Scientists spy rare eclipsing binary brown dwarf system


An artist's rendering depicts a rare eclipsing binary brown dwarf system. Photo by NASA/ESA/A. Feild (STScI)

March 11 (UPI) -- Astronomers have spotted a rare eclipsing binary brown dwarf system using the "first light" observations of a new array of telescopes in Chile.

The new SPECULOOS telescopes were built to search for planets surrounding ultra-cool dwarfs and brown dwarfs. Ultra-cool dwarfs are the smallest stars in the universe, and brown dwarfs are bodies that are less massive than a star but more massive than a planet. Brown dwarfs don't have enough mass to sustain the fusion that powers light-producing stars like our sun.

Models suggest ultra-cool dwarfs are likely to host sizable populations of potentially habitable rocky planets. Many of these systems are predicted to be close by, making them a prime target for planet-hunting operations.

One of the first targets for the SPECULOOS mission was the brown dwarf 2M1510, located in the constellation Libra. The object produced an unusual spectral pattern that suggested the object might be two brown dwarfs.
"Among the first test observations we performed, we turned one of our telescopes to a known brown dwarf," Michaël Gillon, principal investigator of the SPECULOOS project and an astronomer at the University of Liège in Belgium, said in a news release. "But suddenly the object appeared to get dimmer for about 90 minutes, which indicated an eclipse just took place."

"We rapidly realized that we were probably looking at two eclipsing brown dwarfs, one passing in front of the other, a configuration which is much rarer than planetary systems," said Artem Burdanov, a postdoctoral researcher at MIT.

Scientists used the powerful spectrometers of the Keck Telescope, in Hawaii, and the Very Large Telescope, in Chile, to measure the velocities of the two orbiting brown dwarfs that form 2M1510.

"From the very first spectrum we obtained, we could tell we had an exciting binary discovery," said Adam Burgasser, professor of Physics at the University of California, San Diego. "It was thrilling to see the absorption lines move back and forth in perfect synchronicity, and this allowed us to measure the mass of the binary."

Only one other eclipsing binary brown dwarf system has been previously identified. The rare discovery, described this week in the journal Nature Astronomy, allowed scientists to directly measure the radii and masses of the two brown dwarfs -- data that will help astronomers build more accurate stellar models.

"Collecting a combination of mass, radius and age is really rare for a star, let alone a brown dwarf," said lead study author Amaury Triaud, an astrophysicist at the University of Birmingham in Britain. "Usually one or more of these measurements is missing. By drawing all these elements together, we were able to verify theoretical models for how brown dwarfs cool, models which are over 30 years old. We found the models match remarkably well with the observations, a testament to human ingenuity."