Most of the stars in our galaxy are binary stars; two stars in a tight cosmic dance is not a rarity.
With the help of another NASA space observatory, the Galaxy Evolution Explorer (GALEX), which analyzes the ultraviolet light of the stars in Kepler's field of view, the researchers noticed that as the white dwarf passed behind the red dwarf, the starlight would dim, but when the white dwarf passed in front, the light would be slightly brighter than expected. This is counter-intuitive to how transits work, but KOI-256 is anything but intuitive.
As the white dwarf passed in front of the red dwarf, its extreme gravitational field was causing spacetime to bend, focusing the light from the red dwarf, enhancing the starlight. As the white dwarf passed behind the red dwarf, there would be no gravitational disruption of starlight and therefore no starlight enhancement. This finding will be published on April 20 in the Astrophysical Journal.
"Only Kepler could detect this tiny, tiny effect," said Doug Hudgins, Kepler program scientist at NASA Headquarters, Washington. "But with this detection, we are witnessing Einstein's theory of general relativity at play in a far-flung star system."