Astronomers have discovered a third planet in the Kepler-47 system, securing the system's title as the most interesting of the binary-star worlds. Using data from NASA's Kepler space telescope, a team of researchers, led by astronomers at San Diego State University, detected the new Neptune-to-Saturn-size planet orbiting between two previously ...
Astronomers have discovered a third planet in the Kepler-47 system, securing the system's title as the most interesting of the binary-star worlds. Using data from NASA's Kepler space telescope, a team of researchers, led by astronomers at San Diego State University, detected the new Neptune-to-Saturn-size planet orbiting between two previously known planets.
With its three planets orbiting two suns, Kepler-47 is the only known multi-planet circumbinary system. Circumbinary planets are those that orbit two stars.
What is circumbinary planets: As is common with circumbinary planets, the alignment of the orbital planes of the planets change with time. In this case, the middle planet's orbit has become more aligned, leading to a stronger transit signal. The transit depth went from undetectable at the beginning of the Kepler Mission to the deepest of the three planets over the span of just four years.
The SDSU researchers were surprised by both the size and location of the new planet. Kepler-47d is the largest of the three planets in the Kepler-47 system.
With the discovery of the new planet, a much better understanding of the system is possible. For example, researchers now know the planets in in this circumbinary system are very low density – less than that of Saturn, the Solar System planet with the lowest density.
While a low density is not that unusual for the sizzling hot-Jupiter type exoplanets, it is rare for mild-temperature planets. Kepler-47d’s equilibrium temperature is roughly 50 degrees F (10 degrees C), while Kepler-47c is 26 degrees F ( 32 degrees C). The innermost planet, which is the smallest circumbinary planet known, is a much hotter 336 degrees F (169 degrees C).
The inner, middle, and outer planets are 3.1, 7.0, and 4.7 times the size of the Earth, and take 49, 187, and 303 days, respectively, to orbit around their suns. The stars themselves orbit each other in only 7.45 days; one star is similar to the Sun, while the other has a third of the mass of the Sun. The entire system is compact and would fit inside the orbit of the Earth. It is approximately 3340 light-years away in the direction of the constellation Cygnus.
Link of full report: http://newscenter.sdsu.edu/sdsu_newscenter/news_story.aspx?sid=77597
Image Credit: NASA/JPL-Caltech/T. Pyle