They’re called “heartbeat stars”, but not because they expand and contract.  In fact, they’re double star systems in which one star has a highly elongated orbit similar to that of a comet.  As this star swings close to its companion, gravity pulls the latter into a non-spherical shape, changing its light output.  A plot of the brightness of such systems shows a regular intensity variation, reminiscent of an electrocardiogram.  Studying such strange stellar partners, as SETI Institute scientist Susan Mullally does, will tell us more about how binary stars – the most common type of star systems in the universe – get along with one another.  The big mystery: Why don’t such systems eventually settle down into more circular orbits?

Read the Press release at http://www.jpl.nasa.gov/news/news.php?release=2016-277