Around a century after the publication of Albert Einstein’s Theory of
Relativity, a team of astronomers from Tel Aviv University and from the
Harvard-Smithsonian Center for Astrophysics (CfA) has discovered a planet
outside our solar system using a method based on the great physicist’s
For that reason, Prof. Tsevi Mazeh, doctoral student Simchon
Faigler from TAU’s School of Physics and Astronomy and their American colleagues
have dubbed the Jupiter-sized sphere “the Einstein Planet.”
extra-solar planet – officially named Kepler-76b by the US National Aeronautics
and Space Agency – is the first-ever to be discovered using the “induced
relativistic beaming” of light from the host star.
For the past two
years, Mazeh and Faigler have been searching for planets around other stars using a
novel detection method. Their technique is based on identifying three very small
effects that occur simultaneously as a planet orbits a star.
effect is Einstein’s relativistic beaming effect (also known as Doppler beaming)
that causes a star to brighten and dim as it is tugged back and forth by an
Detection of planets via the beaming effect was
predicted in 2003 by Prof. Avi Loeb of Harvard University and Prof.
Gaudi (now at Ohio State University).
The second effect that the
Faigler-Mazeh method looks for is the stretching of a star into a football shape
by the gravitational tides raised by an orbiting planet. Such distorted stars
appears brighter when observed from the side due to the larger visible surface
area; they appear fainter when viewed end-on.
The third, minor effect is
due to starlight reflected by the planet itself.
Because the variations
in brightness are extremely small (in the order of one part per 10,000), these
effects can be detected only with accurate data gathered by space
The TAU team, supported by a European Research Council Advanced
Grant, analyzed data on more than 100,000 stars obtained by NASA’s Kepler
mission for evidence of the beaming and the other two modulations.
potentially discovering a planet, the Israeli scientists collaborated with Dr.
David Latham from the CfA and his team – which includes Dr. Lars Buchhave – to
observe the planetary candidate from the ground for additional spectroscopic
A year ago, Faigler and Mazeh noticed the three effects in
one of the stars observed by Kepler. Ground-based observations to confirm
detection of the planet were performed by Latham and his team at the Whipple
Observatory in Arizona, and by Lev Tal-Or, another TAU doctoral student, at the
Haute-Provence Observatory in France. Both telescopes unequivocally confirmed
the existence of the planet, now called Kepler-76b.
Last week, Faigler,
Tal-Or, Mazeh, Latham and Buchhave announced the discovery in a paper to be
published in the Astrophysical Journal.
Kepler-76b, part of the
constellation Cygnus, is at a distance of about 2,000 lightyears from Earth. The
planet, with a mass double that of Jupiter, orbits its parent star very closely,
with a period of one-and-a-half days.
Because the orbit is so “close,”
the planet is probably “locked” so that the same side of the planet faces the
star at all times. That part of the planet would be heated by stellar
Carefully examining the stellar brightness, the team found
strong evidence that the heat absorbed by the planetary atmosphere is carried
around the planet by jet-stream winds for about 16,000 kilometers – a
substantial fraction of the planetary circumference.
Such an effect has
been observed before only via infrared imaging with NASA’s Spitzer Space
Telescope. This is the first time such a wind effect has been observed in the
optical band. The study of such jets is extremely important for understanding
how planetary atmospheres respond to intense stellar heating, Mazeh
All of the planets found so far by the NASA Kepler mission were
discovered because they transit (eclipse) their parent stars. What is special
about the new technique is that it can locate even non-transiting
“The irony is that Kepler-76b is in fact transiting the edge of
its parent star,” said Faigler.
“This is why originally it was
misclassified as an eclipsing binary. Only through detection of the three small
effects were we able to determine that it is actually a planet.
the first time that this aspect of Einstein’s Theory of Relativity has been used
to discover a planet,” noted Mazeh, who is a participating scientist in the NASA
“We have been searching for this elusive effect for more
than two years, and we finally found a planet! It is amazing that already a
decade ago Loeb and Gaudi foresaw this happening.
“Shay Zucker of TAU, a
former student of mine, called my attention to this prediction,” continued
“At first, I did not believe it is possible, but I slowly got into
it. Luckily, we got the support of the European Research Council to carry this
project forward, and we collaborated with Dave Latham who believed in this
project and kept following the false candidates that Simchon and I were giving
him,” Mazeh said. “In the end we found Kepler-76b! It is a dream come
“The discovery proves the feasibility of the method,” said
Faigler. “We hope to find more planets like Kepler-76b using the same technique.
This is possible only because of the exquisite data NASA is collecting with the
Kepler spacecraft for more than 150,000 stars.”
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