Much ado has been made as of late over the
object 1I/2017 U1, or ‘Oumuamua, or in some circles, Rama. The story began on October 19, 2017 at the
Haleakala Observatory in Hawaii, home of the Pan-Starrs facility, a group of telescopes
and equipment designed to survey the sky for moving objects such as near earth asteroids,
some of which could potentially pose a threat to earth. A researcher there, Robert Weryk picked an
object up 40 days after it made its closest approach to the sun. This object has turned out to be very strange
indeed, and continues to fire debate to this day. From the moment of its discovery, the mystery
of Oumuamua has only deepened. When the object was first spotted, it was
very close to earth, only about 85 times the distance of our moon, or .22 astronomical
units, and it had already passed its closest point to us, which was only about .15 AU. The sun, for comparison, is about 1 full AU
from us, roughly 93,000,000 miles. Needless to say, this was a very close flyby
of our planet by an object in terms of the size of the overall solar system. But, it’s worth nothing here that objects
do pass much closer. For example, in 2004, a very small asteroid
passed earth at only about 1/10th of the distance to the moon. There have been even closer calls, with another
such object grazing the earth’s atmosphere in 1972 where witnesses in western North America
saw a huge fireball and heard double sonic booms only to then watch the fireball leave
the atmosphere and head back out into space. It simply came in at too shallow of angle
to hit us, but did enter the atmosphere. But, as the great Chelyabinsk fireball of
2013 showed, or Arizona’s Barringer crater, objects from space do also smack squarely
into us fairly regularly. Oumuamua, however, was never in any danger
of doing that and never will be. While it passed close, it didn’t pass dangerously
so. Originally classed as a comet, and then an
asteroid when no coma or off gassing characteristic of comets was observed, it then quickly became
evident that the object was neither a normal run of the mill comet nor an asteroid originating
from our solar system based on its trajectory. Instead, it came in at a very odd angle and
speed, which was hyperbolic, meaning it almost certainly had to be of interstellar origin. it was likely that this object had originated
in another star system entirely. This led the International Astronomical Union
to come up with an entirely new classification to fit this object, the I in 1I/2017 U1 stands
for Interstellar. It was then given the name ‘Oumuamua, translating
in Hawaiian to roughly “first distant messenger”, though the name Rama was, as i mentioned,
also floating around after Arthur C. Clarke’s novel, Rendezvous with Rama and subsequent
installments of that series. It’s anyone’s guess which name is more
fitting, since in the months after it’s discovery, murmurs of a possible, though highly
unlikely, alien origin for this object have surfaced within some parts of the scientific
community. But before we move on, let’s first talk
about the interstellar nature of the object. Is it really from another star system? The answer is yes. Up until recently, there was still a chance
it was not. It was possible that something in the outer
solar system might have tossed Oumuamua into a hyperbolic orbit, and that it’s origins
could have been our own Oort cloud. This now seems discounted, and the physics
of Oumuamua seem to exclude it from being from here. So, if interstellar, the natural question
here is to ask what the origins of Oumuamua might be. This is, unfortunately, very murky. While Oumuamua came from the direction of
the star Vega, one of the brightest in the night sky that does happen to have a debris
disk, it doesn’t appear to be related to it and couldn’t have originated there. Rather Oumuamua may have originated from very,
very far away, a very long time ago, with some estimates that before encountering the
solar system, the object may have circled the Milky way multiple times over immense
amounts of time. Given that the origins of Oumuamua are probably
a matter of ancient history, retracing its steps backwards to its origins seems an impossible
task, in the same grain as reconstructing the exact movements of a game of billiards
that was played a hundred years ago by only knowing the trajectory of the last shot. Not enough information is preserved to reconstruct
the whole game. Same story with Oumuamua. But there are some other possibilities. In a paper by Coryn Bailer-Jones and colleagues,
link to all papers mentioned in this video in the description below, several marginally
possible origin candidates are advanced, though the paper itself warns that none of them are
particularly good and in coming years many more candidates may come to light … though
those may not be particularly good either. The study looks at reconstructed close encounters
Oumuamua recently had, at least geologically recent. One of these was with a red dwarf about a
