... 2000 March 20 . Mercury on the Horizon . ... Explanation: Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it is never seen far from the Sun, and so is only visible near sunrise or sunset . If trailing the Sun, Mercury will be visible for several minutes before it follows the Sun behind the Earth . ... An informed skygazer can usually pick Mercury out of a dark horizon glow with little more than determination. ... About APOD | ...

THE 75th NAME-LIST OF VARIABLE STARS. ... The 75th Name-List consists of two tables. ... the literature, taken from positional catalogues, including USNO A1.0/A2.0 and GSC, or determined by the authors); the range of variability (sometimes the column Min gives, in parentheses, the amplitude of light variation; the symbol ( means that the star , in minimum light, becomes fainter, than the magnitude indicated); and the system of magnitudes used ( P are photographic ...

... The distance scales of the objects are matched both by comparing the first derivatives of the angular velocity determined separately from radial velocities and proper motions and by the statistical-parallax method. ... Good agreement between the inferred 0 and our calculations based on space velocities suggests that the Lindblad relation holds throughout the entire sample volume. ... Brandt and Blitz (1993) published the distances and radial velocities for a total of 206 H II-regions. ... Astron. ...