October 19, 2011 by Dan Swinhoe
Science fiction often predicts the future or imagines strange phenomenon that we think impossible.
In Star Wars, Luke Skywalker lived on a planet where there was a double sunset each night.
In a discovery that recalls the film, NASA have discovered a planet which orbits two suns, and is the first time that such a planet has been seen. Named Kepler-16b, the planet was discovered using the Kepler telescope as part of a mission to find Earth-like planets elsewhere in our galaxy.
“This is really a stunning measurement by Kepler,” said Alan Boss of the Carnegie Institution for Science near Washington DC, a co-author of the study. “Once again, what used to be science fiction has turned into reality.”
Binary stars, where two suns turn around each other, have been seen before, and previous research has theorised planets (known as “circumbinary planets”) would orbit them. But Kepler’s discovery is the first confirmation and can provide plenty of detail.
Both the suns are smaller and colder than our own, around 69% and 20% the mass,meaning unlike Skywalker’s desert home, Kepler- 16b would be very cold with the average temperatures around minus 73 to minus 101 degrees Celsius. The gravity on the planet would be very different to our own due to the second star.
The Kepler space telescope is on a mission, orchestrated by NASA, to find other Earth-like planets in our Galaxy. Scouring the Milky Way and over 150,000 stars, the aim is to find planets in the ‘habitable zone’, where the planet isn’t too close nor too far away from the parent star, and could in theory harbour water and sustain life.
Co-author of the study William Borucki, Kelper’s principal investigator, said, “Given that most stars in our galaxy are part of a binary system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now,”
The telescope does this by finding stars that periodically dim in brightness, suggesting something (i.e. a planet) is orbiting between the star and Kepler. This is called planetary transit, and the same thing can be seen from Earth when Venus or Mercury pass between us and the Sun. Kepler’s instruments can calculate the distance from the object from its star, as well as the size and orbital paths, and is in incredibly accurate.
The telescope is able to tell us the planet is similar in size to Jupiter and is a gas giant that orbits around the two suns every 229 days, and is roughly as close to its suns as Venus is to ours. This newly discovered planet is 200 lightyears from Earth. To give a sense of distance, at 80mph it would take 8,390,411 years to travel one lightyear. A lightyear is the distance it takes light to travel in one year, and is the fastest speed possible.
The findings have been published in the Journal Science, and was released last month.