Home > Constellations, Ephemeris Program, stars > 02/23/2018 – Ephemeris – Meet the stars Castor and Pollux

02/23/2018 – Ephemeris – Meet the stars Castor and Pollux

February 23, 2018

Ephemeris for Friday, February 23rd. The Sun will rise at 7:30. It’ll be up for 10 hours and 52 minutes, setting at 6:22. The Moon, at first quarter today, will set at 2:54 tomorrow morning.

The star Pollux is at the head of the same named brother of Gemini the twins. Castor is the slightly dimmer star right above it. Pollux is about 34 light years away. It’s twice as massive as the Sun, and has run out of hydrogen in its core and is in the process of evolving into a red giant star. One planet, recently given the name Thestias, has been detected around it. Castor is at 51 light years away. There are 6 stars in its system. The brightest three are visible in telescopes. Each is a spectroscopic binary, meaning that the companion stars are detected by the Doppler shifts of the lines in their spectra as the stars orbit each other. The Doppler shift is just one of the many pieces of information revealed by the spectroscope.

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


Gemini with the stars Castor and Pollux

Gemini with the stars Castor and Pollux. Created using Stellarium.

Castor star system

The Castor star system exploded in this JPL/NASA infographic.

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