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Planet with reverse orbit around star found
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Research evidence of a “retrograde orbit planet”
Our sun and the planets that revolve around it all move in the same direction. Since 1995, over 400 planets outside our solar system have been found, and many of them are strikingly different than that of us. To explain these differences, a variety of planetary evolution models have been proposed, including the theoretical possibility that some planets orbit in the opposite direction to that of their star rotation. On November 4th, researchers from the National Astronomical Observatory of Japan (NAOJ) announced they have found such a “retrograde orbit planet” for the first time.
Using the Subaru Telescope based in Hawaii, researchers from NAOJ, as well as MIT, studied the movements of HAT-P-7, a star about 1,000 light years away in the direction of the Cygnus constellation (also known as the Swan, or Northern Cross). There they found the retrograde orbit planet that they had been searching for.
Research team leader Norio Narita told Japanese reporters that around HAT-P-7, which is about 1.8 times that of the Sun in diameter, circles a planet that is 1.4 times that the size of Jupiter. This planet, HAT-P-7b, orbits the star at a blistering speed of once every 2.2 days at an angle that is more than 90 degrees off of that which the star itself rotates around, leading to the definition of a retrograde orbit movement. In comparison, all the planets in our system rotate at an angle that is within 10 degrees that of the Sun.
The discovery of HAT-P-7b's retrograde orbit is seen as potentially a major clue into how planets form and evolve around stars, particular in support of dynamic migration theories. Narita commented, “To support planetary evolution hypothesizes, I hope we can find giant planets and other objects that have been influenced by the birth of a retrograde orbit planet.”
Motohide Tamura, another researcher from the team, said, “It’s astonishing to find a planet that breaks common sense. There is the possibility of many unexpected things in the universe like the retrograde orbit planet, and our solar system might have a special existence.”
More theoretical information by the NAOJ researchers can be found in the Publications of the Astronomical Society of Japan vol. 61.
More theoretical information by MIT researchers can be found in the Astrophysical Journal Vol. 703
Read more news from Japan by the Japan Headlines Examiner
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