That Interstellar Asteroid Is Pretty Strange | Hacker News Reader

That Interstellar Asteroid Is Pretty Strange

blogs.discovermagazine.com

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Here is the random astronomer on Reddit claiming that the community didn't rule out that it is an abandoned spaceship yet: https://amp.reddit.com/r/space/comments/7ealls/solar_systems...

"Astronomer here! I will never say this lightly, but we are, swear to God, actually discussing with some seriousness right now what are the odds that this was actually a spaceship. Which I 100% assure you has never happened before in my memory with seriousness."

"Rendezvous with Rama" theorized such an incident. Shame we spent too much of the last century blowing each other to smithereens rather than developing the technology to figure it out for sure.

Well hey... It's possible. Not likely but possible.

It could be a dormant long term hibernation ship en route somewhere. Computing it's trajectory would be a way to look at this. Very long term deep hibernation would be one very plausible way to go to the stars.

It could also be a ship that malfunctioned and died millions or even billions of years ago. If it were traveling very fast it could play stellar gravity ping pong for a long time until eventually settling into an orbit, hitting something, or being ejected from the galaxy. Picture some insectoid alien mummies playing silent vigil in cold intergalactic space until the heat death of the universe and bust out the theramin.

Whatever it is I wish NASA could cook up a flyby. A light small prove could probably get tossed on a high enough energy trajectory to catch it and take some pics. Surely the first extrasolar object is interesting.

Edit: elsewhere several people pointed out that a tumbling object like this might not be an interstellar ship/probe but a spent expendable acceleration stage for one.

If it's a spent stage, then the parent vehicle is also traveling very close to 26 KM/sec and is already here.

... or arrived a while ago? There could be many acceleration and deceleration stages.

Why the hack do you assume it's abandoned? It can be full of lifeforms even and we are just not able to see them, talk to them, etc. Imo at this point any assumption is closing in too much. We don't have a definiton of "life" that for sure would include extraterrestrial lifeforms that are not actors with masks in star trek, right?

Well, it's tumbling end-over-end which suggests that if it's a spaceship, it's no longer in control.

The discussion around the possibility of it being a spaceship rests on the idea that long thin cigar-shaped objects are the most efficient way to travel in space because it minimizes your need for ablative protection from interstellar dust/etc. But if you're tumbling end-over-end you've thrown that advantage away, so presumably that's not a thing you would intentionally do. And if you are assuming that this spaceship has shields or whatever, then there is no reason they would be restricted to a cylindrical shape.

It could be a discarded booster stage or fuel tank, of course. Maybe they were trying to drop it into the sun and missed. Or a a mass-driver shot (maybe they finally took care of that pesky Russell's Teapot for us...)

The presumptive conclusion is of course that it's a natural phenomenon, but it sure is a weird object, and unless we can find a way to catch it (or any future objects) we will never know. Maybe a starshot probe could catch it?

The really interesting prospect raised in that Reddit thread is that while the velocity is likely wrong for an interstellar spaceship, it could be just right for the spent and discarded deceleration stage of an interstellar spaceship. In which case the spaceship would be arriving some time later...

I like this explanation best, as long as they're friendly.

Watch some rocket separations. Usually they end up tumbling.

It's already passed pedigree with the sun. It is traveling slowly enough that if it's a discarded stage the spaceship should already be here.

I'm assuming autocorrect helpfully fixed "perigee" to "pedigree" for you. It's a nice little malapropism though.

Anyway, minor point but "perigee" usually means closest approach to Earth; "-gee" is from the Greek for Earth (as is "geo-"). In the case of the sun, we have the word "perihelion", and for generic orbits around an object, you generally hear "periapsis".

And just for completeness, I'll mention that the counterpoint to periapsis is apoapsis, with apogee and aphelion being the obvious specializations.

There are more words in this pattern for various different objects; Wikipædia has all the gory details:

https://en.m.wikipedia.org/wiki/Apsis

Autocorrect figured out I meant that we need to make sure aliens have sufficient pedigree before we deign to talk to them.

How do you know that, without knowing the non-booster-assisted deceleration rate of the spaceship? (Presumably the hypothetical ship separated from the booster when that was out of fuel, and then the ship continued decelerating on its own to get to a velocity congruent with a stable orbit in our system).

The object is traveling at 26Km/sec, earth is orbiting at 30 Km/sec. To generate a "stable orbit" is a matter of maneuvering at that velocity. So it's really unlikely that the parent ship is traveling much slower than the discarded booster, and so it's arrival is unlikely to be much later.

I can counter this concept about the tumbling meaning it cannot be an active vessel thus: The vessel proceeds in a length aligned manner during its long interstellar traverse under the supervision of an AI which does not care about the time taken and when it nears a star system, its occupants are woken (or created) and a small bit of reaction mass is emitted in order to rotate and provide gravity for them. As it leaves the system, the occupants can go back to sleep and the rotation is halted while it proceeds to the next system.

