It is the brightest star in the earth's night sky.
Most people in the Northern Hemisphere notice Sirius in the southeast – south – or southwest on evenings from winter to mid-spring. February evenings are a grand time to see it. It’s also fun to spot Sirius as it ascends in the east before dawn on late summer mornings. Whenever you see Sirius, you’ll recognize it easily because it is our sky’s brightest star.
Although white to blue white in color, Sirius might be called a rainbow star, as it often flickers with many colors.
The brightness, twinkling and color changes sometimes prompt first-time observers to report Sirius as a UFO. But these changes have nothing to do with Sirius. Rather, they are what happens when such a bright star as Sirius shines through the blanket of Earth’s atmosphere. The light from Sirius, which often appears fairly low in the sky from the mid-north latitudes, passes through a long column of air before it reaches our eyes. Changes in density and temperature of this air affect the light and cause the flickering and shimmering we see when we gaze at this star. This happens for other stars, too, but it is more noticeable for Sirius because it is so bright, and because it appears low in the sky.