Archive for January 21, 2016

01/21/2016 – Ephemeris – Rigel, Orion’s other bright star

January 21, 2016 Comments off

Ephemeris for Thursday, January 21st.  The Sun will rise at 8:12.  It’ll be up for 9 hours and 22 minutes, setting at 5:35.   The Moon, 2 days before full, will set at 6:44 tomorrow morning.

The bright star at the bottom right corner of the big upright rectangle that is the giant hunter Orion’s body in the south-southeast is Rigel.  It is a white star with a bluish tinge.  It compares in brightness with Betelgeuse at the opposite end of Orion’s rectangle, though it’s usually a bit brighter.  The mismatch in color makes brightness comparisons difficult.  Rigel is about 860 light years away, It’s 20 times the mass of the Sun,  120 thousand the times brighter than the Sun, and a diameter about the size of the orbit of Mercury.  It’s age is thought to be about 8 million years.  It has a visual companion star that can be seen in amateur telescopes.  It’s not that dim, but suffers by being close to the arc light brightness of Rigel.

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


Torso of Orion centered on his belt. Created using Stellarium.

Torso of Orion centered on his belt. Created using Stellarium.

Orion photograph

Orion and the head of Taurus photograph by myself January 4, 2016 at 11:30 p.m. It’s a stack of untracked 20 exposures.

Rigel A & B

Rigel with its companion star as photographed through a telescope. No attribution. Source:

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