Starting next week, the moon, Earth’s closest celestial body, will be joined by a new neighbor: a second moon.
From Sept. 29 until Nov. 25, astronomers calculate that 2024 PT5— which is what scientists think is an asteroid but have dubbed a “mini-moon”—will be looping around Earth. It will eventually break free of the planet’s gravitational orbit.
From Sept. 29 until Nov. 25, astronomers calculate that 2024 PT5— which is what scientists think is an asteroid but have dubbed a “mini-moon”—will be looping around Earth. It will eventually break free of the planet’s gravitational orbit.
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NewsTranscript
00:00Hi, I'm Jeffrey Kluger, Editor-at-Large and Space Writer for Time Magazine.
00:06And this week, the coolest space story comes not from my computer, but from that of my
00:10colleague who has written a piece about Earth's newest moon.
00:15And we are getting a second moon.
00:17For 4.5 billion years, Earth got by on the one moon that we know.
00:22But from September 29th to November 25th, we're going to have a second moon.
00:27Now, it's much, much smaller than our original moon.
00:31It's only 10 meters or about 30 feet long.
00:34And it cannot affect us.
00:36It can't affect the tides.
00:38You won't be able to see it, but astronomers and NASA know it's there.
00:43The way we got it was a little bit of gravitational jujitsu.
00:47The new moon comes from a cluster of asteroids called the Arbusia asteroid belt.
00:52Those asteroids were created mostly by collisions with big asteroids and our large moon, which
00:59sent up a lot of ejecta and rubble into space.
01:02That rubble flew out away from the moon and got captured into its own earthly orbit.
01:07The short time this rock will remain circling the Earth has a lot to do with its velocity.
01:12In order to maintain an orbit around the Earth, a rock has to move just slow enough that it
01:18doesn't reach what's called escape velocity, which allows it to rip away gravitationally
01:23and fly back into space.
01:25The new moon is moving too fast to be held in an Earth orbit, and as a result, we'll
01:30only have it for about eight weeks before it rejoins the Arjuna asteroid belt.
01:35The new asteroid, which will become a moon for a little while, is part of a group of
01:40objects in space called near-Earth objects.
01:44NASA has cataloged about 28,000 of them, and they are defined as any asteroid that
01:50moves within 27 million miles of Earth.
01:54That's important because an asteroid that comes that close to Earth could at least in
01:58theory enter the atmosphere and cause all kinds of problems.
02:02If this rock were to do that, it could cause some damage.
02:06In 2013, over Chelyabinsk, Russia, a rock that measured about 20 meters across exploded
02:13in the atmosphere and damaged 2,500 buildings.
02:17Fortunately, nobody was killed, but some people were injured.
02:21This rock, with about half of that mass and a half of that length, would cause about half
02:26of that damage.
02:27But to put it in perspective, the new moon, the little asteroid, measures 10 meters across.
02:32The asteroid that killed the dinosaurs 65 million years ago measured a whopping 9.3
02:38miles.
02:40Our new little moon, which will visit us for a while, poses no such danger.