Coldest Brown Dwarfs Blur Star, Planet Lines

n 2011, astronomers on the hunt for the coldest starlike celestial bodies discovered a new class of such objects using NASA’s WISE Space Telescope. But until now, no one knew exactly how cool the bodies’ surfaces really are. In fact, some evidence suggested they could be at room temperature.

A new study using data from NASA’s Spitzer Space Telescope shows that while these so-called brown dwarfs are indeed the coldest known free-floating celestial bodies, they are warmer than previously thought, with surface temperatures ranging from about 125 to 175 degrees Celsius. By comparison, the sun has a surface temperature of about 5,730 degrees Celsius.

To reach these surface temperatures after cooling for billions of years, these objects would have to have masses of only five to 20 times that of Jupiter.

The diagram above shows the locations of brown dwarfs discovered and mapped by NASA. The view is from a vantage point about 100 light-years away from the sun. At this distance, the sun is barely visible as a speck of light. The vastly fainter brown dwarfs would not even be visible. The red lines all link back to the location of the sun.

The findings help researchers understand how planets and stars form. For more on brown dwarfs, see the NASA press release.

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