Hello Kym Horsell

Sorry for replying late. I had a health problem and could not write.

>Supposedly in the Horizons data distance calculations with respect to either coordinate system are good to a few meters. Different asteroids and comets have different specifications but most have "old data" before a given date as "observations" -- probably more accurately thought of as interpolated observations -- and from a certain point on as the output from their solar system model taking other bodies into account.

Do you think that for computing the orbit of Oumuamua, the used position of the Sun is the actual position good to a few meters at the first observation of Oumuamua? Is the Sun moving with its actual velocity in the computation of Micheli?

>The solar system moves maybe 20 million km per day around the galaxy. That usually can be ignored because it is an inertial frame (mostly). I think about 300m per day is due to the curve of the sun around the galaxy so that is also taken into account. Trying to get something into orbit around Neptune would fail if it was out 10 km after a decade-long run out there.

Since in the galaxy the frame of the Sun is taken as inertial, for the orbit of Oumuamua there should not be much problem.

>I left my little program on the same site. There is something definitely screwy with U1 and gravity. According to a gravity-only sim it is many AU out of position. The JPL data warns only the position inside the limits around Oct 2017 to Jan 2018 are accurate so I squeezed a best fit out of that section of the data and still it would not fit very well.

>But that should be expected when the thing started way above the ecliptic, proceeded to move below the ecliptic, but then came back to end up very near lat 0 and seem to stablise around there.

Many AU out of position? Is it not only 40 000 km out of position?

>At present I have all the outer planets in the gravity model and they dont help explain the yuge differences between what the gravity track predicts and what the Horizons data shows.

If I understand, you have done a computation of the orbit of Oumuamua, and you do not find the same orbit than the page https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3788040 shows.
With eccentricity e=1.201133796102373
and semi major axis a=-1.27234500742808 au

KP

The apparent non‑gravitational acceleration the extra-solar-system ‘Oumuamua exhibits is puzzling. We find that when the position and velocity of the Sun is correctly set in computing the predicted orbit, ‘Oumuamua’s trajectory can be explained with gravity and we have reproduced the unexpected gap by computation. We also propose to search for new extra-solar-system high speed asteroids with SOHO to check our method with their trajectories.

1. ‘Oumuamua’s acceleration

‘Oumuamua, formally designated 1I/2017 U1, is an interstellar object passing through the Solar System which was first detected by Robert Weryk using the Pan-STARRS telescope on 19 October 2017 [1][2][3]. It seems to exhibit non‑gravitational acceleration, making it go further than expected [3][4][5][6][7][8].

In the article « Our Solar System's First Known Interstellar Object Gets Unexpected Speed Boost » June 27, 2018 [9], it was reported that “'Oumuamua had been boosted by 25,000 miles (40,000 kilometers) compared to where it would have been if only gravitational forces were affecting its motion”, see Figure 1 and Figure 2 which are screenshots of the animation in this article and show the predicted orbit and the unexpected gap of 40 000 kilometers between the last observation of ‘Oumuamua and the predicted spot.

Although “the Canada-France-Hawaii Telescope (CFHT) and, in the following days, the ESO Very Large Telescope (VLT) and the Gemini South Telescope, both8-meter-class facilities, found no sign of coma despite optimal seeing conditions”, the authors still “find outgassing to be the most physically plausible explanation” [5].

However, because of the lack of coma we think that the boost of 'Oumuamua can still be attributed to some overlooked effects. For example, what if the Sun is moving in the solar system? What if, due to the motion, the Sun is not exactly at the focus of the predicted hyperbolic orbit? In these cases, the real trajectory of 'Oumuamua will not fit the predicted one.

We know that the Sun is not exactly at the barycenter of the solar system and moves relative to it, as shown by Figure 3 [11] in which the Sun is the central point and the barycenter wanders around it. But in reality the solar system is an isolated system the center of which is its barycenter. The frame of the barycenter is inertial, in this frame the barycenter is fixed and the Sun wanders around it. So, the Sun is always at a distance from the barycenter and moves at nonzero velocity.

