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Beyond Earthly Skies

A Yellow Hypergiant with a Close Companion

19 Mar 2015, 22:00 UTC
A Yellow Hypergiant with a Close Companion ESO
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Yellow hypergiants (YHGs) are extremely rare stars. Only several of them have been identified in the galaxy so far. These stellar oddities are stars that are at a particularly unstable and rapidly changing phase of stellar evolution. They are known to expel prodigious amounts of material, creating complex circumstellar environments. An international team of collaborators using ESO’s Very Large Telescope Interferometer (VLTI) has found that the star HR 5171 is the largest YHG known.HR 5171 measures more than 1,300 times the Sun’s diameter, and it is one of the biggest and rarest stars in the galaxy. If placed in the solar system, its visible surface would extend all the way to between the orbits of Jupiter and Saturn. HR 5171 is located about 12,000 light years away and it shines with roughly a million times the Sun’s luminosity.Artist’s impression of the yellow hypergiant star HR 5171. Image credit: ESO.Observations using the VLTI also show that HR 5171 has a smaller companion star going around it every 1,300 days. The companion star is close enough that it is actually in contact with the main star, resulting in what known as a contact binary. The presence of the companion star distorts the ...

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