An American-led team of astrophysicists including Tel Aviv University Prof. Tsevi Mazeh has discovered two new planets that revolve around a double sun, each of which “chases” the other and reaches the same “starting point” every 7.5 days.

Until now, only a handful of “exo-planets” in galaxies outside our own solar system have been shown to go around a double sun; this is the first double planet to do so.

The discovery was reported in the Wednesday issue of the prestigious journal Science and announced in Beijing by Prof. William Welsh, from the University of California, San Diego, at an international astronomy conference.

The observation has been carried out using only one instrument – a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. This data is transmitted to Earth by Kepler, a space observatory (named in honor of the 17thcentury German astronomer and mathematician Johannes Kepler), then analyzed to detect periodic dimming caused by extrasolar planets that cross in front of their host star.

Orginally due to end this year, the Kepler mission launched in March 2009 by the US National Aeronautics and Space Administration (NASA) to discover Earthlike planets orbiting other stars was extended to 2016.

The mission – according to those involved – was specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets.

One of the newly discovered planets could possibly sustain life, the team said. The discovery proves that planetary systems that are like our solar system could have been created around a double star.

Mazeh explained that this discovery joins that of four previous ones – of Kepler 16, 34, 35 and 38. Thus there are now five double suns that have planets revolving around them. But this is the first time that a system of two planets was found to revolve around a double sun.

This is also important because most of the stars (suns) in the universe “live as couples, like humans,” Mazeh said.

Kepler-47 is located 5,000 light-years away from us. One of the planets circles their double suns every 49 days, while the second one does so in 303 days.

The team is headed by Prof. Jerome Orosz of the University of California, San Diego. The astrophysicists from the US and Israel made the discovery by measuring the power of light from the double sun. This power declines in a cyclical way, which testifies to the fact that planets revolve around it, Mazeh said.

“Life” on a newly discovered planet would be very interesting, even though it cannot actually be seen from here. During some of the “sunsets,”one sun will start “twilight” and only later will the second sun “set” and cause night, he said.

“Every new planet that is discovered is a new world for us that helps us understand the process of creation of the planet,” Mazeh concluded. “This is especially in surroundings so different we are familiar with, in which in the center is only one sun. We can discover new worlds, but only with advanced technology installed on [unmanned] spacecraft that makes it possible to look deep into space.”

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