|
Alpha Centauri Bb is a possible extrasolar planet orbiting the K-type main-sequence star Alpha Centauri B, located 4.37 light-years from Earth in the southern constellation of Centaurus. If verified, it would be the closest extrasolar planet to Earth ever discovered, and the lowest-minimum-mass planet detected so far around a solar-type star.〔〔 Its existence was announced in October 2012 by a team of European observers, and the finding received widespread media attention.〔〔〔 However, the announcement was met with scepticism by some astronomers, who believed that the European team was over-interpreting its data. On June 10, 2013, scientists reported that the earlier claims of an Earth-like exoplanet orbiting Alpha Centauri B may not be supported. The existence of the planet remains a subject of scientific debate, and research by at least three separate groups of astronomers is ongoing. In April 2013, Uwingu, a corporation run by ''New Horizons'' mission director and former NASA Associate Administrator Alan Stern that allows people to pick unofficial names for celestial bodies for a fee, announced that an unofficial name would be given to the planet, ''Albertus Alauda'', after the namer's grandfather. The name received 751 votes. ==Detection== Starting in February 2008, and continuing through July 2011,〔 a team of European astronomers,〔 mainly from the Observatory of Geneva and from the Centre for Astrophysics of the University of Porto, recorded measurements of Alpha Centauri B's radial velocity with European Southern Observatory's HARPS echelle spectrograph at the La Silla Observatory in Chile. The team made 459 observations of Alpha Centauri B's color spectrum over a four-year period, then used statistical filters to remove known sources of variance. On 16 October 2012, the team announced they had detected an Earth-mass planet in orbit around Alpha Centauri B.〔 The discovery was presented in the scientific journal ''Nature'', with lead author credit going to Xavier Dumusque, a graduate student at the University of Porto. He called his findings "a major step towards the detection of a twin Earth in the immediate vicinity of the Sun".〔 The team used the Doppler spectroscopy method to search for a planet. As the body orbits the host star, its gravity would cause extremely small (semi-amplitude of about 0.5 m/s) periodic shifts in the host star's velocity. Variations of the line-of-sight velocity component cause tiny shifts in the star's spectrum. Using an extremely sensitive spectrometer, the team was able to infer variations of 0.51 m/s in Alpha Centauri B's radial velocity. The ESO called the findings the most precise measurements ever recorded using the technique.〔 The team estimated the probability of a spurious detection at 0.02%.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alpha Centauri Bb」の詳細全文を読む スポンサード リンク
|