What are the closest and/or brightest stars? How come alpha centauri does not appear as the brightest star in the night sky, since it is the closest?
There are two things which affect how bright a star appear from Earth. One is how close it is, and the other is how intrinsically bright it appears. Alpha centauri is not intrinsically a very bright star. It has an absolute magnitude of 4.4 only, which means it's slightly brighter than that Sun (which has an absolute magnitude of 4.8 - bigger is dimmer with magnitudes). The brightest star known is Sirius though, which is about twice as far away as Alpha Cen, but has an absolute magnitude of 1.4 (which means it is instrinsically almost 40 times brighter). See the Stars and Constellations website for further explanation of magnitudes.
This page updated on June 27, 2015