MDDM Ch. 11 Sirius

[Otto]

A binary system  . . . of course.
Otto

Sirius
Sirius is the brightest star in the night sky. Intrinsically, Sirius is over
20 times brighter than our Sun and over twice as massive. As Sirius is 8.7
light years distant, it is not the closest star system -- the Alpha Centauri
system holds this distinction. Sirius is called the Dog Star because of its
prominence in the constellation of Canis Majoris (Big Dog). In 1862, Sirius
was discovered to be a binary star system with a companion star, Sirius B,
10,000 times dimmer than the bright primary, Sirius A. Sirius B was the
first white dwarf star discovered, a type of star first understood by
Subrahmanyan Chandrasekhar in 1930. While studying Sirius in 1718, Edmond
Halley discovered that stars move with respect to each other. The Sirius
system is shown above captured in X-ray light.
http://antwrp.gsfc.nasa.gov/apod/ap960902.html

"Sirius A is the brightest star in our sky and can easily be seen in the
winter months in the northern hemisphere. Look for the constellation Orion.
Orion's belt are the three bright stars in a row. Follow an imaginary line
through the three stars to Sirius which is just above the horizon. It is
bluish in color."
http://www.unmuseum.org/siriusb.htm

SIRIUS. From Orion, look down and to the left to find brilliant Sirius, as
if one really needs directions to find the brightest star in the sky. Its
name comes from the Greek word for "searing" or "scorching," certainly
appropriate. It is the luminary of the constellation Canis Major, the
Greater Dog, which represents Orion's larger hunting dog, and as such is
commonly referred to as the "Dog Star." The star is also part of a larger
asterism, the Winter Triangle, the other two of which are Betelgeuse in
Orion and Procyon in the smaller dog, Canis Minor. Sirius is bright in part
because it truly is luminous. Though a "main sequence" star that, like the
Sun, shines by hydrogen fusion, it is over twice as massive as our star, and
as a result is hotter and brighter, its 9400 degree temperature making it
quite white. But it is also bright to us because it is nearby, a mere 8.6
light years away, just double that of the closest star to the Earth, Alpha
Centauri. Sirius's greatest claim to fame may be its dim companion. Though
10,000 times fainter than bright Sirius A, Sirius B is the hotter of the
two. The only way it can be hot and faint is to be small. The star has the
mass of the Sun, yet is smaller than Earth. Called a "white dwarf," on the
average it packs 15 tons into a mere cubic inch. It is the end product of a
star that at one time was much more massive than Sirius A is today.
http://www.astro.uiuc.edu/~kaler/sow/sirius.html