NOTABLE STARS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site R Leonis A Mira star, 390 light-years away in the constellation Leo, that is one the brightest and easiest to observe variable stars in the sky. With a mean visual magnitude range of 5.8 to 10.0, it can be followed throughout its average 312-day-cycle with a small telescope, and for much of that time with binoculars. Discovered by J. A. Koch of Danzig in 1782, R Leonis was the fifth variable star, and fourth long-period variable to be found after Mira itself, Chi Cygni, and R Hydrae. It lies about 5° west of Regulus in the direction of Xi Leonis. As a result of data collected by the Hubble Space Telescope, it is one of handful of Mira stars known to be somewhat egg-shaped, with an apparent diameter of 70 x 78 milliarcseconds. This asymmetry is thought to involve the star's extended atmosphere, but its cause is not properly understood. It may be a result of non-radial pulsations (the star not pulsating equally in all directions) or it may be an optical illusion as a result of large dark spots on the star, perhaps caused by giant convection cells. Similar indications of an oblong shape have been found in the case of Mira itself, R Cassiopeia, R Leonis, and W Hydrae. Related categories    • NOTABLE STARS    • VARIABLE STARS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP