
Interstellar Visitor Found to Be Unlike a Comet or an Asteroid - Bootvis
https://www.quantamagazine.org/interstellar-comet-oumuamua-might-not-actually-be-a-comet-20181010/
======
InclinedPlane
This is a little misleading because it presents the idea that there is a firm
separation between "comets" and "asteroids", each of which have very different
properties. In reality we've discovered in recent decades that there is
significant overlap. Pure comets were formed in the outer solar system beyond
the frost line, and they are composed of a mixture of primarily chondritic
grains and ices. As noted such bodies are not very structurally strong so if
they approach the Sun too closely they will break up from the stress of
gravity as well as from the intensity of off-gassing vaporizing gasses. On the
other hand you have classic asteroids which are formed inside the frost line
and are made up of either chondritic material, stone, or metal (depending on
their histories). Such asteroids can be much stronger but they lack the ices
which might off-gas during a close solar encounter.

Except, that dichotomy is a simplified fiction. The reality is that there are
objects in the middle, sometimes called "iceteroids" which we've discovered
over the years. These could be the cores of comets which have lost most of
their ices or these could be objects with more complicated histories, such as
asteroids which have accreted surface layers of ices through various
processes.

So this is a mystery but it's not some enormous mystery it's a small mystery.
The idea that an asteroid could have acquired a small amount of ices on its
surface isn't exactly world shattering news but because we don't know the
history of the object we don't know the process by which it ended up with its
observed properties.

~~~
Balgair
To me, the interesting thing is that this iceteroid (love the term!) is
definitively extra-solar and that means that it is likely that other systems
have both asteroids and comets. Though we've seen asteroids in other systems
like Fomalhaut [0], we've not been up close and personal with the compositions
of extra-solar material.

Here in the Sol system, we have a pretty strange arrangement of planets [1],
with big ones all in the outer system and smaller ones in the inner system. So
looking at just our system is not very indicative of 'typical' system
evolution, in terms of iceteroids. Once we figure out where Oumuamua came
from, that'll give us some idea of the compositions and evolutions of other
systems (data point of 1 is better than 0), like the frost line. Oumuamua
should be viewed as awesome and exciting, but as the tip of the ... iceberg
... when it comes to the real questions of stellar evolution and all the
awesome stuff happening there.

[0][https://en.wikipedia.org/wiki/Fomalhaut](https://en.wikipedia.org/wiki/Fomalhaut)

[1][https://en.wikipedia.org/wiki/Nice_model](https://en.wikipedia.org/wiki/Nice_model)

~~~
InclinedPlane
Good point. One thing we learned from exoplanet hunting is that there is a
much greater diversity out there than we had originally thought, implying that
planet formation is a lot more of a dynamic process than our previous models
indicated. Prior to the discovery of exoplanets our planet forming models were
very much "over fit" to the example of our own Solar System, giving the
impression that other stellar systems would end up looking similar to our own.
The reality is that our Solar System is, as you say, probably unusual. One
aspect of this is that it seems like planetary migrations are pretty common
(both inward and outward). If that sort of thing happens early during planet
formation then it could easily explain an "asteroid" (which we understand is
almost certainly a planetessimal fragment, though many asteroids are just
that) which has acquired additional material including ices.

The obvious followup here is that we need way, way more closeup observations
of small bodies in our own Solar System, we probably also need to develop
better techniques for observing interstellar interlopers, and we need to
improve our studies of extrasolar planetary systems. Fortunately the first
part is already covered, between the Hayabusa 2, Osiris-REX, Lucy, Psyche, and
New Horizons missions we should collect a lot more information on such bodies.
However, it's probably going to be a long time before we have answers even to
simple questions like the formation histories of most small bodies in stellar
systems and what the "average" stellar system looks like.

~~~
Balgair
I have close friends working on Psyche! You are right that our understanding
of small bodies is going up very quickly, it's quite exciting (in asteroid
terms) to be alive now; a lot is being answered and re-questioned with actual
evidence.

Hopefully (knock on wood) JWST gets up there soon and a LOT more questions can
be answered.

One issue we have is that there is this 'gap' in planet formation modeling. We
can figure out small bodies and large bodies, but things that are ~1m to ~1km
in size don't work in the models; they should all just fly apart. Somehow
planets do form, but getting there is a pickle, theoretically. Asteroids are
likely THE key to understanding that gap, and that should help out with a LOT
of system formation dynamics.

Also, I'm still bullish on finding a LOT of platinum/gold on asteroids,
because space mining. Like, eat your heart out Bruce Willis.

~~~
InclinedPlane
Awesome! I'm constantly bummed out about the failure of the CONTOUR mission, I
can only imagine what we'd know now. Psyche is one of the coolest missions in
the pipeline though, it's kind of crazy how fast our knowledge of small bodies
is growing.

