Sirius is the most luminous Star in the Sky and is easily observed this month about 1/3rd of the way up the southern sky around 9 p.m. Only our Sun, the moon, Venus, and Jupiter, are brighter. Sirius is the 10th closest star to the earth being only 8.7 light years away, about twice the size of our sun, and about 20 times brighter.
In the winter sky, it can flicker with distinct colors when it gets close to the horizon. Once you locate Sirius you can also make out its related constellation Canis Major also referred to as the greater dog.
Hiding within the overwhelming brilliance of Sirius is a small stellar companion named Sirius B. In 1862 an American telescope maker Alvin Graham Clark was the first to glimpse this faint companion. This dim star is a white dwarf somewhat less in size than the earth and is one of the reasons it appears so faint. A white dwarf is a star that has used up its nuclear fuel and has collapsed to a much smaller size.
The white dwarf Sirius B contains almost as much mass as our sun. It, therefore, exerts a large gravitational force on its much brighter companion Sirius A and causes it to wobble slightly as it moves slowly against the background of the sky.