Archive for June 23, 2020

06/23/2020 – Ephemeris – Arcturus: a look at the Sun’s future

June 23, 2020 Comments off

This is Ephemeris for Tuesday, June 23rd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 2 days past new, will set at 11:49 this evening.

Arcturus, a red giant star is about two thirds the way up the sky in the southwest at 11 p.m. It’s one of the earliest stars to appear in twilight, being nearly tied in brightness with Vega, a white star nearly as high in the east. A pointer to Arcturus is the handle of the Big Dipper, following the arc of the handle to Arcturus. Though only 37 light years away, it’s not from around here. It’s passing through the galactic disk from north to south. Arcturus is about 7 billion years old, and is about 8% more massive than our Sun. It appears to be starting its red giant phase, after running out of hydrogen to fuse to helium in its core and is beginning to fuse helium. It’s a preview of coming attractions for our Sun when it gets that old.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


Arcturus finder diagram

Arcturus is easy to find. It’s the brightest star in the southwest in the evening. This is 11 pm tonight June 23, 2020. Note the Big Dipper and its handle to the upper right. Created using Stellarium.