Using the Hubble Space Telescope, an Italian-led team of astronomers has tracked the beautiful slow waltz of two, nearby brown dwarfs. The binary brown dwarf system, known as Luhman 16AB, is a pair of objects located at 6.5 light years in the direction of the southern constellation Vela. These are the closest known brown dwarfs and the closest system found since the measurement of the proper motion of Barnard’s Star in 1916. Only the triple star Alpha Centauri (4.3 light-years away) and Barnard’s Star (5.98 light-years) are closer.
To the unaided eye, all stars appear fixed to the sky, but stars are in constant motion around the center of our Milky Way galaxy. With the eye alone, we can’t see their motion, because space is so vast, and the stars’ distances from us are so huge. Their apparent motions across our sky are very small.
However, astronomers have been able to capture Luhman 16AB’s motion across the sky with respect to more distant stars. That’s in part because this brown dwarf system is so nearby.
Despite its proximity, the pair of binary dwarfs now known as Luhman 16AB was discovered as recently as 2013 by astronomer Kevin Luhman of Pennsylvania State University. The discovery was made from images taken by the NASA’s Wide-Field Infrared Survey Explorer (WISE) orbiting satellite.
Why was it discovered so recently, being so close to us? It’s because Luhman 16AB is close the galactic plane, an area densely populated by stars. Thus very faint objects, such as brown dwarfs, are difficult to detect in that area of the sky.
An analysis of pre-discovery images taken with other telescopes shows Luhman 16AB was present in earlier images, although it appeared as a single star.
But the Hubble Space Telescope, as well as WISE, have an amazing precision and were able to resolve Luhman 16AB into two objects. Astronomers analysed images of Luhman 16AB taken by the Hubble Space Telescope over the course of three years, long enough to capture the two components of the system as they moved both across the sky and around each other.
The two stars orbit each other at a distance of only 3 astronomical units, that is, three times the distance between our Earth and sun. Check out the amazing video below:
Bottom line: Recent Hubble Space Telescope images of the nearby binary brown dwarf system Luhman 16AB. The two objects appear to be waltzing around each other.
Eddie Irizarry of the Sociedad de Astronomía del Caribe (Astronomical Society of the Caribbean) has been a NASA Solar System Ambassador since 2004. He loves public outreach and has published multiple astronomy articles for EarthSky, as well as for newspapers in Puerto Rico. He has also offered dozens of conferences related to asteroids and comets at the Arecibo Observatory.