B Does the Path of an Interstellar Object Curve Due to Solar System Movements?

[DeckSmeck]

When an object is propelled from a solar system, does that object sometimes travel in a curve depending on the direction it travels away from the solar system, relative to the direction the solar system is traveling and to some fixed point in space. And if it enters a second solar system, that is also moving, do current methods of calculating orbital calculations take that curve into account. I was wondering because of the unknown variables in the Oumuamua orbital path around the sun. If it is a curved path, and if those variables are taken into account, can the curve be known by the difference between the expected orbital path and the actual orbital path. Would that give an idea of the direction the orginal solar system was traveling?

 

[DaveC426913]

When an object is propelled from a solar system, does that object sometimes travel in a curve depending on the direction it travels away from the solar system, relative to the direction the solar system is traveling and to some fixed point in space. because of the unknown variables in the Oumuamua orbital path around the sun. If it is a curved path, and if those variables are taken into account, can the curve be known by the difference between the expected orbital path and the actual orbital path. Would that give an idea of the direction the orginal solar system was traveling?

Technically, any object not nailed down is influenced by, not just the sun, but all other stars nearby.
But this is a vanishingly small effect and, more to the point, every other object in the system is under the same effect.
If we don't see the effect in planets, moons and asteroids, it becomes a mystery as to why we might see it in a retreating comet.

 

[Janus]

When an object is propelled from a solar system, does that object sometimes travel in a curve depending on the direction it travels away from the solar system, relative to the direction the solar system is traveling and to some fixed point in space. And if it enters a second solar system, that is also moving, do current methods of calculating orbital calculations take that curve into account. I was wondering because of the unknown variables in the Oumuamua orbital path around the sun. If it is a curved path, and if those variables are taken into account, can the curve be known by the difference between the expected orbital path and the actual orbital path. Would that give an idea of the direction the orginal solar system was traveling?

There is no "fixed place" in space against which we can measure motion absolutely. So all we are left with is measuring the relative velocity the object has with respect to the Solar system. In other words, the fact that it is coming from that direction at this speed. This information by itself is not enough to tell us the relative velocity of the source. For that you would also would need to know the velocity at which it left the source. There are four variables involved: the sources speed( relative to the Earth), the relative direction of the source's movement, the object's initial speed leaving the source, and the direction in which the object left the source. There are numerous combinations of these variables that would result in the measured relative velocity with respect to the Solar system.

 

[russ_watters]

I've re-tagged this thread as "B".

When an object is propelled from a solar system, does that object sometimes travel in a curve depending on the direction it travels away from the solar system, relative to the direction the solar system is traveling and to some fixed point in space.

From your description it isn't clear how much you understand about motion in space. For example, this "curve" you are describing -- what curve is that? I'll assume as a starting point that you are referring to our solar system's orbit around the galaxy...

Our solar system is orbiting the center of our galaxy at 230 km/s. Any object leaving the solar system at any speed we are capable of producing is still pretty much following that orbit.

And if it enters a second solar system, that is also moving, do current methods of calculating orbital calculations take that curve into account. I was wondering because of the unknown variables in the Oumuamua orbital path around the sun. If it is a curved path, and if those variables are taken into account, can the curve be known by the difference between the expected orbital path and the actual orbital path. Would that give an idea of the direction the orginal solar system was traveling?

Again, if the "curve" you are referring to is our solar system's orbit around the center of the galaxy, sure. These dynamics are no different from orbital dynamics inside our solar system. E.G. traveling from one solar system to another in our galaxy is just like traveling from one planet to another in our solar system.

 

[DeckSmeck]

Thanks for responding. I don't know anything about orbital calculations. I probably lack the right terminology to pose the question right. I am a layman looking for educated people who might know. I should have made that clear.

The fixed point in space, let if be considered that space is fixed and not moving. Galaxies and other bodies move around inside it.

I was proposing that and object moving away from a solar system travels in a straight line relative to the solar system it came from but it travels in a curve relative to unmoving space.

Is it true?

 

[russ_watters]

The fixed point in space, let if be considered that space is fixed and not moving. Galaxies and other bodies move around inside it.

Sure, we can establish a frame of reference using the background radiation of the universe; the frame of reference where it appears uniform in all directions.

I was proposing that and object moving away from a solar system travels in a straight line relative to the solar system it came from but it travels in a curve relative to unmoving space.