million years ago, and another with a Type G5 dwarf about 3.8 million years ago. It’s possible that within these systems
Oumuamua might have been ejected by a gas giant, though none of these systems are currently
suspected of having planets, so it more likely simply passed through them, though not as
near is it passed our sun. Perhaps a better option, given the velocities
of Oumuamua, is a binary star system, though no good candidate for a binary star system
in Oumuamua’s reconstructed recent path has yet been found. But the dynamics of such a system might account
for Oumuamua’s behaviour. More likely is that Oumuamua has been wandering
the galaxy for immense amounts of time, in such case its origins will probably never
be known. In a paper by Q. Zhang, the idea of further
trying to backtrack Oumuamua’s path is covered. The problem of tracing the origins of any
interstellar object is discussed, and while data releases from GAIA spacecraft and other
sources will make the task a little easier, it will still be difficult if not impossible
to trace any object’s path backwards more than a few tens of millions of years. That’s about the best we’ll be able to
do for Oumuamua and future interstellar object discoveries. However, for objects more recently ejected
from their star systems, we may have occasional success. For example, it’s known that the relatively
nearby young star Beta Pictoris has a huge debris disk that’s ejecting material that
seems to be passing through our solar system constantly. That system is also known to have comets,
so if one happens to get ejected and sent our way, we should in principle be able to
pin down Beta Pictoris as the origin should that happen. One final possibility, at least out of those
that scientists have thought of so far, is particularly interesting. That Oumuamua may not have been ejected from
a run of the mill star system, but from a more exotic source. In a paper by Roman Rafikov, the idea that
a white dwarf could produce tidal disruptions of rocky planets and planetoids ejecting material
like Oumuamua, or even ejection during a supernova event. This is due in part because of the odd apparent
physical traits of Oumuamua, more on that in a minute, but ultimately this is probably
a less likely scenario than an ejection from a binary star system long ago. Regardless of the origins of Oumuamua, as
the story unfolded it became apparent that this object wasn’t just interesting due
to its potential interstellar nature, but also its shape. As it turns out, Oumuamua is like nothing
else we’ve ever seen as far as objects in our own solar system are concerned. The first hint that something wasn’t quite
normal with this object came in the form of a very unique light curve that showed that
Oumuamua brightened and dimmed relatively rapidly as it moved through the solar system. Initially this was thought to be due to Oumuamua
being a very elongated object that was tumbling. Essentially a cigar shape that reflected more
light at times as it rotated about once every 8 hours. Another possibility is that it was a very
flattened object, something like a pancake. In a paper by Karen Meech and colleagues,
they detail many of the strange aspects of this object. Also, for those interested, I recently interviewed
Dr. Meech on my second channel, Event Horizon, link to that show in the description below
and in the end screen. Then there is the nature of the object. Initially, Oumuamua was suspected of being
a comet. The problem is, a comet passing as close to
the sun as Oumuamua did, should have outgassed as volatile ices evaporated blowing dust off
the surface and forming a coma and tail, as in a normal solar system comet. The researchers note that no such cometary
activity was seen with Oumuamua, and if it were a comet, there’s no reason that the
volatile ices it contained wouldn’t last billions of years as it crossed space. Yet, the composition of Oumuamua, based on
spectroscopic study, show that the surface of the object appears very similar to objects
in our own solar system, some of which incidentally happen to be rich in organics. But there’s a further mystery here. If interstellar comets are common, it seems
likely that in the last few hundred years that we’ve been able to work out cometary
orbits, we’ve yet to see one and we should have. Such objects should be relatively primitive,
ejected from extra-solar Oort clouds. That would mean that their ices should be
fully intact, and encounters with stars rare. So if one did enter the solar system and approach
the sun, it should have produced a detectable, possibly even spectacular, comet tail as objects
from our own Oort cloud do, yet be on a hyperbolic trajectory indicating an interstellar origin. That has never been seen. But the idea of extra-solar comets passing
through the solar system is an interesting idea in itself, because of the organics they
may contain. Comets are a candidate for having delivered
the building blocks of life to earth. There are even meteorites that are thought
