Bob Moler's Ephemeris Blog

This is Bob Moler with Ephemeris for Tuesday, July 23rd. Today the Sun will be up for 14 hours and 58 minutes, setting at 9:18, and it will rise tomorrow at 6:20. The Moon, 2 days past full, will rise at 11:01 this evening.

Alberio is the name given to the star that is in the head of the constellation of Cygnus the swan, which is in the east these evenings, flying south along the Milky Way. It is also at the foot of the asterism or informal constellation of the Northern Cross. To the naked eye and binoculars Albireo looks like a single star. However, even in small telescopes its true nature is revealed. It’s a double star whose individual star colors are strikingly different Its brightest star is yellow, and the dimmer star is blue. While star colors are subtle, these two, due to their apparent closeness, make an obvious color contrast. Unlike what your interior decorator says: In stars, blue is hot, yellow, orange and red are cool. The two stars are too far apart to be considered a binary star system that are gravitationally bound, but appear to move together in space. It is what is called an optical double, though they’re both around 430 light years away.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

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