Love comes in many forms, including, it would appear, that between a planet and its star. In a study aptly published on Valentine’s Day researchers describe a gas giant planet known as HAT-P-2b that induces heartbeat-like pulsations in the star it orbits every time the two bodies get close.
The study, led by Julien de Wit of MIT, and published in The Astrophysical Journal Letters, is based on observations by NASA’s Spitzer Space Telescope of a solar system about 370 light-years from Earth in the constellation Hercules. Discovered in 2007, HAT-P-2b is about eight times the mass of Jupiter, making it a relatively large planet. It orbits a sun-like star and is 100 times less massive than its host, so it is still very small compared to its host star.
HAT-P-2b is a “hot Jupiter,” meaning it is a very warm planet that orbits its star closely. Unlike the planets in our solar system, it has a highly elliptical orbit, making one close flyby of its star every 5.6 days. During these close approaches the planet’s gravity exerts a powerful pull on the star, causing its outer shell to vibrate. Similar interactions have been observed in binary stars known as “heartbeat stars,” but never before between a star and a planet.
The observed effect was serendipitous, as the purpose of the study was to observe the circulation of the planet’s atmosphere. This was of particular interest given HAT-P-2b’s highly elliptical orbit. Most of the time, the planet is relatively far from its star, but every 5.6 days things really heat up during their close rendezvous. At its closest, HAT-P-2b receives about 10 times more light than it does at the farthest point in its orbit.
The effect observed by the Spitzer Space Telescope was very slight, with the star’s vibrations the most subtle light variations the telescope has ever measured from any source. Even this slight effect was unexpected, as available modeling suggested the vibrations should be even fainter, given the relative masses of the star and planet involved. So it may be time for these models to be revised.
According to De Wit, “Our observations suggest that our understanding of planet-star interactions is incomplete. There’s more to learn from studying stars in systems like this one and listening for the stories they tell through their ‘heartbeats.’” As so often in matters of the heart, in the field of astronomy much remains a mystery. It is such mysteries that spur us on, challenging us to ever more intriguing discoveries.
Join the Springfield Stars Club on Tuesday, March 28th at 7:00pm at the Springfield Science Museum for a talk by former Stars Club president Mike Kozicki on “Twenty Years since Comet Hale-Bopp.” Mike’s talk will include images of Hale-Bopp photographed from various western Massachusetts locations in March 1997, as well as more recent images of the comet captured using digital astrophotography. Refreshments will be served, and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per nonmember.
Also on Friday, April 7th at 7:30pm, the Stars Club and the Springfield Science Museum will host “Stars over Springfield,” an astronomy adventure for the whole family. Amateur astronomer Paul Cardone will talk on “The Future of Space Travel – Exploring the ways we will get to Space in the 21st Century, and who will bring us there.” A fee of $3 for adults and $2 for children under 18 will be charged.
Copyright © Amanda Jermyn