What a Sap
Exoplanet WASP-18b sucks the life out of a young star in an illustration released September 16.
Researchers using NASA's Chandra X-ray Observatory noticed that the star, dubbed WASP-18, has low activity levels that make it seem much older than other stars its age. WASP-18 is actually fairly young, between 500 million and two billion years old, compared with our sun, which is about five billion years old and only approaching middle age. (Learn how researchers tell the age of a star.)
WASP-18's exoplanet companion is probably the reason for the star's premature aging, astronomers think. The planet is known as a "hot Jupiter" due to its size—about ten times the mass of Jupiter—and its proximity to the star. WASP-18b completes an orbit around its star in less than 23 hours.
That close relationship probably bodes ill for the star, researchers say. The planet's gravitational pull is likely messing up WASP-18's magnetic field, resulting in a lot less activity in the form of x-ray emissions and flares, making the star act older than it really is.
—Photo gallery by Sherry Brukbacher, text by Jane J. Lee