Archive for July 24, 2014

07/24/2014 – Ephemeris – A look at Altair the third star of the Summer Triangle

July 24, 2014 Comments off

Ephemeris for Thursday, July 24th.  The sun rises at 6:20.  It’ll be up for 14 hours and 56 minutes, setting at 9:17.   The moon, 2 days before new, will rise at 5:21 tomorrow morning.

The Summer Triangle Is high in the east to southeast sky in the evening. The southernmost star of the Summer Triangle is Altair, in the southeast.  Altair is the closest of the three stars at a distance of 16.7 light years away. One light year is nearly 6 trillion miles, that’s 6 followed by 12 zeros. Altair is nearly 11 times the brightness of the sun. If seen at Altair’s distance, the sun would only be as bright as one of the two stars that flank it in our sky. What is rather different about Altair is its rapid rotation. While it’s almost twice the sun’s diameter, it rotates once in only 9 hours, and would show a decidedly squashed appearance if seen close up. Our sun’s a slow poke, taking nearly a month to rotate just once.

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


The constellations Lyra, Cygnus and Aquila

Deneb with the other stars and constellations in the Summer Triangle. Created using Stellarium.

Oblate Altair

False-color image of the rapidly rotating star Altair, made with the MIRC imager on the CHARA array on Mt. Wilson. Credit: Ming Zhao, University of Michigan