NASA Telescopes detect Jupiter-like Storm on Small Star

This illustration shows a cool star, called W1906+40, marked by a raging storm near one of its poles. The storm is thought to be similar to the Great Red Spot on Jupiter. Scientists discovered it using NASA’s Kepler and Spitzer space telescopes. Credit: NASA/JPL-Caltech

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 2 years, and probably longer.”

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 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 3,500F. 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 or days.

Kepler identifies planets by looking for dips in starlight as planets pass in front of their stars. They thought they might be looking at a star spot – which, like our sun’s “sunspots,” are a result of concentrated magnetic fields. Star spots would also cause dips in starlight as they rotate around the star. Follow-up observations with Spitzer, which detects infrared light, revealed that the dark patch was not a magnetic star spot but a colossal, cloudy storm with a diameter of 3 Earths. The storm rotates around the star about every 9 hours. Spitzer’s infrared measurements at 2 infrared wavelengths probed different layers of the atmosphere and, together with the Kepler visible-light data, helped reveal the presence of the storm.
“We don’t know if this kind of star storm is unique or common, and we don’t why it persists for so long,” said Gizis. The researchers plan to look for other stormy stars and brown dwarfs using Spitzer and Kepler in the futurehttp://www.jpl.nasa.gov/spaceimages/details.php?id=pia20055