Last quarter moon and Spica mornings of January 6 and 7

The moon will come up quite late on January 6, and even later on January 7. It’ll be the middle of the night, both nights, for almost everywhere worldwide. The bright star near the moon on these nights is Spica, brightest light in the constellation Virgo the Maiden. In western skylore, Virgo represents a goddess of the harvest. Spica represents an ear of wheat held in the Virgin’s left hand.

If you’re not one to stay up late, your best bet is to wake up early to view the moon and Spica before daybreak. The moon will be at or near its half-illuminated last quarter phase. It reaches the crest of that phase on January 6, 2021 at 9:37 UTC. At time zones in the mainland United States, the moon reaches its last quarter phase on January 6 at 4:37 a.m. Eastern Time, 3:37 a.m. Central Time, 2:37 a.m. Mountain Time and 1:37 a.m. Pacific Time.

Visit Sunrise Sunset Calendars to find out when the moon rises into your sky, remembering to check the moonrise and moonset box.

Visit Heavens-Above to find out the moon’s present position in front of the constellations of the zodiac.

EarthSky lunar calendars are cool! They make great gifts. Order now. Going fast!

Spica, a blue-white gem of a star, ranks as the 15th-brightest star to light up the nighttime sky. When you consider that Spica resides some 262 light-years from our solar system, this star must be intrinsically very luminous to shine at 1st-magnitude brightness in Earth’s sky.

Star chart showing line crossing constellation.
The ecliptic – Earth’s orbital plane projected onto the constellations of the zodiac – crosses the celestial equator (declination of O degrees) in the constellation Virgo. Because Spica resides so close to the ecliptic, it is considered a major star of the zodiac. Virgo constellation chart via the International Astronomical Union (IAU).

Spica’s blue-white color reveals that this star has an extremely high surface temperature (22,400 Kelvin, 39,860 F, 22,127 C). In contrast, our yellow-colored sun has a surface temperature of nearly 6,000 K (10,340 F, 5,727 C) whereas ruddy Antares sports a rather cool surface temperature of 3,500 K (5,840 F, 3,227 C).

Diagram showing colors related to sizes of stars.
A star that is blue or blue-white in color, such as Spica at the upper left, has a high surface temperature. In contrast, a red-colored star, such as Antares and Betelgeuse at the upper right, has a cool surface temperature. Image of Hertzsprung-Russell diagram via ESO.

Spica, like all the stars, rises some four minutes earlier daily, 1/2 hour earlier weekly and two hours earlier monthly. So, instead of rising around midnight at mid-northern latitudes, as it does in January, Spica will rise around sunset in early April. Because Spica shines from dusk till dawn in April, we in the Northern Hemisphere often associate this star with the sweet season of spring.

Bottom line: In January, Spica is out from late night until dawn. Use the moon to guide your eye to Spica before daybreak January 6 and 7, 2021, and look forward to this star’s all-night appearance in April.

January 5, 2021

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Bruce McClure

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