An international team of scientists from Israel and the United States has reported the first-ever discovery of an extrasolar planet using a novel method that relies on Einstein’s special theory of relativity.
This image shows Kepler-76b orbiting its host star, which has been tidally distorted into a slight football shape (David A. Aguilar / Harvard-Smithsonian Center for Astrophysics)
The newly-discovered planet, labeled Kepler-76b, is located some 2,000 light-years from Earth in the constellation Cygnus.
Kepler-76b, also nicknamed ‘Einstein’s planet,’ is a so-called ‘hot Jupiter.’ Its diameter is about 25 percent larger than Jupiter and it weighs twice as much. The planet orbits a type F star every 1.5 days.
It was discovered using data obtained with NASA’s Kepler Space Telescope. Although Kepler was designed to find transiting planets, Kepler-76b was not identified using the classical transit method of detecting exoplanets.
First proposed by Dr Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and Dr Scott Gaudi from Ohio State University in 2003, the new method looks for three small effects that occur simultaneously as a planet orbits the star. Einstein’s beaming effect causes the star to brighten as it moves toward us, tugged by the planet, and dim as it moves away. The brightening results from photons piling up in energy, as well as light getting focused in the direction of the star’s motion due to relativistic effects.
“We are looking for very subtle effects. We needed high quality measurements of stellar brightnesses, accurate to a few parts per million,” explained Dr David Latham of the Harvard-Smithsonian Center for Astrophysics, co-author of a paper reporting the discovery accepted for publication in the Astrophysical Journal (arXiv.org version).
“This was only possible because of the exquisite data NASA is collecting with the Kepler spacecraft,” added lead author Dr Simchon Faigler from Tel Aviv University.
“This is the first time that this aspect of Einstein’s theory of relativity has been used to discover a planet,” said co-author Dr Tsevi Mazeh, also of Tel Aviv University.
The US-Israeli team also looked for signs that the star was stretched into a football shape by gravitational tides from the orbiting planet. The star would appear brighter when we observe the ‘football’ from the side, due to more visible surface area, and fainter when viewed end-on. The third small effect was due to starlight reflected by the planet itself.
Once Kepler-76b was identified, it was confirmed by Dr Latham using radial velocity observations gathered by the TRES spectrograph at Whipple Observatory in Arizona, and by Dr Lev Tal-Or from Tel Aviv University using the SOPHIE spectrograph at the Haute-Provence Observatory in France. A closer look at the Kepler data also showed that the planet transits its star, providing additional confirmation.
The planet is tidally locked to its star, always showing the same face to it, just as the Moon is tidally locked to Earth. As a result, Kepler-76b broils at a temperature of about 3,600 degrees Fahrenheit.
Interestingly, the team found strong evidence that the planet has extremely fast jet-stream winds that carry the heat around it. As a result, the hottest point on Kepler-76b isn’t the substellar point but a location offset by about 10,000 miles. This effect has only been observed once before, on HD 189733b, and only in infrared light with the Spitzer Space Telescope. This is the first time optical observations have shown evidence of alien jet stream winds at work.
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Bibliographic information: Simchon Faigler et al. 2013. BEER analysis of Kepler and CoRoT light curves: I. Discovery of Kepler-76b: A hot Jupiter with evidence for superrotation. ApJ, accepted for publication; arXiv: 1304.6841
