00:00And if we cooked a little? No, no pasta and no hamburgers for today.
00:05What would you say of something more exotic? Or rather, more cosmic?
00:09So here it is, the recipe is simple. You take a team of enthusiastic astronomers
00:14and you add some old images from the James Webb Space Telescope.
00:19You mix well and you get an impressive number of small asteroids,
00:23all located in the big belt between Mars and Jupiter, Miam.
00:28The highlight of the show is the direction in which some of these asteroids are moving.
00:33Because on their way there is our poor planet.
00:36Are we simply condemned because you decided to cook?
00:39The asteroids I'm talking about are much smaller than the huge space rock that destroyed the dinosaurs.
00:45But they can still cause considerable damage. Their size varies.
00:50They can be as small as a bus or as big as a stadium.
00:54But even the smallest are very dangerous.
00:57Let's take a recent and quite spectacular example.
01:00It happened on February 15, 2013.
01:02A small asteroid, just a few dozen meters wide, exploded in the atmosphere above Chelyabinsk,
01:09in Siberia, releasing an incredible amount of energy.
01:13Many people witnessed the event and filmed it,
01:17which allowed scientists to obtain essential clues.
01:20New computer models helped scientists reconstruct the size, speed and impact of the Chelyabinsk meteor.
01:28It was probably a big asteroid like a five-story building,
01:32and it would have exploded at an altitude between 24 and 29 km above the Earth's surface.
01:39And with incredible force.
01:41The explosion broke a million windows and injured more than a thousand people.
01:46Fortunately, it was not powerful enough to cause real damage.
01:49But it gave us an idea of the danger that an air explosion can represent.
01:54An air explosion occurs when an object explodes high in the atmosphere,
01:58never touching the ground, but releasing enough energy to devastate the area below.
02:04But let's go back to our little asteroids.
02:06The most dangerous thing with them is that they hit the Earth much more often than the bigger ones,
02:11about 10,000 times more often.
02:13To make matters worse, their small size makes them more difficult to detect in advance,
02:17which leaves us little time to prepare if one of them is heading for the Earth.
02:22Now let's go back to the time of the dinosaurs.
02:24Oh no, that's too far.
02:26Ah here it is.
02:27A team of astronomers worked on a method consisting of finding small asteroids in telescope images
02:32which were originally taken to study distant stars.
02:36Thanks to this method, they were able to examine with precision a stellar system known as TRAPPIST-1,
02:42located 40 light-years from the Earth.
02:45This is one of the most studied systems outside our solar system.
02:49By analyzing these images, they discovered 138 new asteroids in the main asteroid belt,
02:55in addition to the 8 that they already knew.
02:58And guess what?
02:59Among the newly discovered asteroids,
03:016 seem to have been pushed along trajectories that could bring them closer to the Earth.
03:06Who did that?
03:07Probably close planets.
03:09Do they have a tooth against us?
03:11Interesting fact.
03:12Scientists thought they were only finding a few new asteroids,
03:15but their number turned out to be much higher than expected.
03:18But this is not surprising.
03:20They are currently exploring part of the space they knew little before.
03:24Let's now talk about the hero of the day, the James Webb Space Telescope.
03:28If it is so effective in finding small asteroids, it is because it can detect their heat.
03:33These asteroids emit an infrared radiation,
03:36much more visible than the weak sunlight reflecting on their surface.
03:40This technology has allowed scientists to detect the smallest asteroids ever observed in the main asteroid belt.
03:47The asteroids they found are fragments from collisions between larger space rocks.
03:53Discoveries allow astronomers to understand the history of this belt
03:57and to improve the tracking methods of the small asteroids likely to threaten the Earth.
04:02Researchers plan to use the James Webb to observe other stellar systems for at least 500 hours.
04:09They hope this work will allow them to discover thousands of other small objects in the solar system.
04:15Other high-end telescopes, such as the Verace Rubin Observatory in Chile, will also be useful.
04:20As of 2025, this observatory will use the largest digital camera in the world
04:26to photograph the starry sky every night for at least 10 years.
04:30Each image will cover a vast area of the sky, about 40 times the size of the full moon.
