Astronomers have discovered a new Earth-like planet orbiting a single star in a binary star system located 3,000 light-years from Earth. The discovery is expected to help astronomers better understand how Earth-like, or even potentially habitable, planets can form and how to find them.
The new planet, dubbed OGLE-2013-BLG-0341LBb, is twice the mass of Earth and it orbits its host star at almost the same distance from which Earth orbits the sun. But, the host star is a lot dimmer than the sun, which makes the new planet much colder than Earth.
Although the planet is too cold -- colder than Jupiter’s icy moon Europa -- to be habitable, the same type of planet orbiting a sun-like star in such a two-star system would be in the so-called “habitable zone,” the region which is believed to be suitable for life, astronomers said in a study, published in the journal Science on Thursday.
“This greatly expands the potential locations to discover habitable planets in the future,” Scott Gaudi, a professor of astronomy at the Ohio State University and the study’s co-author, said in a statement. “Half the stars in the galaxy are in binary systems. We had no idea if Earth-like planets in Earth-like orbits could even form in these systems.”
To find the new planet, astronomers used a technique called “gravitational microlensing,” in which the gravity of a star focuses the light from a more distant star and magnifies it like a lens. To find a planet using this technique, astronomers look for a small blip within that magnified light signal.
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According to astronomers, the new planet briefly disrupted one of the images formed by its host star as the system crossed in front of a more distant star 20,000 light-years away in the constellation Sagittarius, which is the largest constellation in the southern hemisphere and is home to many bright stars.
“Now we know that with gravitational microlensing, it’s actually possible to infer the existence of a planet—and to know its mass, and its distance from a star—without directly detecting the dimming due to the planet,” Gaudi said. “We thought we could do that in principle, but now that we have empirical evidence, we can use this method to find planets in the future.”
More intensive computer analysis of various data eventually revealed information about the planet’s mass, separation from its star and orientation. According to astronomers, the new planet orbits its star from a distance of about 90 million miles and has a surface temperature of -352 degrees Fahrenheit.
Two-star systems composed of dim stars like these, astronomers said, are the most common type of star system in the Milky Way galaxy, meaning that there could be many more Earth-like planets out there that could possibly be warm enough to harbor life.
“In the past, whenever we saw a binary system we just stopped looking for planets,” Andrew Gould, an astronomer at Ohio State University and the study’s lead author, told the Los Angeles Times. “Now we realize it is a pretty big planet hunting ground.”