Bob Moler's Ephemeris Blog

Ephemeris for Thursday, July 18th.  Today the sun will be up for 15 hours and 7 minutes, setting at 9:22.   The moon, 3 days past first quarter, will set at 2:56 tomorrow morning.  Tomorrow the sun will rise at 6:15.

Of the three stars of the Summer Triangle Altair in the constellation Aquila the eagle is the farthest one south and the closest.  Altair is at a distance of 16.8 light years away. One light year is nearly 6 trillion miles. Altair is 10 times the brightness of the sun. While it’s almost twice the sun’s diameter, it rotates once in only 9 hours, and has a decidedly squashed appearance when seen close up. There are techniques that can actually accomplish this.  Our sun’s a slow poke, taking nearly a month to rotate once.  In science fiction the Altair system was the scene for the classic film Forbidden Planet, one of the few science fiction classic films of the 1950s.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

The Summer Triangle. Created using Stellarium and The Gimp.

False-color image of the rapidly rotating star Altair, made with the MIRC imager on the CHARA array on Mt. Wilson.

United Planets Cruiser C57-D lands on Altair IV in the 1956 movie Forbidden Planet.