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According to a new study, a strange interstellar object that would have roamed the inner solar system last fall could be an extraterrestrial spaceship with a veil of light.
Indeed, an artificial origin would explain quite well the many strange characteristics of this cosmic visitor, called "Oumuamua," said the study's co-author, Avi Loeb.
And Loeb said that his colleagues should not rule out this assumption, just because it invokes intelligent extraterrestrials. [‘Oumuamua: Solar System’s 1st Interstellar Visitor Explained in Photos]
"It's a prejudice we should not have," said Space.com Loeb, chairman of Harvard University's Department of Astronomy and director of the Institute of Theory and Economics. (ITC) of the Harvard-Smithsonian Center for Astrophysics. "Science should be open minded."
The oddity of 'Oumuamua
Illustration of an artist representing the interstellar visitor – Oumuamua, presenting a comet-like degassing behavior. A new study suggests that the mysterious object could actually be an alien spacecraft with a light sail like a gossamer. Credit: NASA / ESA
& # 39; Oumuamua was discovered on October 19, 2017 by astronomers using the pan-survey telescope and rapid response system (Pan-STARRS) in Hawaii. (The name of the object means "messenger from afar" in Hawaiian.)
& # 39; The Oumuamua trajectory indicates that it is not here, making it the first confirmed interstellar object observed in our solar system. And & # 39; Oumuamua is unique in other respects – in its form, for example.
'Oumuamua's observations indicate that the object is extremely long and narrow, measuring perhaps 1,300 feet long and 130 feet wide (400 meters by 40 meters). No other known cosmic object has such a needle-shaped shape.
Nobody really knows what Oumuamua looks like or how big it is. Astronomers have not been able to capture a resolute image of the object and visitor size estimates are based on its luminosity (and a practical knowledge of the reflectivity of comets and asteroids).
It has been difficult to say what Oumuamua really is. The scientists initially considered the object as a comet, but they reclassified it as an asteroid after the observations did not reveal a fuzzy tail or coma. But earlier this year, a team of researchers re-qualified Oumuamua as a comet after finding non-gravitational acceleration. This movement can not be attributed to the sun, planets, or other objects in the solar system and, therefore, (according to the authors of this previous study) probably resulted from degassing of comets.
This brings us to Loeb's new study with lead author Shmuel Bialy, a postdoctoral fellow at ITC. Bialy and Loeb do not think that the comet's explanation holds up because astronomers have still not seen any tail or coma around "Oumuamua."
In addition, the degassing would have changed the rotation period of "Oumuamua", an effect that "would have been easy to identify," said Loeb. "But we have not seen such a change."
There is another possible natural explanation, he added. If "Oumuamua" is just a fragment of a larger object, the observed motion could come from the "kick" that dropped that fragment. But such a kick would be a one-off thing, while "Oumuamua showed a not-so-serious acceleration repeated," said Loeb.
Bialy and Loeb have therefore formulated a new hypothesis: sunlight can be responsible. In the new study, the duo determined that solar radiation pressure could cause the non-gravitational movement observed if 'Oumuamua' had only a thickness of 0.3 to 0.9 millimeters.
What kind of structure could be so thin? Bialy and Loeb suggested a candidate: a light sail, designed to harness the power of photons as a propulsive force. Mankind has already demonstrated this technology in the space; The Japanese IKAROS spacecraft successfully made its way into the Venus district in 2010. (NASA's LightSail spacecraft NanoSail-D2 and LightSail of the Planetary Society was zipped around the Earth in 2011 and 2015, but their missions consisted mainly of proving the deployment of the sail.)
Bialy and Loeb also calculated that a light-winds Oumuamua could probably survive a long interstellar journey. Given the concentration of gas and dust in the interstellar medium and the rate at which the object would encounter these far-space spots, the researchers determined that Oumuamua could do this at the same time. at least 16 000 light-years from its original system (whatever it is). – & # 39; The provenance of Oumuamua remains a mystery).
