Exciting discovery of a planet in a microlensing event!
Artist’s impression of the binary star system and the newly discovered planet. Adapted from image by Cheongho Han, Chungbuk National University, Korea.
Here is the University of Auckland’s press release:
Astronomers discover terrestrial planet in binary star system
New Zealand scientists are among an international team that has discovered an Earth-sized planet with an Earth-like orbit in a binary star system, the first terrestrial planet with an Earth-like orbit ever discovered in this commonly found star system.
Binary star systems are made up of two stars orbiting each other. Half the stars in our Galaxy are in binary systems.
The latest discovery expands astronomers’ understanding of where Earth-like planets can form and, potentially at least, whether or not they might be habitable.
The new planet is 3000 light years away and twice the mass of Earth. It orbits one of two stars in its binary system at about the same distance Earth orbits the Sun. But the star it orbits is much dimmer than our Sun, meaning the planet is extremely cold, around -210C, and unlikely to harbor life on its surface as we know it.
“This discovery is exciting because we weren’t certain that terrestrial planets could form around one star of a binary star system,” says University of Auckland Department of Physics senior lecturer Nicholas Rattenbury. “This tells us there are many more stars in our Galaxy that could potentially be the host star to habitable planets.”
New Zealand astronomers from Auckland, Massey and Canterbury universities contributed to this latest discovery along with amateur astronomers and staff at Auckland’s Stardome Observatory. The results are published today in Science with sixty-four authors named.
Scientists used a technique known as microlensing to detect the planet. Microlensing discovers planets by measuring how the gravity of a planet and its host star deflects light coming from background stars. By measuring how a background star appears to change brightness through the gravitational “lens” effect of the foreground star, astronomers can tell whether there is also a planet orbiting the foreground star.
Dr Rattenbury said working with such a big team of astronomers from around the world had been a thrill.
“Twenty years ago, the first extra-solar planet discoveries were being made. Today, we find it likely the Galaxy is teeming with planets. Will some of them harbour life? That is of course the big question.”
The research appears in the July 4th issue of Science:
A terrestrial planet in a ~1-AU orbit around one member of a ∼15-AU binary, A. Gould et al., Science, 4 July 2014: 46-49.