Scientists observe first planet-induced stellar pulsations

MIT-stellar-pulse_0

It is stars that affect planets, for the most part, and not the other way around. But researchers now claim to have found the first example of stellar pulsations caused by an exoplanet. The star HAT-P-2 is emitting visible pulses that seem to be a result of a particularly large exoplanet in a highly eccentric orbit.

HAT-P-2 is about 400 light years away in the constellation Hercules. It’s what is known as an class F star, which has a yellow-white hue. This star in particular is a bit larger and hotter than our sun. HAT-P-2b is one of the largest exoplanets ever discovered, with a mass more than eight times that of Jupiter. The highly eccentric orbit of HAT-P-2b is what attracted MIT researcher Julien de Wit to study it more closely.

HAT-P-2b has an extremely quick orbit of around five and a half Earth days. It gets close to the star at one end of the orbit, absorbing a great deal of energy before moving farther out. The MIT team originally wanted to generate a map of how that energy is circulated in the exoplanet’s atmosphere, which could offer clues to its atmospheric composition. What they found was quite unusual.

The team acquired 350 hours of observational data between July 2011 and November 2015 of HAT-P-2 via the Spitzer Space Telescope. Analysis showed the star’s brightness oscillated slightly every 87 minutes. The vibration has harmonics matching multiples of the planet’s orbital frequency. That indicates the two are linked and HAT-P-2b might actually be massive enough to affect the behavior of its parent star.

, Scientists observe first planet-induced stellar pulsations, #Bizwhiznetwork.com Innovation ΛI

The first order of business after detecting this signal was to make sure it wasn’t a flaw in Spitzer’s measurements. The team modeled various instrumental effects that could cause similar apparent vibrations in observational data, but none of them could have produced the same pulsations the team spotted. That left the exoplanet as the culprit. However, that doesn’t mean we know how HAT-P-2b is doing it.

The team has a number of hypotheses that might explain the data. The gravity of HAT-P-2b might simply distort the upper atmosphere of the star on every pass, causing repeating patterns of flairs. Some stars also pulse naturally, and it could be that HAT-P-2 is nearly in that state. The gravitational effects of HAT-P-2b could be pushing the star into a pulsating phase on a regular schedule. More study is needed to figure it all out, but it could improve our understanding of how planets and stars interact. We might even be able to find more exoplanets by better understanding what’s going on here.

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