X-rays are produced in X-ray tubes by the deceleration of energetic electrons (bremsstrahlung) as they hit a metal target or by accelerating electrons moving at relativistic
velocities in circular orbits (synchrotron radiation; see above Continuous spectra of electromagnetic radiation).
On October 16, 2012, a team of astronomers announced the discovery of a planet with around 1.13 + / - 0.09 Earth - masses
in a very hot and tight,
circular orbit around Alpha Centauri B, using the European Southern Observatory's the High Accuracy Radial
velocity Planet Searcher (HARPS) instrument on the 3.6 - metre telescope at ESO's La Silla Observatory
in Chile.
On October 16, 2012, a team of astronomers announced the discovery of a planet with around 1.13 + / - 0.09 Earth - masses
in a very hot and tight,
circular orbit around Alpha Centauri B, using the European Southern Observatory's High Accuracy Radial
velocity Planet Searcher (HARPS) instrument on the 3.6 - metre telescope at ESO's La Silla Observatory
in Chile.
Planets «b, c, and d» - On December 14, 2009, a team of astronomers (Steven S. Vogt; Robert A. Wittenmyer, R. Paul Butler, Simon O'Toole, Gregory W. Henry, Eugenio J. Rivera, Stefano Meschiari, Gregory Laughlin, C. G. Tinney, Hugh R. A. Jones, Jeremy Bailey, Brad D. Carter, and Konstantin Batygin) announced the discovery of one innermost
orbiting super-Earth and two outer -
orbiting, Neptune - class planets (with at least 5.1, 18.2, and 24.0 Earth - masses, respectively)
in moderately
circular, inner
orbits around 61 Virginis with periods of 4.2, 38.0, and 124.0 days, based on radial -
velocity observations over 4.6 years with the Keck Observatory's High Resolution Echelle Spectrometer (HIRES) and the Anglo - Australian Telescope (U.C. Santa Cruz news release; AAO press release; Keck press release; the Lick - Carnegie Exoplanet Survey Team's «Systemic Console;» and Vogt et al, 2009).