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BD−07 436
Star in the constellation Cetus From Wikipedia, the free encyclopedia
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BD−07 436, also known as WASP-77 since 2012,[5] is a binary star system about 344 light-years away. The BD−07 436 system's concentration of heavy elements is similar to the Sun. Its stars display moderate chromospheric activity, including x-ray flares.[6]
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The primary is a G-type main-sequence star, BD−07 436A (WASP-77A). The star is rotating rapidly, being spun up by the tides raised by the giant planet WASP-77Ab on its close orbit.[9] The secondary is a K-type main-sequence star BD−07 436B orbiting at a distance of 461+200
−140 AU.[7]
When calculated using spin rates, the two components appear to have different ages, with the secondary one billion years old, while the primary's age is 0.4 billion years.[5] When calculated from X-ray luminosity, the ages are radically different and even more inconsistent at 4.5 and >8.9 billion years respectively. [6] These ages may be unreliable, with the spin rates and X-ray luminosities affected by binary evolution, and ages inferred from the stars' positions in the H-R diagram are 7.99 and 7.3 billion years respectively.[10]
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Planetary system
In 2012 a transiting hot Jupiter planet b was detected on a very tight, circular orbit.[5] The planet may have an extended gaseous envelope and is losing mass.[6] Its equilibrium temperature is 1715+26
−25 K,[8] the nightside temperature is 1786±84 K,[12] and dayside planetary temperature is 1842+34
−33 K.[13]
Water vapour was detected on the planetary dayside of WASP-77Ab, indicating C/O ratio similar to solar or even lower.[14]
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References
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