Look Up! The Ursid Meteor Shower Is an Early Holiday Present

A screenshot of the Earth (blue orbit) crossing the debris stream (sparkly white path) left by comet 8P/Tuttle during the comet's 14-year orbit around the Sun. Image Credit: Ian Webster

Two days before Hanukkah and three before Christmas, the cosmos will bring you an early holiday gift—no telescope required. The Ursid meteor shower peaks in the early morning hours of December 22, after midnight through dawn. It's not the most spectacular shower of the year, but it is the last one of 2016, and it'll tide you over until the Quadrantids next month. (And making a big production of going outside to watch the sky is a pretty good way to drop a big hint about that telescope you want for Christmas or Hanukkah.)

Danielle Moser, a meteor scientist with the Meteoroid Environment Office at NASA's Marshall Space Flight Center, tells mental_floss that you can expect to see a handful of meteors if you're patient. "Not all of the meteors you’ll see while out observing belong to the Ursid meteor shower—some are sporadic background meteors and some belong to other active showers. If you see a meteor, try to trace it backwards. If you end up near the Little Dipper, there’s a good chance you’ve seen an Ursid."


The Ursids among the constellations. Image Credit: Stellarium

While some meteor showers have been studied for millennia, the Ursids have only been observed for a relatively short time. The shower's parent is comet 8P/Tuttle, discovered in 1790 by Pierre Méchain. Decades later, in 1858, it was rediscovered by Horace Tuttle, and thus earned its name. (Don't feel bad for poor Pierre, though. He discovered so many things in his lifetime that he probably wouldn't remember this meager little comet anyway.)

Around the turn of the century, William Denning, an amateur astronomer and renowned comet hunter from England, recognized the radiant, or the seeming point of origin, of the Ursid meteor shower. The association with the Tuttle comet was immediately suspected, and later observations would confirm it.

It turns out Tuttle is a "contact binary"—a small, solar system object made of two bodies that have gravitated toward each other until they touch, like the rubber-ducky shaped 67P/Churyumov–Gerasimenko. We know now that Tuttle's orbit around the Sun takes just under 14 years. As it goes about its orbit, it leaves behind a trail of particles that, over the centuries, has organized. When the Earth crosses into this debris field, those particles slam into our atmosphere and burn away. That release of energy takes the appearance of "shooting stars." A meteor shower is born.


The shower appears to originate in the Little Dipper, which is how it gets its name. The formal name of the Little Dipper is Ursa Minor, which translates as Little Bear. (Of course, some will argue it looks a lot more like a spoon.)

The shower will appear highest in the sky in the hours before sunrise on December 22, so set your alarm clock accordingly. The shower can produce around 10 meteors per hour, and to see them, all you’ll need is to find a place with no light and look up.

Moser suggests that you keep a thermos of hot chocolate in your hands and your phone in your pocket. "You'll see more meteors if you let your eyes adjust to the dark," she says. "As soon as you look at a bright light source like your phone, you have to start the adjustment process all over again! And hot chocolate will keep you warm and awake while patiently braving the cold December weather."

The Ursids have had some pretty spectacular showings—most notably in 1986, with spikes on the order of 100 meteors per hour. Don't get your hopes up for a wild display in 2016, however. Rather, appreciate the Ursids for what they are: an annual tradition of rare and romantic shooting stars in a beautiful, wintry, night sky. Enjoy the last big meteor shower of the year, and if it convinces someone to gift you a telescope, get ready: There are some astounding celestial wonders waiting for us in the new year.

How Often Is 'Once in a Blue Moon'? Let Neil deGrasse Tyson Explain

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]

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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