A blood-red moon will dominate the sky Sunday night, delighting some sky watchers while leaving others in fear that the apocalypse is nigh.
The lunar eclipse and supermoon will happen simultaneously, an event the world hasn't seen in more than three decades. The last one was in 1982, according to NASA.
Earthlings who miss Sunday night's celestial show will have to wait about 18 years for their chance to catch another supermoon eclipse, which NASA calculates will return in 2033.
"That's rare because it's something an entire generation may not have seen," says NASA's Noah Pedro in a statement about the event.
A red moon
Late Sunday evening, people in many areas of the world will be able to look up at the sky and see a total lunar eclipse, strengthened by a supermoon.
On average, the moon passes through some of the Earth's shadow two to four times every year resulting in an eclipse, according to NASA.
Depending on which portion of the Earth's shadow it passes through, humans can glimpse a very subtle, partial or total lunar eclipse. The latter make up about 35 per cent of eclipses.
'When the moon is as close to the Earth as it possibly can be, then it appears as large as it can ever be in our sky.' - Paul Delaney, York University professor
During a total eclipse, the Earth blocks nearly all direct sunlight from reaching the moon.
Indirect sunlight still manages to make it there, though. First it passes through the Earth's atmosphere, which filters out most of the light, except for much of the red or orange hues.
This makes the moon appear a "rusty, reddy, orange colour," says Paul Delaney, a professor at York University's physics and astronomy department.
The amount of dust and clouds in Earth's atmosphere during the total eclipse determine what colour the moon appears. It could be red, orange, yellow or brown.
This total lunar eclipse is a special treat for Canadians, he says, as they'll likely be able to see it from anywhere in the country.
"This is a goodie," he says. "Everyone will be able to see it."
That is, unless bad weather, like clouds or rain, persists at the same time.
A partial eclipse will be visible starting at 9:07 p.m. ET on Sunday, and the total eclipse is expected to begin about an hour later, at 10:11 p.m. After it wanes around 11:23 p.m., a partial eclipse will remain visible until 12:27 a.m. Monday.
What makes a moon super?
The second celestial event of the night, a supermoon, will make the moon seem bigger and brighter in the night sky. A supermoon appears when the moon is in its full phase and the orbit brings it closer to Earth than usual.
The moon ranges from roughly 355,000 to 405,000 kilometres away from Earth during its orbit, Delaney says, and on Sunday it'll be just 357,000 kilometres away.
This makes it look 14 per cent larger and 30 per cent brighter than when it's farther away, according to NASA.
While the size difference is nearly imperceptible to the naked human eye, "when the moon is as close to the Earth as it possibly can be, then it appears as large as it can ever be in our sky," Delaney says.
Both a supermoon and lunar eclipse are fairly common on their own, but the pair occur together only once every few decades.
Final eclipse of the tetrad
Adding to the mystique of Sunday's events, this lunar eclipse also happens to be the final one in a tetrad, a series of four total eclipses separated by about six months.
In this tetrad, the previous three total lunar eclipses took place on April 15 and Oct. 8 in 2014 and April 4 this year.
Delaney estimates eclipses align into a tetrad roughly once every decade. However, between 1600 and 1900, not a single full tetrad occurred.
This century, NASA calculates that there will be eight tetrads. The last one started in 2003 and was completed on Oct. 28, 2004. The next one is set to begin April 25, 2032.
Blood moon prophecies
Not everyone, however, is excited about this soon-to-be completed total lunar eclipse sequence.
Some Christian pastors have dubbed this particular sequence the "four blood moons" — perhaps due to the reddish tone of a moon during a total lunar eclipse.
They say it is a biblical prophecy heralding a big event.
John Hagee, a pastor for his self-named ministry, wrote a book called Four Blood Moons: Something Is About to Change. He points to several Bible passages that indicate events similar to a tetrad will lead to the second coming of Christ.
These pastors' prophecies have given wave to a blood moon apocalypse belief system, where some predict the end of the world will come after the total supermoon eclipse on Sunday.
Astronomers aren't buying into any greater significance of the tetrad, supermoon and total lunar eclipse than geometric alignment.
"The only thing that will happen on Earth during an eclipse is that people will wake up the next morning with neck pain because they spent the night looking up," said NASA's Petro.
Delaney hopes people will do just that, especially considering "the really neat stuff" takes place before midnight for many time zones.
"This is a great opportunity to go and see astronomy at its best."
When you can see Sunday night's eclipse across Canada
The following times are averages for the listed regions and will vary somewhat depending on exact location.
Halifax/East Coast: At 9:11 p.m. AT on Sunday, the penumbral eclipse begins, when the Earth's partial shadow starts to touch the moon's face. At 10:07, the partial eclipse starts and the moon will begin to become red. Total eclipse starts at 11:11 p.m., peaks at 11:47 p.m. and ends at 12:23 a.m. The whole show will be over by 2:22 a.m. Look for the moon between about 23 and 45 degrees up from the horizon.
Montreal/Toronto/Ottawa: The penumbral eclipse begins at 8:11 p.m. ET. At 9:07, the partial eclipse starts. Total eclipse starts at 10:11, peaks at 10:47 and ends at 11:23 p.m. The whole show will be over by 1:22 a.m. The spectacle will begin fairly low on the horizon, at about 12 to 15 degrees depending on location, while during its peak the eclipse will be between 36 and 38 degrees degrees above the horizon.
Prairies: Viewers in the Prairies will miss some of the preshow because the moon will still be below the horizon for the early penumbral stage. The partial eclipse, when the moon will start turning red, begins at 8:07 p.m. CT in Winnipeg and 7:07 p.m. CST in Regina and Saskatoon, where it will be particularly close to the eastern horizon. Total eclipse starts at 9:11 in Winnipeg and 8:11 in Regina and Saskatoon, peaks at 9:47 and 8:47, respectively, and ends at 10:23 CT and 9:23 CST. Try to watch from an area without tall buildings or trees to the east and southeast, because the eclipse won't be high in the sky.
Calgary/Edmonton: The sun won't set, and the moon won't rise, until after the eclipse has begun, so viewers in Alberta will miss the early part of the show. Moonrise is around 7:20 p.m. MT, when the moon will already be partially eclipsed. Total eclipse starts at 8:11, peaks at 8:47 and ends at 9:23 p.m. The whole thing will be over by 11:22 p.m. Be sure to find a viewing spot with a clear sightline, because at its peak, the eclipse will appear only about 12 degrees above the southeastern horizon.
Vancouver: Don't expect to see any of the preliminaries on the West Coast. The celestial show will only barely be visible just above the eastern horizon as the total eclipse is already beginning, around 7:11 p.m. PT. It will peak at 7:47 – when it will be just seven degrees above the horizon – and end at 8:23, with the closing penumbral stages over by 10:22 p.m.