Some of the faintest stars that are visible to the unaided eye are really some of the most impressive stars of all. They look faint only because they’re a long way off. In fact, they’re so far away that they must be truly remarkable for us to see them at all.
A prime example is in the constellation Perseus, which is high in the south at nightfall.
To the eye alone, Xi Persei is faint. In fact, you can’t see it at all from a light-polluted city. In reality, though, the star is a stunner — more than 10,000 times brighter than the Sun. And when you add in the ultraviolet, it’s more than 300,000 times brighter than the Sun. It looks faint only because it’s about 1,800 light-years away.
Xi Persei is so bright in the ultraviolet because its surface is extremely hot; in fact, it’s one of the hottest stars that’s visible to the naked eye. That energy has an impressive effect on a nearby cloud of gas and dust: It causes the gas to glow like a fluorescent bulb. The visible part of the cloud spans about a hundred light-years, so Xi Persei’s radiation is energizing enormous amounts of material.
The cloud resembles the outline of the state of California, so it’s known as the California Nebula. But it won’t look that way forever. Some of its gas and dust are collapsing to make new stars. And Xi Persei is blasting away some of the material that’s closest to it like a celestial blowtorch — constantly resculpting the California Nebula.
Script by Damond Benningfield, Copyright 2013