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TangoTrotFox
This article is excellent. I wondered about this exact issue before.
Prograde/forward acceleration only from outgassing from a constant surface
just seemed difficult to visualize. It would make some sense for an object
with minimal spin since the side facing the sun would heat up more than the
rest of the surface and so you'd have an outward acceleration primarily from
the rear, but when you're spinning how could the outgassing not also
[strongly] affect that spin, excepting some highly improbable scenario where
your axis of spin is directly perpendicular to the sun and the 'thing' is
perfectly balanced, like a propeller facing the rear of a plane?

I also wish more media ran articles like this. It's fun to let your
imagination run wild, apply a bit of math and visualization, and also learn
lots in the process. And there's no division. Even if somebody says something
completely wrong, people can have fun correcting and adjusting their views
like a collaborative project instead of some competition to 'prove' your
subjective interpretation right, as so many other topics devolve into.

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yitchelle
I am truly surprise that we don't get more interstellar visitors into our
solar system. It kind shows how small our solar system is, or other way, how
big the universe is.

~~~
ceejayoz
There's a good chance these sorts of things are whizzing past us all the time,
and we're just not detecting them.

I mean, we just discovered ten new moons of Jupiter this year:
[http://earthsky.org/space/10-new-moons-discovered-
jupiter-1-...](http://earthsky.org/space/10-new-moons-discovered-
jupiter-1-oddball)

~~~
dmix
And two the year prior, bringing the count to 12 since 2016, for a total of 79
moons around Jupiter.

~~~
ecnahc515
How many moons are discovered per-year on average? Is there something about
these recent ones that made it difficult to discover earlier, eg size?

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newnewpdro
It's too bad we're not ready to launch probes to visit and explore such
transient objects at a moment's notice.

~~~
_ph_
I think it would make sense to plan a probe mission where the probe would be
put into storage to stand by for these kind of events. It would still be a
challenge and might be impossible to find a launch window and reach the
passing object in time, but it would be worth trying.

Just imagine how tragic it would be, if an ancient artifact of an alien
civilization drifts by earth and we don't manage to have at least a look at
it.

~~~
holografix
Wouldn’t such an object be emitting radio signals that earth could receive?

~~~
newnewpdro
Not if it's something like another civilization's Tesla Roadster.

~~~
westurner
> _Not if it 's something like another civilization's Tesla Roadster._

'Oumuamua is red and headed toward Pegasus (the winged horse) after a very
long journey starting longtime in spacetime ago. It is wildly tumbling off-
kilter and potentially creating a magnetic field that would be useful for
interplanetary spacetravel.

They're probably pointing us to somewhere else _from somewhere else_.

If this is any indication of the state of another civilization's advanced
physics, and it missed us by a wide margin, they're probably laughing at our
energy and water markets; and indicating that we should be focused on asteroid
impact avoidance (and then we will really laugh about rockets and _red_
electromagnetic kinetic energy machines and asteroid mining).
[https://en.wikipedia.org/wiki/Asteroid_impact_avoidance](https://en.wikipedia.org/wiki/Asteroid_impact_avoidance)

"Amateurs"

[We watch it fly by, heads all turning]

Maybe it would've been better to have put alone starman in the passenger seat
or two starpeoples total?

Given the skull shape of October 2015 TB145 [1] (due to return in November
2018), maybe 'Oumuamua [2] is a pathology of Mars and an acknowledgement of
our spacefaring intentions? Red, subsurface water, disrupted magnetic field.

[1]
[https://en.wikipedia.org/wiki/2015_TB145](https://en.wikipedia.org/wiki/2015_TB145)

[2]
[https://en.wikipedia.org/wiki/%CA%BBOumuamua](https://en.wikipedia.org/wiki/%CA%BBOumuamua)

In regards to a red, unshielded, earth vehicle floating in solar orbit with a
suited anthropomorphic creature whose head is too big for the windshield:

"What happened here?"

~~~
westurner
"That's not a knife... _This_ is a knife." \-- Crocodile Dundee

------
nrjames
This reminds me of Rendevous with Rama, which I’m currently reading with my
daughter.

~~~
divbzero
’Oumuamua’s “mysterious thrust” [1][2] is obviously from rocket thrusters
which undoubtedly come in threes.

1: _[’Oumuamua] was being slightly accelerated by an unseen force, which they
argued could only be attributed to comet “outgassing” acting like a thruster._

2: _Now in a new study that is currently under peer review, Roman Rafikov, an
astrophysicist at the University of Cambridge, argues that the same forces
that appeared to have accelerated ’Oumuamua — the same forces that should have
also produced a tail — would have also affected its spin. In particular, the
acceleration would have torqued ’Oumuamua to such a degree that it would have
spun apart, breaking up into smaller pieces. If ’Oumuamua were a comet, he
argues, it would not have survived._

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xrayzerone
I'll ask what everyone is thinking but won't say. If the acceleration is in
fact being caused by artificial thrusters, what kind of thruster configuration
can produce prograde acceleration while maintaining the observed tumble? And
why would someone engineer this configuration?

