Assuming 3i/Atlas is experiencing a deceleration 0,00000002 m/s², would its detection be unavoidable?

Edited September 27Sep 27 by Bjarne-7

46 minutes ago, Bjarne-7 said:

Assuming 3i/Atlas is experiencing a deceleration 0,00000002 m/s², would its detection be unavoidable?

It has already been detected.

Also, Atlas will speed up when it approaches the Sun not decelerate.

3 hours ago, Bjarne-7 said:

Assuming 3i/Atlas is experiencing a deceleration 0,00000002 m/s², would its detection be unavoidable?

v=at

An acceleration of 2 x 10^-8 m/s^2 for a duration of just over 3 years (10^8 s) would result in a speed change of about 2 m/s. The current speed is 58 km/s, so detecting such an anomaly would depend on the precision of measurement and length of time of observation

for the curious,

https://en.m.wikipedia.org/wiki/3I/ATLAS

2 hours ago, pinball1970 said:

It has already been detected.

The comet or the acceleration anomaly? I’m assuming the OP was asking about the latter. If that’s what you meant, do you have a reference?

4 minutes ago, swansont said:

The comet or the acceleration anomaly? I’m assuming the OP was asking about the latter. If that’s what you meant, do you have a reference?

The comet.

In terms of the velocities/ trajectories, I got those from wiki.

The velocity goes from 62km per s to 68 as it reaches perihelion.

https://en.m.wikipedia.org/wiki/3I/ATLAS

3 hours ago, pinball1970 said:

The comet.

Right. I think the OP is asking about whether the acceleration can be detected.

Which is a “no” given the precision of measurement.

1 hour ago, swansont said:

Which a “no” given the precision of measurement.

I'll take your word for it, perhaps they will get more accurate data on its way through. Vera Rubin maps the sky every few days so they will be probably using that and others.

Just now, pinball1970 said:

I'll take your word for it, perhaps they will get more accurate data on its way through. Vera Rubin maps the sky every few days so they will be probably using that and others.

It’s by inspection. If the reported speed is 52 km/s, then it’s fair to conclude that they don’t know it to much better precision. You need a lot more digits (even with a longer observation time) to see a perturbation on the order of less than 1 m/s

I doubt you could discern it from deviations of the trajectory, either. At our distance, the acceleration from the sun is 0.006 m/s^2, so the anomaly is still very small.

We simply don’t have or get the precision we need

After one year of such deceleration, 3iAtlas would have lost 10,000 km

5 minutes ago, Bjarne-7 said:

After one year of such deceleration, 3iAtlas would have lost 10,000 km

Did you mean a distance, or speed?

And what's this all about, anyway?

13 minutes ago, Bjarne-7 said:

After one year of such deceleration, 3iAtlas would have lost 10,000 km

Which only matters if you know where it started, and you also have to know what other accelerations it is undergoing, to that precision.

IOW, you can’t “lose” anything inside the error bars

At 50 km/s, it will travel ~1.5 billion km in that time, modified by whatever net acceleration it undergoes. 10,000 km is literally lost in the noise.

6 hours ago, swansont said:

10,000 km is literally lost in the noise.

..and when you calculate whether an object will hit the Earth in a few or several decades, you have to be much more precise. 10,000 km in one direction or the other, and it will either hit the Earth or not (some/any object)..

@Bjarne-7 Even the arrangement of the planets at a given time causes some gravitational acceleration.

So, first you have acceleration in one direction, and then you have acceleration in the other direction (deceleration), simply because the planets change their position relative to the Sun.

Take the positions of your object and some/every planet. Calculate the distance between them. Find the mass M of the planet (Wikipedia) and use F=ma, a=GM/r^2 to calculate its approximate influence on your object.

The easiest way to do this is in a spreadsheet.

The wobble of a star was one of the first methods used to check whether a star had any massive exoplanets orbiting around it (=the center of mass of a star system is not located in the center of the star) (=a star attracts planets to itself, and planets attract their star to themselves). So you reverse Newton's equation and you get the mass that an exoplanet must have in order to have such an effect on its star.

Edited September 28Sep 28 by Sensei

10 hours ago, pzkpfw said:

Did you mean a distance, or speed?

And what's this all about, anyway?

distance

10 hours ago, swansont said:

Which only matters if you know where it started, and you also have to know what other accelerations it is undergoing, to that precision.

