Artist's impression of CW Leonis.
CW Leonis is the second brightest extrasolar object in the sky at an infrared wavelength of 10 microns, after Eta Carinae; in addition to its variable star designation, it is catalogued as the infrared source (IRC 10°216).
Visually, an 18th magnitude long-period pulsating variable, CW Leo is an asymptotic giant branch (AGB) star that lies about 650 light-years away in the constellation Leo. A luminous giant star, with a surface temperature of 2,330 K and a radius of about 500 solar radii, it is cocooned within a shell of gas and dust in which carbon and dozens of different types of molecules have been detected. This shell has been formed from material lost in the form of a stellar wind that is blowing at a speed of about 14.5 km/s and carrying away about 3 × 10-5 solar masses per year. CW Leo is believed to be a rare case of a protoplanetary nebula – a system in the early stages of evolving to the planetary nebula stage.