The Search for Extra-Terrestrial Intelligence effort is valuable not so much because it might find an alien intelligence but because of all the scientific endeavours it stimulates
Perhaps you didn’t notice that we’ve had a recent interstellar visitor? Or did you?
Admittedly, I use “we" in a rather wide sense here—meaning not just you readers of Mint and myself, not just all of India, not even just the entire planet Earth. Instead, that “we" refers to our little corner of the universe—our sun and its orbiting planets. Over the last few months, a certain somewhat peculiar object has been barnstorming through our solar system. Now there are actually plenty of objects that do this—comets and asteroids of various shapes. But this one’s origins are somewhere outside the solar system, which makes this the first time humans have observed such an object make such a flyby. By itself, that was interesting enough. But there were some peculiar things about this visitor that got scientists the world over excited.
Could this be, they wondered, an alien spaceship of some kind?
But first, some details. The astronomer Robert Weryk was the first to observe this object, on 19 October 2017. At the time, it was over 30 million kilometres away, having already passed the sun and heading out of the solar system. That path is why astronomers first thought it was a comet. Only, it didn’t have a tail of streaming ice and dust, like every other comet does. So a week later, astronomers decided it had to be an asteroid. But its phenomenal speed as it passed the sun—nearly 90km per second —suggested, for reasons I won’t get into here, that unlike comets and asteroids, it had to have come to us from outside the solar system.
The International Astronomical Union, which names cosmic objects according to certain rules—“C" for comets, “A" for asteroids—had none for this visitor from outer space. So the IAU had to come up with new nomenclature. They used “I" for “interstellar" and called this streaking object “1I". For a more user-friendly name, they considered “Rama", after the alien spacecraft in Arthur C Clarke’s novel “Rendezvous with Rama". But given that it was first observed from Hawaii, they finally assigned it the Hawaiian name “‘Oumuamua", which means “scout". (Yes, the word does include the single quote at the start, representing what’s called a “glottal stop" in Hawaiian).
‘Oumuamua is one strange celestial traveller. The early observations showed that it was red and small. (Aside: think what it must take to determine that a speedy little object, some 100 times further than us than the moon is and moving away, is red).
But its shape was what particularly intrigued astronomers. It is about 250m long, but only about 35m wide— which means it most resembles a gigantic cigar. No other asteroid we know of looks anything like that. In general, many millennia worth of friction with their surroundings tend to make objects rounded. (Think of stones on a riverbed). But a long cigar?
In fact, it is ‘Oumuamua’s unusual shape that suggested to astronomers that it might not be just another rock. If you wanted to design a spaceship to hurtle through space and avoid collisions, you might just choose to make it cigar-shaped. So had ‘Oumuamua been built by some alien civilization and sent out to explore the universe? Was it filled with alien civilized beings observing us? Seeking to establish contact?
Most likely, the answers to those questions would be “No". After all, mankind has been searching for signs of extra-terrestrial intelligence for many years now, with no success at all. We have not yet found evidence of a single celestial object that might be artificially made; thus not yet found any evidence of an alien civilization. But if you’re inclined to think of that as a failure, consider for a minute the challenges SETI (the Search for Extra-Terrestrial Intelligence) is up against.
Studying ‘Oumuamua for a paper they published in December, Fitzsimmons and his colleagues concluded that it probably has an inner core of ice, surrounded by an outer “carbon-rich mantle. The mantle is thick enough to protect the ice from melting even as it flew close to the Sun—and that’s why ‘Oumuamua lacked a comet-like tail.
