Moon and Spica rise at late evening

On February 22, 2019, you’ll have to stay up fairly late to view the moon and Spica, the constellation Virgo’s brightest star, rising into your eastern sky. At mid-northern latitudes, look for the twosome to be up by around 10 to 11 p.m. At more southerly latitudes, the moon and Spica will rise earlier in the evening.

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Want to know when the moon rises in your sky? Click here and check the moonrise and moonset box.

Want to know when Spica rises? Click here and chose Spica as your celestial object of interest.

Spica serves as a prime example of a 1st-magnitude star; in other words, it’s one of the brightest stars in our sky. You should have little trouble picking it out, even in the glare of the waning gibbous moon, over these next few nights.

Keep watching, and try to recognize patterns of stars around Spica if you can. If you do, once the moon leaves the evening sky in another few days, you’ll easily note Spica’s color. It is a blue-white gem of a star, and, for stars, color reveals temperature. Spica’s blue-white complexion shows that its surface temperature is extremely high (39,860 degrees Fahrenheit, or 22,127 degrees Celsius). In contrast, our yellow-colored sun has a much cooler surface (only 9,980 degrees F, or 5,527 degrees C). The surface temperature of a red star, such as Antares, is even cooler (5,840 degrees F, or 3,227 degrees C).

Chart with colors from blue at top (high temperatures) to orange at bottom (low temperatures).

Color/temperature chart via Wikipedia.

Spica lies nearly on the ecliptic, the annual pathway of the sun in front of the background stars. If you could see stars during the day, you’d see the sun in front of Virgo from approximately September 16 to October 31 each year.

The moon (more or less) follows the ecliptic as well, and thus – as the moon makes its monthly rounds in front of the constellations of the zodiac – it spends several days each month in front of Virgo, routinely passing near Spica.

Star chart.

Virgo constellation chart via the International Astronomical Union (IAU).

But the moon’s motion along the ecliptic is not so steadfast as that of the sun. The moon undergoes an 18.6-year cycle, whereby the moon – as it passes Spica – can swing anywhere from 5 degrees (10 moon-diameters) to the north of the ecliptic to 5 degrees (10 moon-diameters) south of the ecliptic.

Since Spica lies 2 degrees (4 moon-diameters) south of the ecliptic, that means the moon has periods when it occults (passes in front of) this star. The next occultation series of Spica will start on June 16, 2024, and will conclude on November 17, 2025, featuring a total of 20 occultations.

By the way, when the moon is no longer there to guide you, use the Big Dipper to arc to the star Arcturus and then spike Spica.

On springtime evenings in the Northern Hemisphere, extend the handle of the Big Dipper to arc to Arcturus, spike Spica and slide into the constellation Corvus the Crow. We sometimes call this extended arc the spring semicircle.

Bottom line: On February 22, 2019, find the moon in front of the constellation Virgo and close to Spica, Virgo’s brightest star.

Bruce McClure

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