moonshine

The First and Last Supermoon of 2017: What It Is, and Why It Matters

On Sunday, a rare synergy will bring a brilliant spectacle of a giant full moon.

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On Sunday evening, a spectacular supermoon will rise above the horizon.

Even if you aren’t the type to pay much heed to lunar activities—after all, Earth has enough going on as it is—this is one of those astronomical events that will catch the eye of even the most downward-gazing, grumpy amongst us.

What makes this particular moon “super” is quite simple. According to NASA, Sunday’s moon will be up to 16 percent brighter and, at its largest, up to 7 percent larger than usual, thanks to the shape of the moon’s orbit, which is not perfectly circular but rather elliptical. The apogee is the far end of the moon’s orbit; the perigee is the closer end of the moon’s orbit.

Full moons can occur at any point in the moon’s elliptical orbit, but when the full moon occurs right at the perigee, the moon appears larger and brighter, resulting in what astronomers call the supermoon. It’s also important to remember that the moon’s distance from Earth can vary from 226,000 to 252,000 miles away—a variability that is longer than the circumference of the Earth.

This supermoon—often referred to as the “cold moon” in the Northern Hemisphere, a marker that winter is here—will be visible on Sunday morning as the sun rises at 10:47 a.m. EST. But the best time to view it will be in the earliest hours of dawn on Monday at 4 a.m. EST, when it will be most visible. That said, if waking up early on a cold December Monday morning doesn’t appeal to you, the supermoon will also be viewable at night. A difference of a few percentage points in brightness and light might seem shrug-worthy, but the fact that the moon is close to Earth will magnify its visual power.

If this year’s total solar eclipse was any indicator, the supermoon could be the harbinger of a few moments of beautiful, awestruck silence and wonder. In a time when we are glued to the constant, eerie glow of our digital lives and are endlessly pinged with anxiety-inducing news, the chance to stretch our necks and direct our gaze skyward, to what our ancestors stared at as they explored our young, untouched world, will be, well, nice. It’s not as rare as a total solar eclipse, and not as brief and fleeting, but its infrequent appearance and sheer beauty is a gorgeous, timely reminder that the universe holds secrets that go far beyond the slog of daily life on Earth.

NASA has made sure to let us know that the usual lunar conspiracies are afoot—and flat-out wrong. “A supermoon will not cause extreme flooding, earthquakes, fires, volcanic eruptions, severe weather, nor tsunamis, despite what incorrect and non-scientific speculators might suggest,” they warned.

If you happen to live in an area that gets annoyingly clouded over the night of the first and last supermoon of 2017, don’t worry: You can still view it through a free webcast from the Virtual Telescope Project. Time is on your side, too: Sunday’s supermoon is the first in a set of three supermoons set to shine down on Earth. The next two full moons—in January and February of 2018—are going to be supermoons as well. It might be a cold winter, but the moon will be consistently, awesomely bright.