I'm not saying that its a vessel, just saying that if it is one, then it presumably has some level of active ability, which could include the above. Thats not so far from Rama, actually.

But it could rotate about its long axis for artificial gravity no? Seems more "natural"...

Coriolis effects would be more pronounced with a smaller radius? Also, the rotational speed would need to be a lot higher to get the same gravitational effect, so the effects might end up many times greater. Its difficult to suggest what conditions these hypothetical aliens would need, of course..

The reddit thread has the following calculation. "At a spin rate of 1 rotation every 7.3 hours and a radius of 200 metres, an object on the inner surface of the very end of the "spaceship" would experience gravity at 0.000001g"

That's really far to small to simulate any type of artificial gravity.

0.000001g doesn't even seem like its enough to make liquids pourable.

Maybe it’s still spinning up to a higher rate?

As its already passed through the system (I think?) that would be spinning down.. though realistically for my scenario, it would fully exit the system before it did that.

How is it tumbling? Could that provide a force to simulate gravity?

Wouldn't tumbling a spaceship give you some basic gravity? Isn't that a desired outcome?

It appears to be tumbling end over end. It's possible that it's spinning end over end in order to generate artificial gravity at the ends, but this contradicts one basic design star-ship design principle. You build a long narrow ship so you can have heaviest particle shielding only at the narrow front to reduce shielding mass required.

But maybe since it's traveling so slow, they didn't need any excessive shielding. Maybe they have super light super strong shielding technologies. That itself would seem to be contradictory, given you'd think they'd have access to far more energy than would produce only 40 km/sec velocity.

This has always been my argument too! I understand that scientists want to start with what they know to narrow stuff down but is it not entirely possible that there's life on a planet that just doesn't work like ours? Obviously the organic structures that we're familiar with need a certain series of parameters to survive but that doesn't mean that any other kind of object couldn't end up being a sentient being.

It’s really traveling far too slowly to be a viable interstellar transport.

What does “viable” mean, though? For us, it might not be viable, but for organisms that live on a different (or even variable) time scale it might be just fine.

I loved Rendezvous with Rama, and one of it's central lessons is anything is possible when you talk about alien civilizations. We can't assume to know their motivations and technologies. But looking at the basic physics/engineering involved, if it's an alien vehicle it raises some interesting questions and skepticism. Imagine we wanted to build a similar vehicle.

If we wanted to send people to nearby stars, we'd likely need vehicles as big, or likely larger, than Oumuamua. If we were in a hurry to do it with present day technologies we'd have to build hundreds of SLS boosters to launch payloads so that astronauts could assemble a vehicle weighing tens of thousands of tons in orbit. And then we'd fuel it with tens of thousand of tons of fuel.

So we could build it. What would we use for propulsion? Not chemical rockets, 40KM/sec is only achievable for tiny payloads to fuel ratios with chemical rockets. Maybe we could do it with Nuclear rockets, which were tested and proven to be twice as efficient in the 1960s, ala NERVA.

Even then we'd only be able to use a bit more than half the fuel to accelerate towards our destination, if we wanted to stop there. So 40 km/sec would be extremely difficult to reach given how heavy it would be.

And at 40 km/sec it would take 8,000 years, nearly a hundred generations before reaching the nearest star. Assuming the life support systems could last that long, they didn't run out of food, water, air, etc. That the engines weren't degraded by radiation over 8,000 years so they would still work when reaching the target. It's extremely unlikely we could count on any of this being true.

But if we were ever to launch such a vehicle it would likely be outclassed very quickly. We already know how to build better propulsion systems. Existing ion drives are far more efficient, and theoretically offer over 100KM/sec speeds, we just haven't been able to scale them up yet.

If we can scale up ion drives or similar technologies, we already have designs for Project Orion are entirely feasible, and offer massive speed increases. Freeman Dyson's interstellar designs offer 1,000-10,000 KM/sec speeds. If it took us a hundred years to build one, it would likely pass a hundred year old NERVA ship within a year or two.

My point is we'd never launch such a slow vehicle as Oumuamua, because it would be relatively easy to build a significantly faster one. Even with todays technologies.

So it's reasonable to think that an Alien civilization that could build a ship the size and speed of Oumuamua, could build much larger, faster ships for interstellar travel. If Oumuamua is a ship, the question would be why didn't they?

One possible answer if Oumuamua is artificial, that it's not an interstellar vehicle. It's an interplanetary vehicle that had a complete failure of it's systems, and had just enough velocity to leave it's star system, and has been drifting for tens of thousands of years.

