This famous double star is the brightest star in the sky. It is only 8.6 light years away. There is nothing particularly noteworthy about the brighter component. It a fairly small, type-A star. It appears bright only because it is close.
The companion, however, Sirius B, was one of the first white dwarf stars discovered. Sirius B is nearing the end of its life cycle. It used to be a large, blue star, but it burned up its nuclear fuel. With fusion no longer radiating energy outward, gravity shrunk the star's core. Sirius B retains as much mass as our Sun but is now roughly the size of Earth. With no fusion taking place, it will gradually cool (over hundreds of millions of years). What an amazing object!
Sirius A and B are difficult to see separately when they are closest together, but now they are quite far apart, over 10 arcseconds. Even now, though, the brighter star might overwhelm the dimmer one when viewed through a telescope. I caught them on a steady night and took 500 0.02-second frames, weeded out the blurriest 193 of these, then stacked the remaining 307. The four diffraction spikes around the bright star are a result of light interacting with the pieces of metal holding up a mirror in the light path of my telescope. Telescope: CFF 290 Classical Cassegrain (@ effectively f/8.1). Camera: SXVF-H9. Filter: Astronomik 6nm H-alpha.
