NASA discovers an alien planet with a 563,000-km-long tail outside our Solar System

Artist's concept depicts new research that has expanded our understanding of exoplanet WASP-69 b's "tail." (Image: NASA)

Astrophysicists have unveiled a fascinating feature of WASP-69 b, an exoplanet 160 light-years away. This hot Jupiter showcases a comet-like tail of gas, stretching an astonishing 563,000 kilometres into space.

The planet’s tail forms as it loses atmosphere due to intense radiation from its host star. This discovery, detailed in The Astrophysical Journal, was led by Dakotah Tyler from the University of California, Los Angeles (UCLA).

WASP-69 b orbits its star every 3.9 days. The planet, like other hot Jupiters, experiences extreme atmospheric loss, shedding about 200,000 tons of gas per second. Most of the escaping gas consists of hydrogen and helium.

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This atmospheric loss occurs through photoevaporation, where stellar radiation heats the planet’s outer layers. Instead of dispersing randomly, the escaping gases form a tail shaped by stellar winds. These winds, carrying charged particles from the star, sculpt the tail like a windsock.

“The stellar wind not only aids gas escape but shapes its form,” explained Tyler, noting the tail’s structured appearance. The observed tail is seven times longer than the planet itself.

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Scientists emphasised that WASP-69 b is not losing its entire atmosphere. Over 7 billion years, the planet has shed gas equivalent to seven Earth masses. The gradual loss offers astronomers a real-time look at atmospheric changes.

This discovery enriches the understanding of exoplanets’ evolution and their interactions with host stars. Researchers aim to explore similar phenomena in other planets, deepening insights into cosmic environments.