Moon and Spica on November 20 and 21

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Moon and Spica

The old waning crescent moon can guide you to the bright star Spica on the mornings of November 20 and 21, 2022. A good time to look is roughly an hour before sunrise.

By the way, if you are up early the following day, November 22nd, look for a very slender old crescent moon near the horizon. November 23 is the new moon, and the beginning of the next lunar cycle.

Also, watch for lovely earthshine illuminating the dark side of the moon.

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Spica is the brightest star in Virgo

Spica is the brightest star in the constellation Virgo the Maiden. It’s located 260 light-years away and appears to us on Earth as a single bluish-white star. It shines at magnitude +1.04.

However, Spica is a pair of blue giant stars. Both stars are larger and hotter than our sun, and they’re separated by only 11 million miles (nearly 18 million km). In fact, Spica’s two stars are so close, and they orbit so quickly around each other, that their mutual gravity distorts each star into an egg shape. You’d have to look at the stars’ spectra to even know that there are two of them and not one.

Spica is one of the hottest 1st-magnitude stars. The hottest of the pair is 22,400 Kelvin (about 40,000 F or 22,000 C). That’s scorching in contrast to the sun’s 5,800 Kelvin (about 10,000 F or 5,500 C). By the way, this star might someday explode as a Type II supernova.

Bottom line: Catch the old crescent moon by Spica before sunrise on November 20 and 21, 2022. If you are lucky, you may notice the beautiful glow of earthshine on the thin crescent moon.

For more great observing events in the coming weeks, visit EarthSky’s night sky guide