Death of a Planet

A Planet Soon to Meet Its Demise[1]

The image at left is an artist’s impression of a transiting hot-Jupiter planet. It is so close to its host star that it zips around it in less than a day.

In an era of ever larger observatories, you might think that there’s no longer a place for small-aperture ground-based telescopes. But small ground-based telescopes have been responsible for the discovery and characterization of around 250 exoplanets so far—and these are the targets that are especially useful for exoplanet science, as they are more easily followed up than the faint discoveries made by telescopes like Kepler.

The Kilogree Extremely Little Telescope (KELT) consists of two telescopes—one in Arizona and one in South Africa—that each have a 4.2-centimeter aperture. In total, KELT observes roughly 70% of the entire sky searching for planets transiting bright hosts. And it’s recently found quite an interesting one: KELT-16b. In a publication led by Thomas Oberst (Westminster College in Pennsylvania), a team of scientists presents their find.

KELT-16b is what’s known as a hot Jupiter. Using the KELT data and follow-up observations of 19 transits, Oberst and collaborators estimate KELT-16b’s radius at roughly 1.4 times that of Jupiter and its mass at 2.75 times Jupiter’s. Its equilibrium temperature is a scalding 2453 K — caused by the fact that it orbits so close to its host star that it completes each orbit in a mere 0.97 days!

This short period is extremely unusual: there are only five other known transiting exoplanets with periods shorter than a day. KELT-16b is orbiting very close to its host, making it subject to extreme irradiation and strong tidal forces.

Based on KELT-16b’s orbit, Oberst and collaborators estimate that the planet began a runaway inspiral by the age of 1 billion years. Now, at ~3.1 billion years old, KELT-16b is orbiting at a radius of just over 3 stellar radii above its host’s surface. The authors estimate that KELT-16b’s continuing inward spiral could end in the planet’s destruction by tidal forces in as little as another 550,000 years.

By studying this planet we can hope to gain overall insight into hot Jupiter formation and migration.

[1] Susanna Kohler, “A Planet Soon to Meet Its Demise,”from the American Astronomical Society (February 22, 2017). Also Thomas E. Oberst et al 2017 AJ 153 97. doi:10.3847/1538-3881/153/3/97


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