Major conjunction of the Moon and Venus next Saturday

Conjunctions don't mean anything, astronomically speaking. With an occultation, when one object passes in front of another, you can glean all sorts of information from optical effects. But in a conjunction, objects in the sky just appear to be close to each other. No real information can be derived. It's just pretty. And maybe that means that more people will look up at the sky on that night.

Next Saturday, May 19, a very young, thin crescent Moon will snuggle up close to Venus, the third-brightest object in the sky (after the Sun and the Moon) - much closer than last month. They will be visible in the Western sky (the direction where the sun sets) just after sunset. If you're a determined observer, you'll be able to see them before sunset. The crescent Moon should be easy to find, and Venus will be right near it.

As the sky begins to darken, look for another fascinating sight: the dark parts of the Moon will take on a faint, ghostly glow. This is called "Earthshine", and it is caused by sunlight being reflected off of Earth's atmosphere illuminating the parts of the Moon that are facing away from the Sun. (See this post from last month or this post from March for illustrations of Earthshine. Remember, the phases of the Earth as seen from the Moon are the opposite of the phases of the Moon as seen from the Earth. While we are looking at a mostly-darkened Moon with a thin crescent illuminated, an observer on the Moon would see a mostly-illuminated Earth with a thin crescent of darkness. The sunlight reflected from the Earth lights up the Moon much like a bright Moon will light up an otherwise unlit landscape at night.)

So, if you have clear skies next Saturday, May 19, try to see this conjunction. It should be beautiful!