Stars follow a life-long weight-loss program. They blow hot gas off their surfaces. Over time, the amount of material in these “winds” can add up. Heavier stars, in fact, can expel enough gas to make several stars as massive as the Sun.

An example is Antares, the leading light of Scorpius. It’s in good view tonight, to the left of the Moon as night falls.

Antares is a supergiant – one of the biggest and brightest stars in the galaxy. It’s more than a dozen times the Sun’s mass. And it’s so big that if you placed it at the center of the solar system, it would extend past the orbit of Mars.

But when Antares was born, about 11 million years ago, it was even heavier. Studies in recent years have placed its initial mass at about 15 to 17 times the Sun’s mass. Most of the difference has been blown into space on the star’s winds.

Antares has lost so much of its original weight because it was heavy to begin with. A massive star “burns” through its nuclear fuel quickly, making its core extremely hot. Radiation from the core causes the star’s outer layers to puff outward. That far from the core, the surface gravity is fairly low, so it’s easy for radiation to push gas out into space.

Antares is fated to expel even more of its mass. At the end of its life, its core will collapse, causing its outer layers to explode as a supernova – blasting most of its remaining gas out into the galaxy.

Script by Damond Benningfield