Why Do Some Stars Appear Brighter Than Others?

stars-appear-brighter-others Credit: Preserved Light Photography/Image Source/Getty Images

The apparent brightness of a star viewed from Earth varies based both on the type of star and its distance from the planet. The apparent magnitude differs from a star's absolute magnitude, which describes its brightness from a set distance, rather than the varying distances of stars seen from Earth. The lower the apparent magnitude, the brighter the star is as seen from Earth.

Other than the sun, the brightest star from the Earth, or the star with the lowest apparent magnitude, is Sirius, with an apparent magnitude of -1.46. Sirius is 8.6 light years from Earth and is a class A star, which is the third-hottest type of star, burning at a temperature between about 13,000 and 17,500 degrees Fahrenheit. The third brightest star as seen from Earth is Rigil Kentaurus, with an apparent magnitude of -0.27. It is 4.3 light years from Earth and is a G-class star. G-class stars burn at a lower temperature than A-class stars, burning at a maximum heat of 8,900 degrees Fahrenheit. Even though Rigil Kentaurus is much closer to the Earth than Sirius, its lower emission levels mean that it burns less brightly than Sirius, both in relative and in absolute terms.