Aussie and Kiwi Amateurs Help Discover Earth-sized Planet in Binary Star System

Artists conception of a planetary system discovered with help from amateur astronomers.  Credit:    Cheongho Han, Chungbuk National University, Republic of Korea

Artists conception of a planetary system discovered with help from amateur astronomers. Credit: Cheongho Han, Chungbuk National University, Republic of Korea

Astronomers used a new technique called gravitational microlensing to discover a planet twice the size of Earth in a binary star system 3,000 light years away. The discovery of OGLE-2013-BLG-0341LBb... [Chris says: Since the planet’s official name is unpronounceable, I hear-by declare its new name - Oglebogle-b] The discovery of Oglebogle-b depended on contributions from amateur astronomers across Australia and New Zealand.

Light doesn’t always travel in a straight line. As it passes massive objects like stars, galaxies and black holes, the light’s path bends much like it does when it passes through a telescope’s lens. Gravitational lensing magnifies our view of distant objects, giving astronomers a chance to study ancient galaxies in more detail than they could through direct observations. Check out this Hubble Space Telescope project that used the lensing of galactic cluster Abell 2744 to study galaxies 12 billion light years away.

Astronomers at Poland’s Warsaw University Observatory proposed using gravitational lensing to study the thing that bends the light rather than the light’s source. They created the Optical Gravitational Lensing Experiment to explore the dark matter in the Milky Way  and its satellite galaxies. 

Lensing isn’t limited to dark matter, though. If the gravitational lens is a star with a planetary system, then the amount of lensing will change as the planets orbit the star. Measuring these small-scale variations - the gravitational microlensing - lets astronomers calculate the orbit and mass of the planet or planets causing the variations. More common exoplanet search techniques, such as the Kepler Mission’s transit search, work best with large planets in close orbits. Gravitational microlensing, on the other hand, works well for smaller planets orbiting relatively far from the parent star.

Using gravitational microlensing to discover Oglebogle-b required a multinational effort. The report’s 64 co-authors come from Australia, Canada, Chile, Israel, Japan, Korea, New Zealand, Poland, the United Kingdom, and the United States. Oglebogle-b orbits 0.8 astronomical units from its parent star - 80% of the distance between Earth and the Sun. Oglebogle is a red dwarf star, smaller and cooler than the Sun. As a result Oglebogle-b is much colder than Earth: less than -213˚ C.

Making the discovery required more observations than professional astronomers could make through traditional observatories. So they turned to 7 amateur astronomers in Australia and New Zealand. The paper’s lead author, Ohio State University astronomer Andrew Gould, told that “amateur astronomers really helped make this discovery possible.” In OSU’s announcement Gould “singled out the work of amateur astronomer and frequent collaborator Ian Porritt of Palmerston North, New Zealand.” 

Auckland’s Stardome Observatory and Planetarium's research astronomer, Dr. Grant Christie, explained the discovery to New Zealand TV One’s Breakfast. If you want the full details, you can find the peer-reviewed article at the Science Magazine site (doi:10.1126/science.1251527 paywall) or you can find a preprint on the Ogle website (PDF).