In a manner of speaking, Albert Einstein just helped an international team of astronomers find a hot Jupiter that’s 2,000 light-years away. It’s the first time in history that the theory of relativity was used to locate another planet.
Normally, astronomers use the transit method to detect exoplanets, a technique that tells astronomers a planet has passed in front of its parent star. There’s also the wobble method, where astronomers can measure the periodic back-and-forth between gravitationally bound objects.
But the new technique, which the scientists are conveniently calling BEER (relativistic BEaming, Ellipsoidal, and Reflection/emission modulations), works by exploiting an effect predicted by Einstein’s Special Theory of Relativity.
The effect is known as beaming (sometimes called Doppler boosting), and it happens when a star’s brightness is increased as it moves towards the Earth, and dims as it moves away. It moves toward us because a planet is there to pull it (hence evidence of its presence). The brightening is caused by light particles, called photons, that are piling up in energy.
What’s more, the gravitational tides from the orbiting planet cause the star to stretch into an elliptical shape (the top image shows an exaggerated depiction of this), which causes it to appear brighter — and also expose more surface area — when its wider side faces Earth. And lastly, the planet reflects a small amount of detectable starlight.
It's these three components that make up BEER, a technique that, moving forward, will help astronomers find similar celestial bodies. And indeed, it'll be particularly useful for finding objects that don't require a precise alignment of planet and star as seen from Earth. Regrettably, it can't be used to find small, Earth-sized worlds (at least not with today's technology).
The astronomers, a team at Tel Aviv University and the Harvard-Smithsonian Center for Astrophysics (CfA), used the BEER formula to find the so-called Einstein planet, which is more formally known as Kepler-76b. It’s about 25% larger than Jupiter and weighs about twice as much, thus qualifying as a hot Jupiter.
The Astrophysical Journal has accepted the paper for publication, but you can read it here.
Images: David A. Aguilar (CfA).