Castor

Castor (α Geminorum) is a white main-sequence star in the constellation Gemini. With an apparent magnitude of 1.98 it is the 48th-brightest star in the night sky, and it is about 51 light-years from Earth.

Finder chart showing where Castor is in the constellation Gemini
Castor (circled) in Gemini, with the surrounding constellations and bright stars.
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Facts

ConstellationGemini
Designationα Geminorum (Alpha Geminorum), HR 2891
Apparent magnitude1.98 (48th brightest)
Spectral typeA1V
Colorwhite (B−V 0.03)
Distanceabout 51 light-years
Right ascension7 h 34.6 min
Declination+31.89°
Best monthFebruary (at about 9 pm)

Sources: star positions, magnitudes and colors from the Yale Bright Star Catalogue; constellation boundaries and star names from the IAU; areas and distances from Wikidata; stick figures by M. van der Sluys. How the maps are made.

How to find Castor

Castor is in Gemini. From 40° N it is highest in the south in February evenings, about 82° above the horizon. From 35° S it reaches about 23° in the north. Nearby bright stars: Pollux (5° away), Alhena (20° away) and Menkalinan (23° away).

Gemini constellation →

Other named stars in Gemini

PolluxAlhenaTejatMebsutaPropusAlzirrWasatMekbudaJishui

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