The Big Dipper has a secret, invisible to the unaided eye, according to a new paper published in
The Astrophysical Journal, which says that one of the stars that makes the bend in the ladle s handle, Alcor, has a smaller red dwarf companion.
Newly discovered Alcor B orbits its larger sibling and was caught in the act with an innovative technique called common parallactic motion by members of Project 1640, an international collaborative team that includes astrophysicists at the American Museum of Natural History, the University of Cambridge s Institute of Astronomy, the California Institute of Technology, and
NASA s Jet Propulsion Laboratory. Alcor is a relatively young star twice the mass of the Sun. Stars this massive are relatively rare, short-lived, and bright. Alcor and its cousins in the Big Dipper formed from the same cloud of matter about 500 million years ago, something unusual for a constellation since most of these patterns in the sky are composed of unrelated stars.