But in that were the case, how did it came so close to our Sun? It's reasonable to assume that many billions or trillions of asteroids and comets have been ejected by star systems, so that occasionally a few come close enough to ours to make the tight orbit around the Sun that Oumuamua did. But it's hard to imagine there are billions or trillions of space wrecks wandering the milky way such that one randomly passes this close to our sun.

> My point is we'd never launch such a slow vehicle > as Oumuamua, because it would be relatively easy > to build a significantly faster one. Even with > todays technologies.

There is one plausible reason. If a civilisation had serious doubts about surviving much longer, they might launch a slow ship as a last ditch effort, in case they didn't make it soon after. After all, even we could theoretically keep improving propulsion tech before sending out probes, but that didn't stop us from launching with our best efforts so far, even if only to test. And that's another reason. Maybe this is a test craft...

We will never know for certain unless we can send a probe to this rock.

We could have built project Orion in the 70s to get to another star system in hundreds of years or less.

There is no way we'd use chemical rockets, or even NERVA type nuclear to go to another star system, there is simply no hope they'd even get there as anything other than dead hulks in thousands or tens of thousands of years.

> If Oumuamua is a ship, the question would be why didn't they [build a larger and faster ship]?

Because they didn't know we were here?

Supposing you're exploring the galaxy, hyper advanced technology doesn't free you from efficient resource use as a priority until you can easily build enough to explore every star.

Given how many stars there are, I wouldn't be surprised if high tech civilizations still used the cheapest ships they could build.

I'd be curious if our EM emissions would have yet reached any potential source of the object...

Time always matters. Getting information back in 1,000 years instead of 10,000 years is huge.

And faster ships aren't necessarily less efficient, in many ways they are more efficient. Chemical rockets are incredibly inefficient.

Is that still the case if it intends to stop in our solar system?

It didn't stop. It's been on it's way out of the system for a while now.

> Occam’s Razor says it’s unlikely that the very first object we ever see from interstellar space just happens to be a spaceship.

Well, isn't this kind of self fulling thing?

Because we assume first that this is an interstellar asteroid, then the following statement is "proven":

> Researchers had long theorized that space should be full of comets and asteroids ejected from other solar systems during their early days. Their models showed that planetary formation is a messy business, with many small objects kicked out as big proto-planets form. `Oumuamua is the first proof that they were right

And at this point, yes, it appears very unlikely that the first interstellar object we meet would be artificial.

But if we start by saying we don't know what it is, then the above theory is just speculation, and might be false (what if planeraty formation is a clean process?). If the theory above can be false, then it could make sense that the first interstellar object we encounter would be artificial, no?

It seems to me that Occam's Razor doesn't tell us much in this instance.

Unfortunately, Occam's Razor can say whatever you want by fiddling the apriori probabilities. Here, the probability you need is how likely that theory is to be true - just because it could be false doesn't mean it's 50-50.

If all the models show planet formation is messy, it seems reasonable to estimate its probability as much greater than 0.5 (note that even if it's 0.9999, they still could be wrong).

Totally agree. My point is just that I find it a bit weird/circular to use Oumuamua as the `first proof` for a theory that is subsequently used with Occam's Razor to demonstrate that Oumuamua is likely not something else.

What I thought. The absence of a priori knowledge prohibits the application of Occam's Razor in this case.

Exactly what I was thinking reading this article.

Perhaps Oumuamua is a piece of evidence that fits this theory, but, is it really the first one? If it is the first one, it hardly proves the theory. At this point (from what I can see) we have a sample size of 1 (Oumuamua). Now, we also haven't been watching for very long (10 years or so where we could track this sized object) and aren't watching too much of the sky, but, this still doesn't prove anything.

So why exactly can we not get a better look at it as it is leaving? With all our earth- and spacebound telescopes [1] (some are sitting at Earth-Sun Lagrange points) I would imagine we could. Being too far away behind the sun seems an unlikely argument to me.

===

[1] https://en.wikipedia.org/wiki/List_of_space_telescopes

The only working telescope at a Lagrange point is Gaia [0] at Earth-Sun L2, but it is an astrometry instrument, designed to measure the position and brightness of various stars, rather than generic deep-space imaging. The Herschel Space Observatory [1] is also at the Earth-Sun L2 point, and has a 3.5m IR telescope, but ran out of coolant in 2013 and is now defunct. Interestingly, these are both ESA missions, not NASA.

0. https://en.wikipedia.org/wiki/Gaia_(spacecraft)

1. https://en.wikipedia.org/wiki/Herschel_Space_Observatory

NASA was involved in Herschel to an extent.

Seems like this is the same problem/discussion a distant civilization would have with Voyager

Voyager is much smaller, though. Can someone with relevant knowledge tell us if this object would be still detected if it was the same size as Voyager 1?

