Like the lyrics to an old Credence Clearwater Revival song, there's a bad—or rather a blood—moon on the rise. A super blood moon, to be exact.
Sky gazers will see a few unusual lunar events at work all at once on Sunday. While certain cultures view the blood moon as a bad omen, it will be their last chance to witness such an event for nearly 20 years.
This rare event's full name is a supermoon lunar eclipse, and it combines a lunar eclipse with a full moon at its closest point to Earth, creating a red-colored moon that appears slightly larger than normal.
To understand this, it is worth breaking it down into pieces. First, why will the moon seem larger in the sky?
The moon does not orbit the Earth in a perfect circle—its orbit is more elliptical. As a result, it does not maintain a steady distance from the planet—sometimes it is closer to Earth, sometimes it is farther away.
The moon is at "apogee" when it is furthest from Earth and "perigee" when closest. A true "supermoon" is a moon that is full, or nearly full, at perigee, which makes it appear roughly 14 percent larger to viewers on Earth than normal.
But, on Sunday, a lunar eclipse will happen at the same time—the Earth will be exactly between the moon and the sun. The Earth will block the light from the sun, giving the moon a reddish hue, a phenomenon sometimes called a "blood moon."
The combination of these different, uncommon events gives us the supermoon lunar eclipse. Supermoon lunar eclipses have only happened five times since 1900—the last occurrence was in 1982, according to NASA.
Sunday night's supermoon lunar eclipse will be visible to people in the United States and much of the rest of the world, according to NASA. It may be worth watching, especially because it will not occur again until 2033.
The eclipse will be visible to North and South America, Europe, Africa, and parts of West Asia and the eastern Pacific. The Earth's shadow will begin to darken the moon after 8pm EDT, but the full eclipse will start at 10:11pm EDT and peak at 10:47pm EDT, according to NASA.
For those outside the viewing area, NASA TV will also broadcast the event, from 8pm EDT until at least 11:30pm EDT.