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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.