This Star Gets Really Nervous Every Time Its Companion Planet Comes Near

NASA's Spitzer Space Telescope has detected an unusual display of affection between a parent star and its companion planet.

Their observations, described in a paper published in the Astrophysical Journal Letters, showed that the star called HAT-P-2 is having what appears to be unusual pulsations every time the planet HAT-P-2b gets close to it.

"Just in time for Valentine's Day, we have discovered the first example of a planet that seems to be causing a heartbeat-like behavior in its host star," said Julien de Wit, a postdoctoral associate at the Massachusetts Institute of Technology and lead author of the study, in a press release.

The pulsation of stars is not an uncommon event. It usually occurs in binary systems called "heartbeat stars." However, this is the first time that astronomers observed similar interactions between a parent star and its companion planet.

The planet, dubbed as HAT-P-2b, is a hot Jupiter with an elliptical orbit. Due to the shape of its orbit, the planet can get really close or very far from its parent star HAT-P-2. Every 5.6 days, HAT-P-2b gets really close to its star. During this time, the planet appears to give a "kiss" to its star, as NASA describes, due to their interacting gravitational forces.

Just like how humans respond to a kiss, the host star beats like a heart as the planet travels around its orbit again. The unusual pulsations of the star, in response with its companion planet, were observed by the Spitzer Space Telescope. The telescope watched the interaction between the star and its planet for 350 hours between July 2011 and November 2015.

The astronomers were able to see the planet during its transit and secondary eclipse. During transit, a planet crosses in front of its host star. On the other hand, a secondary eclipse occurs when the planet crosses behind the planet.

Because the astronomers were able to observe the planet during its secondary eclipse, they are sure that the pulsations came from the host star. However, the astronomers still don't exactly know the exact mechanism at play that makes the star pulsate.