Happy equinox, Earthlings! March 20 marks the spring equinox, one of two seasonal markers in Earth’s year-long orbit when the Sun appears to shine directly over the equator, and daytime and nighttime are nearly equal lengths–12 hours–everywhere on the planet.
It’s the start of astronomical spring in the Northern Hemisphere, meaning more sunlight and longer days. From here until the beginning of fall, daytime will be longer than nighttime as the Sun travels a longer, higher arc across the sky each day, reaching a peak at the start of summer. It’s just the opposite in the Southern Hemisphere, where March 20 marks the fall equinox.
What’s more? The first full Moon of spring will rise tonight, lighting the skies on the equinox. Usually, a full Moon arrives a few days to weeks before or after the equinox. It’s close, but not a perfect match. Tonight’s full Moon, however, reaches maximum illumination less than four hours after the equinox. There hasn’t been a comparable coincidence since the spring equinox in 2000.
And because the Moon is near perigee, it qualifies as a supermoon–the third and final of 2019. It’s not a big supermoon, so you won’t really be able to see the difference between this full Moon and any other one with your eyes. But keep an keep an eye on the Moon as it rises and creeps above the eastern skyline. A low-hanging Moon can appear strangely inflated. This is the Moon illusion at work.
Super or seemingly not, it’s a rare celestial coincidence to usher in springtime.
According to many Native American traditions, July is normally the month when the new antlers of buck deer emerge from their foreheads in coatings of velvety fur — hence one of the names for the full moon.
The full moon in July also is called the Thunder Moon because of the frequency of thunderstorms during this hot, dry month.
Yet another name for the seventh full moon of the calendar year is the Hay Moon — likely no surprise to anyone living on a farm, who may have spent recent weeks cutting, baling and storing hay for the coming winter. And for those of us who suffer from summer allergies, the Hay Moon may be the most familiar moon of all.
On Mar. 19 the full moon will brighten the night sky as the biggest full moon seen in almost two decades. The moon will be at perigee, its closest point to Earth — only 221,565 miles (356,575 km) away.
The moon’s orbit around Earth is not circular — it’s elliptical. One part of the orbit, the perigee, is closer to the Earth than the other, the apogee. The image is NOT to scale — the eccentricity of the moon’s orbit has been exaggerated.
The last time the full moon coincided with an extreme perigee was Mar. 8, 1993 when it was a distance of 221,536 miles (356,528 km) from the Earth.
This Saturday night, the moon will appear 14 percent bigger and 30 percent brighter in the sky than lesser full moons — when the moon is farthest from the Earth. But to the casual observer, it may difficult to tell the difference.
For the best viewing — and dependent upon clear skies, of course– look when the moon is near the horizon at sunset. The orbital geometry combined with the moon’s location near the horizon, put in scale next to buildings and trees, will combine to produce an awesome sight.