Astronomers Measure Wind Pace on a Brown Dwarf for the First Time

Brown Dwarf Magnetic Field

Artist’s conception of a brown dwarf and its magnetic discipline. The magnetic discipline, rooted deep in its inside, rotates at a special fee than the highest of the environment. The distinction allowed astronomers to find out the article’s wind pace. Credit score: Invoice Saxton, NRAO/AUI/NSF

Astronomers have used the Nationwide Science Basis’s Karl G. Jansky Very Massive Array (VLA) and NASA’s Spitzer Area Telescope to make the primary measurement of wind pace on a brown dwarf — an object intermediate in mass between a planet and a star.

Primarily based on details identified concerning the big planets Jupiter and Saturn in our personal Photo voltaic System, a crew of scientists led by Katelyn Allers of Bucknell College realized that they presumably might measure a brown dwarf’s wind pace by combining radio observations from the VLA and infrared observations from Spitzer.

“When we realized this, we were surprised that no one else had already done it,” Allers mentioned.

The astronomers studied a brown dwarf known as 2MASS J10475385+2124234, an object roughly the identical measurement as Jupiter, however roughly 40 instances extra large, about 34 light-years from Earth. Brown dwarfs, typically known as “failed stars,” are extra large than planets, however not large sufficient to trigger the thermonuclear reactions at their cores that energy stars.

“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,” Allers mentioned.

That distinction, she defined, is as a result of the radio emission is attributable to electrons interacting with the planet’s magnetic discipline, which is rooted deep within the planet’s inside, whereas the infrared emission comes from the highest of the environment. The environment is rotating extra rapidly than the inside of the planet, and the corresponding distinction in velocities is because of atmospheric winds.

Brown Dwarf and Jupiter

Brown dwarf, left, and Jupiter, proper. Artist’s conception of brown dwarf illustrates magnetic discipline and environment’s high, which had been noticed at completely different wavelengths to find out wind speeds. Credit score: Invoice Saxton, NRAO/AUI/NSF

“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,” mentioned Johanna Vos, of the American Museum of Pure Historical past.

They noticed 2MASS J10475385+2124234 with Spitzer in 2017 and 2018, and located that its infrared brightness diversified repeatedly, seemingly due to the rotation of some long-lived characteristic in its higher environment. The crew did VLA observations in 2018 to measure the rotation interval of the article’s inside.

Simply as with Jupiter, they discovered that the brown dwarf’s environment is rotating quicker than its inside, with a calculated wind pace of about 1425 miles per hour. That is considerably quicker than Jupiter’s wind pace, about 230 mph.

“This agrees with theory and simulations that predict higher wind speeds in brown dwarfs,” Allers mentioned.

The astronomers mentioned their approach can be utilized to measure winds not solely on different brown dwarfs, but additionally on extrasolar planets.


Animation illustrates how measuring the rotation pace of the brown dwarf’s magnetic discipline and of its environment allowed astronomers to calculate the wind pace. Credit score: Invoice Saxton, NRAO/AUI/NSF

“As a result of the magnetic fields of big exoplanets are weaker than these of brown dwarfs, the radio measurements will should be accomplished at decrease frequencies than these used for 2MASS J10475385+2124234, mentioned Peter Williams of the Middle for Astrophysics, Harvard & Smithsonian, and the American Astronomical Society.

“We’re excited that our method can now be used to help us better understand the atmospheric dynamics of brown dwarfs and extrasolar planets,” Allers mentioned.

Allers, Vos, and Williams, together with Beth Biller of the College of Edinburgh, reported their findings within the journal Science.

Learn NASA Measures Wind Speed on a Brown Dwarf 200 Trillion Miles Away for extra on this matter.

Reference: “A measurement of the wind speed on a brown dwarf” by Katelyn. N. Allers, Johanna M. Vos, Beth A. Biller and Peter. Okay. G. Williams, 10 April 2020, Science.
DOI: 10.1126/science.aaz2856

The Nationwide Radio Astronomy Observatory is a facility of the Nationwide Science Basis, operated beneath cooperative settlement by Related Universities, Inc.

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