Interstellar meteors may be common, and could potentially help life travel from star to star throughout the Milky Way, according to Harvard astronomer’s Amir Siraj and Avi Loeb who report that they have uncovered possible evidence of an extrasolar object striking the Earth back in 2014 from their study of the Center for Near-Earth Object database. They were searching the data for telltale objects that traveled faster than normal, suggesting that it was likely ejected out of an alien star system.
The first known visitor from interstellar space, a cigar-shaped object named ‘Oumuamua, was detected in 2017. Scientists deduced the origins of the 1,300-foot-long (400 meters) object from its speed and trajectory, which suggests it may have come from another star, or perhaps two.
Avi Loeb, the chair of astronomy at Harvard University, noted that one would expect smaller interstellar visitors would be far more common, with some of them perhaps colliding with Earth often enough to be noticeable.
Loeb made headlines around the globe last fall 2018 when he suggested that the interstellar object known as ‘Oumuamua might an alien spacecraft. ‘Oumuamua was believed to have come from outside of the solar system because its trajectory showed it was not gravitationally bound to the sun—also, it traveled faster than traditional space objects. In this new effort, Loeb and his undergraduate assistant Siraj claim to have found evidence of another object from outside of the solar system.
The Harvard team report that they found three hits, two of which they dismissed because of incomplete data. But the third described a meteor that was believed to be slightly less than a meter wide that had been observed disintegrating in the atmosphere on January 8th, 2014, at a height of 18.7 kilometers near Papua New Guinea. Its speed had been measured by a government sensor at 216,000 km/h. By tracing its trajectory backward, the researchers report that it likely came from outside of our solar system.
Trajectory of the January 8, 2014 meteor (red), shown intersecting with that of Earth (blue) at the time of impact, ti = 2014-01-08 17:05:34. Credit: arXiv:1904.07224 [astro-ph.EP]
If their finding proves valid, it would be the first known instance of an extrasolar object striking the Earth.
Our first documented interstellar visitor, Oumuamua, was discovered Oct. 19 using the Pan-STARRS telescope, which is operated near the summit of Maui’s Haleakala volcano by the Institute for Astronomy at the University of Hawaii as it traveled through the inner solar system, at a distance of about 19 million miles from Earth. An analysis of its trajectory suggests that it came in from a place far beyond the solar system, somewhere in the constellation Lyra, heading towards the constellation Pegasus.
Named Oumuamua, Hawaiian for “Messenger from Afar”, it’s believed to be the first interstellar object observed passing through our solar system. Many tried listening to it for radio signals, to see if they could determine what it was. Was it a shard from an ancient asteroid, a weird comet? Or was it something else?
So The Daily Galaxy emailed Loeb. Here’s what we asked: “We’d like to include a quote (of any length) from you on your thoughts about human implications of the Oumuamua “spacecraft” debate. In short, it seems that we are rooting beyond the science for validation of the spacecraft hypothesis. In the rancorous, tribal environment we’re living through, it appears the human species is yearning for validation of intelligent life beyond our fragile Blue Dot.”
Avi Loeb’s reply:
I was very surprised about the reaction of the media to our paper. We did not have a press release. The paper was submitted for publication ten days ago and posted on the online arXiv at the same time. It was reviewed and accepted for publication within a record time of only a few days. I received positive reactions from distinguished astronomers, such as the Astronomer Royal in the UK, Lord Martin Rees.I am glad to see the excitement about the paper, but it was not written for that purpose. We just followed the standard practice of scientific research.
I prefer not to assign probabilities to the nature of `Oumuamua, we just need to be practical and collect more data on it or other members of its population. The interpretation of existing and future data is my plan for the future.
It is exciting to live at a time when we have the scientific technology to search for evidence of alien civilizations. The evidence about `Oumuamua is not conclusive but interesting. I will be truly excited once we have conclusive evidence.
`Oumuamua deviates from a trajectory that is solely dictated by the Sun’s gravity. This could have been the result of cometary outgassing, but there is no evidence for a cometary tail around it. Moreover, comets change the period of their spin and no such change was detected for `Oumuamua. The excess acceleration of `Oumuamua was detected at mutiple times, ruling out an impulsive kick due to a break up of the object. The only other explanation that comes to mind is the extra force exerted on `Oumuamua by sunlight. In order for it to be effective, `Oumuamua needs to be less than a millimeter in thickness, like a sail. This led us to suggest that it may be a light-sail produced by an alien civilization.
I welcome other proposals, but I cannot think of another explanation for the peculiar acceleration of `Oumuamua.
The response to my paper with my postdoctoral fellow, Shmuel Bialy, has been truly remarkable. We submitted it for publication only a week ago. It was accepted for publication in The Astrophysical Journal Letters merely three business days later. The attention was created by blogs on Centauri Dreams and Universe Today. But by now, Twitter is humming continuously about it.
Our own civilization is currently engaged in developing the light-sail technology. The solar-sail principle was already demonstrated by the Japanese IKAROS projectand is being developed towards the goal of reaching high speeds by the Starshot project of the Breakthrough Prize Foundation, for which I chair the advisory board. It is conceivable that more advanced civilization are using this technology routinely, and this resulted in space debris of the type of `Oumuamua.
Looking ahead, we should search for other interstellar objects in the sky. Such a search would resemble my favorite activity with my daughters when we vacation on a beach, namely examining shells swept ashore from the ocean. Not all shells are the same, and similarly only a fraction of the interstellar objects might be technological debris of alien civilizations. But we should examine anything that enters the Solar System from interstellar space in order to infer the true nature of `Oumuamua or other objects of its mysterious population.