What is the brightest star in the sky?

sirius a and b

Sirius A and B.
NASA / ESA / G. Bacon (STScI)

The brightest star in the sky is Sirius, also known as the “Dog Star” or, more officially, Alpha Canis Majoris, for its position in the constellation Canis Major. Sirius is a binary star dominated by a luminous main sequence star, Sirius A, with an apparent magnitude of -1.46. Sirius A’s apparent brightness can be attributed both to its inherent luminosity, 20 times that of the Sun, and its proximity. At just 8.7 light years away, Sirius is the seventh closest star to Earth.

In 1844, Friedrich Wilhelm Bessel suggested that the star’s slightly wavy path through the sky, compared to that of background stars, indicated a fainter companion. Alvan Clark confirmed the companion’s existence in 1862. Now known to be a white dwarf, Sirius B is easily spotted in a large telescope, but contributes little to the system’s total apparent brightness.

Find Sirius A, and even Sirius B if you're up for the challenge, with our Northern Hemisphere star wheel.

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