to be cometary in origin that contain amino acids. While there’s no reason to suspect this
happened with earth, it’s possible that interstellar objects may play a role in the
universe in seeding exoplanets with the building blocks for life to get started. And it may also be possible, given the right
circumstances, for these objects to seed life itself through panspermia. On the other hand regarding extra-solar comets,
there are currently two candidates in our solar system that may have once been interstellar
comets. But it’s unclear how old they are, or when
they were captured. So perhaps comets passing through the solar
system are uncommon, but not particularly rare. Or, perhaps it’s just a fluke that we haven’t
seen one, and in coming years, one might yet pass through. But if Oumuamua isn’t a comet, then the
natural alternative would seem to be an asteroid, though the line between an exhausted comet
and an asteroid is rather thin. But it doesn’t seem likely that Oumuamua
would be an exhausted comet, rather that it’s more likely that this is the closest it’s
ever approached a star and outgassing should have been clearly evident. It wasn’t. An asteroidal nature for Oumuamua would be
a bit more surprising however, since asteroids are thought to be significantly more rare
in the universe than comets, based on what we know about the formation of star systems. Add in the odd shape of Oumuamua -- no other
like object has been seen in the solar system to date -- and we have an object that stops
fitting neatly into either category. That puts Oumuamua potentially into odder,
more unconventional territory. One possibility is that Oumuamua might be
a fragment of a tidally disrupted planet, in other words a shard of material from a
destroyed world. That would make Oumuamua a much rarer object
in the universe than a comet or asteroid, enough that it should probably be intercepted
and studied, since we aren’t likely to run across things like that every day, in fact,
it could be thousands of years before such a thing is seen again. But, there’s one last possibility on the
table, unlikely thought it is. This is where the story of Oumuamua takes
an even more bizarre turn. As noted by Dr. Meech in her TED talk on this
object, it can’t be ruled out, no matter how remote the possibility might be, that
Oumuamua may instead be of artificial alien origin. That’s not to say that it is, it probably
isn’t, but simply that it cannot be ruled out. But the story of Oumuamua grew even stranger
in late June of 2018. In a paper by Marco Micheli and colleagues,
they detail the discovery that Oumuamua accelerated as it left the inner solar system. Accelerated is perhaps too strong of a word
here, it’s more like Oumuamua left the solar system less slowly than it should have given
the gravitational effects on it from the sun. This would seemingly have a mundane answer;
that Oumuamua was in fact a comet even though it didn’t entirely look like one. Cometary outgassings can act as a kind of
natural thruster and impart a bit more speed to an object than the effects of gravity alone
can account for. The problem is, no such outgassing was observed
with Oumuamua. It could possibly be that we somehow simply
missed it when it happened, or that it was imperceptibly slow, or that the outgassing
was difficult to detect with the data we have, such as outgassing from pure water ice, but
that still should have blown off dust which should have been detectable. And, there’s another issue. Given Oumuamua’s odd shape, any outgassing
should have upset it’s tumbling and that should have been detectable, though it’s
also possible that the outgassing came from a point on the object where it wouldn’t
have changed anything. But, more recent research by Rafikov shows
that it’s likely that any kind of outgassing should have changed Oumuamua’s rotational
torque enough to destroy it. This mystery has since further deepened. In November of 2018 in a paper by David Trilling
and colleagues, again link below, they detail the results of an observation, or more precisely
a non-observation, of Oumuamua using the Spitzer space telescope. By non-observation, I mean that they looked
for the object in infrared and didn’t see it. That in itself is telling because they should
have. It means that Oumuamua must be very small,
on the order of hundreds of meters in size. This is odd indeed, because to have been seen
at all in the earlier observations, it would require Oumuamua to also be very highly reflective,
unusually so. As Oumuamua revealed itself to be an increasingly
strange object, the notion that it may be of alien origin has been increasingly looked
at, remote though the possibility is. SETI teams, for example, just to be sure,
listened to Oumuamua for radio emissions. None were detected. And while it’s highly unlikely for this
object to be of artificial origin, it’s very likely a weird natural object, accumulated
weirdness surrounding this object is raising some eyebrows. In a paper by Abraham Loeb of Harvard, he
details six of these strange attributes of this object. He points out that Oumuamua should never have
