We know that storms can be found on planets, but until recently there’s been little evidence showing they can also form above the scorching-hot surface of a star. According to NASA, the L-dwarf star known as W1906+40 is the first living star that’s been observed hosting an active storm system.
NASA first discovered the star during their Wide-field Infared Survey of 2011, but it wasn’t until it was spotted by the Kepler telescope that they noticed something unusual. Kepler is designed to detect periodic dips in starlight like those that occur when a planet passes in front of a star. Astronomers knew that the dark blot over W1906+40 wasn’t a planet, and they first suspected a star spot created by concentrated magnetic fields. Upon further inspection with the infared Spitzer telescope, it was revealed that the spot was actually a colossal storm system.
The star is roughly the size of Jupiter, and the storm is similar in size to that planet’s Great Red Spot—or to three Earths. Scientists believe that W1906+40 is able to host the storm due to its status as an L-dwarf, a class of cooler stars. While our own Sun measures in at 10,000°F, this star is estimated to be about 3500°F. That makes it cool enough to support an atmosphere but still too hot to sustain liquid water. The clouds and rain swirling over the star are instead made from minerals like iron.
Astronomers have found evidence of storms lasting for hours or even days on L-dwarfs in the past, but these had always been “brown dwarfs” or bodies that failed to become true stars because they lack atomic fusion. Not only is this the first storm observed over a living star, but it has been brewing for at least the past two years.