The Kepler 47 system

Two Planets Share two Suns

The Kepler 47 system
Isabelle Esteves's image for:
"Two Planets Share two Suns"
Caption: The Kepler 47 system
Image by: NASA

Since the beginning of time, man has stared at the sky and wondered what the twinkling lights were. The science of Astronomy grew up around this fascination. Today, with the sophisticated telescopes that are available, scientist are able to see things that were only dreamed of a generation ago. The recent discovery of a pair of planets in the Kepler-47 solar system that orbits two suns is proof of that.  Known as a circumbinary planetary system, it is located in the constellation Cygnus, 4900 light years away from Earth. The information was released in a paper in the journal Science on August 28, 2012.

The suns in this system are very different, one is similar to our sun but only 84% as bright and the other is small, about a third the size of the other and only about 1% as bright as our sun. The stars eclipse each other every 7.5 days.

 According to Jerome Orosz, associate professor of astronomy at San Diego State University and lead author of the paper  "In contrast to a single planet orbiting a single star, the planet in a circumbinary system must transit a 'moving target.' As a consequence, time intervals between the transits and their durations can vary substantially, sometimes short, other times long. The intervals were the telltale sign these planets are in circumbinary orbits."

The inner planet, named Kepler 47b, has a short orbit of 49.5 days. It is three times larger than Earth and because of its location in relation to the stars, is believed to be super-hot possibly with a haze covering the planet.  

The outer planet, Kepler-47c, thought to be larger than our planet Neptune, orbits the two suns every 303 days and is believed to be a gaseous giant where water might exist on the surface of the planet. It is located within the habitable zone but could not sustain human life.

 William Borucki, Kepler mission principal investigator at NASA’s Research Center at Moffett Field, California commented  "Unlike our sun, many stars are part of multiple-star systems where two or more stars orbit one another. The question always has been - do they have planets and planetary systems? This Kepler discovery proves that they do.  In our search for habitable planets, we have found more opportunities for life to exist."

“The presence of a full-fledged circumbinary planetary system orbiting Kepler-47 is an amazing discovery," said Greg Laughlin, professor of Astrophysics and Planetary Science at the University of California in Santa Cruz. "These planets are very difficult to form using the currently accepted paradigm, and I believe that theorists, myself included, will be going back to the drawing board to try to improve our understanding of how planets are assembled in dusty circumbinary disks."

 One of the many missions that NASA is involved in is called Kepler, The Search for Habitable Planets.  According to NASA, Kepler is the first mission capable of finding planets of a similar or smaller size orbiting around other stars. What they are looking for are planets that might possibly sustain life where water, in a liquid form might be present on the planet surface. 

 The way that these far away planets are detected is by observing the suns, planets that orbit occasionally pass in the front of their sun, when this happens, it is called a transit and these transits are visible with telescopes from Earth. By observing how often this happens and how much the brightness of the star decreases with the transit, scientist  are able to calculate the planets size and orbit. With this information, the habitability of the planet can be determined. Scientist cannot however determine if the planet does have life on it.

Johannes Kepler, who gave his name to this project, was a Renaissance scientist who formulated many theories about planets and stars that are still used to this day.  

More about this author: Isabelle Esteves

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