Have you ever wondered how the world will end? Astronomers know the answer. The Sun is a furnace, powered by the burning of hydrogen in its core. That hydrogen will last for billions more years, but when it runs out, the end is near. In the final stages of its life, the Sun will greatly expand, increasing to hundreds of times its original size. As it swells, it will engulf the terrestrial planets: first Mercury, then Venus, and then the Earth. If an astronomer on a distant world is observing the Sun with a telescope, they might notice our demise – the Sun will get brighter after the Earth is eaten, before settling back to its usual state.

A team of scientists recently observed such a planetary engulfment for the first time. The team initially found the signal with the Zwicky Transient Facility, a survey conducted using Caltech’s Palomar Observatory. Transients are astrophysical phenomena that vary on timescales that we can observe, like the brightening and dimming of a star after the ingestion of a planet. In this case, the star brightened by a factor of 100 over the course of ten days, then slowly dimmed over six months. After collecting additional data, the scientists inferred that the outburst was caused by a Sun-like star engulfing a Jupiter-like planet. The planet was likely orbiting very close to the star, with gravitational interactions between the star and planet causing the planet to migrate inward and become engulfed.

While this discovery is the first of its kind, the scientists predict that future surveys will routinely detect engulfment events. The demographics of these dying planets will ultimately shed light into the evolution of exoplanetary systems, as well as the fate of our own world.

This study was led by Kishalay De, a postdoc with the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology.

Managing Correspondent: Emily Pass

Press Article: In a first, astronomers spot a star swallowing a planet (MIT News)

Original Journal Article: An infrared transient from a star engulfing a planet (Nature)

Image Credit: NASA/GSFC/Frank Reddy

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