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Ephemeris: 06/29/2026 – Red stars large and small

June 29, 2026 Leave a comment

This is Ephemeris for Monday, June 29th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:32, and it will rise tomorrow at 6:00. The Moon, at full today, will rise at 9:53 this evening.

There are two kinds of red stars very bright ones and very dim ones. The bright red ones are very few. One of them in the evening sky now is Antares in the heart of Scorpius the scorpion. Another one is in the winter sky and the most famous red giant of all, Betelgeuse in the shoulder of Orion the hunter. These are giant stars have exhausted the hydrogen in their cores to produce helium and are working on helium or even heavier elements fusing them to still heavier elements at even higher temperatures to keep them alive, but since they are working on the ash of the previous reaction, they won’t last very long, and the star dies, possibly cataclysmically. The higher internal heat bloats the star to be, huge, making its outer layers are actually cooler.

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

Size comparison between the Sun and two famous red giant stars.
Size comparison between the Sun and two famous red giant stars. However, believe the numbers, not the image size comparisons, which are not to scale and actually too small.
Graphic of the Sun and Barnard's Star.
Graphic of the Sun and Barnard’s Star. Until we found a planet in the habitable zone of Proxima Centauri, the nearest star to the Sun, Barnard’s Star was the most famous red dwarf star. Bernard’s star’s claim to fame that is it has the fastest proper motion of any known star, mainly because it’s only 6 light years away. Proper motion is the apparent star’s motion against more distant stars. In 1916 E. E. Barnard discovered it above the right shoulder of the constellation Ophiuchus the serpent bearer. It moves at a rate of 10.3 arcseconds per year that is 10.3/3600ths of a degree. It can only be seen in a telescope.

Categories: Concepts, Ephemeris Program, Stars Tags: ,

07/03/2023 – Ephemeris – The Sun is more massive than most stars

July 3, 2023 Comments off

This is Bob Moler with Ephemeris for Monday, July 3rd. Today the Sun will be up for 15 hours and 29 minutes, setting at 9:31, and it will rise tomorrow at 6:02. The Moon, at full today, will rise at 10:28 this evening.

The Sun appears to be a singular object in the sky. There is none other. But is that true? No, it’s not. The Sun is a star, middle-aged for a star of its mass. The Sun is bigger than most stars, because most stars are runty red dwarf stars. In fact the closest star to our Sun is a red dwarf, called Proxima Centauri, the third, outlying star in the triple star system whose brightest star is called Rigil Kentaurus, though better known by its 1603 Bayer catalog designation, Alpha Centauri. Proxima is a challenge to spot even with binoculars. It turns out that stars visible to the naked eye are all brighter than the Sun. As far as the range of stellar masses go, the Sun is pretty much in the middle. Rigil Kentaurus itself is 8 percent more massive than the Sun and 50 percent brighter. Both Rigil Kentaurus and Proxima are too far south to see from Michigan.

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

The Hertzsprung-Russell Diagram showing the stars by luminosity (actual brightness) and surface temperature. There are a lot more stars at the bottom of the main sequence (Stars that create helium from hydrogen to produce energy) than anywhere above them. Credit NASA/Chandra with an addition by the author.
Categories: Ephemeris Program, Stars Tags: , , , ,