If you stay up very late tonight, you’ll get rewarded with a near-total lunar eclipse.
Weather permitting, this eclipse — the longest lunar eclipse in almost 600 years — should be widely visible across North America.
During a lunar eclipse, the Earth finds itself between the sun and the moon. The moon goes dark as it passes through Earth's shadow, Sky & Telescope senior editor Kelly Beatty says.
"There’s an outer faint shadow and then a really dark core," he says. "The moon is almost but not quite going to be completely within that dark core."
This "slow-motion event" could last for several hours depending on how clear the sky is, Beatty says.
Depending on the location, earthlings may first notice some dinginess on one side of the moon, like a bite was taken out of it. Observers can tell the moon is moving into Earth's shadow as the bite gets bigger.
"The bite will get bigger until there’s just a little sliver left on the bottom of the moon," he says. "That’s the 1% of the moon’s disk that didn’t make it inside this umbra, the dark core."
That's right, this eclipse will cover 99% of the moon's area and 97% of its diameter, Beatty says. Because it's almost a total eclipse, the moon should take on a reddish color.
"Wherever you are, if the moon is in your sky when this eclipse takes place, it’s all happening for everybody at the same time," he says. "But based on your time zone, it’ll be different clock time."
In Eastern Time, the eclipse will start around 1 a.m. Friday morning, he says. At 2:18 a.m., the first bite of the moon will be visible at the edge.
The eclipse will peak at 4:03 a.m. Eastern Time. If you can only keep your eyes open for a few minutes, Beatty says this is the moment you don't want to miss. Then, the eclipse will reverse and end at 5:47 a.m. The last vestige will come right before dawn at 7 a.m.
The last time a lunar eclipse lasted this long was in the year 1440, he says, and the next time won't be until 2669.
There's nothing too rare about this eclipse — but it will look amazing. Beatty likes to watch the moon enter and leave the Earth's shadow.
"To me, lunar eclipses and solar eclipses, too, are sort of a manifestation of the clockwork of the solar system," he says.
Onlookers can see the eclipse with the naked eye. Beatty recommends locating the moon before the eclipse begins in case the sky gets hazy.
Stargazers can use binoculars or a telescope to see the Pleiades star cluster several degrees above the moon, he says.
And over the next several weeks, you can see three of the four brightest planets in the sky in one full swoop — a shining cosmic coincidence. Beatty says folks can see "a brilliant beacon in the sky" toward the west right after sunset.
"That’s the planet Venus," he says. "Now swing your gaze over to the left, do a left turn and above the southern horizon, you’ll see another bright beacon. That’s Jupiter. And in between them, closer to Jupiter, is Saturn."
Julia Corcoran produced and edited this interview for broadcast with Peter O’Dowd. Allison Hagan adapted it for the web.
This article was originally published on WBUR.org.
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