Scientists have found a strange seemingly inverted planet that may hold the key to studying binary star systems in the future. The new found binary star system displayed unusual gravitational lensing characteristics resulting in the first ever "self-lensing" binary system ever discovered.
The self-lensing binary star system was found by an astronomer from the University of Washington. Doctoral student Ethan Kruse and astronomer Eric Agol from the UW worked to together to confirm the existence of the strange new system. The researchers published their findings in the online journal Science.
"I found what essentially looked like an upside-down planet," said Kruse. "What you normally expect is this dip in brightness, but what you see in this system is basically the exact opposite -- it looks like an anti-transit."
Gravitational lensing is a phenomenon that occurs when light from a more distant source bends around a nearer object of sufficient mass. Due to the gravity of the nearer object, the light exhibits a form of lensing similar to what happens when light passes through an optical lens. In the newfound binary star system with an "upside-down planet," the pair of researchers from UW were able to measure the mass of the nearer star due to the way it magnified that light of companion star located further away. In the context of observing and measuring the mass of distant galaxies, gravitational lensing is a very useful phenomenon. Occurances of gravitation lensing that occur within our home galaxy is reffered to as microlensing.
"The basic idea is fairly simple," Agol said. "'Gravity warps space and time and as light travels toward us it actually gets bent, changes direction. So, any gravitational object - anything with mass - acts as a magnifying glass,' though a weak one. 'You really need large distances for it to be effective.'"
Back in 1973, an astronomer used currently existing stellar evolution models to predict the existence of a self-lensing binary star system. However, Kruse and Agol's discovery marks the first time that such a system was observed. Moreover, the discovery was made largely by accident when Kruse was looking at data gathered by the Kepler Space Observatory. Kruse found the system in the constellation Lyra.
As the twin stars of the binary system KOI-3278 rotate around each other in a location 2,600 light years away from Earth, the novel gravitational lensing phenomenon was observed by the UW researchers. The two stars of the system are separated by a mere 43 million miles, which is approximately the distance between the sun and Mercury.
"The cool thing, in this case, is that the lensing effect is so strong, we are able to use that to measure the mass of the closer, white dwarf star. And instead of getting a dip now you get a brightening through the gravitational magnification," Agol said.
Agol also said that the phenomenon was much more pronounced in the KOI-3278 system. In binary star systems, the lensing effects can be easier to observe with larger distances.
While scientists have been using gravitational lensing as a tool for making astronomical observations and measurements for years now, there are still details about the phenomenon that scientists are still trying to understand. This type of lensing is also one of the more practical predictions made by Albert Einstein when he proposed his general theory of relativity.
