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51 Pegasi, fifth-magnitude star located 48 light-years away from Earth in the constellation Pegasus, the first sunlike star confirmed to possess a planet. 51 Pegasi, which has physical properties (luminosity and temperature, for example) very similar to those of the Sun, became the focus of attention in 1995 when Swiss astronomers Michel Mayor and Didier Queloz announced the detection of a planet orbiting it. (Mayor and Queloz won the 2019 Nobel Prize for Physics for their discovery.) The extrasolar planet, 51 Pegasi b, is not visible from Earth, but its presence was deduced from the wobble that its gravity induces in the parent star’s motion in a 4.23-day cycle. It has a mass 46 percent that of Jupiter and orbits surprisingly close (7.8 million km [4.8 million miles]) to the star—much closer than Mercury orbits the Sun (at a distance of 57.9 million km [35.9 million miles]).
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solar system: Studies of other solar systems…planet moving around the star 51 Pegasi was announced. By the end of 1996 astronomers had indirectly identified several more planets in orbit around other stars, but only in 2005 did astronomers obtain the first direct photographs of what appeared to be an extrasolar planet. Hundreds of planetary systems are…
Didier QuelozObservations of the star 51 Pegasi began that September. In January 1995 Queloz and Mayor detected a planet, 51 Pegasi b, with a mass about half that of Jupiter and a period of 4.23 days, which they confirmed and announced later that year. The existence of 51 Pegasi b,…
Star, any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources. Of the tens of billions of trillions of stars composing the observable universe, only a very small percentage are visible to the naked eye. Many stars occur in pairs, multiple systems, or…