Would we have detected a Voyager-size or Voyager-like object entering our solar system? I really, really doubt it.

Or it would become a sentient being somehow while in deep space and haunt us back in 2271.

V'GER ..

>It’s also our first direct look at an intact visitor (as opposed to dust specks) from another solar system.

Would it not be possible to calculate the origin system based on speed, trajectory, star positions?

The problem is that the star positions change over time via galactic orbit. 'Oumuamua's trajectory appears to originate from Vega, but Vega would have been at a different position in relation to our solar system back when 'Oumuamua was at the same distance from the Sun as Vega.

Not only is the system in question dynamic, as another pointed out, but also subject to perturbations. Worse, orbital mechanics with many bodies is chaotic, in the strict sense.

I don't think so... it slungshot around the sun, which implies that its in a very large sun oriented orbit. (eg: some random object passing bit for the first time would be likely only slightly disturbed by the suns gravity, not coming so close to it... the latter seems to imply it has been caught by the suns gravity.... or just happened to be aimed nearly directly at the sun.)

No, they distinctly say it is hyperbolic, not an ellipse, so not orbiting the sun

These actually sound like last famous words.

Are there yet any credible theories for why we see so few of these? AIUI, if we're correct about how planets form, there should be far more of these than we're seeing. Is it that we're probably wrong about how planets form, or there's something strange about our part of the galaxy, something else or do we just have no clue?

Estimate is that there might be about ~10 of these object passing through every year, so it's not a lot to start with. In addition asteroids are relatively small and hard to spot since they are inert. We managed to spot this one because we were lucky it came so close to earth.

The general consensus amongst astronomers is that these objects are far too faint to be seen. As more sensitive instruments are developed/deployed, we should begin seeing more of them.

Is there any possibility we could launch a really fast space probe that could overtake this object and report back, maybe within the next decade or so? Do we have the technology now to pull alongside this rock (and it's going to be slowing down)?

I've seen a couple of suggestions for ways we could theoretically catch it. One is high-Isp rocket motors, which I think would have to be nuclear-thermal like NERVA. If we had one of those already lying around, it might be possible to catch up.

The other possibility I've seen discussed are extremely lightweight probes — chip-scale probes weighing less than a gram — accelerated by zillion-gigawatt laser arrays on Earth (or maybe in low Earth orbit). Since those probes don't have to carry their own fuel, they can reach much higher speeds, a sizable fraction of the speed of light, and could catch up to 'Oumuamua even if it took us a few years to develop the technology.

Neither of those are technologies we have (though we did build and test some NERVA prototypes back in the day) but they are things that we, as a civilization, could plausibly develop.

Probably. Strap a big overpowered upper stage behind a little lightweight payload and you can fire something pretty fast.

Unfortunately it's almost impossible at this point. The object passed pedigree a while ago and is headed back out, earth is in a very poor position for an intercept. The calculations I've seen say even if you use the largest possible booster, the SLS (which doesn't exist now, won't exist for another 3 years, if ever) it couldn't even get a small probe to catch up for a very long time, if ever.

There may be options in using Jupiter for slingshot maneuvers to overcome our bad positioning, and using super advanced hall effect motors, or project slingshot type probes. But it seems pretty slim at this point.

UPDATE: The reddit thread has this comment "Not a chance. Velocity relative to the sun is presently > 39 km/sec and relative to the earth is > 64 km/sec. This is far faster than anything we have ever launched or even could plausibly launch in the near future".

Which explains why you need Jupiter to redirect your probe so you can have it go only 40Km/sec to catch up, rather than 65 Km/sec direct from earth.

Relevant XKCD : https://xkcd.com/1919/

tell me it's no the vanguard of a galactic police squad coming to arrest humans for universal misconduct

Say whatever you want, I know it is Silkie spaceship.

What's really shocking is the drawing from the article [1]

This Astroid was Discovered when already passed by the Earth!!

And was actually very close to it! While I am pretty certain Astronomers knew it won't hit us, the amount of time it took to discover it would be way too late for us to even hold hands and kiss our children goodbye!

http://blogs.discovermagazine.com/outthere/files/2017/11/eso...

The earth gets hit by similarly sized asteroids every 30,000 to 100,000 years, albeit not quite at this velocity. Average impact velocity for asteroids from our system is 17 Km/sec, so about 2/3s the speed of this visitor. Either way, it's not even close to an extinction event.

And "very close to it" is a misnomer. It came within 24 million kilometers of Earth, about 60 times farther away than the moon is.

Well, if it had hit Earth, it would have happened without astronomers (or anyone else) knowing about it beforehand. As you point out, it was discovered after it had passed us, so there was no advance warning at all, however this is quite common with asteroids.

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