Though our Sun stands alone, about 40 per cent of similar stars are in binary or multi-star systems, orbiting their companions in a gravitational dance. Working with University of Washington (UW)Â astronomer Eric Agol, doctoral student Kruse has confirmed the first “self-lensing” binary star system, in which the mass of the closer star can be measured by how powerfully it magnifies light from its more distant companion star.
Like so many interesting discoveries, this one happened largely by accident. Kruse was looking for the dimming in light when a world transits its host star, in data from the planet-hunting Kepler Space Telescope when he saw something in the binary star system KOI-3278 that didn’t make sense.
“I found what essentially looked like an upside-down planet,” Kruse said. “What you normally expect is this dip in brightness, but what you see in this system is basically the exact opposite â€” it looks like an anti-transit.”
The two stars of KOI-3278, about 2,600 light-years away in the constellation of Lyra, take turns being nearer to Earth as they orbit each other every 88.18 days. They are about 43 million miles Â (69 million km) apart, roughly the distance the planet Mercury is from the Sun. The white dwarf, a cooling star thought to be in the final stage of life, is about Earth’s size but 200,000 times more massive.