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00:00 In 2017, a strange object was spotted in our solar system.

00:06 It had an oblong shape, a bit like a pancake.

00:09 None of the asteroids or comets we have ever observed look like this.

00:14 Its surface was also singular.

00:16 It was at least ten times more reflective than the average objects drifting in space.

00:21 Some have claimed that it had an envelope comparable to polymethyl.

00:25 When it passed near the sun and moved away from our orbit, it accelerated beyond what our gravity would explain.

00:34 At first glance, we would have said that this thing had a rocket attached to its back.

00:39 This unusual visitor even received its own name, Uumuamua.

00:44 It comes from the Hawaiian language and translates as "lighter" or "visitor of a distant land".

00:49 And because of these characteristics, scientists soon wondered if it was really a visitor from an alien people.

00:56 Before getting into deep science fiction, astronomers first gathered the information they were "sure" about.

01:07 Starting with the fact that Uumuamua must have come from another solar system.

01:11 An unexpected event in its original system probably led to its ejection.

01:17 What we did not know was whether it was a comet or an asteroid.

01:22 Both are celestial objects orbiting around a sun.

01:26 But they have their compositions and their components radically distinct.

01:30 Comets are mainly composed of ice, dust and rocks, and are sometimes called "dirty snowballs".

01:38 When a comet approaches the sun, the heat causes the vaporization of the ice, releasing gas and dust particles into space.

01:47 This creates a luminous and sparkling tail that can extend for millions of kilometers.

01:52 Comets generally have an elliptical orbit, often taking them to the farthest edges of the solar system, closest to the sun.

02:04 Asteroids, for their part, are mainly composed of rocks and metals.

02:08 In our immediate neighborhood, they are the remains of the formation of the solar system

02:13 and are generally found in the asteroid belt that extends between Mars and Jupiter.

02:18 Unlike comets, asteroids do not have a tail when they approach the sun because they do not have ice.

02:26 Their orbits generally follow a more circular trajectory compared to comets.

02:32 According to all likelihood, Oumuamua should be a comet, because it seems to come from a different place in the universe.

02:39 However, it does not present the typical signs of a cometary activity.

02:43 Wait a minute, does the cometary have a commentary?

02:47 It's up to you to see.

02:49 Oumuamua does not have a tail and does not spit out gas when it passes, unlike me.

02:54 Although it behaves more like a comet, it looks more like an asteroid.

03:00 Another big question is how scientists were able to locate Oumuamua in the first place.

03:08 Given the immensity of space-time, it is quite remarkable.

03:12 Stars have life spans extending over millions, if not billions of years.

03:17 And the formation of a solar system takes several hundred million years.

03:21 Even the fastest objects take tens of millennia to travel from one star to another.

03:27 On the other hand, humans have only observed the sky with their telescopes for about 400 years,

03:33 an infinite fraction of space-time.

03:35 And it is only in recent decades, if not recent years, that we have obtained the technology

03:41 allowing us to detect and track fast and low-light objects.

03:45 Either such rocks are very common, or we were very lucky with our instruments.

03:50 Or Oumuamua just wanted to be seen.

03:56 Another question concerns the origin region of such objects.

03:59 It is very unlikely that Oumuamua comes from a mature and stable solar system.

04:04 It is because such systems do not eject enough matter to spread across the galaxy.

04:10 A rock can sometimes be projected, but it can rarely go that far.

04:15 Younger systems, however, act differently.

04:19 In these chaotic environments, collisions, fusions and other migrations occur all the time.

04:26 Many small rocks are here, and are the perfect candidates for ejection.

04:31 The solar system that ejected Oumuamua must have had a planet similar to Jupiter.

04:36 Its massive size and gravity could influence other objects through the system,

04:41 potentially causing ejections.

04:43 But all solar systems do not develop planets the size of Jupiter.

04:48 Often, these massive planets end up getting closer to their stars,

04:53 becoming warmer versions of the gas giant.

04:57 Such planets, in orbit close to a sun, are less likely to eject matter in the distance.

05:04 Planets similar to Neptune could also have played a role.

