NASA Telescopes Detect Jupiter-like Storm on Small Star

Astronomers have discovered what appears to be a tiny star with a giant, cloudy storm, using data from NASA's Spitzer and Kepler space telescopes. The dark storm is akin to Jupiter's Great Red Spot: a persistent, raging storm larger than Earth.

"The star is the size of Jupiter, and its storm is the size of Jupiter's Great Red Spot," said John Gizis of the University of Delaware, Newark. "We know this newfound storm has lasted at least two years, and probably longer." Gizis is the lead author of a new study appearing in The Astrophysical Journal.

While planets have been known to have cloudy storms, this is the best evidence yet for a star that has one. The star, referred to as W1906+40, belongs to a thermally cool class of objects called L-dwarfs. Some L-dwarfs are considered stars because they fuse atoms and generate light, as our sun does, while others, called brown dwarfs, are known as "failed stars" for their lack of atomic fusion.

The L-dwarf in the study, W1906+40, is thought to be a star based on estimates of its age (the older the L-dwarf, the more likely it is a star). Its temperature is about 3,500 degrees Fahrenheit (2,200 Kelvin). That may sound scorching hot, but as far as stars go, it is relatively cool. Cool enough, in fact, for clouds to form in its atmosphere.

"The L-dwarf's clouds are made of tiny minerals," said Gizis.

Spitzer has observed other cloudy brown dwarfs before, finding evidence for short-lived storms lasting hours and perhaps days.
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► Paper: Kepler Monitoring of an L Dwarf. II. Clouds with Multi-year Lifetimes. The Astrophysical Journal, 2015; 813 (2)>>http://dx.doi.org/10.1088/0004-637X/813/2/104

► Animation: This illustration shows a cool star, called W1906+40, marked by a raging storm near one of its poles.

The location of the storm is estimated to be near the north pole of the star based on computer models of the data. The telescopes cannot see the storm itself, but learned of its presence after observing how the star's light changes over time. The storm travels around with the star, making a full lap about every 9 hours. When it passes into a telescope's field of view, it causes light of particular infrared and visible wavelengths to dip in brightness.
The storm has persisted for at least two years. Astronomers aren't sure why it has lasted so long.
W1906+40 is located 53 light-years away in the constellation Lyra.

Image credit: NASA/JPL-Caltech
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