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Look Up Again! The Final Supermoon of 2016 Rises Tonight

Last month's supermoon: on November 14, you could see it rising above Athens through the propylaea of the Acropolis. Image Credit: AFP/Aris Messinis/Getty Images

 
You might be sick to death of hearing about "supermoons." If that's the case, I bring good news: tonight, December 13, you'll see the final supermoon of 2016. If you're not sick of them, I also bring good news, because you have one more supermoon to see.

Of course, where there is good news there is bad, and it's this: The supermoon will make it very difficult to catch the Geminid meteor shower, which peaks tonight. Don't give up, however; because of the sheer volume of meteors that comprise the Geminids, you might see some shooting across the sky.

WHAT IS A SUPERMOON?

Before last year, when the red harvest supermoon took over the world, you might never have heard of a supermoon. And now we've had three in a row to close out the year: October's super hunter's moon, November's super beaver moon, and now December's full cold or long nights supermoon. This is true in part because supermoon is not an astronomy term, but rather, one of astrology. (In case you are wondering about the difference: astronomy is science; astrology is make believe.) The name has stuck of late because it's Twitter-friendly and a lot easier to remember than the actual name for the phenomenon: perigee-syzygy of the Earth–Moon–Sun system.

If you want to understand what's going on and why there are so many supermoons recently, you really do need to look at the proper name. Perigee occurs when the Moon is closest to the Earth in an orbit. Remember: the Moon's orbit is not a perfect circle; rather, it's elliptical. Sometimes it's close to Earth. Sometimes it's farther away.

Syzygy means three celestial objects are in alignment. (It can be the Sun, Earth, and Moon, but it might be the Sun, Venus, and Earth, for example, when astronomers can view Venus cross the solar disc.) So when do the Earth, Sun, and Moon experience syzygy? In one of two instances: either the Moon is between the Sun and the Earth (that's a new moon, because from our vantage, the Moon is completely black; the far side of the Moon is in full illumination) or the Earth is between the Sun and the Moon (a full moon, when the Sun's rays are lighting the side we see).

Bear in mind that this does not mean perfect alignment. The phases of the moon have nothing to do with the Earth's shadow.

So a perigee-syzygy of the Earth–Moon–Sun system means an alignment that occurs when the Moon is near to the Earth. It could be a full moon. It could be a new moon. Easy, right? Inasmuch as a made-up term from a made-up belief system can have a proper definition, a supermoon generally means a full moon.

WHY ARE THERE SO MANY SUPERMOONS THIS YEAR?

Not every full moon is at perigee (or its opposite, apogee, when the Moon is farthest from the Earth). The lunar cycle—the number of days it takes the Moon to experience each of its phases, new moon to new moon—lasts about 29 and a half days. Every 14 lunar cycles, the full moon coincides with perigee.

Supermoons tend to come in threes, however. The reason is that the full moons preceding and succeeding perigee-syzygy are still inordinately close to the Earth, and thus appear a lot larger than normal. Moons that are 224,641 miles or closer to the Earth are considered supermoons. The result: a supermoon trifecta, three in a row.

So if you've experienced supermoon overload this year, take comfort that it'll be more than a year before you have to hear the term again. Enjoy it: 2016 has been a year of wildly unexpected and sometimes awful events. Something as predictable and wonderful as the cosmos can be a great comfort indeed.

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How Often Is 'Once in a Blue Moon'? Let Neil deGrasse Tyson Explain
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From “lit” to “I can’t even,” lots of colloquialisms make no sense. But not all confusing phrases stem from Millennial mouths. Take, for example, “once in a blue moon”—an expression you’ve likely heard uttered by teachers, parents, newscasters, and even scientists. This term is often used to describe a rare phenomenon—but why?

Even StarTalk Radio host Neil deGrasse Tyson doesn’t know for sure. “I have no idea why a blue moon is called a blue moon,” he tells Mashable. “There is nothing blue about it at all.”

A blue moon is the second full moon to appear in a single calendar month. Astronomy dictates that two full moons can technically occur in one month, so long as the first moon rises early in the month and the second appears around the 30th or 31st. This type of phenomenon occurs every couple years or so. So taken literally, “Once in a blue moon” must mean "every few years"—even if the term itself is often used to describe something that’s even more rare.

[h/t Mashable]

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Space
Neutron Star Collision Sheds Light on the Strange Matter That Weighs a Billion Tons Per Teaspoon
Two neutron stars collide.
Two neutron stars collide.

Neutron stars are among the many mysteries of the universe scientists are working to unravel. The celestial bodies are incredibly dense, and their dramatic deaths are one of the main sources of the universe’s gold. But beyond that, not much is known about neutron stars, not even their size or what they’re made of. A new stellar collision reported earlier this year may shed light on the physics of these unusual objects.

As Science News reports, the collision of two neutron stars—the remaining cores of massive stars that have collapsed—were observed via light from gravitational waves. When the two small stars crossed paths, they merged to create one large object. The new star collapsed shortly after it formed, but exactly how long it took to perish reveals keys details of its size and makeup.

One thing scientists know about neutron stars is that they’re really, really dense. When stars become too big to support their own mass, they collapse, compressing their electrons and protons together into neutrons. The resulting neutron star fits all that matter into a tight space—scientists estimate that one teaspoon of the stuff inside a neutron star would weigh a billion tons.

This type of matter is impossible to recreate and study on Earth, but scientists have come up with a few theories as to its specific properties. One is that neutron stars are soft and yielding like stellar Play-Doh. Another school of thought posits that the stars are rigid and equipped to stand up to extreme pressure.

According to simulations, a soft neutron star would take less time to collapse than a hard star because they’re smaller. During the recently recorded event, astronomers observed a brief flash of light between the neutron stars’ collision and collapse. This indicates that a new spinning star, held together by the speed of its rotation, existed for a few milliseconds rather than collapsing immediately and vanishing into a black hole. This supports the hard neutron star theory.

Armed with a clearer idea of the star’s composition, scientists can now put constraints on their size range. One group of researchers pegged the smallest possible size for a neutron star with 60 percent more mass than our sun at 13.3 miles across. At the other end of the spectrum, scientists are determining that the biggest neutron stars become smaller rather than larger. In the collision, a larger star would have survived hours or potentially days, supported by its own heft, before collapsing. Its short existence suggests it wasn’t so huge.

Astronomers now know more about neutron stars than ever before, but their mysterious nature is still far from being fully understood. The matter at their core, whether free-floating quarks or subatomic particles made from heavier quarks, could change all of the equations that have been written up to this point. Astronomers will continue to search the skies for clues that demystify the strange objects.

[h/t Science News]

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