Astronomers measure wind speed on a brown dwarf
Scientists have used a new technique to take the first-ever measurement of atmospheric wind speed outside the solar system.
A team of Astronomers, including the Institute for Astronomy’s Dr Beth Biller, have used NASA's Spitzer Space Telescope and the National Science Foundation's Karl G. Jansky Very Large Array (VLA) to take the first measurement of wind speed on a brown dwarf - an object intermediate in mass between a planet and a star.
Method of measurement
The method the team used is similar to that used to measure winds on Earth. To explain: imagine a cloud being blown by some wind. If you are looking down at Earth from space, you could measure the speed of a continent as it rotates in and out of view and a different speed for the cloud as it rotates in out of view. The difference in speed occurs because wind has pushed that cloud relative to the surface.
For planets and brown dwarfs outside of our solar system, we cannot see the clouds themselves, but when a cloud rotates into view or out of view, it changes the brightness of the planet. With that in mind, the team monitored the brightness of brown dwarf 2MASS J1047+21 and used periodic changes in its brightness to determine the rate at which the atmosphere was rotating.
As continents on objects outside of our solar system cannot be observed, the team relied on observations at radio wavelengths to look at the rotation of a planet’s magnetic field below the atmosphere.
Since the magnetic field originates deep in the planet, or in this case brown dwarf, the radio data allowed the team to determine the interior period of rotation. Once they had an interior rotation rate and an atmospheric rotation rate, they could compare them to see how fast the wind was blowing.
The researchers measured a wind speed of 650 meters per second (1,450 miles per hour) for the brown dwarf they studied, which is 33.2 light years from earth.
The team of collaborators, lead by Bucknell University‘s Professor Katelyn Allers also includes Dr Johanna Vos, from the American Museum of Natural History and Peter K. G. Williams, from the Center for Astrophysics and the American Astronomical Society.
Dr Beth Biller commented:
Pioneering this new technique is quite exciting, as it will enable future researchers to better understand the physics of atmospheres outside of our solar system.