Astronomers discover the third planet in the Kepler-47 circumbinary system

Astronomers have discovered a third planet in the Kepler-47 system, thus ensuring the title of the system as the most interesting of the binary star worlds. Using data from NASA's Kepler Space Telescope, a team of researchers, led by astronomers from San Diego State University, has detected the new planet from Neptune's size to Saturn orbiting two known planets up to the age of 15. ;now.

Kepler-47, with its three planets orbiting two suns, is the only known multi-planet circumbinary system. Circumbitinary planets are those that revolve around two stars.

The planets of the Kepler-47 system were detected via the "transit method". If the orbital plane of the planet is aligned laterally as seen from Earth, the planet can pass in front of the host stars, resulting in a measurable decrease in the observed luminosity. The new planet, named Kepler-47d, was not detected earlier because of weak transit signals.

As is the case with circumbinary planets, the alignment of orbital planets changes with time. In this case, the orbit of the central planet is more aligned, which has reinforced the transit signal. The depth of transit went from undetectable at the beginning of the Kepler mission to the deepest of the three planets in just four years.

The researchers of SDSU were surprised by the size and location of the new planet. Kepler-47d is the largest of the three planets in the Kepler-47 system.

"We had seen a third planet in 2012, but with only one transit, we needed more data to be sure," said SDSU astronomer Jerome Orosz, the newspaper's lead author. "With additional transit, the orbital period of the planet could be determined and we were then able to discover more transits that were hidden in the noise in the previous data."

William Welsh, SDSU astronomer and co-author of the study, said that he and Orosz expected all the other planets in the Kepler-47 system to orbit around the previously known planets. "We certainly did not expect it to be the planet's biggest planet – it was almost shocking," said Welsh. Their research was recently published in the Astronomical Journal.

With the discovery of the new planet, a better understanding of the system is possible. For example, researchers now know that the planets of this circumbinary system have a very low density, lower than that of Saturn, the planet of the solar system having the lowest density.

Although a low density is not unusual for hot Jupiter-type exoplanets, it is rare for planets with mild temperatures. The Kepler-47d equilibrium temperature is about 10 ° C, while that of Kepler-47c is 26 ° F (32 ° C). The innermost planet, which is the smallest known circumbinary planet, has a much higher temperature (169 ° C).

The inner, middle, and outer planets are 3.1, 7.0, and 4.7 times larger than the Earth's, and have 49, 87, and 303 days in orbit around their suns, respectively. The stars themselves revolve around 7.45 days only; a star is like the sun, while the other has a third of the mass of the sun. The entire system is compact and would fit into the orbit of the Earth. It is approximately 3340 light-years away from the constellation Cygnus.

"This work builds on one of Kepler's most interesting discoveries: compact and compact planet systems are extremely common in our galaxy," said Jonathan Fortney, astronomer of the University of California to Santa Cruz, which was not part of the study. . "Kepler47 shows that any process that forms these planets – a result that has not occurred in our solar system – is common to both single-star and circumbinary planetary systems."