East of the Sun and West of the Moon

It’s easy to get distracted by what we can see in the sky this week, given that all the naked eye planets in our system and the Moon will be visible, but of course, it’s what we can’t see that’s got my attention.

Okay so here’s the set up: In the morning sky we’ve got this spectacular line up of Jupiter, Venus, Mars, and Saturn. Overnight all week, the Moon is waxing toward Full Phase. And then in the evening, about 45 minutes after sunset, Mercury is emerging over the western horizon.

Then comes Saturday, April 16. There will be about ten minutes between sunset and the Full Moon rising, depending on where you are. And here’s the thing about this particular Full Moon ~ it’s the first one of the year that will occur in the southern celestial hemisphere. We’ll be seeing it in the North, but relative to the stars, it’s below the celestial equator, in the region of Virgo stars. The Moon passes through Virgo every month, but only once every year will the Moon come to Full Phase in this region of the sky, and it’s always, always after the Equinox in March.

So what’s the big deal? Relative to the Earth, the Sun is rising and setting every day. Relative to the stars, the Sun crosses the celestial equator going north only once every year, in March. And because the Full Moon will always be opposite the Sun, when the Sun is above the celestial equator, the Full Moon is below.

Here comes the tricky part: On Saturday, April 16, when the Full Moon rises and the Sun sets, we come to this crazy contradiction when Sun is above the celestial equator but below the horizon, while the Moon is above the horizon but below the celestial equator. That’s the moment of the year’s deep mystery, and now you’ve got a week to prepare!

Meet you in the mystery!


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In the image above from Sky & Telescope, you can see that the planets have lined up to watch Sun and Moon trade places in the hemispheres and perform their cosmic contradiction