Why should not we cry "aliens" about this interstellar space rock

The head of the Harvard Astronomy Department thinks it is possible that a strange object that has visited our solar system from interstellar space is an extraterrestrial probe sent by a distant civilization. He and a colleague exposed their idea in an article published this week badyzing what could be this mysterious space object, triggering a media frenzy.

But let's catch our breath before shouting jubilant "extraterrestrials". The object could actually not the only explanation, and many scientists still argue that a natural explanation is more plausible. To add a bit of context, one of the scientists who formulates this "exotic" statement is currently working on an initiative to search for extraterrestrial life in deep space, by sending Earth probes to people. 39, other star systems.

The document that caught everyone's attention is written by Harvard astrophysicists Avi Loeb and Shmuel Bialy, who tried to describe a strange behavior presented by a stone from the space called "Oumuamua". Spotted last October, `Oumuamua is a mysterious object that crosses our solar system and comes from an unknown origin of deep space. Objects like this are thought to traverse our solar system all the time, but it is the first exo-comet – or comet outside our cosmic neighborhood – that we have ever detected.

In addition to being rare. to find, `Oumuamua is a bit weird. Astronomers expected that a visitor of this type would be an icy comet, surrounded by a trail of gas and dust as it pbaded near the Sun. But `Oumuamua seems to lack this type of cloud, which makes it rather resemble an asteroid, which is mainly composed of rock and metal. So, no one was really sure what it was: a comet, an asteroid or something totally new. Then, after badyzing the orbit of Oumuamua, scientists from the European Space Agency found that the object was accelerating more than it should if it only interacted with the gravity of the planets and the Sun. our solar system. They concluded that "Oumuamua must be a comet; the sun probably warms the ice inside the object, which creates a gas that speeds up even faster.

ESO / K. Meech et al.

However, Loeb and Bialy are skeptical about this badertion of "degbading", mainly because no one was able to observe the gases and dust from 'Oumuamua. They also point to recent research from another lab, which is still under review by other scientists, who say that if the gas came from this object, it would change the rotation of the rock – which was not observed. "That excludes the possibility that it is a comet," says Loeb The Verge .

So they decided to look at another possible explanation of acceleration: could Oumuamua accelerate faster thanks to the Sun? The light of our Sun can really exert a force on the objects, giving them a slight push. Perhaps this phenomenon is enough to explain why 'Oumuamua is becoming faster. However, if this mechanism – known as solar radiation pressure – is at the origin of the extra speed, Oumuamua would have to be extremely lightweight and super-thin, not exceeding one millimeter in thickness .

This gave Loeb the idea that 'Oumuamua could be what we calls a light sail – a thin artificial sail that rolls in the sunlight and this light sail may have been sent here on purpose. "A more exotic scenario is this:" Oumuamua could be a fully operational probe sent intentionally near the Earth by an extraterrestrial civilization, "they write with Bialy.

Loeb has been interested in lightweight sails for years. He is chairman of the Breakthrough Starshot Advisory Committee, an initiative that calls for sending an ultra-thin light-space spacecraft into an interstellar space powered by a giant laser. Loeb admits that his work with Starshot gave him the idea that `Oumuamua could be a light extraterrestrial sail. "Our imagination is limited to what we know," he says. "And the fact that I'm involved in a project using light-sailing has allowed, or even encouraged me, to think about it."

Loeb says he's favorably welcoming it. Other explanations do not involve strangers, but it is almost certain that his idea is correct. "I can not think of another explanation for Oumuamua's particular acceleration," he explains.

But other scientists claim that a natural explanation can still apply here. It is not because we have not seen the gases and dust of 'Oumuamua that this material is not there. The scientists had only about two weeks to observe this object at the end of October, before it moved too far from the Earth and fainted incredibly with the telescopes on the ground. The Hubble Space Telescope was then the only tool we had to observe `Oumuamua until December and the observatory was mainly following its orbit around the Sun.

It was therefore quite possible that the telescopes we were observing previously 'Oumuamua' were simply not able to see the materials flowing out of the object. This may be because we did not observe the object under the right kind of light or that some crucial telescopes were not available to visualize this particular space rock. "Because of the weather and weather conditions with the planet's telescopes, we could not see the dust," said Michele Bannister, an astronomer who studied'Oumuamua at Queen's University & # 39; Belfast, but who did not participate in this research. The Verge .

Image: NASA

It is also possible that `Oumuamua does not emit a lot of dust, which would make this degbading effect is more difficult to observe. "You can adapt that to a simple comet-like object," says Bannister. "It just does not have to emit as much dust as normal comets." The comets of our solar system usually give off countless microscopic dust particles that reflect sunlight, which can then be seen from the Earth. If 'Oumuamua does not have a lot of dust on its surface, it may only release gas, which is easier to miss. And there are examples of this type of objects in our own solar system. "We have comets of which we are aware – rare comets that have to be told – in our solar system, which emit so little dust that we have to look for gas to see the result," Alan Fitzsimmons, astronomer at the Queen & University Belfast, The Verge

In general, astronomers find it to be a comet . good practice to exhaust all possible natural explanations of a phenomenon observed before resorting to the extraterrestrial argument. There is a quote, popularized by astronomer Carl Sagan, which many astronomers use when extraterrestrials are staged as an explanation: "Extraordinary demands require extraordinary evidence." "All the observations we have on this object generate great uncertainty, because we have very little data," says Katie Mack, theoretical astrophysicist at North Carolina State University The Verge . If anything, this extraterrestrial artifact seems to be out of control, as it is chaotic to rock across our solar system. "If it was an extraterrestrial spaceship, it was the Brexit of the alien space ship. Fitzsimmons said it was pure madness.

However, astronomers sometimes write wacky theories like this one, so that community members can dissect the claim and separate it. "Sometimes you write an article about something you do not believe at all, just for the sake of it," says Mack. Loeb, on the other hand, does not want people to discredit his idea simply because it could be incendiary. "We should not dismiss this possibility simply because some people do not like to hear it," he says. "The fact is, we should not be prejudiced in science. We should base our conclusions on evidence, on data, not on prejudice. "

But whenever strangers are invoked, it is usually the explanation that gets the most attention. A similar situation occurred in 2015, when astronomers proposed the idea that the strange behavior of a distant star could be explained by extraterrestrial megastructures in its orbit. The theory, on which many have been skeptical, became so ubiquitous that the star was eventually called the star of the "foreign megastructure".

Of course, the possibility exists. But aliens are a very daring pretense to do when natural explanations are still on the table. "I can understand the excitement and, as a scientist, I can not stay here and say that I have 100% proof that it is a natural object," says Fitzsimmons. "It's just that all observations can be badociated with a natural object."

And that could be a problem if we ever find signs of extraterrestrial life. Astronomers are constantly discovering new planets outside our solar system, and we are working on a more sophisticated technology to scrutinize the atmospheres of these worlds. Someday we may find irrefutable evidence of the existence of life in distant places, but it may be difficult for the public to swallow when he thinks that extraterrestrials have already been discovered. "I do not want people to think we've seen that when it's really happening," says Mack. "I do not want people to be too cynical about claims about extraterrestrials until we actually have solid evidence."

Mary Beth Griggs contributed to this report.