Look Up Tonight! The Super Beaver Moon Is Here

Have you heard about the supermoon tonight? Have you heard that it’s going to be big? Huge! Terrifying! The last time a full moon appeared this large, they say, the astronaut corps consisted of a single monkey named Albert, who would soon be shot into space on a V2 rocket. (Things did not end well for Albert, nor for his successor, Albert II.) It hasn’t seemed this big since 1948! What celestial chaos can we expect?

Take a deep breath. Technically, the supermoon’s peak will occur tomorrow morning, November 14, at 8:52 a.m. EST. But we think you should go out tonight (and maybe tomorrow night too). It’s going to be a pretty big full moon, and yes, it will likely be the biggest you’ve ever seen (and will not see again until November 25, 2034), but “biggest” is a relative term. If you didn’t already know that this supermoon would be juicing, you probably wouldn’t have really noticed. So what’s going on up there?


Relative to the Earth, the Moon is really big. Only gas giants Saturn and Jupiter possess larger moons, though it seems more through attrition than anything else. They’re working with overwhelmingly superior planetary sizes and moon totals, in comparison to our pale blue dot. Jupiter’s diameter is 11 times that of the Earth; Saturn’s diameter, 9.5 times. The two colossal planets have in their orbits a total of 129 known moons—and yet all but four of them are smaller than the lone Moon of our little world (our newly discovered mini-moon–like asteroid excluded).

If our moon is unique, its orbit is even wackier. Some might call it downright weird. The Moon's orbit is really far from Earth, and the tilt of its orbit is large to the point of being inexplicable. Scientists are pretty certain that a massive collision between the Earth and another planet sent debris into space that would eventually coalesce to form the Moon. Existing models for this, however, have never adequately been able to account for the moon’s large tilt.

One recent hypothesis for the Moon’s odd behavior states that the “Big Whack” changed our axial tilt by as much as 80 degrees and sent us spinning incredibly fast. That initial high tilt―the Earth might once have spun on its side―would explain how we managed eventually to slow back down. According to the same model, the Moon’s orbit of the Earth on the outset was 15 times closer than it is today, and that as it migrated away from the Earth, the Sun began to exert influence on its orbit. The whack, the tilt, the speed, the Sun―taken together, they offer a compelling explanation for the Moon’s odd orbital tilt today.


Because the Moon’s orbit is elliptical, when it is closest to the Earth in a revolution―a.k.a. at perigee―it appears larger; when it is at apogee, or farthest away, it appears smaller. Perigee and apogee are not identical from orbit to orbit. The Earth and the Moon both fall under the gravitational influence of the Sun.

When perigee coincides with a full moon, you get what is colloquially called a “supermoon.” (Not an astronomy term.) The full moon in November is called the Beaver Moon. (Also not an astronomy term.) Long ago, this was considered the time to set your beaver traps so that you would have enough pelts to make winterwear. Because tonight’s perigee brings the surfaces of the Earth and the moon a scant 216,486 miles apart, the supermoon will appear up to 14 percent bigger. But unless you’re a devoted Moon watcher, you might have a hard time spotting that. The moon will also be 30 percent brighter, NASA says, because of the Earth’s proximity in its orbit from the Sun. In all, it’s going to be a gorgeous super beaver moon, but it won’t change your life. Set your expectations accordingly.

So hope for clear skies, go outside―maybe even dust off the telescope, uncork a bottle of wine, and make an evening of it―and enjoy the Moon for the same reason you enjoy the constellations, meteor showers, the movement of the planets, and the appearance of the International Space Station. (If it's cloudy, check out the livestream from Slooh.) Because space isn’t somewhere out there. Earth is as much “in space” as any other object in the universe. We are part of space. And to peer into the night sky is to look simultaneously at the distant past of the universe, and the near future of humankind.

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Remembering Comet Hale-Bopp's Unlikely Discovery
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Comet Hale-Bopp was a sensation in the mid-1990s. It was visible to the naked eye for 18 months, shattering a nine-month record previously set in 1811. It inspired a doomsday cult, wild late-night radio theories about extraterrestrials, and plenty of actual science. But a year before it became visible to normal observers, two men independently and simultaneously discovered it in a coincidence of astronomical proportions.

On the night of July 22-23, 1995, Alan Hale was engaged in his favorite hobby: looking at comets. It was the first clear night in his area for about 10 days, so he decided to haul out his telescope and see what he could see. In the driveway of his New Mexico home, he set up his Meade DS-16 telescope and located Periodic Comet Clark, a known comet. He planned to wait a few hours and observe another known comet (Periodic Comet d'Arrest) when it came into view. To kill time, he pointed his telescope at M70, a globular cluster in the Sagittarius system.

Comet Hale-Bopp streaks through a starry night sky.
Comet Hale-Bopp streaks through the sky over Merrit Island, Florida, south of Kennedy Space Center.
George Shelton // AFP // Getty Images

Hale was both an amateur astronomer and a professional. His interest in spotting comets was actually the amateur part, thought it would make his name famous. Hale's day jobs included stints at JPL in Pasadena and the Southwest Institute for Space Research in Cloudcroft, New Mexico. But that night, peering at M70, he wrote, "I immediately noticed a fuzzy object in the field that hadn't been there when I had looked at M70 two weeks earlier." He double-checked that he was looking in the right place, and then started to get excited.

