Astronomers at the Open University have discovered the first quintuple star system containing two eclipsing binary stars. Details of the five star system, the first of its kind to be found, will be presented by Marcus Lohr of the Open University in a talk on Wednesday 8 July at the National Astronomy Meeting at Venue Cymru, Llandudno, Wales.
The light curve of the new quintuple system, designated as 1SWASP J093010.78+533859.5, initially revealed the presence of a contact eclipsing binary - a system in which the two stars are orbiting so close together that they share an outer atmosphere. Contact binaries are quite common, but this particular system is notable because its orbital period - the time the two stars take to complete one orbital cycle - is so short, just under six hours.
Then it was spotted that the light curve contained some additional unexpected eclipses, and the data were reanalysed to reveal a second eclipsing binary at the same location on the sky. The new binary is detached - its component stars are well-separated by a distance of about 3 million km, or about twice the size of the Sun - and it has a longer orbital period of one and a third days.