Is it true?

...edit...
Ehh...I guess it could look that way, but objects tend to move in curves at all levels because they are in orbits.

 

[PeroK]

I was proposing that and object moving away from a solar system travels in a straight line relative to the solar system it came from but it travels in a curve relative to unmoving space.

Is it true?

It's not true. Instead you have Newton's first law of motion:

Newton's first law: An object at rest remains at rest, or if in motion, remains in motion at a constant velocity unless acted on by a net external force.

https://www.khanacademy.org/science...ns-laws-of-motion/a/what-is-Newtons-first-law

 

[Bandersnatch]

All orbits, including those that aren't closed, are curved paths (apart from one special case). But the curvature is not induced by the relative motion of the two star systems and the resulting velocity at which an object enters one system or another. It's there by the virtue of there being gravitational fields that the object is free-falling through.

Unpowered objects follow specific and unique curved paths as they orbit massive bodies. This uniqueness means that you can take measurements of position and velocity in one part of the orbit, and calculate the entire rest of the path before and after the measurement, because this small measured bit fits only one possible orbit. You take measurements e.g. as the object passes the Sun, and you know which direction and at what speed it arrived from, and will leave towards. You don't need to know anything about the relative speed of the solar system and the star system of origin, because that small section of the orbit already gave you all the information you need.

This simple picture changes if there are some additional forces acting on the orbiting body (and there almost always are). These forces can come from gravity of planets in the system, from pressure of solar radiation, from recoil of material ejected from the surface as it heats up, from collisions with dust, etc. One would try and account for all such forces, to calculate how the orbit is modified as a result.

The relative motion of the two star systems means that the object will enter solar system with some specific speed, and in some specific direction. But, because this is relative velocity, and not a force, it only determines the shape of that unpowered orbit that can be calculated from measurements taken anywhere. It doesn't make the orbit deviate as the object moves.

The Oum...nomnom (what a name to remember) has an orbit that deviates from the unpowered one, in-flight, more than what was expected after accounting for all obvious forces it ought to be subject to.

Which probably only means that some less-obvious force was not taken into account, and which is not unexpected given how little is known of the object.

 

[stefan r]

...
The Oum...nomnom (what a name to remember) ...

Oumuamua

 

[LURCH]

The leader of the international team studying the object has released a statement that they have concluded that the acceleration is a result of outgassing. Given that we know the rate of that acceleration, and the speed/direction of the object as we watched it pass, it sounds like it should be possible to calculate the past trajectory, and possibly determine the system from which it came. However, I have not heard of any guesses. Has anyone else?

I’m sure it would be a fairly monstrous mathematical task, but it seems like such a natural question to ask, that someone must be working on it.

 

[DeckSmeck]

Thanks for the replys. I think I see my mistake now about the curvature of the flight path. An object has to have acceleration or de-acceleration outside of gravitational force to make a curve. Right?

 

[Janus]

The leader of the international team studying the object has released a statement that they have concluded that the acceleration is a result of outgassing. Given that we know the rate of that acceleration, and the speed/direction of the object as we watched it pass, it sounds like it should be possible to calculate the past trajectory, and possibly determine the system from which it came. However, I have not heard of any guesses. Has anyone else?

I’m sure it would be a fairly monstrous mathematical task, but it seems like such a natural question to ask, that someone must be working on it.

From the Wikipedia article on the Oumuamua:
"Accounting for Vega's proper motion, it would have taken ʻOumuamua 600,000 years to reach the Solar System from Vega.[30] But as a nearby star, Vega was not in the same part of the sky at that time.[41] Astronomers calculate that one hundred years ago the asteroid was 561 ± 0.6 AU (83.9 ± 0.090 billion km; 52.1 ± 0.056 billion mi) from the Sun and traveling at 26.33 km/s with respect to the Sun.[9] This interstellar speed is very close to the mean motion of material in the Milky Way in the neighborhood of the Sun, also known as the local standard of rest (LSR), and especially close to the mean motion of a relatively close group of red dwarf stars. This velocity profile also indicates an extrasolar origin, but appears to rule out the closest dozen stars.[55] In fact, the strong correlation between ʻOumuamua's velocity and the local standard of rest might mean that it has circulated the Milky Way several times and thus may have originated from an entirely different part of the galaxy."