~~~
TheOtherHobbes
It's maybe worth pointing out the tumbling is a hypothesis used to explain
variable brightness measurements and not something that was observed directly.

[https://arxiv.org/pdf/1712.00437.pdf](https://arxiv.org/pdf/1712.00437.pdf)

For all anyone knows the intrinsic brightness was variable.

(This is probably not very likely without some supporting spectroscopic
anomalies. But still.)

As for thrusters - that's the same problem as the comet and outgassing
hypothesis. No known mechanism can explain the acceleration.

And if you were alien race and wanted to look at a planetary system without
attracting attention, something that looks like a tumbling rock with a
plausibly improbable trajectory would be ideal.

It could just be a coincidence that the first large proven extra-solar object
slingshotted around the Sun in a way that happened to pass close by the Earth.

But considering the size of the Solar System and the convenient phasing of the
Earth's orbit, what are the odds? It's certainly very curious.

~~~
checkyoursudo
If aliens could do this to make the object look inconspicuous, then why not
make it look _not_ suspicious as well?

Someone just f'ed up the config files?

~~~
rdtsc
They deployed on a Friday. They should have known better :-)

Sorry couldn't resist and hey, it's also Friday today.

I wonder if it was aliens and they made it just slightly interesting without
making it look completely obvious. Then they'd monitor and see how we would
react. Would we be able to detect. Would we go chase it? Beam microwaves at
it. Do we have the capability to fire projectiles at it.

~~~
checkyoursudo
So you're saying it's possibly an interstellar alien cat toy to test our
curiosity and willpower? Plausible.

------
xab9
The Dig comes to my mind from 1995.

~~~
artificial
“I miss you too darlin’...” such an epic soundtrack. Bah, I gotta listen to it
now!

------
DaveSapien
Would gravitational pull account for the acceleration? Meaning if it were made
(or part of it) of some very dense element like Iridium, there would be an
unexpected attraction to our sun?

~~~
Cthulhu_
Nope; gravity is very predictable and very constant (see also the difficulty
in detecting gravitational waves), they calculated how much it should
accelerate under influence of gravity and found the actual acceleration to be
different.

As for the unexpected attraction, as one of the moon astronauts displayed,
objects of different mass are attracted (fall) equally quickly by gravity in a
vacuum.

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sjclemmy
I'm still convinced this is an alien probe. I mean look at that trajectory.
0.163 AU from Earth - what are the odds? The spinning is irrelevant surely - I
mean, it's all relative, so as far as ’Oumuamua is concerned, we're spinning.
Maybe it was spinning that way to stay aligned with a distant companion for
communication.

~~~
p2detar
This has always fascinated me. We can actually build giant spaceships (space
stations) inside asteroids and use them for interstellar travel. All the
resources we need, including ice would be at our disposal. Like traveling with
your own mini-planet.

Dirk Schulze had taken that as a subject into his sci-fiction book - Alien
Encounter.

~~~
tomp
From an energy perspective, it's likely better to build your own station (from
an asteroid - or alternative, remove all the mass from the asteroid that you
don't need) - that way, you're only accelerating _exactly_ the mass that you
need, not wasting any energy accelerating the rest of an asteroid.

~~~
neuronic
I think he is talking about chilling on the asteroid while it follows its
known trajectory undisturbed, simply because they are packed with useful
resources we can gobble up while waiting.

Asteroid are per definition not interstellar though (until Oumuamua?).

~~~
rbanffy
An interesting approach would be to send an automated ship builder robot fleet
to dismantle an asteroid and board the fully furnished ship when it makes
another close approach, and then boosting it to its final destination.

I'd love to see a scenario where we'd build robot terraforming fleets that'd
land on an uninhabited planet, make it habitable, complete with spaceports,
cities, factories, crops (all permanently tended for robots), build a couple
extra fleets and launch to their next most promising targets.

And then, for some reason, humans lose interest in all that and someone else
wakes up to find a universe full of 60's futuristic utopian planets nobody
ever lived in.

~~~
p2detar
_someone else wakes up to find a universe full of 60 's futuristic utopian
planets nobody ever lived in_

Reminds me of the paperclips game [1]. Would be horrid to find those people
wake up and find the universe transformed into nothing but paperclips. [1]

[1]
[http://www.decisionproblem.com/paperclips/index2.html](http://www.decisionproblem.com/paperclips/index2.html)

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santoriv
Based on the comments in this thread, I'm sure this will soon be an episode of
'Ancient Aliens' on the "History" Channel. If it isn't already.

~~~
goatlover
How Oumuamua inspired the Egpytians to use logs and slave labor to build stone
pyramids, like any advanced ancient alien would.

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drwasho
’Oumuamua, I’ve come to bargain!

~~~
goatlover
There was no other way.

