1SWASP J093010.78+533859.5

There shouldn’t be much more out of there. Five stars with two eclipsing binary system. Considering that only a third of stars is believed to be in pairs or multiple systems (and, irony of fate, also the star system closer to our Sun, alpha centaury is a triple star system), a quintuple system is almost unique…

Here I stumbled on the discovery of such a system (made, by the way, in the context of the SuperWASP project where low-cost cameras are used for the detection of extra solar planets), made with the usual strategy of detecting any small dip in the star light curve (the same approach used for detecting exoplanets).

A star passing in front of its companion causes an eclipse and from the regular patter of dips in the light curves, multiple star systems (and their characteristics) can be identified. In the begin the measurements reveled a contact eclipsing binary system (where the two stars share their outer atmosphere) with an orbital cycle of just six hours. Carefully looking at dips, additional eclipses have been found, thus a second eclipsing binary system appeared. In the same location, within the Ursa Major at about 250 light years from us. This second binary system, with about 32 hours of period, is well separated from the first one (21 billion km!).

But the story does not end here. Analyzing the star spectra, thus dividing their signals in different wavelengths, a fifth star appeared. 2 billion km away from the binary system and (apparently) without any companion.

The five stars are gravitationally bounded together. Wow.

Small stars (smaller and cooler than our Sun) revolving around a common center and also bounded in couples, a planet up there would see up to five suns in the sky and very occasional nights…


PS. More in detail ” […] The detached binary is found to contain components of masses 0.837(8) and 0.674(7) M_sol, with radii of 0.832(18) and 0.669(18) R_sol and effective temperatures of 5185(-20,+25) and 4325(-15,+20) K respectively, the contact system has masses 0.86(2) and 0.341(11) M_sol, radii of 0.79(4) and 0.52(5) R_sol respectively, and a common T_eff of 4700(50) K. The fifth star is of similar temperature and spectral type to the primaries in the two binaries. Long-term photometric observations indicate the presence of a spot on one component of the detached binary, moving at an apparent rate of approximately one rotation every two years. Both binaries have consistent system velocities around -11 to -12 km/s […]”. From this technical paper.



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