Galaxies on Instagram: "Sirius is the brightest star in the night sky, located 8.6 light-years away in the constellation Canis Major. What looks like one star is actually two: Sirius A, a large, luminous star about twice the Sun’s mass, and Sirius B, a faint white dwarf about the size of Earth. They orbit each other every 50 years, and Sirius shines so brilliantly because it’s both massive and very close to us."