The chances of astronomers finding life on other planets could have possibly expanded after a team of astronomers from all over the world discovered a frozen Earth-like planet circling a single star in a binary star system 3,000 light years away.
The planet, which was given the lengthy name of OGLE-2013-BLG-0341LBb, has twice the mass of Earth and revolves around one of two stars in a binary system by approximately 93 million miles, the same distance from which the Earth circles its own sun. However, the star is 400 times dimmer than our own sun, which means the newly discovered exoplanet's surface is several times much colder than the coldest points on Earth.
Before the discovery, scientists were not aware that rocky planets could form Earth-like orbits around a star in a two-star system, which is the most common star system in the Milky Way galaxy. The researchers believe that although the exoplanet itself is too cold for Earth-like life to form, other planets in a binary system with a similar orbit could be categorized into what is called the "habitable zone," where conditions are ripe for life to thrive.
"This greatly expands the potential locations to discover habitable planets in the future," says Scott Gaudi, astronomy professor at Ohio State University and one the researchers. "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."
The planet was discovered using a complex century-old technique proposed by Albert Einstein called gravitational microlensing. Einstein said that when a star moves directly in front of another star, the gravitational pull of the foreground star serves like a lens that magnifies the light of the star behind it. In the case of this planet, its star system magnified the light signal of a more distant third star located in the Sagittarius constellation 20,000 light years away.
Team leader Professor Andrew Gould, also of the Ohio State University, says that this was "just another microlensing event" before their equipment, particularly the Optical Gravitational Lensing Experiment (OGLE), discovered a slight dip in the light signal caused by the planet shifting into alignment with its host star and the star 20,000 light years away.
Gould and Gaudi enlisted the help of professional and amateur astronomers from places as far as New Zealand, Australia, Chile and Israel and organized them into the Microlensing Follow Up Network (MicroFUN) to observe the continuously brightening star. At that time, the researchers still did not know that a second star was close by, until it announced its presence with an unexpected eruption of bright light known as a caustic crossing.
Weeks after the first planetary distortion was first observed as a "dip" in light signal, a second distortion caused by the planet was seen in the light from the caustic crossing. Professor Cheongho Han of Korea's Chungbuk National University analyzed the data and confirmed the information captured from the distortion. His analysis also reveals that the planet has a surface temperature of -352 degrees Fahrenheit, making it colder than Jupiter's ice moon Europa. The second star is located as far as Saturn is from our own sun, but it is also very dim like the first star.
The details of the discovery are published in a paper on the Science journal.