00:00Did you know that over the past year, around 150 asteroids whizzed closer to Earth than the Moon?
00:07But that's not the scary part.
00:09It's that some were only noticed after they flew by.
00:12And if even one of those had taken a slightly different path, whole cities would be gone.
00:19That's what keeps the scientists worried.
00:21The invisible stuff hiding where our telescopes can't see.
00:25Let's explore what that means.
00:26Astronomers keep a list of asteroids that wander into our neighborhood.
00:33If a rock's orbit comes close to Earth, it joins a special club we call Near-Earth Objects, or NEOs.
00:41That list can include anything from a harmless little space pebble that wouldn't break a window
00:46to a rock big enough to cause an Earth-shattering kaboom!
00:52NEOs are leftover materials from when the planets were forming.
00:55Some of that rubble ended up tucked safely in the asteroid belt between Mars and Jupiter.
01:00But some pieces got nudged onto paths that cut across Earth's orbit.
01:06Those are the ones we care about, because they're still wandering around today,
01:11looping around the Sun, and every now and then, passing uncomfortably close to us.
01:16The biggest objects are the easiest to locate.
01:20They are rare and bright enough that they stand out in sky surveys.
01:24So far, none of those big ones seem to be heading our way anytime soon.
01:29However, the real anxiety comes from the middle class of asteroids.
01:33On paper, many of them sit in the potentially hazardous object category, or PHOs, but the nickname
01:42City Destroyer explains them better.
01:46These rocks aren't huge enough to wipe out the planet, but they could flatten a city and mess with the
01:50climate for a few seasons.
01:52Some are as wide as a football stadium, and hit the atmosphere faster than a speeding projectile.
01:58NASA estimates there are around 25,000 near-Earth asteroids at least 460 feet wide, but we've
02:06only discovered a fraction of them.
02:09Basically, we have solid orbits for less than half of the City Destroyer crowd.
02:15The rest only exist as numbers in simulations.
02:18We know they should be out there.
02:20We just haven't seen them yet.
02:22Why are they so hard to spot?
02:25Some asteroids are nearly coal black, blending into the cosmic night.
02:30Others hang out close to the Sun from our perspective, so our telescopes get overwhelmed by brightness.
02:36It's like trying to locate a mosquito while staring directly at the sunlight.
02:41Please don't do this.
02:42From Earth, these rocks are mostly lost in the Sun's glare.
02:46We only catch a glimpse just after sunset, or right before sunrise.
02:50And that chance only exists if the sky is perfectly clear and the asteroid happens to be in exactly the right spot.
02:59If not, it slips back into the Sun's blind spot, playing hide-and-seek with us.
03:05We were caught by surprise quite recently.
03:08In 2013, the Chelyabinsk meteor came from the direction of the rising Sun.
03:12No one saw it in time because it was coming from the wrong direction.
03:17It exploded high above the region, shattering windows across the city, and sent more than a thousand people to the hospital.
03:24The scariest part is that the meteor was only about 60 feet wide.
03:29Now imagine a city destroyer coming from that same direction.
03:33A stadium-sized rock stepping out of the Sun's glare would give us very little warning,
03:39maybe a few days or a week instead of decades.
03:43And we know that the blind zone is not empty.
03:46Observations have already revealed at least one large asteroid in that region
03:50that scientists can seriously consider a planet destroyer.
03:55It's called 2022 AP7, and it's huge.
03:59This thing is more than half a mile wide,
04:02big enough that if it ever hit Earth, it would be a catastrophic day for everyone.
04:08Astronomers found it by using the super-sensitive dark energy camera during twilight,
04:13pointing the telescope at the region of the sky most surveys normally avoid it.
04:17The good news is that AP7 isn't headed straight for Earth.
04:21Its orbit crosses the orbit of our planet, but the timing doesn't line up,
04:26so we won't encounter it this past, the next one, or even for several centuries.
04:30The bad news is what that discovery hints at.
04:35If it took this much effort to notice something like this, what else are we missing?
04:41And 2022 AP7 is just one PHO.
04:45Other asteroids closer to the Sun were also spotted during those same twilight searches.
04:51New simulations say some of those hidden rocks are not random.
04:55A bunch of them seem to share an orbit with Venus.
05:00They do not orbit Venus itself.
05:03They orbit the Sun in almost the same length,
05:05sometimes a bit ahead of the planet,
05:08sometimes a bit behind,
05:10like kids jogging on the same track but spread out along the lab.
05:14Astronomers already know about roughly 20 of those Venus co-orbitals,
05:19and their paths are anything but stable.
05:22Gravity from Venus, Earth, and other planets keep tugging on them.
05:27And over thousands of years,
05:28those poles could stretch their paths until they start crossing Earth's orbit.
05:34Most flybys are harmless,
05:36but one unlucky pass could be the one that counts.
05:39So what can we do about this?
05:43The first step is simple in theory.
05:46Find them earlier.
05:47The goal for astronomers is to launch infrared telescopes and get them into space.
05:53While we do have amazing telescopes like JWST or the Hubble Space Telescope,
05:58they're never pointed at the Sun,
06:00as the brightness of our star can damage them.
06:03That's why we need a telescope in orbit around Venus,
06:06or one that travels along with it.
06:08It would be in a much better spot to keep an eye on the asteroids that hang out there.
06:12NASA is launching the NEO Surveyor project that aims to solve the problem.
06:19It should scan the inner solar system to spot dangerous asteroids in time.
06:24Also, we're learning that we can actually move asteroids.
06:28NASA's DART mission rammed a small spacecraft into a rock,
06:32which affected its orbit slightly.
06:34Not by much, just enough to prove that it can be done.
06:37It's like turning a plane just one degree while it's still across the ocean.
06:43By the time it reaches you, that tiny change can make it miss by thousands of miles.
06:49Teams around the world spend their days babysitting space rocks.
06:53And yes, that's a real paying job.
06:56NASA has the Planetary Defense Coordination Office.
07:00Europe has the NEO Coordination Center.
07:02Observatories feed them nightly sky data and computers immediately check each dot's orbit.
07:08If a rock might wander too close, it joins the risk list and gets extra attention.
07:14Each new photo updates the orbit a little more.
07:17Sometimes that make the danger level rise for a moment.
07:20That is exactly what happened with 2024 YR4,
07:24when it briefly reached level 3 on the Torino scale
07:27before better measurements calmed everyone down.
07:30The scale itself runs from 0 to 10,
07:33and anything that climbs above 3 is rare enough to raise eyebrows.
07:37The whole system works that way on purpose.
07:40Notice something strange, collect more data,
07:43then decide whether to relax or stay alert.
07:46Most of the job is actually pretty dull.
07:49It's a lot of number checking, orbit fixing, and crossing out false alarms.
07:54That quiet, careful routine is what lets the world respond quickly
07:58when a rock finally appears that isn't just passing by.
08:03So how worried should we be?
08:05For those huge planet-destroying rocks, the short answer is, not much.
08:10Nothing that size is on the near-term schedule.
08:13Smaller, city-level threats are trickier.
08:16The odds of one hitting Earth anytime soon are still tiny, but they're not zero.
08:22Think of it as a cosmic lottery that has been running for billions of years.
08:26Every once in a very long while,
08:29the universe draws a number that makes astronomers sit up and pay attention.
08:34It's not a reason to panic.
08:35It's a reason to build better eyes in space
08:38and make sure that if a bad ticket ever comes up,
08:41we see it in time to do something about it.
08:48That's it for today.
08:49So hey, if you pacified your curiosity,
08:51then give the video a like and share it with your friends.
08:54Or if you want more, just click on these videos and stay on the bright side.
