Astronomers for the first time discovered two alien planets that surround the two stars: a complete solar system with the sun as the fictional twins Luke Skywalker, Tatooine.
Most stars like the sun is not a single, but a pair of orbiting each other. Scientists discover planets in binary systems, called circumbinary (planets circling two stars) with two suns like Tatooine in "Star Wars."
To find more circumbinary planets, astronomers analyze data from the Kepler space telescope, NASA's has detected more than 2,300 potential alien planets since March 2009. Kepler to date have detected four of the solar system with a circumbinary planet - Kepler-16, 34, 35 and 38.
Scientists have now announced the detection of Kepler-47 system, the solar system first seen with a pair of planets circling stars. Stars and planets, called Kepler-47b and Kepler-47c, located at a distance of about 5,000 light-years away in the constellation Cygnus, the Swan.
"Kepler-47 shows us that binary stars can have planetary systems that gather, as we see in the lone star," said study leader Jerome Orosz at San Diego State University told SPACE.com. "Most of the stars in the galaxy are in binary or multiple systems even more, so the fact that planetary systems can appear in the type system is very important. If we just limit the search for planets around a single star, we would have missed most of the stars in the galaxy. "
Finding the solar system "Tatooine"
The planets are too far away to be seen with the naked eye. Instead, they found because they starlight overcast condition when crossing, or transiting, in front of the star.
Dimming was small, only 0.08 percent for the planet Kepler-47b and 0.2 percent for the planet Kepler-47C. By comparison, about 0.1 percent Venus blocking the sun's surface transit time recently. Data from Kepler allows researchers to infer the relative size of the object and its orbit. They also rely on further observations made by telescopes at the McDonald Observatory in West Texas.
One of the star similar to our sun, and the other one-third size smaller and 175 times fainter. Planet in size 3 times the diameter of Earth, while the outer planet 4.6 times the size of Earth's diameter - the smaller planet is the smallest circumbinary planet ever seen.
It is complete orbit around the planet every 49.5 days, while the outer takes 303.2 days, making it the largest orbit transiting planets outside our solar system has ever known. The stars themselves revolve around each other every 7.5 days.
The scientists published their findings online Aug. 28 in the journal "Science". They will also reveal detailed results on August 29 at the General Assembly of the International Astronomical Union in Beijing.
Planets in the habitable zone?
Interestingly, the outermost planet in the habitable zone of the system, with rocky planets like Earth that is the right temperature to have liquid water on its surface.
"We have learned that circumbinary planets could be like the planets in our solar system, but with two suns," said one study author Joshua Carter at the Harvard-Smithsonian Center for Astrophysics.
Although the outer planet is probably a gas giant slightly larger than Uranus, and therefore are not suitable for life, the finding suggests that circumbinary planets can and do exist in the habitable zone.
"The thing I find most interesting is the potential for habitable circumbinary system," said study author William Welsh at San Diego State University. "Kepler-47C may not have a life, but if the planet has a big moon, the planet would be a very interesting world."
Strange weather on the planet Tatooine
Circumbinary planet may experience extreme climate change.
On Earth, the sun is the light source is relatively stable, with solar energy we receive (insolation) varies only by 0.1 percent or more. "Consequently, we do not have to worry about what the sun did, at least in the time scale of a few years to several decades," said Orosz. "For a planet in a binary system, there may be changes in insolation by a few percent in the time scale of a few days to a few weeks. Moreover, if the planet's rotation axis tilt, then it will also be affected. Therefore the fast-changing and complex . "
"Also, let's say for the sake of discussion that the planet's rotation period is 24 hours, like the Earth," he added. "Since you have two suns instead of one, you can see during the day more than 12 hours, depending on the position of the stars at sunrise or sunset."
In addition, because the space telescope Kepler discovered that circumbinary planets have orbits closely related to orbit their star held each other, "you will often see a solar eclipse," said Orosz. "In the case of Kepler-47, when the secondary star passes in front of the primary, the total amount of light down by 15 percent. Thing is going to happen every 7.5 days or so."
The solar system is more exotic
Recent findings indicate that planetary systems can form and persist even in chaotic environments around binary stars.
The researchers estimate that the planets in the Kepler-47 are further away than their current orbits, in locations where the conditions for the formation of giant planets is more likely. They then eventually migrate into because of the interaction with the disk of gas and dust that surrounds the star too.
"We think the planets and most of the other planets formed from a disc of debris left over from the star formation process," said Orosz. "Yet it is clear that these discs can survive near a newly formed binary star, given the orbital motion of the two stars. However, it now appears that in spite of the small differences in orbital distances, planetary systems around stars similar to the binary planetary system around a single star. "
In the future, the researchers want to find alien planets smaller around binary stars.
"Our ability is limited to simple visual search, so we need better software to help automate the process," said Orosz. "If there was more time and data, I think we can find more circumbinary planetary systems in the data Kepler."