This month’s full moon has everything: As the first one post–fall equinox, it is known as the harvest moon. On its closest approach to Earth for the year, it will also be a super moon—the most super in a year of super moons.
And, the pièce de résistance: Just when it gets plumpest, this most super of moons will give us an eclipse the color of blood. Not only that, but Turtle Island, especially the East Coast, will get the full show. It is the fourth, and most spectacular, in a tetrad that has been going on since April 2014.
“On the night of September 27–28, the Full Moon plunges through Earth’s shadow for the second time this year, and this time, it’s the biggest Full Moon of 2015,” says Astronomy.com. “The resulting total lunar eclipse lasts more than an hour and occurs during the evening across the Americas.”
The fun starts imperceptibly at 8:12 p.m. Eastern Daylight Time with the first hint, the penumbral eclipse.
“This moment marks when the Moon enters Earth’s lighter outer shadow,” says Astronomy.com. “If you don’t notice the start, you won’t be alone. Most people don’t spot any change to the Moon’s appearance until just before the partial eclipse begins.”
The partial eclipse, when the moon enters the dark inner shadow of Earth (the umbra), begins at 9:07 p.m. By 10:11 p.m., the moon will be completely engulfed by the shadow, and full totality will have begun. And then it will last … and last … for a full 72 minutes, Astronomy.com says, with the point of greatest eclipse coming at 10:47 p.m.
Then oglers will get to watch it unspool, with totality ending at 11:23 p.m. as the moon begins to emerge from the umbra into a partial eclipse. That portion will end at 12:27 a.m. on September 28, with the moon easing out of the penumbra, or secondary shadow (the imperceptible part) at 1:22 a.m.
The stages of partial eclipse will be dark, but during its fully total phase, the moon will suddenly appear blood red. This is because of the way the sun’s light reflects and bounces off Earth’s atmosphere, filtering out all but the rosy and copper wavelengths.
What makes this a pizza-pie supermoon? The moon’s orbit is elliptical, so its distance from Earth varies throughout the year. Other super moons occurred when the moon was the closest it gets to Earth for the month. This one happens to be the moon’s closest approach for the year, making it the 2015 super moon to end all super moons. That puts it 221,753 miles from us, according to Earthsky.org. In contrast, the farthest the moon ever gets from us is 252,088 miles, says Space.com. In total, there have been six super moons this year, three of them new (thus invisible) and three, including this one, big and bright.
Here’s what all that translates to in the sky.
The moon hits fullness on September 27 at 10:51 p.m. EDT and makes its closest approach to Earth about an hour later, Earthsky.org says. To have this many factors converging makes for a truly unique celestial event.
“Supermoon eclipses are rare; the last one occurred in 1982 and the next won’t happen till 2033,” notes Universetoday.com.
More from NASA on this rare sight is below.