An object that appeared to be an upside-down planet helped researchers find a new way to look at binary star systems.
The research team successfully confirmed the existence of a "self-lensing" binary star system for the first time, a University of Washington news release reported.
In this phenomenon "the mass of the closer star can be measured by how powerfully it magnifies light from its more distant companion star," the news release reported.
Our solar system only has our lone Sun, but about 40 percent of all systems have two stars or more.
This new discovery confirms a prediction made in 1973 through stellar evolution models. The discovery was made by accident.
Doctoral student Ethan Kruse was scanning the skies for a dimming of light, called a "transit," that indicated a planet had passed in front of a distant star. While looking for these transits Kruse noticed something unusual.
"I found what essentially looked like an upside-down planet," Kruse said in the news release. "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."
The stars are located in the Lyra constellation and orbit eachother; one is a white dwarf that is believed to be in the last stage of its life. The increase in light spotted by Kruse was a result of the white dwarf "bending and magnifying" the light of its neighbor.
"The basic idea is fairly simple," UW astronomer Eric Agol said in the news release. "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."
"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," he said.
The researchers can use this lensing technique to gain insight into white dwarfs, which can help us determine the age of the universe.
In the future the researchers hope to discover more of these "self-lensing" binary systems.
"If everyone's missed this one, then there could be many more that everyone's missed as well," Kruse said.
