NASA Discovers Six Dwarf Stars

A group of NASA scientists has discovered the coldest class of star-like bodies, with temperatures as cool as the human body, the agency announced on Wednesday.

Astronomers unsuccessfully tracked these dark orbs, termed Y dwarfs, for more than a decade as they are almost impossible to see when viewed with a visible-light telescope. However, with the use of NASA’s Wide-field Infrared Survey Explorer (WISE), which has infrared vision, scientists were able to finally spot the faint glow of six Y dwarfs relatively close to the sun, within a distance of about 40 light-years.

The Y’s are the coldest members of the brown dwarf family. Brown dwarfs are sometimes referred to as “failed” stars. They are too low in mass to fuse atoms at their cores and thus do not burn with the fires that keep stars like the sun shining steadily for billions of years.

Instead, these objects cool and fade with time, until what little light they do emit is at infrared wavelengths.

“WISE scanned the entire sky for these and other objects, and was able to spot their feeble light with its highly sensitive infrared vision,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground.”

Information gathered from WISE has revealed 100 new brown dwarfs to date, but further discoveries are expected as scientists continue to examine the enormous quantity of data from WISE. From January 2010 to last February, the telescope performed the most advanced survey of the sky at infrared wavelengths to date, scanning the entire sky about 1.5 times.

Of the 100 brown dwarfs, six are classified as cool Y’s. One of the Y dwarfs, called WISE 1828+2650, is the record holder for the coldest brown dwarf with an estimated atmospheric temperature cooler than room temperature, or less than 80 degrees Fahrenheit (25 degrees Celsius).

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This artist’s conception illustrates what a “Y dwarf” might look like. Y dwarfs are the coldest star-like bodies known, with temperatures that can be even cooler than the human body. Image NASA/JPL-Caltech

Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, California, said the brown dwarfs they had been finding before were more like the temperature of a regular oven. But the recently discovered Y dwarfs are much cooler.

The Y dwarfs are in our sun’s neighborhood, approximately nine to 40 light-years away, and the Y dwarf approximately nine light-years away, WISE 1541-2250, may become the seventh closest star system, bumping Ross 154 back to eighth. By comparison, the star closest to our solar system, Proxima Centauri, is about four light-years away.

Astronomers study brown dwarfs to better understand how stars form and understand the atmospheres of planets beyond our solar system. The atmospheres of brown dwarfs are similar to those of gas giant planets like Jupiter, but they are easier to observe because they are alone in space, away from the blinding light of a parent star.


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