Tag Archives: brown dwarfs

A failed star with cloud bands like Jupiter’s

The uncertainty of science: Astronomers think they have detected cloud bands similar to Jupiter’s on a brown dwarf about 6.5 light years away.

A team of astronomers has discovered that the closest known brown dwarf, Luhman 16A, shows signs of cloud bands similar to those seen on Jupiter and Saturn. This is the first time scientists have used the technique of polarimetry to determine the properties of atmospheric clouds outside of the solar system, or exoclouds.

Brown dwarfs are objects heavier than planets but lighter than stars, and typically have 13 to 80 times the mass of Jupiter. Luhman 16A is part of a binary system containing a second brown dwarf, Luhman 16B. At a distance of 6.5 light-years, it’s the third closest system to our Sun after Alpha Centauri and Barnard’s Star. Both brown dwarfs weigh about 30 times as much as Jupiter.

Despite the fact that Luhman 16A and 16B have similar masses and temperatures (about 1,900° F or 1,000° C), and presumably formed at the same time, they show markedly different weather. Luhman 16B shows no sign of stationary cloud bands, instead exhibiting evidence of more irregular, patchy clouds. Luhman 16B therefore has noticeable brightness variations as a result of its cloudy features, unlike Luhman 16A.

This conclusion is based on studying the polarized light coming from both brown dwarfs. For Luhman 16A, the result suggested bands. For Luhman 16B, the result suggested patchy, irregular clouds like on Earth.

The emphasis should be on the words “suggested” and “uncertainty.” This is good science, but the data is very sparse. We will need to actually see at these objects to really determine their weather.

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Astronomers have found two new brown dwarf stars only 15 and 18 light years away

Astronomers have found two new brown dwarf stars only 15 and 18 light years away.

Most brown dwarfs have reached surface temperatures below the “oven temperature” of about 500 Kelvin (about 230 degrees Celsius), may be even as cool as the temperature at the surface of the Earth. The search for these elusive neighbours of the Sun is currently in full swing. It cannot be excluded that ultracool brown dwarfs surround us in similar high numbers as stars and that our nearest known neighbour will soon be a brown dwarf rather than Proxima Centauri.

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