Achernar, a blue-white star in the constellation Eridanus. Achernar has an apparent magnitude of 0.5, making it one of the brightest stars in the nighttime sky. It is visible only from locations south of about 32 North latitude. The star has an absolute magnitude of -2.3 and is approximately 118 light-years from the earth.
Our knowledge of space changes all the time as new discoveries are made. But some ideas about the universe have never really held water – including the one that everything is made of frozen H2O.
A look at the night sky at any time of year will reveal a faint band of light stretching across the sky -- our solar system's home, the Milky Way. How much do we really know about it?