"Einstein's
planet," formally known as Kepler-76b, is a "hot Jupiter" that
orbits its star every 1.5 days. Its diameter is about 25 percent larger
than
Jupiter and it weighs twice as much. This artist's conception shows
Kepler-76b orbiting its host star, which has been tidally distorted into
a slight football shape (exaggerated here for effect). The planet was
detected using the BEER algorithm, which looked for brightness changes
in the star as the planet orbits due to relativistic BEaming,
Ellipsoidal variations, and Reflected light from the planet. Credit: David A. Aguilar (CfA). High Resolution Image (jpg) - Low Resolution Image (jpg)
This graphic
shows Kepler-76b's orbit around a yellow-white, type F star located
2,000 light-years from Earth in the constellation Cygnus. Although
Kepler-76b was identified using the BEER effect (see above), it was
later
found to exhibit a grazing transit, crossing the edge of the star's face
as seen from Earth.
Cambridge, MA - Detecting
alien worlds presents a significant challenge since they are small,
faint, and close to their stars. The two most prolific techniques for
finding exoplanets are radial velocity (looking for wobbling stars) and
transits (looking for dimming stars). A team at Tel Aviv University and
the Harvard-Smithsonian Center for Astrophysics (CfA) has just
discovered an exoplanet using a new method that relies on Einstein's
special theory of relativity.
"We are looking for very subtle effects. We needed high quality
measurements of stellar brightnesses, accurate to a few parts per
million," said team member David Latham of the CfA.
"This was only possible because of the exquisite data NASA is collecting
with the Kepler spacecraft," added lead author Simchon Faigler of Tel
Aviv University, Israel.
Although Kepler was designed to find transiting planets, this planet was
not identified using the transit method. Instead, it was discovered
using a technique first proposed by Avi Loeb of the CfA and his
colleague Scott Gaudi (now at Ohio State University) in 2003.
(Coincidentally, they developed their theory while visiting the
Institute for Advanced Study in Princeton, where Einstein once worked.)
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.
"This is the first time that this aspect of Einstein's theory of
relativity has been used to discover a planet," said co-author Tsevi
Mazeh of Tel Aviv University.
The 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 the new planet was identified, it was confirmed by Latham using
radial velocity observations gathered by the TRES spectrograph at
Whipple Observatory in Arizona, and by Lev Tal-Or (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.
"Einstein's planet," formally known as Kepler-76b, is a "hot Jupiter"
that orbits its star every 1.5 days. Its diameter is about 25 percent
larger than Jupiter and it weighs twice as much. It orbits a type F star
located about 2,000 light-years from Earth in the constellation Cygnus.
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
("high noon") 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.
Although the new method can't find Earth-sized worlds using current
technology, it offers astronomers a unique discovery opportunity. Unlike
radial velocity searches, it doesn't require high-precision spectra.
Unlike transits, it doesn't require a precise alignment of planet and
star as seen from Earth.
"Each planet-hunting technique has its strengths and weaknesses. And
each novel technique we add to the arsenal allows us to probe planets in
new regimes," said CfA's Avi Loeb.
Kepler-76b was identified by the BEER algorithm, whose acronym stands
for relativistic BEaming, Ellipsoidal, and Reflection/emission
modulations. BEER was developed by Professor Tsevi Mazeh and his
student, Simchon Faigler, at Tel Aviv University, Israel.
The paper announcing this discovery has been accepted for publication in The Astrophysical Journal and is available online.
Headquartered in Cambridge, Mass., the
Harvard-Smithsonian Center for Astrophysics (CfA) is a joint
collaboration between the Smithsonian Astrophysical Observatory and the
Harvard College Observatory. CfA scientists, organized into six research
divisions, study the origin, evolution and ultimate fate of the
universe.
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu
