Ultra-cold neighbor star discovered — or is it a planet?

WISE_J085510.83–071442.5_movement_(PIA18002)

Time-lapse image of of WISE 0855–0714’s movement in the sky. [Credit: NASA/JPL-Caltech/Penn State University]

Think all stars are hot? Think again. The coldest star ever discovered, a sub-brown dwarf called WISE J085510.83-071442.5, has been found to have a surface temperature somewhere in the range of -54 to 9 degrees F. It’s also one of the closest stars to our solar system at 7.2 light-years. 

That is, IF it is a star.

WISE J085510.83-071442.5 (the WISE stands for Wide-field Infrared Survey Explorer; the numbers stand for its celestial coordinates) is only 3-10 times the mass of Jupiter. We know of exoplanets — planets orbiting stars other than the Sun — with masses greater than this. So, with such a low mass, one might reasonably wonder why this object isn’t classified as a planet — and the distinction is not always clear to scientists, either. At such low masses, the distinction is how the body formed. In the case of our super-cold neighbor, it is believed to have formed by the collapse of a gas cloud rather than as a planet that formed in a star system and was later ejected. But scientists haven’t ruled out the latter scenario.

relative star sizes

Relative star sizes [Credit: NASA]

As the image above shows, there is a gradual progression from “normal” stars, like our Sun, to cooler, redder stars down to gas giant planets. Sometimes distinctions in science are a bit arbitrary — unlike, say, the distinction between a human and a volcano — but scientists make them in an attempt to better understand what they’re studying. 

Want to discuss this article? See 'Questions and Comments' for the rules.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s