Most of us venture out early to watch a sunrise. Today (March 28) I pursued the setting full moon instead. Somehow it felt wrong to turn my back on the sun, but I summoned the will and fixed my gaze on its distant cousin.

During a moonrise, the squished, pink-orange moon at the horizon rounds out into a brilliant, stone-white disk a hour later. This morning the sun rose shortly before moonset, so the low-hanging, golden moon turned pale blue as it approached the horizon. Trees soon obscured it from view, so I drove to a hilltop hoping for one last look. No dice.

Now I'm waiting for the Earth to rotate another 12 hours to carry the orb of night back to the eastern horizon. If you'd like to join me for the moonrise, click here to find out exactly when it will pop up for your location Sunday night (March 28).

What a haul! A robin holds several worms with its beak. (Brocken Inaglory / CC BY-SA 4.0)
What a haul! A robin holds several worms with its beak. (Brocken Inaglory / CC BY-SA 4.0)

The Full Worm Moon will rise a little south of east close to sunset and remain visible all night. The time of greatest "fullness" occurs this afternoon Central Time, so the moon will appear ever so slightly less than full by tonight. Worm Moon refers to the worms that begin to emerge from the ground this time of year. Worms are a favorite food of robins which also return in March, at least where I live. According to bird expert Laura Erickson, when a robin cocks its head it's using one eye to look for worms in their underground tunnels, with the other eye focused above, keeping watch for predators.

WDAY logo
listen live
watch live
Newsletter signup for email alerts

The full lies opposite the sun in the sky, rising around the time the sun sets. The diagram shows the moon's position for March 28. (Stellarium)
The full lies opposite the sun in the sky, rising around the time the sun sets. The diagram shows the moon's position for March 28. (Stellarium)

The moon shines from the constellation Virgo exactly opposite the sun, which is currently in Pisces. Virgo sits halfway between the full moon's high point in Taurus, which it occupies in late December, and its low point in Sagittarius, where you'll find it around the summer solstice. When you're out looking at tonight's full moon, recall how much higher it appeared in the early winter sky. Three months from now, it will describe a lower arc yet.

This is how the sun, Earth and moon line up at full moon as seen from space. The sun and moon lie opposite one another with the Earth in between. (Bob King)
This is how the sun, Earth and moon line up at full moon as seen from space. The sun and moon lie opposite one another with the Earth in between. (Bob King)

Since a full moon by definition lies directly opposite the sun, it keeps pace with it, sliding down the sky as the sun moves up the sky during the six months from winter to summer. After the summer solstice, the sun begins moving down the sky again, leaving the full moon nowhere to go but up! This tandem, up-and-down cycle of the sun and moon occurs because of Earth's tilted axis, which makes the sun appear to bob up and down the sky during the year. If the axis weren't tilted the sun's path would never vary, and there would be no seasons.

You don't have to think about any of that when you watch Sunday night's moonrise. Find a comfortable spot with a horizon view to the east and let the Earth do its work. As the planet spins, the moon will come into view, squished and yellowed by the atmosphere. Enjoy the weirdness of the sight and the transition to a normal, circular disk. At rising, binoculars will enhance the appearance of the moon's green-fringed upper edge and red-fringed bottom. This is caused by the air acting like a prism and refracting the moon's light into a pseudo-rainbow.

Despite the clear difference in the apparent size of a close supermoon and a distant or "micromoon," it's nearly impossible to compare their sizes in real life because you can only see one full moon at a time. (NASA/JPL-Caltech)
Despite the clear difference in the apparent size of a close supermoon and a distant or "micromoon," it's nearly impossible to compare their sizes in real life because you can only see one full moon at a time. (NASA/JPL-Caltech)

Tonight's full moon is the first of three supermoons this year. Supermoon is the name given to a full moon that occurs around the time it's closest to the Earth in its orbit, called perigee. Perigee occurs on March 30 when the moon will lie 226,886 miles (360,310 km) from Earth, about 12,000 miles closer than average. That will make the moon look a little bigger and brighter than normal. The next supermoons happen on April 27 and May 26. May's will be the closest of the year with the moon just 222,021 miles (357,309 km) from your rooftop on the 27th.

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.