Wind speed measured on a brown dwarf for the first time

In an unprecedented study, scientists have managed to measure the wind speed on a brown dwarf. The technique can be used to measure winds on other celestial objects like extrasolar planets, according to the experts.

A brown dwarf is a substellar object that is not as large as a planet yet not as small as a star. The object is sometimes referred to as a “failed star.” It is more massive than a planet, yet lacks the mass needed to activate the thermonuclear reactions that power stars.

Based on what is known about giant planets in Earth’s solar system, scientists at the National Radio Astronomy Observatory realized that a combination of radio and infrared observations could be used to measure a brown dwarf’s wind speed. “When we realized this, we were surprised that no one else had already done it,” said study lead author Katelyn Allers of Bucknell University.

The team used radio observations from the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and infrared observations from the NASA Spitzer Space Telescope to study a dwarf called 2MASS J10475385+2124234. This particular space object is about the same size of Jupiter and is located about 34 light-years from Earth. 

“We noted that the rotation period of Jupiter as determined by radio observations is different from the rotation period determined by observations at visible and infrared wavelengths,” said Allers. She explained that the difference is due to the fact that radio emission is caused by electrons interacting with the planet’s magnetic field, while infrared emission comes from the top of the atmosphere. 

“Because we expect the same mechanisms to be at work in the brown dwarf, we decided to measure its rotation speeds with both radio and infrared telescopes,” said Johanna Vos of the American Museum of Natural History.

Like Jupiter, the brown dwarf’s atmosphere is rotating faster than its interior. The object’s wind speed was found to be about 1,425 miles per hour, which is significantly faster than Jupiter’s wind speed of 230 mph.

“This agrees with theory and simulations that predict higher wind speeds in brown dwarfs,” said Allers. “We’re excited that our method can now be used to help us better understand the atmospheric dynamics of brown dwarfs and extrasolar planets.”

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer