How Einstein's theory of special relativity helped find a new planet (+video)
To find the planet, astronomers used Einstein's theory as it pertains to the intensity of a beam of light. The method could add more exoplanets to a growing list, no 'wobble' or 'transit' required.
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Indeed, to an astronomer looking directly into the beam, the effect can lead to the illusion that the light is traveling faster than its 186,000-mile a second speed limit. Such beams emanate from the poles of supermassive black holes that have gone on feeding binges. Researchers call them superluminal jets.Skip to next paragraph
In Pictures Looking into the skies: Telescopes
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Loeb says he wondered if the effect were noticeable enough at slower velocities to use beaming to detect planets orbiting other stars. As a planet orbits, its gravity would tug the star to and fro. Perhaps the starlight would intensify slightly as the planet reaches the points along its orbit where it's pulling the star toward Earth.
After some back-of-the-envelope calculations to see if the question was worth pursing beyond the "I wonder if" stage, Loeb approached Gaudi, who calculated the intensity of the beaming effect for the types of stars that missions such as Kepler would examine.
"We estimated that it should be possible to detect it," Loeb says, although others were unconvinced.
Since then, researchers have refined the approach by looking for two other effects that change during a planet's orbit. A star can appear to brighten as gravity from a close-in giant planet gives the star more of a rugby-ball shape as seen from Earth. And a giant planet can go through phases, much like the moon's, as an observer watches it swing around its star.
A star's natural variations in light could make detecting the beaming effect more difficult, so having the additional tests provides a more reliable indicator.
The team discovering the planet, led by Simchon Faigler at Israel's Tel Aviv University, picked its target star from one of the stars in Kepler's catalog – one for which no planet had yet been discovered.
After designing a computer program that hunts for the three features, the team analyzed 26 stars that looked like they'd give the new approach the best chance of succeeding. One of these, known as Kepler 76, yielded the evidence for the planet, Kepler 76b. The discovery was confirmed when additional observations detected the wobble in the star's spectrum, the so-called radial-velocity method.
One side benefit from using the new technique, which bears the whimsical name BEER (BEaming Ellipsoidal Reflection), is that it appears to have given the discovery team a window on the planet's atmosphere. The intensity of the tug implied by the BEER's beam was higher than the intensity of the tug the radial-velocity measurement provided. Mass estimates for the planet based on the approaches BEER uses also were inconsistent.
Additional calculations suggested that the difference could be attributed to a wide belt of superfast air circulating around the planet – a jet stream that has downed one shot of espresso too many.
Dr. Faigler and colleagues note that the approach so far can be used to detect exoplanets whose masses are at least half of Jupiter's mass and orbit their stars in 30 days or less. But with additional refinements, the team hopes to improve the approach's ability to detect planets with weaker light that it now requires – a development they say could add yet more objects to the burgeoning catalog of extrasolar planets.
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