"This is good news for SETI," said Loeb, referring to the search for extraterrestrial intelligence.
"This is not speculation," he added. "We have an anomaly in the data, the anomaly is that the orbit diverts from a Keplerian orbit – from what gravity alone would do. [viable] explanations on this subject do not exist, other than the one we propose. " [13 Ways to Hunt Intelligent Aliens]
Space junk or craft spying?
To be clear, Bialy and Loeb do not claim in this study that "Oumuamua is definitely an extraterrestrial spacecraft. But they think it's a real possibility.
The object could be a piece of extraterrestrial space bomb, a dead sailing boat that accidentally found its way to us. The researchers also wrote in this study: it can be an active reconnaissance device sent here to check our solar system.
There are reasons to favor this last explanation, said Loeb. To begin with, "the very discovery of Oumuamua was an anomaly. If the visitor belongs to a random population, his discovery suggests that each star of the Milky Way ejects in interstellar space 1,000 trillion objects of this type during his lifetime, said Loeb. (These figures are based on calculations made by Loeb and his colleagues ten years ago.) Our own solar system does not lose as many objects resembling Oumuamua, he added.
In addition, the movement of Oumuamua coincides roughly with the average movement of materials in our Milky Way galaxy plot – a kinematic space known as the local standard of rest. Indeed, that is why the system of origin of the object has been so difficult to pin down.
"If I created an instrument that I would like to hide, I would put it to the local standard of rest," said Loeb.
Astronomers have used the Green Bank Telescope, West Virginia, and the Allen Telescope, in northern California, to detect possible pings from Oumuamua. To date, the object has remained silent.
The IKAROS satellite of the Japan Aerospace Exploration Agency is seen in the space after the deployment of the aircraft on June 14, 2010.
Credit: JAXA
Get an answer
"Oumuamua is moving so quickly to the outer solar system that we will never be able to catch up with traditional chemical rockets. But that does not mean that we will never be able to examine the subject closely.
If we find a way to accelerate lasers with robotic probes equipped with tiny veils and sails, we could eventually launch a mission to Oumuamua, said Loeb. Projects such as Breakthrough Starshot aim to launch such a business in the coming decades. (Loeb chairs the Breakthrough Starshot Advisory Board.)
Whether or not we succeed in hunting Oumuamua, we should learn a lesson from his visit and be ready to hold a full blitz of observation the next time such an object will pass in our neighborhood, Loeb said.
And such detection could happen relatively soon. The mighty big Synoptic Survey telescope, due to be put online in the early 2020s in the Chilean Andes, may well bring up one or two other Oumuamua, Loeb said.
The example provided by "Oumuamua should also entice astronomers to take a closer look at other intriguing objects currently in view," said Douglas Vakoch, president of METI (Messaging Extraterrestrial Intelligence), an organization with nonprofit based in San Francisco.
As an example, he mentioned KIC 8462852, also known as Tabby's Star or Boyajian's Star, according to the researcher who had noticed his strange gradation events and drama a few years ago.
"It's exciting to imagine that" Oumuamua is an extraterrestrial solar sail traversing our solar system, but we lack the essential feature required by SETI scientists. We can not duplicate the observations because "Oumuamua is already out of reach of our best telescopes," Vakoch told Space.com by email.
"Astronomers have insisted on the importance of gathering more data to try to understand the strange darkening of KIC 8462852, without affirming the existence of Dyson Spheres," he said. added. "But there is a critical difference between Boyajian Star and Oumuamua – one of them is still visible and the other is gone."
The new study will be published next week in The Astrophysical Journal Letters. You can read the document for free at the arXiv.org online preprinting site.
Mike Wall's book on the quest for extraterrestrial life, "Out There," will be published on November 13 by Grand Central Publishing. Follow him on Twitter @michaeldwall. follow us @Spacedotcom or Facebook. Originally posted on Space.com.
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