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Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

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Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#101

Post by rdtsc »

checkyoursudo wrote: post #67
TheOtherHobbes wrote: post #38

Earlier quoted context omitted.

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 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 hyp…

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?

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.

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#102

Post by burke »

justinpombrio wrote: post #76
sjclemmy wrote: post #71

Earlier quoted context omitted.

I really misunderstand my relativity then.

You've got the right general idea, but the principle of relativity only applies to constant velocity motion. If two astronauts float past each other in space, either of them can claim that they're motionless and the other is moving past them. However, if one of them is accelerating or spinning, they'll both agree on who it is. https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Inertia…

To add on to this, here's a simple thought experiment to explain why spinning is different from constant velocity:

Imagine you're off somewhere space. You're holding a ball in each hand.

1. You're motionless with reference to the Earth. You let go of the balls. They stay put.

2. You're moving away from the earth with a constant velocity. You let go of the balls. They continue to move at the same velocity as you do: This is indistinguishable from case 1.

3. You're accelerating away from the Earth (using rocket boots). You let go of the balls. They do not continue to accelerate with you.

4. You're motionless with respect to Earth, except that you're spinning. Think of the fastest you've ever spun. You'll be really dizzy when you stop. You let go of the balls. They fly off into space, because in order to stay spinning, they need acceleration toward the center of the spin plane. By letting them go, you stop that acceleration, and their trajectory changes (or really, their trajectory change stops).

Velocity is all relative, but acceleration is not. Spinning is acceleration.

---

Here's another example:

You occupy a cosmos consisting only of you and an apple. You accelerate away from the apple for a moment, then stop accelerating. You now have a constant velocity away from the apple, but it's meaningless to say which of you is actually moving. You each perceive the other as moving away at constant velocity.

Now imagine you start spinning. You feel like you're spinning, and visually, you perceive the apple orbiting you at a bizarrely fast rate. From the apple's perspective, you are spinning. These two perceptions are not symmetric.

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#103

Post by kidsnow »

ianai wrote: post #47
yitchelle wrote: post #37

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.

We could have many more and not know. This one was seen because it came so close to the earth.

We have telescope technology to thank. The quality and the number of telescopes is constantly increasing. We don't just look in the sky any more, we watch the same spot over time and look for changes. We are seeing more spots, more time, and more changes. An investment in telescopes is an investment in physics.

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#104

Post by tantalor »

sjclemmy wrote: post #3

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.

> what are the odds?

100%, because it happened

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#106

Post by checkyoursudo »

rdtsc wrote: post #101
checkyoursudo wrote: post #67

Earlier quoted context omitted.

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?

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.

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

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#107

Post by InclinedPlane »

Balgair wrote: post #100
InclinedPlane wrote: post #95

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…

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…

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.

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#108

Post by Balgair »

InclinedPlane wrote: post #107
Balgair wrote: post #100

Earlier quoted context omitted.

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…

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…

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.

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#109

Post by sjclemmy »

burke wrote: post #102
justinpombrio wrote: post #76

Earlier quoted context omitted.

You've got the right general idea, but the principle of relativity only applies to constant velocity motion. If two astronauts float past each other in space, either of them can claim that they're motionless and the other is moving past them. However, if one of them is accelerating or spinning, they'll both agree on who it is. https://en.wikipedia.org/wiki/Principle_of_relativity https://en.wikipedia.org/wiki/Inertia…

To add on to this, here's a simple thought experiment to explain why spinning is different from constant velocity: Imagine you're off somewhere space. You're holding a ball in each hand. 1. You're motionless with reference to the Earth. You let go of the balls. They stay put. 2. You're moving away from the earth with a constant velocity. You let go of the balls. They continue to move at the same velocity as you do: T…

I’m really interested in understanding this. So please indulge me... So, I’m Oumuamua rocking my way through interstellar space. I see nothing around me so as far as I know I’m not spinning. Then, all of a sudden I happen upon a solar system that is spinning around me. Who is spinning? Me or the solar system?

Is the point here that I’m spinning with reference to my direction of motion?

Re: Interstellar Visitor Found to Be Unlike a Comet or an Asteroid

#110

Post by njarboe »

elorant wrote: post #39
jobigoud wrote: post #19

Earlier quoted context omitted.

Let's say it takes us another 50 years to fund and prepare a mission, could we still catch up with it?

In 50 years it would be some 41bn kms away (it travels at a speed of 26km/s). Say you want to reach it within a five year span that would mean we'll need to build a spacecraft that could travel 0,1% the speed of light. Probably within our future capabilities considering all the theories that have been proposed for interstellar travel. For example the Breakthrough Starshot project has predictions for 10%-20% of the sp…

We could revive Project Orion[1] and use up some of the world's nukes in a productive way. If there was high confidence that ’Oumuamua was an alien constructed object, I would support it.

[1]https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...

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