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07/23/2012 – Ephemeris – The star Vega up close
Ephemeris for Monday, July 23rd. The sun rises at 6:19. It’ll be up for 14 hours and 57 minutes, setting at 9:17. The moon, 3 days before first quarter, will set at 11:14 this evening.
The star Vega, which is high in the east, near overhead or the zenith is a special star for astronomers. It’s part of the small constellation or Lyra the harp, which includes the parallelogram of stars near it. Vega is kind of a standard calibration star. It is the 5th brightest night time star with a brightness of 0.0 magnitude, although recent measurements place it at 0.03. Of the spectral types which denote the star’s color and surface temperature, Vega comes out to be pure white, with a surface temperature nearly twice the sun’s. It’s almost exactly 25 light years away, and so is one of the closer stars. It’s a tenth the sun’s age and 40 times the sun’s brightness. [It has perhaps a Jupiter sized planet, and a Kuiper belt of Pluto like objects.]
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Lyra in Binoculars. Created using Stellarium.
07/24/2012 – Ephemeris – The star Antares up close
The constellation Scorpius with Antares. Created using Stellarium.
Ephemeris for Tuesday, July 24th. The sun rises at 6:20. It’ll be up for 14 hours and 55 minutes, setting at 9:16. The moon, 2 days before first quarter, will set at 11:44 this evening.
Antares is a most interesting star. It’s low in the south and red in color. Its the heart of the Scorpius the scorpion. Its name means Rival of Mars with which it shares its color. Antares is a huge star, a red giant star. Its mass is 12 times the mass of the sun, but it’s bloated out to a diameter somewhat larger than the orbit of Mars, over 300 million miles. This what happens to a star that has exhausted hydrogen in its core and is now fusing helium to produce energy and even more massive elements. Its surface temperature is close to the temperature of the filament of an incandescent light bulb, about 2/3rds the temperature of the sun. Antares also has a dim companion star.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Bob Moler's Ephemeris Blog 