In order to verify that the fuzzy object wasn't something astronomers already knew about, Hale consulted his deep-sky catalogues and also ran a computer search using the International Astronomical Union's computer at Harvard University. Convinced that he had found something new, Hale fired off an email very early on the morning of July 23 to the IAU's Central Bureau for Astronomical Telegrams, telling them what he had found, along with detailed instructions on how to verify it themselves. Hale also tracked the object as it moved, until it moved out of view. It was definitely a comet, and it was definitely new.

Meanwhile, Tom Bopp was in Arizona, also hunting for comets. At the time, Bopp was working at a construction materials company in Phoenix, but he was also an accomplished amateur astronomer, with decades of experience observing deep-sky objects. That night, Bopp vas visiting the remote Vekol Ranch, 90 miles south of Phoenix, known as a great location for dark-sky viewing. He was with a group of friends, which was important because Bopp didn't actually own a telescope.

The Bopp group looked through their various telescopes, observing all sorts of deep-sky objects late into the night. Bopp's friend Jim Stevens had set up his homemade 17.5-inch Dobsonian reflector telescope and made some observations. Stevens finished an observation, then left his telescope to consult a star atlas and figure out what to aim at next. While Stevens was occupied, Bopp peered into Stevens's telescope and saw a fuzzy object enter the field of view, near M70. He called his friends over to have a look.

The Bopp group proceeded to track the fuzzy object for several hours, just as Hale was doing over in New Mexico. By tracking its movement relative to background stars, they (like Hale) concluded that it was a comet. When the comet left his view, Bopp drove to a Western Union and sent a telegram to the Central Bureau for Astronomical Telegrams. (For historical perspective, telegrams were extremely outdated in 1995, but technically they were still a thing.)

Brian Marsden at the Central Bureau received Bopp's telegram hours later, after getting a few followup emails from Hale with additional details. Comparing the times of discovery, Marsden realized that the two men had discovered the comet simultaneously. According to NASA, it was the farthest comet ever to be discovered by amateur astronomers—it was 7.15 Astronomical Units (AU) from our sun. That's 665 million miles. Not bad for a pair of amateurs, one using a homemade telescope!

The Central Bureau verified the findings and about 12 hours after the initial discovery, issued IAU Circular 6187, designating it C/1995 O1 Hale-Bopp. The circular read, in part: "All observers note the comet to be diffuse with some condensation and no tail, motion toward the west-northwest."

Four men smile, posing outdoors next to a large telescope at night.
Comet hunters (L to R): David Levy, Dr. Don Yeomans, Dr. Alan Hale and Thomas Bopp pose next to a telescope during a public viewing of the Hale-Bopp and Wild-2 comets.
Mike Nelson // AFP // Getty Images

Less than a year later, Comet Hale-Bopp came into plain view, and the rest is history. It was a thousand times brighter than Halley's Comet, which had caused a major stir in its most recent appearance in the 1980s. Comet Hale-Bopp will return, much like Halley's Comet, but it won't be until the year 4385. (And incidentally, it was previously visible circa 2200 BCE.)

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NASA/JPL-Caltech/Space Science Institute
Big Questions
How Many Rings Does Saturn Have?
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NASA/JPL-Caltech/Space Science Institute

Of all the planets surrounded by rings, Saturn is the most famous. These planetary rings are massive enough that Galileo was able to see them using a simple telescope way back in 1610, though it wasn't until half a century later that another scientist was able to figure out what the "arms" Galileo saw actually were. NASA has since called them "the most recognized characteristic of any world in our solar system."

So how many rings does Saturn have, anyway? If you can see them from your backyard, there must be a lot, right?

Scientists don't know for sure exactly how many rings Saturn has. There are eight main, named ring groups that stretch across 175,000 miles, but there are far more than eight rings. These systems are named with letters of the alphabet, in order of their discovery. (Astronomers have known about ring groups A, B, and C since the 17th century, while others are newer discoveries. (The most recent was just discovered in 2009.)

The rings we can see in images of the planet—even high-resolution images—aren't single rings, per se, but are in fact comprised of thousands of smaller ringlets and can differ a lot in appearance, showing irregular ripples, kinks, and spokes. The chunky particles of ice that make up Saturn's rings vary in size from as small as a speck of dust to as large as a mountain.

While the gaps between Saturn's rings are small, the 26-mile-wide Keeler Gap is large enough to contain multiple moons, albeit very small ones. The largest ring system—the one discovered in 2009—starts 3.7 million miles away from Saturn itself and its material extends another 7.4 million miles out, though it's nearly invisible without the help of an infrared camera.

Researchers are still discovering new rings as well as new insights into the features of Saturn's already-known ring systems. In the early 1980s, NASA's Voyager missions took the first high-resolution images of Saturn and its rings, revealing previously unknown kinks in one of the narrower rings, known as the F ring. In 1997, NASA sent the Cassini orbiter to continue the space agency's study of the ringed planet, leading to the discovery of new rings, so faint that they remained unknown until Cassini's arrival in 2006. Before Cassini is sent to burn up in Saturn's atmosphere in September 2017, it's taking 22 dives through the space between the planet and its rings, bringing back new, up-close revelations about the ring system before the spacecraft dives to its death.

Though it's certainly possible to see Saturn's rings without any fancy equipment, using a low-end telescope at your house, that doesn't mean you always can. It depends on the way the planet is tilted; if you're looking at the rings edge-on, they may look like a flat line or, depending on the magnification, you might not be able to see them at all. However, 2017 happens to be a good year to see the sixth planet, so you're in luck.

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