THE STELLAR WIND : SCIENCE

 

A Trail Like A Comets : A distant planet that is being blown away in stellar winds.

HUMANITY has detected more than 5,500 worlds orbiting other stars, and some are truly exotic. One seems to have titanium clouds ; on another, storms of glass may rain down.

WASP-69b, a planet orbiting a star 160 light-years away, is the latest addition to the eccentric menagerie.

As disclosed at a meeting of the American Astronomical Society in New Orleans, this exoplanet has a tail of helium gas 350,000 miles long [ 565,000 kilometres] that billows out behind it like a comet's.

WASP-69b is slightly larger than Jupiter, although considerably less dense, and it is so close to its stars that one full orbit takes just 3.9  Earth days. That makes it what astronomers call a Hot Jupiter, a common type of exoplanet.

Its flamboyant tail, however - which is 50 percent longer than the distance between Earth and the moon - is far from ordinary.

As the star's intense radiation broils WASP-69b, the planet's atmosphere heats to around 17,500 degrees Fahrenheit [ 9,700 degrees Celsius ] and expands. The outermost matter is buffeted by stellar wind and is blown into space, reaching speeds of 50,000 miles per hour.

'' Most Hot Jupiters are losing mass in this way, but not all of them have tails,'' said Dakotah Tyler, a doctoral candidate in astrophysics at the University of California, Los Angeles, and an author of an accompanying study published in The Astrophysics Journal.

'' The only way to get the tail is if you have an excessive stellar wind.''

The World Students Society thanks Robin George Andrews.