Scientists Discover 563,000-Km Comet-Like Tail On Exoplanet WASP-69 B

A team of scientists has discovered that WASP-69 b, an exoplanet, possesses a comet-like tail of gas stretching up to 563,000 kilometers into space. The tail forms as the planet gradually loses its atmosphere, with light hydrogen and helium particles from its outer layers escaping over time.

These gas particles don't escape evenly around the planet. They rather are swept into a tail of gas by the stellar wind from its star, according to the latest study, published in The Astrophysical Journal.

WASP-69 b, which is 160 light-years away, is a super-hot gas giant that orbits around its host star closely. 

"WASP-69 b's star strips gas from the planet's outer atmosphere over time. What's more, something called the stellar wind can shape this escaping gas into an exoplanetary tail," according to NASA.

The stellar wind is a continuous stream of charged particles flowing outwards into space from the star's outer atmosphere. In the case of WASP-69 b, the stellar wind comes from its host star and shapes the gas escaping from its outer atmosphere. 

Instead of the gas just escaping evenly around the planet, "strong stellar winds can sculpt that outflow in tails that trail behind the planet," said lead author of the study Dakotah Tyler, an astrophysicist at the University of California, Los Angeles. 

"If the stellar wind were to taper down, then you could imagine that the planet is still losing some of its atmosphere, but it just isn't getting shaped into the tail," Dakotah Tyler added.

If there were no stellar wind, the gas escaping on all sides of WASP-69 b would be spherical and symmetrical, "But if you crank up the stellar wind, that atmosphere then gets sculpted into a tail," Dakotah Tyler said.

In this study, Dakotah Tyler and his team have linked this process to a windsock blowing in the breeze. 

Interestingly, the tail discovered by Dakotah Tyler and his research team on WASP-69 b extends over 7.5 times the radius of the planet. The tail could be even longer than that since the team had to end its observations with the telescope before the tail's signal disappeared.

The measurement was a lower limit on the tail's true length at the time. 

Since exoplanet tails continue to be mysterious, especially when they are subject to change, this study can help scientists to better understand how such tails form along with the relationship between the stellar and planetary atmospheres.