NASA’s Spitzer and Swift space telescopes, together, located an elusive brown dwarf. In a first-of-its-kind collaboration, NASA’s Spitzer and Swift space telescopes joined forces to observe a microlensing event, when a distant star brightens due to the gravitational field of at least one foreground cosmic object.
The technique, mentioned above, is useful for finding low-mass bodies orbiting stars, such as planets. This time, the observations unveiled a brown dwarf. Brown dwarfs are thought to be the missing link between planets and stars, with masses up to 80 times that of Jupiter. Like stars, these brown dwarfs are not hot and dense enought to generate energy through nuclear fusions.
According to the scientists, for stars roughly the mass of our sun, less than 1 percent have a brown dwarf orbiting within 3 AU (1 AU is the distance between Earth and the sun). This phenomenon has been named as “brown dwarf desert.” The newly discovered brown dwarf, which orbits a host star, may inhabit this desert.
Spitzer and Swift observed the microlensing event after being tipped off by ground-based microlensing surveys, including the Optical Gravitational Lensing Experiment (OGLE). This Brown Dwarf discovery, with the unwieldy name OGLE-2015-BLG-1319, marks the first time two space telescopes have collaborated to observe a microlensing event.
“We want to understand how brown dwarfs form around stars, and why there is a gap in where they are found relative to their host stars,” said Yossi Shvartzvald, a NASA postdoctoral fellow based at NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California. “It’s possible that the ‘desert’ is not as dry as we think,” added Yossi Shvartzvald.
A little about Microlensing: According to JPL (Jet Propulsion Laboratory), in a microlensing event, a background source star serves as a flashlight for the observer. When a massive object passes in front of the background star along the line of sight, the background star brightens because the foreground object deflects and focuses the light from the background source star. Depending on the mass and alignment of the intervening object, the background star can briefly appear thousands of times brighter.
Both space telescopes, Spitzer (July 2015) and Swift (June 2015), had observed the binary system during the last weeks of that year’s Space Telescope’s Microlensing Campaign. Spitzer is over 1 AU (Astronomical Unit) away from Earth in an Earth-trailing orbit around the sun and ,on the other hand, Swift is in a low Earth orbit encircling our planet. No parallax was measured between the two as Swift is not far enough away from ground-based telescopes to get a significantly different view of this particular event.
By combining data from these space-based and ground-based telescopes, researchers determined that the newly discovered brown dwarf is between 30 and 65 Jupiter masses. Researchers have also found that brown dwarf orbits a K dwarf, a type of star that tends to have about half the mass of the sun.
“In the future, we hope to have more observations of microlensing events from multiple viewing perspectives, allowing us to probe further the characteristics of brown dwarfs and planetary systems,” said Geoffrey Bryden, JPL scientist and co-author of the study.