05:08 Although they are not as massive as Jupiter,

05:11 they tend to nest near the periphery of solar systems.

05:16 Our own system thus has the belt of Jupiter, a real comet reservoir, in its periphery.

05:23 During the first stages of the formation of a solar system,

05:26 interactions between planets similar to Neptune and such debris are common.

05:31 However, the discovery of such planets tends to alter the system if it is verified.

05:36 Our methods of detecting such exoplanets work better with massive objects

05:41 near their stars, which complicates the detection of their further homologues.

05:46 Oumuamua also found himself associated with a certain theory

05:52 about how life would have appeared in the universe.

05:55 Permian thought.

05:57 It is a hypothesis that suggests that life exists everywhere in the universe

06:01 and can be distributed between planets by various means,

06:05 such as asteroids, comets and even spatio-vices.

06:10 It claims that life would have originated somewhere in the universe,

06:14 after which it spread to other celestial bodies.

06:19 Adepts of this theory suggest that such interstellar objects

06:23 could potentially carry tiny microbes,

06:26 these fundamental components of life, between stellar systems.

06:30 If such objects were to hit a planet or a moon,

06:34 they could transfer this organism and its monster, a celestial body.

06:40 For the moment, there is no supporting evidence

06:43 that this object in particular would transport life between solar systems.

06:48 After years of research, the general consensus is that Oumuamua was indeed a comet.

06:56 The reason why it moves in such a strange way

06:59 is that it could present hydrogen frozen on its surface,

07:02 which reacts to the contact of sunlight.

07:05 The closer it got to our star, the faster it went,

07:08 releasing this hydrogen and also changing its trajectory through our solar system.

07:13 Its color also tends to support this theory.

07:16 It is red, which could mean that it has been hit by cosmic rays for a long time.

07:22 The more it was bombed by these rays,

07:24 the more hydrogen it accumulated during the process.

07:28 But as they cannot be entirely sure,

07:30 astronomers have planned to follow this visitor.

07:33 The idea is to send a mission to examine it.

07:36 It is already far from us, but it may not be too late.

07:40 We could be able to send a fairly fast probe to catch the comet.

07:45 This plan was called "Projet Lyra"

07:47 and aims to exploit the orbit of Earth and Jupiter

07:51 in order to send a probe far enough to reach Oumuamua.

07:54 If it works, it will be the fastest spacecraft we have ever sent into the universe.

08:00 The trajectory of the space probe would involve using the attraction of our planet

08:05 and that of Jupiter as a gravitational front effect.

08:09 The probe would first leave our planet,

08:11 then return to Earth's orbit before leaving to meet the attraction of Jupiter.

08:17 It would be sent back to our planet a second time,

08:20 where it would be ejected with enough force to reach the comet.

08:25 The "Projet Lyra" also aims to follow a second distant visitor,

08:31 named Borisov.

08:33 This comet was discovered by an amateur astronomer and now bears his name.

08:38 What is fascinating about it is that, well, it is truly impeccable.

08:43 Just like our experience with Oumuamua,

08:46 we have never observed anything similar to Borisov either.

08:49 Studies of light coming from its dust and gas envelope

08:53 show that it is quite clean compared to other space objects.

08:57 After being spotted for the first time in August 2019,

09:01 astronomers studied its trajectory through our solar system

09:05 and concluded that it also came from another star.

09:08 But Borisov gave us more time to study it,

09:11 because we spotted it earlier in its journey through our neighborhood.

09:15 Researchers used advanced telescopes to examine Borisov's dust.

09:21 They discovered that it released more than 180 kg of dust every second.

09:26 We also found that Borisov contained more carbon monoxide

09:30 than the comets of our solar system in general.

09:33 However, this quantity is not the same everywhere on the comet.

09:37 This indicates that the space object

09:40 probably began to form near its original star before moving away from it.

09:45 Perhaps because of larger planets in its immediate neighborhood.

09:49 Borisov's light is much more polarized than the light coming from other comets

09:53 that we have observed, and its cloud is perfectly homogeneous.

09:57 This suggests that Borisov never interacted with another star.

Les Scientifiques Décryptent Enfin les Secrets d’Oumuamua

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