Stormy Jupiter-like Stars

The L-dwarf star W1906+40 was discovered by scientists with the Wide-field Infrared Survey Explorer in 2011. With a temperature of about 3,500 F, the star is cool compared to other stars in the universe. It’s cool enough that tiny mineral clouds form in its atmosphere.

According to NASA, this presents the best evidence for cloudy storms on a star.

“The star is the size of Jupiter, and its storm is the size of Jupiter’s Great Red Spot,” said John Gizis, who is the lead author of a study appearing in The Astrophysical Journal.“We know this newfound storm has lasted at least two years, and probably longer.”

L-dwarfs can come in two flavors. Some are considered stars because they fuse atoms and generate light. Others, due to their lack of atomic fusion, are known as brown dwarfs, or failed stars.

NASA’s Kepler spacecraft, which hunts for planets by gauging dips of starlight, was pointed at W1906+40 for years. According to NASA, astronomers had realized that W1906+40’s dips in starlight were not due to planetary bodies. “They thought they might be looking at a star spot—which, like our sun’s ‘sunspots,’ are a result of concentrated magnetic fields.” Such spots would appear visibly dark.

Follow-up observations were performed with the Spitzer Space Telescope, which is designed to detect infrared radiation. Using two infrared wavelengths that probed different atmospheric layers paired with the Kepler visible-light data, the dark patch of interest ended up revealing itself as a gargantuan storm the diameter of three Earths. It rotates around the star every 9 hrs.

Previously, the Spitzer program “Weather on Other Worlds” watched 44 brown dwarfs for up to 20 hrs. Findings suggested some of the brown dwarfs experience tumultuous weather.

With W1906+40, astronomers studied atmospheric changes for two years.

“We don’t know if this kind of star storm is unique or common, and we don’t know why it persists for so long,” said Gizis.

The researchers involved in the study hope to use Kepler and Spitzer to look at more brown dwarfs and stormy stars in the future.