Our Universe is thought to contain about 100 billion galaxies. As far as we can tell, our own galaxy, the Milky Way, is ordinary and average in every way—and yet it contains about a trillion stars. So if our SETI efforts focus only on the Milky Way, that is by itself an unimaginably large task which is by itself an unimaginably tiny fraction of what it would take to examine every galaxy out there. Though of course it’s foolish to set out to examine every galaxy, and nearly as foolish to examine every star in the Milky Way. Instead, we look for evidence of planets around stars. That’s no easy thing either, because stars are blindingly bright compared to any possible planets. So what we’re really looking for is a star whose brightness varies regularly, because that could suggest planets orbiting around it (see my column “The variation tells the tale", bit.ly/2CGJ4uz)
But let’s say we locate a star that has planets orbiting it. That would be encouraging, but we’d still need to determine if they are just sterile lumps of rock and ice or if there is life of some kind on them. To support life, a planet needs to be at least a certain age, but also a certain distance from its star. And if there is life, what kind of life is it? Just bacteria? Or is there intelligence? Might we run into a civilization like ours? If so, what would it take to communicate with it? How technologically advanced might it be?
There are various ways to make educated guesses that would help answer all these questions.
One MIT analysis, for example, concluded that there are about “100,000 planets in our galaxy [that are] candidates for talking with us." (John A. Ball, Extraterrestrial Intelligence: Where is Everybody?, 1985). That number is a huge improvement from the trillion stars in the Milky Way; but as you can imagine, examining even 100,000 planets for signs that someone wants to talk remains a huge task.
And then there’s the occasional challenge of examining unusual objects. Is there a civilization out there that’s technologically advanced enough to send out interstellar probes?
Maybe one that’s shaped like a cigar and programmed to zoom through a solar system with planets named Jupiter and Mars, Mercury and Earth? Given all this uncertainty, it was indeed overwhelmingly likely that ‘Oumuamua would turn out to be just another rock tumbling through space.
But even so, scientists knew we couldn’t let it get away without at least checking if it was more than that. If it was made by some alien beings, they reasoned, ‘Oumuamua should be emitting some kind of radio signal—whether to communicate with its home, or with us, or simply as those aboard—if anyone—go about their spacefaring lives. Searching for such signals is the foundation of SETI efforts.
Breakthrough Listen is a SETI initiative by the Russian billionaire Yuri Milner. He also sent tiny Sprites into space last June (see my column “Tiny SpaceChips to take us to stars" bit.ly/2Co5VXR). Milner plans to “survey one million nearby stars … and 100 nearby galaxies" in the “search for evidence of technological life in the Universe." Naturally such a survey will generate vast amounts of data; Breakthrough Listen’s software is designed to search for patterns in the data that would suggest an artificial source.
Isro’s latest Polar Satellite Launch Vehicle (PSLV) launch takes the idea of interstellar travel beyond conception to early execution, if only to show that it can become a reality someday
On 13 December, Breakthrough Listen began observing ‘Oumuamua, looking for artificially produced radio signals. But you guessed it: they found nothing. As Alan Fitzsimmons, astronomer at Queen’s University in Belfast, commented to Forbes magazine: “This is a natural object. Absolutely. Pretty much a space cucumber."
Studying ‘Oumuamua for a paper they published in December, Fitzsimmons and his colleagues concluded that it probably has an inner core of ice, surrounded by an outer “carbon-rich mantle". The mantle is thick enough to protect the ice from melting even as it flew close to the Sun—and that’s why ‘Oumuamua lacked a comet-like tail.
Again, think what it must take to learn that much about a tiny, faraway rock speeding through space. It’s why I always feel that the whole SETI effort is valuable not so much because it might find an alien intelligence—which hasn’t happened yet—but because of all the scientific endeavours it stimulates.
So as you read this, our cigar-like interstellar visitor is whizzing away from us very quickly indeed. It will pass Jupiter’s orbit in May, Neptune’s in 2022. If you think that’s a flavour of the great distances out there, try this: reaching the very outer edges of the solar system will take intrepid ‘Oumuamua more than 20,000 years. So here’s a tip: Don’t go breaking your heart waiting for it to return.
As Fitzsimmons also commented: “We’re done with this chap now. ‘Oumuamua is headed back out to the stars."
Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. His Twitter handle is @DeathEndsFun
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