IOW, you can’t “lose” anything inside the error bars

At 50 km/s, it will travel ~1.5 billion km in that time, modified by whatever net acceleration it undergoes. 10,000 km is literally lost in the noise.

At 3 AU, accelerations on the order of 10⁻⁹–10⁻¹⁰ m/s² can typically be detected over a year, or around 10⁻⁸ m/s² over time spans of a few months. The value of 2×10⁻⁸ m/s² is clearly detectable over 3 months or longer, but it would be close to the noise threshold if only a 1-month observational arc were available.

Let’s say such a deceleration is real — would it inevitably be detected?

3 hours ago, Sensei said:

..and when you calculate whether an object will hit the Earth in a few or several decades, you have to be much more precise. 10,000 km in one direction or the other, and it will either hit the Earth or not

Not the point

10 hours ago, pzkpfw said:

And what's this all about, anyway?

Oumuamua was accelerating, some fly by-space-probes was accelerating + decelerating , - would it surprise you if it happened again ?

Edited September 28Sep 28 by Bjarne-7

1 hour ago, Bjarne-7 said:

Oumuamua was accelerating, some fly by-space-probes was accelerating + decelerating , - would it surprise you if it happened again ?

Not at all.

As I said, to understand why such things happen, you should start by analyzing and calculating the influence of the planets on a given object, at a given time or even time span.

I gave you the formulas, all you had to do was plug in the values, and you would have seen that for example Jupiter, which is 100 million km away from the object, exerts a force 635 times greater than the 2*10^-8 m/s^2 you mentioned:

Jupiter’s gravitational acceleration becomes equal to 2.0*10^-8 m/s^2 (the value from your OP) at a distance of approximately 8 billion km (53 AU = 10 times as much as it is from Sun to Jupiter).

1 hour ago, Sensei said:

Not at all.

As I said, to understand why such things happen, you should start by analyzing and calculating the influence of the planets on a given object, at a given time or even time span.

I gave you the formulas, all you had to do was plug in the values, and you would have seen that for example Jupiter, which is 100 million km away from the object, exerts a force 635 times greater than the 2*10^-8 m/s^2 you mentioned:

Jupiter’s gravitational acceleration becomes equal to 2.0*10^-8 m/s^2 (the value from your OP) at a distance of approximately 8 billion km (53 AU = 10 times as much as it is from Sun to Jupiter).

One would think that when NASA, ESA etc. claim that anomalies have been measured, that they then included the influence of Jupiter and other planetary perturbations (?)

Let say: 3i/Atlas first decelerates at a rate of: a1=7×10−8m/s² while approaching the Sun, and subsequently accelerates at a rate of a2=5×10−8m/s² as it moves away from the Sun. This results in a situation where both deceleration and acceleration are present during the trajectory. Such a pattern is characteristic of a significant number of flyby anomalies. Given this dual-phase acceleration profile, one can reasonably exclude planetary perturbations as the primary cause.

Edited September 28Sep 28 by Bjarne-7

5 hours ago, Bjarne-7 said:

At 3 AU, accelerations on the order of 10⁻⁹–10⁻¹⁰ m/s² can typically be detected over a year

But this was first observed in July, and it will be leaving the solar system in less than a year.

5 hours ago, Bjarne-7 said:

Oumuamua was accelerating

And was 250x larger than the number you cited

50 minutes ago, swansont said:

But this was first observed in July, and it will be leaving the solar system in less than a year.

And was 250x larger than the number you cited

Right ; Oumuamua was much also closer to the sun, and was moving "straight" out of the solar system, - now lets see whats happening and if there are more big or small surprised out there ?

It will fly very close to Jupiter, so its influence on acceleration will be very significant. It is clear that Jupiter's gravity will change its trajectory.

https://science.nasa.gov/solar-system/comets/3i-atlas/

28 minutes ago, Bjarne-7 said:

Right ; Oumuamua was much also closer to the sun, and was moving "straight" out of the solar system, - now lets see whats happening and if there are more big or small surprised out there ?

2 hours ago, Sensei said:

It will fly very close to Jupiter, so its influence on acceleration will be very significant. It is clear that Jupiter's gravity will change its trajectory.

https://science.nasa.gov/solar-system/comets/3i-atlas/

Of course, but this will be taken into account don’t you think ?.

