Exoplanet caught masquerading as brown dwarf

What was previously thought to be a brown dwarf has been discovered to be an exoplanet lying on the cusp between the two. The exoplanet could help in the study of exoplanet atmospheres.

Brown dwarf

Artist’s impression of a brown dwarf. Image credit: NASA


The closest brown dwarf to Earth has been unmasked as a free-floating exoplanet.

It’s thought that the object bridges the gap between brown dwarf and planet, and could be useful to the study of atmospheres around gas giants.

Brown dwarfs share properties of both planets and stars, and so act as a bridge between the two in our knowledge. Credit: NASA/JPL, slightly modified by Jonathan Gagné

Brown dwarfs are larger than planets, but still too small to sustain the hydrogen fusion which fuels stars.

Instead, after formation brown dwarfs slowly cool and contract over time.

“This means that the temperatures of brown dwarfs can range from as hot as stars to as cool as planets, depending on how old they are,” says Jackie Faherty, from the American Museum of Natural History, who helped make the discovery.

The team used the temperature of an object previously thought to be a brown dwarf, known as SIMP J013656.5+093347, in a group of stars called Carina-Near to help determine the planet’s mass.

As all stars in the group are 200 million years-old, the researchers knew the object’s age and could use this along with the temperature to find its mass.


They discovered SIMP0136 was around 13 times the mass of Jupiter, putting it right on the boundary that separates brown dwarf from planet.