been discovered in the first place. This is based in an earlier paper co-authored
by Loeb where it was predicted that the abundance of interstellar asteroids would be too small
for it to be likely that we’d just happen to catch such an object serendipitously as
happened with Oumuamua, meaning that whatever spawned Oumuamua must be more common than
what we see with our own solar system. Loeb also points out that Oumuamua originates
from a weird frame of reference, the LSR or local standard of rest. He goes on to point out that this is ideal
if you want to camouflage an object if you want to hide its origins, though it’s also
possible that Oumuamua has just been wandering so long in the galaxy that it simply settled
into this frame of reference. But there’s more. Oumuamua would have had to leave it’s star
system of origin with an unusually high velocity, meaning that whatever the circumstances of
it’s ejection were, they are very likely rare and unusual. Also, there’s the shape, Oumuamua would
have to have a length at least 5 times its width, or possibly as much as ten. The most we’ve seen with solar system objects
is three. And then there is the Spitzer observation,
which means the object must be small, and lastly there was the unexplained acceleration. These attributes led Bialy and Loeb to author
a paper that the acceleration could be due to solar radiation pressure, if Oumuamua were
very thin, a millimeter or less. This begins to look consistent, and I stress
that, look consistent, with a light sail of artificial origin. For it to be that, it would have had to have
been targeted towards our solar system. Standing for that possibility is the age of
the earth. Earth’s oxygen has been visible to the galaxy
for a very long period of time, well enough for astronomers from other star systems to
have spotted Earth as an exoplanet, and concluded that the unusual amounts of oxygen in our
atmosphere was most likely the result of a biosphere. Perhaps at some other point they might have
found further evidence through the detection of other biosignatures of life on this world
and sent a probe. Also marginally going for it would be the
acceleration, which is still unexplained, but slow outgassing from a natural object
seems far more likely there. Standing against it are several things. Firstly, what are the chances of just happening
to spot an alien probe just as it passed through the solar system? Not very likely, unless they pass through
constantly. It seems more likely that rocks and ice coming
in from interstellar space would be pretty common, especially if dying stars lose their
Oort clouds into space, even if bearing odd attributes unfamiliar, so far as we know,
to objects in our own solar system. Another issue is that Oumuamua appears to
be tumbling, and that doesn’t seem to be a good fit with a light sail. Also Oumuamua seems to be traveling counterintuitively
slow for an artificial object, it presumably took millions of years to get here, though
who knows how an alien civilization might perceive time. Also there’s the apparent consistency in
spectral studies of Oumuamua with objects in the outer solar system, it essentially
looks like a reddish object that’s been bombarded by radiation in the interstellar
medium for long periods of time. On the other hand, it might have accumulated
that dust over time. That’s also a possibility to explain it’s
high reflectivity. If Oumuamua were a piece of water ice that
had a layer of material deposited on its surface , and that material was slowly stripped away
during its encounter with the sun, that might not have been seen, and bright fresh ice might
explain the reflectivity. At the same time, it pays to weigh all options,
both natural and artificial. I personally suspect that Oumuamua is a natural
object that encountered unusual circumstances in past encounters with stars, or within it’s
home star system, at least from what we know from our own solar system. But, with new instrumentation coming online,
more light might be shed on just how unusual of an object Oumuamua was. And while it’s close pass to earth is weird,
and it might be consistent with an alien light sail checking us out, it seems more likely
that there are many such interstellar objects passing through the solar system on a constant
basis, and if so, many should come to light when the Large Synoptic Survey Telescope comes
online in 2019, with first science light in 2021. If, however, the LSST does not reveal many
such objects, then Oumuamua will fast become the most interesting object we’ve ever seen,
and intercepting it, which would be difficult but is possible, will become a priority very,
very quickly. Thanks for listening! I am futurist and science fiction author John
Michael Godier and be sure to check out my books at your favorite online book retailer
and subscribe to my channel for regular, in depth explorations into the interesting, weird
and unknown aspects of this amazing universe in which we live.
