When we picture the moon we think of its changing phases — crescent, half, full and new. But throughout the course of its orbit its apparent size also changes. This is because the moon orbits the Earth in an ellipse, not a circle. An ellipse resembles an oval with the Earth positioned off-center, so that with one side of the moon's orbit is closer to the planet than the other. Virtually every orbiting body follows an elliptical path. That includes planets around the sun, moons around other planets, stars around stars, and even little galaxies around big ones. While circular orbits may be possible in theory, ellipses are the rule. Circles are just too hard to maintain. Gravity operates over long distances, so the slightest tug from another massive body even millions of miles away will soon warp a circle into an ellipse. The moon's distance from Earth typically varies from about 222,000 miles at its closest point, called perigee , to 253,000 miles at apogee its most distant. That's a difference of more than 30,000 miles or about four times Earth's diameter. A full perigee moon, also popularly known as a supermoon, is about 14% larger than an apogee moon, also called a micromoon. If we could see them side by side, the size difference would be immediately obvious. As the moon's distance changes, so too its brightness and velocity. When the moon approaches perigee, it speeds up and gets brighter because it's closer to us. Around the time of apogee, it's a little fainter and moves more slowly. April's full moon is called the Pink Moon and named for moss pink, a phlox found in the eastern U.S. In our region, it might be better named the Mud Moon, what with our bounty of thawing earth. If you live in Duluth, you can watch it rise from Lake Superior on Saturday evening, April 12 at 7:56 p.m., just 3 minutes after sunset. The Pink Moon will also be the most distant full moon of the year — the micro-est of micromoons. April's apogee occurs close to the time of full moon, making for a close fit. May's moon won't be quite as distant because it will be full when it's farther from the apogee point. The distance to the full moon keeps decreasing each month until it reaches a minimum on Nov. 4. That night, perigee happens within hours of full moon, making the Beaver Moon the closest supermoon of 2025. People often ask if you can see the difference between a micromoon and supermoon with your eyes. It's really tough because there's no way to view them side by side. Here's an experiment you might try. Use a fixed object like a power pole and stand in a spot where the pole exactly covers the moon on April 12 (or close to that date). Measure your distance to the pole's base and also note the moon's altitude above the horizon. Then return on Nov. 4 during the supermoon, stand the exact same distance from the pole and observe the moon at the same height above the horizon. This time, its light should "spill" beyond the pole's edges. Or you can take photos of both the micromoon and supermoon with your smartphone, arrange the images side-by-side with a photo program, and voila! You'll see the difference right in front of your eyes. Saturday's Pink Moon will rise in Virgo the virgin, very close to the constellation's brightest star Spica (SPY-kuh). During early evening hours the moon will sit just one full-moon-diameter below the star. Will you be able to spot Spica through the lunar glare? If you look carefully I'm confident you'll see it, but if you have any difficulty, bring binoculars along. Spica is a massive binary star about 250 light-years from Earth. The larger of the pair is more than 20,000 times as luminous and 11 times as massive as the sun. These hefty numbers make it a candidate to explode as a supernova sometime in the distant future. The companion is no slouch either, with a diameter almost four times that of the sun and a mass seven times solar. The two behemoths are only about 12 million miles apart — three times closer than Mercury to the sun — and orbit each other every 4 days.
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