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Hagai Perets

Astronomers: Multiple Cosmic Collisions May Have Created Our Moon

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Hagai Perets

It looks so tranquil up there. So still. But we know space is neither tranquil nor still. Our own Moon is no exception. New research suggests the Moon was the product of some very, very violent moshing: Around 4.5 billion years ago, a rowdy gang of stellar objects smashed into our young planet, creating the debris that would one day become the Moon. The astronomers published their report in the journal Nature Geoscience.

We’ve known for a while now that the Moon is made at least partially out of pieces from a banged-up Earth. But we’re still trying to sort out the details of the collision itself. At first, scientists thought Earth had been hit by one big object, like another planet. Then they thought there must have been a bunch of objects all striking around the same time. As we learned more, the single-impactor theory returned to prominence and stayed there for decades.

One 2016 study named the object—the planet Theia—and even the angle of impact. The researchers theorized that the extremely similar molecular makeup of Earth and the Moon could only have resulted from a head-on collision.

Other astronomers disagree. The authors of the new paper ran hundreds of simulations, and they argue it’s far more likely that Earth was walloped by a score of different objects called planetesimals. Each of the repeated impacts smashed up a huge amount of the young planet’s matter. That debris then drifted into orbit around Earth, where it settled into disks, which then resolved into little (gargantuan) chunks called moonlets. Over time, the baby moonlets merged into one single, spinning rock.

“Our model suggests that the ancient Earth once hosted a series of moons, each one formed from a different collision with the proto-Earth,” co-author Hagai Perets said in a statement. “It’s likely that such moonlets were later ejected, or collided with the Earth or with each other to form bigger moons.”

Perets says the moonlets could easily have crossed orbits with one another, smashed together, and been rolled up into larger bodies. “A long series of such moon-moon collisions could gradually build-up a bigger moon—the Moon we see today.”

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Space
What Solar Eclipses Look Like on Different Planets
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Triple solar eclipse on Jupiter.

On Monday, August 21, North America will be treated to dazzling views of a total solar eclipse. But what if humans lived someplace else in the solar system—would eclipses be regarded with the same excitement and awe as they are here on Earth?

In her new video, Physics Girl Dianna Cowern investigates what these celestial events look like beyond our home planet. She discovers that, on some planets, total solar eclipses aren't even possible. The two moons orbiting Mars, for example, are too small to completely block the Sun. Move on to other parts of the solar system and you'll find places where total eclipses aren't rare at all. On Jupiter, which has 69 moons, it's possible for there to be multiple eclipses occurring at the same time. On Pluto, whose moon appears much larger in its sky than the Sun, total eclipses can happen every day for years on end.

Considering all the factors required to make a perfect solar eclipse, we're pretty lucky to be able to see one from Earth at all. And if you're close enough to the path of totality to view this year's North American eclipse, you can consider yourself even luckier.

[h/t Physics Girl]

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IMAGE CREDIT: David Prasad, Flickr Creative Commons // CC BY-SA 2.0
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Space
Space Fanatics Are Paying Top Dollar to Fly Through the Eclipse
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IMAGE CREDIT: David Prasad, Flickr Creative Commons // CC BY-SA 2.0

A spectacular solar eclipse is coming soon. While the rest of us suckers will be gazing, awestruck, from the ground (except for the winner of this contest), a small group of space enthusiasts will take a more proactive approach, chartering jets to fly directly into the path of the moon’s shadow.

Barring bad weather, the August 21 eclipse should be visible from everywhere in the continental United States. But for some people, "visible" is just not good enough. Teams of astronomers are sending balloon cams up to livestream the spectacle from the sky. Others will use plane-mounted telescopes to get an extremely rare glimpse of the happenings on the surface of the Sun and Mercury. Elsewhere, diehard eclipse lovers will board specially chartered flights for the sole purpose of spending a little more time in the all-consuming darkness.

"A total solar eclipse is one of nature's most awesome events," Sky & Telescope editor Kelly Beatty told Business Insider. "Anyone who's seen one knows that.” But from the air, Beatty said, “The sky is that much clearer and that much blacker. And that makes the corona that much brighter and more electric. It's really an electric-looking phenomenon."

The jets are small and the demand is high, which means a single seat can easily cost $10,000 or more. At most, the flight will buy passengers a few extra minutes in the dark.

Those who’ve done it before say the trip is worth every penny.

“I have no intention of ever missing an eclipse for the rest of my life. I don't care where it is, even in the remotest area of the Earth," said passenger Craig Small. "I have to be there, I will be there."

Co-passenger Joel Moskowitz agreed.

"When you see one, you want to see more,” he said. “You get hooked. Seeing the corona during totality is better than sex."

[h/t Business Insider]

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