Scientists Intrigued by Planet With Long Tail

Just the tail measures a whopping 350,000 miles in length.

Being Tailed

Astronomers have discovered an unusual exoplanet with a long "tail" of gas trailing behind it, not unlike a giant comet.

As NASA details in a recent article about the discovery, the planet, dubbed WASP-69 b, is steadily shedding its atmosphere of hydrogen and helium particles, which are being shaped into the astonishing tail by harsh stellar winds blowing its way.

WASP-69 b is a hot Jupiter, which means it's a gas giant roughly the mass of Jupiter but orbits its host star in the Aquarius constellation — some 164 light-years away from earth — at a much shorter distance, causing its surface temperatures to soar.

The sheer amount of radiation from its host star causes lightweight gases including hydrogen and helium to "photoevaporate" into outer space, trailing the planet in an epic wake.

"Strong stellar winds can sculpt that outflow in tails that trail behind the planet," University of California astrophysicist Dakotah Tyler, lead author of a paper published in the journal The Astrophysical Journal, told NASA.

Breaking Wind

Tyler and his colleagues found that the exoplanet is losing an estimated 200,000 tons of gas per second. While that may sound like a lot, we're talking about planetary scales; every one billion years, the team found, the planet is losing the mass equivalent to planet Earth, which means it's unlikely to ever run out of gas in its atmosphere (WASP-69 b is roughly 90 times the mass of Earth.)

The exoplanet's tail is astonishingly long, extending more than 7.5 times its radius behind it, or 350,000 miles, which is roughly 1.5 times the distance between the Earth and the Moon.

But as the stellar winds shift, WASP-69 b's unusual appendage's size and shape can change, and astronomers are only beginning to understand this unusual phenomenon.

"Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical mechanisms that shape the demographics of close-in planets," the paper reads.

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