Home > Ephemeris Program, stars > 02/10/2015 – Ephemeris – Orion’s bright red star, Betelgeuse

02/10/2015 – Ephemeris – Orion’s bright red star, Betelgeuse

February 10, 2015

Ephemeris for Tuesday, February 10th.  The sun will rise at 7:50.  It’ll be up for 10 hours and 13 minutes, setting at 6:03.   The moon, 1 day before last quarter, will rise at 12:51 tomorrow morning.

The bright red star in constellation Orion’s shoulder is Betelgeuse, and its now thought to be about 640 light years away give or take a couple of hundred light years*.  The name Betelgeuse means “Armpit of the central one” in Arabic.  Orion is seen in the south at 9 in the evening.  Even at Betelgeuse’ great distance it’s the star whose surface is easiest seen, after the sun of course.  That’s because it’s so big.  As large around as the size of the orbit of Jupiter.  Betelgeuse is losing mass in a huge cloud around it.  It is a massive star in the late stages of its life even though it’s only 7 million years old. Some astronomers speculate that it will explode in a massive supernova within the next million years.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.


* I’m being a bit facetious here. See the addendum, and also by coincidence a post from EarthSky today How far is Betelgeuse?


Orion upright and due south. Created using Stellarium.

Orion upright and due south. Created using Stellarium.

Our estimates of the size, mass and luminosity of Betelgeuse depend on knowing its distance.  The distance is not well-known because Betelgeuse is a single star, it is not a binary for which can be applied Newton’s laws to calculate these values.  Therefore these values in the broadcast program, where I have 59 seconds total, appear more certain than they really are.  Wait for Thursday’s program when I cover Rigel and see how close the values are between the two.  But Rigel appears to be a different star altogether.  Somebody’s wrong.

Betelgeuse drawing

“This artist’s impression shows the supergiant star Betelgeuse as it was revealed thanks to different state-of-the-art techniques on ESO’s Very Large Telescope, which allowed two independent teams of astronomers to obtain the sharpest ever views of the supergiant star Betelgeuse. They show that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface. These discoveries provide important clues to help explain how these mammoths shed material at such a tremendous rate. The scale in units of the radius of Betelgeuse as well as a comparison with the Solar System is also provided.” Credit: ESO/L. Calçada (ESO is the European Southern Observatory)

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