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Neither Star Nor Brown Dwarf

8 May 2014, 22:00 UTC
Neither Star Nor Brown Dwarf
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EF Eridani is an ultra-short period binary system consisting of a white dwarf and a substellar companion of unknown type. In a study by T.E. Harrison et al. (2004), astronomers used the NIRI on Gemini-North (7:21 to 9:00 UT on 24 December 2002) and NIRSPEC on Keck II (6 September 2003) to learn more about this unusual binary system. Estimates indicate that the white dwarf has ~60 percent the Sun’s mass, while the substellar companion has only ~5 percent the Sun’s mass. Both objects are separated by merely ~400,000 km and they whiz around each other in 81 minutes.Figure 1: Artist’s impression of the EF Eridani system as it might appear today. Image credit: Gemini Observatory.The white dwarf in EF Eridani is a dense, burnt-out remnant of a Sun-like star. It is roughly the same size as Earth and has a modelled surface temperature of about 9500 K. Circling around the white dwarf is a substellar companion of unknown type. It is thought that ~500 million years ago, the companion was a typical star that began losing mass to the smaller but more massive white dwarf. Over time, the companion lost so much mass to the white dwarf that it ...

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