Astronomers Measure Wind Speed on a Brown Dwarf

Astronomers have used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and NASA’s Spitzer Space Telescope to make the first measurement of wind speed on a brown dwarf — an object intermediate in mass between a planet and a star.

Based on facts known about the giant planets Jupiter and Saturn in our own Solar System, a team of scientists led by Katelyn Allers of Bucknell University realized that they possibly could measure a brown dwarf’s wind speed 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 said.

The astronomers studied a brown dwarf called 2MASS J10475385+2124234, an object roughly the same size as Jupiter, but roughly 40 times more massive, about 34 light-years from Earth. Brown dwarfs, sometimes called “failed stars,” are more massive than planets, but not massive enough to cause the thermonuclear reactions at their cores that power 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 said.

That difference, she explained, is because the radio emission is caused by electrons interacting with the planet’s magnetic field, which is rooted deep in the planet’s interior, while the infrared emission comes from the top of the atmosphere. The atmosphere is rotating more quickly than the interior of the planet, and the corresponding difference in velocities is due to atmospheric winds.

“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.

They observed 2MASS J10475385+2124234 with Spitzer in 2017 and 2018, and found that its infrared brightness varied regularly, likely because of the rotation of some long-lived feature in its upper atmosphere. The team did VLA observations in 2018 to measure the rotation period of the object’s interior.

Just as with Jupiter, they found that the brown dwarf’s atmosphere is rotating faster than its interior, with a calculated wind speed of about 1425 miles per hour. This is significantly faster than Jupiter’s wind speed, about 230 mph.

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

The astronomers said their technique can be used to measure winds not only on other brown dwarfs, but also on extrasolar planets.

“Because the magnetic fields of giant exoplanets are weaker than those of brown dwarfs, the radio measurements will need to be done at lower frequencies than those used for 2MASS J10475385+2124234, said Peter Williams of the Center 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 said.

Allers, Vos, and Williams, along with Beth Biller of the University of Edinburgh, reported their findings in the journal Science.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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NRAO Director Tony Beasley Appointed to New Five-Year Term

 

Dr. Tony Beasley, Director of the National Science Foundation’s National Radio Astronomy Observatory (NRAO), has been appointed to a new five-year term. The Board of Trustees for AUI— which operates NRAO under a cooperative agreement— and the NRAO Director Review Committee conducted a thorough review of Beasley’s leadership and performance earlier this year, and have appointed the Director to the new term through May 2027.

 

“Tony is an outstanding leader and stalwart champion for NRAO, the field of radio astronomy, the beauty of science, and the critical role of big facilities in the R&D ecosystem,” said Adam Cohen, President and CEO of AUI, which operates NRAO under a cooperative agreement. “He continues to support very innovative education and outreach programs to help build the workforce of the future, as well as programs and activities to enhance diversity, equity, and inclusion in our workplaces.” 

 

Over the course of more than two decades, Beasley’s leadership has shaped the present and future of NRAO’s leading-edge radio astronomy facilities, including the Atacama Large Millimeter/submillimeter Array (ALMA), Very Long Baseline Array (VLBA), and Very Large Array (VLA). More recently, he has collaborated on efforts to encourage cooperation between commercial spectrum users and research facilities and has created partnerships to explore the use of Green Bank Observatory’s radar systems in planetary science and defense applications. 

 

Beasley recently has generated significant support for the future of NRAO’s facilities, reaching major milestones in 2021. The observatory’s proposed next generation Very Large Array (ngVLA) received high priority for new ground-based observatories in the U.S. National Academy of Sciences’ Astronomy and Astrophysics Decadal Survey (Astro2020). Late last year, NRAO’s Central Development Laboratory (CDL) received approval and funding through the ambitious ALMA2030 Development Plan to upgrade its Band 6 receivers, which are ALMA’s most productive receivers. 

 

An ardent supporter of diversity, equity, and inclusion in astronomy and astrophysics, Beasley has elevated the efforts of NRAO’s Office of Diversity and Inclusion, Broader Impacts, and community development initiatives, including the National Astronomy Consortium (NAC), RADIAL, National and International Non-traditional Exchange (NINE), Research Experiences for Undergraduate students (REU), and most recently, grants for women in engineering fellowships and the development of a next generation Learning Center (ngLC). 

 

“Being a part of NRAO for more than 20 years has given me the opportunity to observe, contribute to, and lead growth and change in astronomy that positively impacts our facilities and allows us to collaborate with other like-minded institutions,” said Beasley. “I am proud of the work our teams have accomplished in research, engineering, outreach, and equity, and look forward to serving the NRAO community for another five years.”

 

Beasley, who holds a Doctorate in Astrophysics from the University of Sydney, was first appointed as NRAO Director in February 2012, after previously serving the observatory and the radio astronomy community in multiple capacities. He joined NRAO as a Postdoctoral Fellow in 1991 and served as Deputy Assistant Director in 1997 and Assistant Director from 1998 to 2000. He briefly left NRAO that year to become Project Manager for the Combined Array for Research in Millimeter-wave Astronomy (CARMA). In 2004, he returned to NRAO as Assistant Director, as well as Project Manager for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. From 2008 to 2012, Beasley served as the Chief Operating Officer and Project Manager of NSF’s National Ecological Observatory Network (NEON). In addition to his role as NRAO Director, Beasley presently serves as the AUI Vice President for Radio Astronomy Operations. 

 

In January 2022, Beasley was honored as a Lifetime Fellow of the American Association for the Advancement of Science (AAAS) in recognition of his significant contributions to the field of radio astronomy. 

 

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