. They can be considered potential stars that, during their formation phases, did not reach the mass necessary to ignite nuclear fusion in the stars’ cores. But they are also larger than the largest known planets.
“A brown dwarf is an object that bridges the gap between a planet and a star. They are formally defined as objects that can burn a heavy form of hydrogen called deuterium, but not the basic, more common form of hydrogen,” said Sam Whitebook, a graduate student in Caltech’s division of physics, mathematics and astronomy and lead author of one of the studies, published in the Astrophysical Journal Letters.
“In practice, this means that they have a mass of approximately 13 to 81 times that of Jupiter. Because they can’t fuse hydrogen, they can’t ignite the fusion channels that power most stars. This causes them to only glow dimly as they cool,” he explained.
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This content was originally published in Three decades later, the first “brown dwarf” discovered in space reveals a surprise on the CNN Brasil website.
Source: CNN Brasil
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