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Using the Theory of Relativity and BEER to Find Exoplanets

"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)

“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)

A new method of detecting alien worlds is full of awesome, as it combines Einstein’s Theory of Relativity along with BEER. No, not the weekend beverage of choice, but the relativistic BEaming, Ellipsoidal, and Reflection/emission modulations algorithm. This new way of finding exoplanets was developed by Professor Tsevi Mazeh and his student, Simchon Faigler, at Tel Aviv University, Israel, and it has been used for the first time to find a distant exoplanet, Kepler-76b, informally named Einstein’s planet.

“This is the first time that this aspect of Einstein’s theory of relativity has been used to discover a planet,” said Mazeh.

The two most-most used and prolific techniques for finding exoplanets are radial velocity (looking for wobbling stars) and transits (looking for dimming stars).

The new method looks for three small effects that occur simultaneously as a planet orbits the star. A “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.

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 is due to starlight reflected by the planet itself.

“This was only possible because of the exquisite data NASA is collecting with the Kepler spacecraft,” said Faigler.

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. Credit: Dood Evan.

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.
Credit: Dood Evan.

Although scientists say this 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 Avi Loeb from the Harvard-Smithsonian Center for Astrophysics, who first proposed the idea of this planet-hunting method back in 2003.

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.

The planet has been confirmed 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.

The paper announcing this discovery has been accepted for publication in The Astrophysical Journal and is available on arXiv.

Source: CfA

About 

Nancy Atkinson is Universe Today's Senior Editor. She also works with Astronomy Cast, and is a NASA/JPL Solar System Ambassador.

Comments on this entry are closed.

  • vruz May 13, 2013, 8:35 PM

    Amazing work! Thanks Nancy for sharing this, truly mindboggling.

  • Torbjörn Larsson May 13, 2013, 9:35 PM

    In vino veritas – it is obviously an ad hic method.

  • baxbsg May 14, 2013, 9:07 AM

    Can a gas giant be tidally locked?

    • lcrowell May 14, 2013, 12:55 PM

      Yes

      • baxbsg May 14, 2013, 5:29 PM

        In that case, what does it mean for a gas planet to be tidally locked? For a chunk of rock like the moon it is obvious. For a gas planet does it mean that the net angular momentum is zero (my guess, I think) or that there is no circulation of gas in the planet or what? Thanks.

        • lcrowell May 15, 2013, 2:47 AM

          The angular rotation has a periodicity equal to the orbital periodicity. Any massive body, whether solid or gas can have a net angular momentum. The sun for instance rotates, as does Jupiter.

          LC

      • baxbsg May 14, 2013, 6:15 PM

        Also, how do we know this planet is tidally locked? Is it an assumption based on some parameters of the system or actually determined by some observations? Thanks.

        • lcrowell May 15, 2013, 2:50 AM

          There is some physics behind calculating the time a body becomes tidally locked. It is a rather messy calculation to arrive at a fairly complicated formula. It can be concluded that this planet is tidally locked.

          LC

  • lcrowell May 14, 2013, 12:56 PM

    This looks like very subtle aspects of relativistic and gravitational Doppler effect.

    LC

  • Jeffrey Scott Boerst May 17, 2013, 6:18 PM

    “A new method of detecting alien worlds is full of awesome”… Nancy… you’re hanging around with Fraser and Jason too much! lol!

  • Jay Theede May 18, 2013, 10:11 PM

    Disappointed it wasn’t actually beer. :(

  • John P. Tarver May 24, 2013, 12:12 AM

    Although the photon is a mathematical contrivance derived from relativity, the actual phenomenon detected is mass bending Time to form gravity. (ref. “the Meaning of Relativity”, by Albert Einstein) The path length of the light is longer near a mass, due to there being more Time there, therefore we “see” the energy as deflected. Relativity and the photon are actually mutually exclusive and I have to wonder at this discovery’s basis.

  • John P. Tarver May 25, 2013, 3:14 PM

    The photon is derived from relativity; relativity and the photon are mutually exclusive. A century behind in physics, but making a living writing about it.

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