04:36The observatory could find up to 2.4 million asteroids in just 6 months,
04:41almost double the number we know.
04:43Recently, NASA identified two small asteroids.
04:47They were to pass near Earth on December 16, 2024.
04:51Fortunately, neither one nor the other posed any danger to the planet.
04:55The first asteroid was 21 meters wide,
04:58about the size of a large plane, and moved at 17,400 km per hour.
05:03The second asteroid was slightly smaller, with a width of 17 meters,
05:08but it moved faster, at 23,800 km per hour.
05:12But hey, even if this time we avoided disaster, who knows what the future holds for us.
05:17Ouch, ouch, ouch.
05:19It may seem strange nowadays,
05:21but astronomers have not really been interested in small asteroids for quite a long time.
05:26They considered them as simple spatial debris that hindered the observation of the stars.
05:32Some even called them the parasites of the sky.
05:36But today, the way we see these small space rocks has completely changed.
05:41In fact, until recently, we could only spot the very large asteroids,
05:45those over 1.6 km wide.
05:48The smaller ones were found in the background noise, images taken by telescopes.
05:53But then, an ingenious trick allowed to combine several images of the same part of the sky,
05:58and to finally make visible these small objects that are not very bright.
06:01The data from some telescopes, such as TRAPPIST and SPECULOOS,
06:05as well as from the James Webb Space Telescope,
06:08help us to improve planetary defense.
06:11But it is not only about protecting our planet.
06:14The study of these small asteroids also teaches us how the solar system has evolved.
06:19If they are so numerous, it is because they are fragments
06:22from collisions between larger space rocks.
06:25A researcher said that it was as if we were looking at old data in a new way.
06:30These small asteroids, which were previously considered as simple debris,
06:34are essential to understand our solar system,
06:37and even to prepare for what the future holds for us.
06:40Among these hundreds of millions of rocks orbiting around the Sun,
06:44in the asteroid belt, located between Mars and Jupiter,
06:47some are particularly worrying.
06:49They are close enough to Earth to be worrying.
06:53NASA classifies asteroids orbiting less than 48.28 million km from our planet
06:59as geocrossing objects.
07:01And this could be a serious threat if they were to collide with our planet.
07:06Currently, NASA is closely monitoring an asteroid named Bennu.
07:10It is a fairly large space rock measuring about 490 meters in diameter.
07:15It could potentially crash on Earth in 159 years.
07:19Astronomers spotted it for the first time in 1999.
07:23Currently, experts estimate that there is a low probability that Bennu will drift into Earth's orbit
07:29and collide with our planet by September 24, 2182.
07:34Would that be serious?
07:36Well, to put things in perspective, Bennu is larger than the Empire State Building.
07:41If it hit Earth, it would release 1,200 megatons of energy,
07:45a quantity so huge that nothing on Earth could generate it.
07:49NASA scientists are particularly concerned about the probability
07:53that this asteroid will pass through a gravitational lockhole
07:57during its passage to the 22nd century.
08:00This lockhole is a region of space that could place the asteroid
08:04on a direct collision path with Earth.
08:07Bennu passes near Earth every six years and has already approached it three times,
08:11in 1999, 2005 and 2011.
08:14At present, scientists estimate that the probability that the asteroid will hit Earth by 2182
08:20is about 1 in 2700,
08:23a risk more than five times higher than that of a person being hit by lightning.
08:28Although the chances that the asteroid Bennu will collide with Earth are very low at the moment,
08:33this space rock is still classified as potentially dangerous,
08:38because it could approach up to 7.48 million kilometers from Earth.
08:43The asteroid Apophis is another space rock that we must monitor.
08:47It is a geocruiser object of about 335 meters in diameter, discovered in 2004.
08:52At first, it was considered one of the most dangerous asteroids ever detected.
08:57Apophis quickly attracted the attention of experts,
09:00because they thought it could represent a serious threat to Earth
09:04due to its proximity to our planet in 2029.
09:07However, after a more in-depth study of its orbit,
09:11astronomers have determined that there was no risk of collision before at least a century.
09:16Phew, we can be calm for a little while longer.
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