This star is one of Earth's closest galactic neighbors, but it's impossible to see it with the naked eye.

Two NASA space telescopes have discovered a "brown dwarf" that's as cold as the North Pole, according to the space agency.

"It is remarkable that even after many decades of studying the sky, we still do not have a complete inventory of the sun's nearest neighbors," NASA scientist Michael Werner said in a statement Friday.

This artist's conception shows the object named WISE J085510.83-071442.5, the coldest known brown dwarf. Brown dwarfs are dim star-like bodies that lack the mass to burn nuclear fuel as stars do. (JPL/NASA)

The star is surprisingly close: it ranks as the fourth-closest star system to Earth's sun at 7.2 light-years away (the closest star system, Alpha Centauri, is four light-years away).

"It's very exciting to discover a new neighbor of our solar system that is so close," said Kevin Luhman, a Pennsylvania State University astronomer. "And given its extreme temperature, it should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures."

The temperatures on this brown dwarf - a star without the mass to burn nuclear fuel and radiate light - is between minus-54 and 9 degrees Fahrenheit. Brown dwarfs lack the mass to shed light or much heat, making them hard to detect without a telescope that can use an infrared lens.

Other brown dwarf stars that humans have discovered have been approximately room temperature.