Tuesday’s night sky will treat us to a partial lunar eclipse during a supermoon. It’s an astronomical wonder that almost everyone in the Western Hemisphere can see under clear skies, and it’s the latest reminder that our planet is part of a larger cosmic system.
When is the lunar eclipse and where can I see it?
This lunar eclipse will occur between 8:41 p.m. Eastern Time on Tuesday and 12:47 a.m. Wednesday, with the maximum partial phase occurring at 10:44 p.m. It will be visible across much of the United States, Canada, Latin America and the Caribbean, Africa, and Europe.
Bruce Betts, the Planetary Society’s chief scientist, will watch the spectacle from his backyard in Pasadena, California.
Eclipses provide an opportunity to feel “the three-dimensional nature of everything,” Dr. Betts said. “It’s something that, in a visceral way, feels like ‘wow.’”
What causes a lunar eclipse?
Lunar eclipses are caused by an alignment of the Sun, Earth, and Moon. Unlike April’s solar eclipse, when the Moon obscured the Sun, this time the Earth’s shadow will spread across the Moon, blocking some or all of its illuminated surface.
There are three types of lunar eclipses. In a penumbral eclipse, the last one occurring in March, the Moon passes only through the outer part, or penumbra, of the Earth’s shadow. The face of the Moon then darkens slightly.
A total lunar eclipse, on the other hand, occurs when the Moon is engulfed by the darkest part of Earth’s shadow, the umbra. In this scenario, the lunar surface glows red, which is called a blood moon.
There are also partial lunar eclipses, like the one observers will see Tuesday night if the sky is clear. Only part of the Moon will pass through Earth’s shadow, blackening part of its surface.
“You’ll see the Earth’s shadow start to eat away at the Moon,” Dr. Betts said, “as if you were taking a little dark bite out of the Moon.”
But, he added, be sure to limit your expectations: Only 3.5 percent of the lunar surface will be obscured during Tuesday’s eclipse.
You may be wondering if such a limited lunar eclipse is really that impressive.
“It’s always worth seeing,” Dr. Betts said. “But if the sky is cloudy, there’s no need to be too sad.”
He recommends taking a moment to scan the night sky for familiar planets and constellations while you’re looking at the moon. “It’s worth a look,” he added.
How to observe a lunar eclipse?
Anyone on the night side of the planet can observe the lunar eclipse, although the view will be better in darker locations. It will be visible to the naked eye, but binoculars or a telescope can be used to zoom in on the finer details of the moon during the event.
The most spectacular part of the show, when the Earth’s shadow obscures part of the lunar surface, will last about an hour. Before and after that, the Moon will pass through the shadow of the Earth’s penumbra, during which its surface will remain full, but with a dimmed brightness.
The penumbral phases of the eclipse will each last about an hour and a half.
The portion of the eclipse you’ll be able to see depends on where you are. In North America, skywatchers on the West Coast will miss most of the first penumbral phase because the Moon will be below the horizon. Those on the East Coast, however, will be able to see the entire event.
After about four hours, the show will be over.
Does this really happen during a supermoon?
September’s full moon is a supermoon. These are the largest and brightest full moons because they occur at the point in the lunar orbit closest to Earth. And this month’s is actually the second of four supermoons in a row this year.
The most recent supermoon, which was also a blue moon, occurred on August 19. The next two supermoons will occur on the evenings of October 17 and November 15.
Are there more astronomical events coming?
Lunar eclipses always precede solar eclipses, which occur when the Moon orbits the other side of Earth, coming directly between our planet and the Sun.
The upcoming solar eclipse won’t look much like April’s widespread event: On October 2, an annular solar eclipse will be visible only from the Pacific Ocean and the tip of South America.
Next March, a total lunar eclipse will grace the night skies of Western Europe, Western Africa and the Americas.