When comparing the perihelion distance for Oumuamua, it was 0.25 AU

For 3i/Atlas it will be 1.36 AU.

Based on that , as well as on the radial in/out direction, - I think it is realistic to expect a declaration in and acceleration out = 5×10⁻7 m/s².

Let’s see what will happen. - Maybe nothing.

Edited September 28Sep 28 by Bjarne-7

I’m getting an uneasy feeling here. Your original question was about detecting a specified acceleration. That was addressed.

But now there’s discussion that’s not centered on measurement precision, and a somewhat cryptic prediction that does not reference how it was produced. It hints at an agenda.

Further, your username suggests you’ve posted here before under a similarly-named account.

13 hours ago, swansont said:

I’m getting an uneasy feeling here. Your original question was about detecting a specified acceleration. That was addressed.

But now there’s discussion that’s not centered on measurement precision, and a somewhat cryptic prediction that does not reference how it was produced. It hints at an agenda.

Further, your username suggests you’ve posted here before under a similarly-named account.

Do you mean me? I’ve never posted under a similar name. And yes, there are many different influences affecting comets — including perturbations (as Sensei suggested), well-known outgassing, and possibly other factors we don’t yet understand. This isn’t necessarily cryptic or secret. By the way, I don’t believe in alien spacecraft, which — once again — is being proposed by a Harvard professor (and many others) , in this context.

Edited September 29Sep 29 by Bjarne-7

44 minutes ago, Bjarne-7 said:

Do you mean me? I’ve never posted under a similar name. And yes, there are many different influences affecting comets — including perturbations (as Sensei suggested), well-known outgassing, and possibly other factors we don’t yet understand. This isn’t necessarily cryptic or secret. By the way, I don’t believe in alien spacecraft, which — once again — is being proposed by a Harvard professor (and many others) , in this context.

Yeah but only by Avi "Frontal" Loeb, who has notorious form for this sort of thing.

14 hours ago, swansont said:

But now there’s discussion that’s not centered on measurement precision, and a somewhat cryptic prediction that does not reference how it was produced. It hints at an agenda.

We have had three interstellar objects pass through the solar system recently:

Oumuamua (with an acceleration anomaly of approximately 5×10⁻⁶ m/s²),
Borisov (no anomaly),
and now 3I/Atlas.

The key parameters influencing the strength of ʻOumuamua’s anomaly undeniably appear to be the perihelion distance and the distance to the Sun. Therefore, the perihelion distance along with the inbound and outbound trajectory angles are crucial factors.

Based on this, one can estimate—through proportional reasoning—how much weaker a possible similar anomaly might be for 3I/Atlas. I believe most would arrive at a value around 10% of ʻOumuamua’s anomaly (i.e., approximately 5×10⁻⁷ m/s²). There is nothing mysterious or cryptic about such a calculation.

However, if I had instead calculated that the anomaly would be a deceleration of 7×10⁻⁷ m/s² on the inbound leg and an acceleration of 3×10⁻⁷ m/s² on the outbound leg, I could understand why someone might think it was a cryptic message.

2 hours ago, Bjarne-7 said:

There is nothing mysterious or cryptic about such a calculation.

You didn’t provide the calculation and hadn’t provided any reasoning behind it, and now you’re saying it’s proportional but not why or how you arrive at 10%. Nor have you explained why you think it would be behaving like Oumuamua and not Borisov. In addition, we don’t know anything about Oumuamua on its inbound journey as it was discovered some 40 days after perihelion.

"3I/Atlas moved predominantly in a vertical trajectory through the solar system, much like ‘Oumuamua did when the anomaly was first detected — and not horizontally, as Borisov did. I expect that the laws of nature (which I believe are responsible for the ‘Oumuamua anomaly) are consistent, and therefore 3I/Atlas should exhibit similar behavior. I have repeatedly stated that the 10% figure is derived from simple ratio calculations, where perihelion distance and the angles of entry and exit are the determining factors."

Edited September 30Sep 30 by Bjarne-7

Correction: "3I/Atlas moved predominantly in a horizontally trajectory through the solar system, much like ‘Oumuamua did when the anomaly was first detected — and not vertical , as Borisov did.