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Posts Tagged ‘Boötes’

Ephemeris: 05/08/2026 – The story of Boötes and Ursa Major

May 8, 2026 Comments off

This is Ephemeris for Friday, May 8th. Today the Sun will be up for 14 hours and 33 minutes, setting at 8:56, and it will rise tomorrow at 6:21. The Moon, 1 day before last quarter, will rise at 2:55 tomorrow morning.

Appearing in the eastern sky at 10 p.m. tonight is the kite shaped constellation of Boötes the herdsman. The bright star Arcturus is at the bottom of the kite which is horizontal to the left, pointed to by the arc of the handle of the Big Dipper, higher in the east. The Big Dipper is the hind end of the constellation Ursa Major, the Great Bear. In one story, Boötes represents a young hunter named Arcas, son of Callisto, a beautiful young woman who had the misfortune of being loved by god Zeus. Zeus’ wife, Hera, found out about the affair, and since she couldn’t punish Zeus, turned the poor woman into a bear. Arcas, many years later, unaware of why his mother disappeared, was about to kill the bear when Zeus intervened and placed them both in the sky, where he continues to chase her across the sky nightly.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

A GIF finder image for the constellations Boötes, Ursa Major, and Canes Venatici. It shows, in three frames: the sky as it would appear high in the east, the same image with constellation lines, and the art from the Stellariam app. See the caption for the image below for the inclusion of Canis Venatici.
A Google Gemini AI image created from a prompt I made which encapsulated the encounter of Arcas and the bear.
This is a Google Gemini AI image created from a prompt I made which encapsulated the encounter of Arcas and the bear in very sketchy terms. The source that it referenced turned out to be my April 26, 2019 Ephemeris post which is virtually identical to the one today. It was illustrated with a 17th century woodcut, which looked nothing like this image. I was kinda hoping it would have found another source, somewhere. I can’t be the only one. This is the second mythological image I requested from Gemini, and in both cases it created an image in the style of a renaissance painter. I noticed too that the bear has a look of recognition on its face. Gemini also included hunting dogs. Of course, Arcas would have had hunting dogs, and there is a constellation of the hunting dogs nearby. It’s just two stars, called Canes Venatici. I’ve ignored its part of the story all these years, so starting now I’m adding it in.
Categories: Constellations, Ephemeris Program, Mythology, Observing Tags: , , , , ,

Ephemeris: 05/06/2024 – The star Arcturus: Not from around here

May 6, 2024 Comments off

This is Ephemeris for Monday, May 6th. Today the Sun will be up for 14 hours and 29 minutes, setting at 8:54, and it will rise tomorrow at 6:23. The Moon, 1 day before new, will rise at 5:53 tomorrow morning.

Arcturus, a red giant star in the constellation of Boötes the herdsman, is about two thirds the way up the sky in the east-southeast at 10 pm. It’s one of the earliest stars to appear in twilight, being nearly tied in brightness with Vega, a white star low in the northeast. 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 into helium in its core, and is beginning to fuse the helium. It’s 25 times the size of the Sun and 170 times brighter, and a preview of our Sun when it gets that old.

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.

Addendum

Arcturus Finder diagram
A finder chart for the star Arcturus with the Big Dipper part of Ursa Major and Boötes: first showing the stars without the constellation lines and labels, second, showing constellation lines and labels. finally, adding red tracks showing a stars movement over 10,000 years. Arcturus has the greatest motion of any of the stars on this chart. Created using Cartes du Ciel (Sky Charts), LibreOffice Draw, and GIMP.
Evolutionary track of the Sun
An H-R* Diagram showing how the Sun’s brightness and temperature will change over its lifetime. Credit: Sloan Digital Sky Survey.

* Hertzsprung-Russell Diagram of a star’s surface (photosphere) temperature vs luminosity. The Main Sequence is where a star lives when it is burning hydrogen, and spends most of its life.

    Categories: Ephemeris Program, Observing, Stars Tags: , , ,