20 January 2009

Waning moon meets red giant before dawn

Many of the brightest stars in the sky are located on or very near to the Ecliptic, the path across the sky that the Sun, Moon and planets follow. The Ecliptic crosses over all 12 of the Zodiac constellations as well as pieces of other constellations. Every 29 days as the Moon wanders on its journey around the Earth, we see it crossing through all 12 Zodiac constellations, often with close encounters with the stars in these constellations.

On January 21st, the Moon will cross very near to the bright red star Antares in the constellation Scorpius. Antares is in fact a red supergiant star, thousands of times larger than our Sun but considerably cooler, hence the red color of the light emitted from it. For those in South America, the Moon will appear to pass directly over ("occult") Antares but for us here in San Francisco we will see the Moon and Antares several hours later when they are going to be very near each other but not overlapping.

All of this is visible in the final minutes of the night just before the first light of dawn, but given good weather conditions lately in San Francisco, it should be very visible and quite striking indeed. The view in the above illustration is what you will see from 5:30 to about 6:30 AM, before the light of dawn begins to brighten the sky.

1 comment:

Sidewalk Universe said...

This was a beautiful and sublime astronomical event! I had the opportunity to enjoy this the other morning with my wife as we were getting ready for the day. Lunar conjunctions are awesome!