Astronomers have announced the discovery of an uncommon planet that is located some 200 light years away from Earth with two suns.
The rare planet orbits two stars, as portrayed in the sci-fi movie Star Wars more than 30 years ago. Star Wars portrayed the existence of a planet called Tatooine which has two sunsets. Now, it has become a reality after 34 years.
Unlike Tatooine, the planet is cold, gaseous and not thought to harbor life, but its discovery demonstrates the diversity of planets in our galaxy.
First recognized by NASA's $600 million Kepler space telescope, the rare planet is the first confirmed solar system of its kind. Named Kepler-16b, the planet is about the size of Saturn and 200 light years from the Earth.
This discovery confirms a new class of planetary systems that could harbor life. 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, said Kepler principal investigator William Borucki in a NASA statement.
The existence of circumbinary planets had been previously hinted by earlier researches, but the detection now confirms such planets. Kepler detected the planet by observing transits, where the brightness of a parent star dims from the planet crossing in front of it.
Laurance Doyle of the SETI Institute led a research team in Mountain View, Calif., by using data from Kepler space telescope, which traces dips in the brightness of over 150,000 stars, in order to search transiting planets.
The research team discovered the new planet in the Kepler-16 system, a pair of orbiting stars that darkens each other from the vantage position on Earth. When the smaller stars partly block the bigger star, a primary eclipse happens, and a secondary eclipse takes place when the smaller star is occulted, or entirely blocked, by the bigger star.
Researchers further discovered that the darkness of the system dipped even when the stars were not eclipsing each other, indicating at a third body. The further dimming in brightness events, called tertiary and quaternary eclipses, resurfaced at odd hours, hinting the stars were in different places in their orbit every time the third body passed.
This showed the third body was circling, not just one, but both stars, in a wide circumbinary orbit.
The two stars which Kepler-16b orbits are said to be smaller and cooler than our sun. The stars are 20 and 69 percent as massive as the sun and circle each other every 41 days, said researchers in their report published online in the Sept.16 issue of journal Science.
Around both of them circles the Saturn-mass planet in a period of 229 days. Even though the planet has an orbital period of less than a year, it is still outside the habitable zone of the stars as the stars are much dimmer than our Sun.
When you have a binary star with planets orbiting that, the binary star produces gravitational perturbations that can be very severe for planets, Greg Laughlin, an astronomer at the University o fCalifornia, Santa Cruz, told CNet. Planets can get tossed out of the system or tossed into one of the stars.
But Kepler-16b seems to be stable, probably because it is so far from the stars it orbits that it effectively is feeling them as a single gravitational attraction, Laughlin said.
Lead author Doyle explained the excitement another way.
This is an example of another planetary system, a completely different type that we've never seen before. That's why everyone's making a big deal out of it. Nobody's ever seen a place like this before, he told CNet. Then he added cheekily, With one exception -- I seem to remember seeing a place like this about 30 years ago in a galaxy far, far away.
Kepler 16b's interaction with two different suns means that temperatures on its surface can vary by about 50 degrees, between roughly minus 100 degrees Fahrenheit and minus 150 degrees Fahrenheit.