An schematic of a tertiary star system. An observer located along the pictured line of sight would observe the binary pair to eclipse during their orbit, while the third star orbited the center of mass of the system, interacting with the eclipsing pair. Credit: Karen Teramura (UH Institute for Astronomy) with background photograph by Wei-Hao Wang.

Three’s a Crowd: Potential Triple-Star Systems in the Kepler Field

BY BEN MONTET
FEBRUARY 8, 2013
FILED UNDER BINARY STARS, KEPLER, OBSERVATIONS, STARS, TRANSITS
TITLE: Triple-Star Candidates Among the Kepler Binaries
AUTHORS: Saul Rappaport, Katherine Deck, Alan Levine, Tamas Borkovits, Josh Carter, I. El Mellah, Roberto Sanchis Ojeda, & Belinda Kalomeni.
FIRST AUTHOR’S INSTITUTION: Massachusetts Institute of Technology

Binary star systems, in addition to being awesome, are an astrophysically important class of object. Binaries are one of the only ways we can recover dynamical masses of stars and are the baseline to which stellar models are calibrated. We’ve given them a lot of press lately, specifically with respect to planetary systems. However, as much as binaries have taught us about stellar structure and evolution, there’s a lot we still don’t understand about these systems. Many binaries are in extremely compact orbits: some have orbital periods of only hours. How these ultracompact systems form is a bit of an open question. Astronomers know these stars could not have formed in such a tight configuration. Young stars contract from very large gas clouds; during the “protostar” phase, as these stars are heating up and contracting, protostars in a binary system would have been larger than the current orbits of the stars! Therefore, they must have started in wider orbits which became more compact in time. We also know very little about the occurrence rate of triple (and higher multiple) systems in the galaxy. Triple stars in systems may be responsible for driving a pair of bodies into a compact pair. Significantly, triple system occurrence has not been systematically explored by searching for additional companions over a large sample of binary stars.

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