• January 19, 2006

    Episode 19: Measuring a White Dwarf

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    The mass of Earth's nearest white dwarf has finally been measured. White dwarf stars are the collapsed remains of low- to medium-mass stars that have burned out. For over 140 years, astronomers have known that Sirius, the brightest star in the northern sky, is actually a pair of stars: a bright blue-white star and a dim white dwarf. Unfortunately, Sirius A, the brighter of the two, overwhelms the light of Sirius B, the white dwarf. Using the Hubble Space Telescope, astronomers have been able to separate the light of the two stars. They measured Sirius B's mass by studying the effect its strong gravity has on the light it emits. Measuring the mass of white dwarfs is critical to understanding how stars like our Sun evolve.