So it doesn't appear to ave originated form any of the nearby stars. All our information on it's trajectory is obtained from its single pass through the Solar system, which puts a limit on to just how accurately we can measure it. The further back or forward we try to extrapolate its path, the greater the uncertainty of its position grows due to these inaccuracies. Compounding this is the fact that the stars themselves have relative motions with respect to the solar system, and there are uncertainties in those relative motions. There just isn't enough information to pin its origin to any given star.

 

[LURCH]

It would seem to me that this would suggest that this is a very old object. Hope that in the future we can intercept and sample one of these objects.

What do you all think of these potential fields of inquiry:

One possible implication of the correlation between ʻOumuamua's velocity and the Local Standard of Rest might be that it has spent so long in the interstellar medium (which is not completely empty) that it was “brought to rest” relative to that environment. Another is that ʻOumuamua's orbital path matched that of the galaxy because both are dictated by the same conditions, which might make this fly-by a source of new data regarding dark matter, if we could just figure out the right questions to ask.

One thing seems certain; this encounter opens up a lot of possibilities, and will continue to yield new discoveries long after the object is gone.

 

[stefan r]

This paper showed the near misses that are in the Gaia database. It says it is unlikely that anyone of them was the origin but it is possible if the star has a very massive planet. That goes back a few million years. Not all brown dwarfs are in the Gaia database.

Going very far back in time gets fuzzy because a very slight deviation builds up to larger changes in position and velocity.

 

[DaveC426913]

Just so I'm clear: They calculated 'Oamuamau's trajectory as best they can, and projected it backward in time (presumably tracing out a bugle).
They calculated the nearest likely dozen stars, projected their paths backwards in time, and found that the bugle intersects none of them with any reasonable amount of plausibility.

Do they have a leading hypothesis as to its origin? Surely it falls into one of four categories:
- measurements for extrapolation are off
- there's a source currently undetected
- the source is even farther back than any meaningful projection can go
- they have not factored in some as-yet unknown amount of acceleration (+ive or -ive) related to its current mysterious accelerationUnrelated question: how much unaccounted-for acceleration is it actually undergoing?

(Now I want some bugles.)

 

[DeckSmeck]

Maybe it's intergalactic. Who knows. Sounds like they did the best they could. Perhaps whatever was out there is gone now. If it was that long ago.

Davide Farnocchia sent me this link. Karen Meech and Davide are very kind (to over enthusiastic newbs, in this case. Maybe I should rather say YouTube audience members. I don't think i would consider myself as knowledgeable as a newb, actually).

http://iopscience.iop.org/article/10.3847/1538-3881/aae3eb/meta

 

[stefan r]

...
- there's a source currently undetected
- the source is even farther back than any meaningful projection can go
...

It is most likely combination, the source is further back. The Sun is moving 20km/s relative to nearby stars. A typical age for an asteroid might be 10¹⁷ seconds. We do not know which direction Oumuamua left its star. That gives your bugle a few thousand parsec radius but Earth is not in the center of that volume.

...
...

Unrelated question: how much unaccounted-for acceleration is it actually undergoing?

4.92 ±0.16 x 10^-6 m/s²
[page 1, right column]

 

[DaveC426913]

We do not know which direction Oumuamua left its star. That gives your bugle a few thosand parsec radius but Earth is not in the center of that volume.

Earth is at the apex of the bugle. The possible origin is within the body of the bugle, whose cross-section increases as we move away from Earth.

4.92 ±0.16 x 10^-6 m/s²
[page 1, right column]

Ah. So about 5 micrometers per s².

 

[TEFLing]

Maybe it's intergalactic. Who knows. Sounds like they did the best they could. Perhaps whatever was out there is gone now. If it was that long ago.

Davide Farnocchia sent me this link. Karen Meech and Davide are very kind (to over enthusiastic newbs, in this case. Maybe I should rather say YouTube audience members. I don't think i would consider myself as knowledgeable as a newb, actually).

http://iopscience.iop.org/article/10.3847/1538-3881/aae3eb/meta

well, who knows... if it was intergalactic, it has since lost an enormous amount of energy. It's now firmly bound within our galaxy, the escape velocity from which would be many hundreds of km/s, not merely 8 km/s or so net velocity relative to our solar system. 'Twould require thousands of times more KE to escape the MWG