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Bob Moler's Ephemeris Blog

05/21/2019 – Ephemeris – The bright star Arcturus

21 May 2019, 04:01 UTC
05/21/2019 – Ephemeris – The bright star Arcturus
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Ephemeris for Tuesday, May 21st. Today the Sun will be up for 15 hours and 2 minutes, setting at 9:10, and it will rise tomorrow at 6:07. The Moon, 3 days past full, will rise at 12:07 tomorrow morning.
Let’s take a look at the star Arcturus, which with its pointer, the curve of the Big Dipper’s handle is very high in the southeastern sky at 11 p.m. Arcturus, one of the first stars to appear after sunset, is the 4th brightest night time star, though some think the star Vega, low in the northeast is brighter. They are different colors because Arcturus is orange, while Vega is whiter than the Sun. Arcturus is a preview of what the Sun will become in four or five billion years from now. It is only 10% more massive than the Sun and is that much older than the Sun, so it is turning into its red giant stage, after running out of hydrogen to turn into helium in its core to produce energy. The helium is now compressing and heating up, bloating size of the star.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for ...

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