Pursuing this direction we propose this hypothesis: the unexpected gap could be the consequence of erroneous position and velocity of the Sun with which the predicted orbit was computed.

For checking this hypothesis we will compute the trajectory of ‘Oumuamua by adjusting the position and velocity of the Sun such as to reproduce approximately the gap of 40 000 km.

2. Static and shifting orbits

The basic parameters of the predicted orbit for ‘Oumuamua are published by JPL / NASA in the page 'Oumuamua (A/2017 U1) [12]. The eccentricity , the semi-major axis a, the orbital elements [15] and the standard gravitational parameter of the Sun GM☉ [13] are given in Table 1.. The semi-latus rectum l and specific relative angular momentum h are computed in (2) and (3). The predicted orbit is a hyperbolic orbit which is expressed by equation (1) [14].

Just for the purpose of checking our hypothesis, we put the focus of the predicted orbit at the barycenter of the solar system. This orbit is static and we call it the static orbit. The orbit of 'Oumuamua is a hyperbola the focus of which is the moving Sun. So this orbit shifts in the frame of the barycenter and is called shifting orbit.

…

3. Search for high speed asteroids near the Sun

Beside of computing the trajectory of ‘Oumuamua, a better way to check our hypothesis is by experiment, that is, by observing new high speed asteroids and compare their trajectory with prediction. However, recorded asteroids and comets coming into the solar system from the outside are scarce.. But I think that in reality such objects are not so rare, only that far from the Sun they are too faint to be detected. When they are near the Sun they become very bright and can be detected by Sun gazing satellites such as SOHO (Solar and Heliospheric Observatory).

Many such alien asteroids and comets are already recorded by SOHO and are dormant in great number in the archives of SOHO. Thanks to NASA Goddard’s YouTube Movie “Decades of Sun from ESA & NASA’s SOHO” [19], which is a video made with all the photos taken by LASCO/C3 between 1998/01/06 and 2020/10/23, I have found several high speed asteroids and comets in it.

For example, the asteroid that was recorded from 2004/02/26 to 2004/02/28. I have computed its visual velocity which is the velocity of the dot on the image and got 160 km/s, see Figure 7. The comet recorded from 2015/02/18 to 2015/02/21 is measured at 182 km/s, see Figure 8. For comparison, the speed of ‘Oumuamua at perihelion is 87.71 km/s [8]. I used the diameter of the view field of LASCO/C3 which equals 30 radii of the Sun [20] and the time printed on the images to compute its visual velocity. As the actual trajectories make an angle with the plane of the image, their real velocity are forcefully bigger. Only objects coming from the outside of the solar system can be as speedy.

I have made a clip of the asteroid and put it here: Super-fast alien asteroid (160 km/s), taken by SOHO in 2004, https://youtu.be/GTGuEKndNIc

The alien asteroids and comets in the archives of SOHO are interesting. We can count their number, mapping their direction and measure their record breaking speed and size. On the other hand, we can monitor in real time the appearance of new alien asteroids and comets, work out their orbits for observing them later.

In searching asteroids in the Movie “Decades of Sun from ESA & NASA’s SOHO” [19], the background stars and the streaks left by space particles are very dizzying which makes the researcher miss interesting asteroids and comets. So, I suggest that the background stars and streaks be removed for this research.

For those who are interested in seeing the asteroids and comets that I have found I have put in the appendices the links that point to the frames of the Movie “Decades of Sun from ESA & NASA’s SOHO” [19] where they appear. I have seen more comets because they are brighter and easy to see. I have also put the few visual velocities that I have computed, which show that some comets are very fast and could have come from the outside of the solar system.

4. Discussion

The analysis above shows that the unexpected gap can be well explained by the gravity of the Sun provided that the position and velocity of the Sun be correctly set in computing the predicted orbit. What matters is that the position and velocity of ‘Oumuamua be given with respect to the Sun’s actual position and velocity. If ‘Oumuamua were located with respect to the barycenter of the solar system while the Sun is not there, the predicted orbit would be wrong.

We have shown that because the combined trajectory is not a hyperbola and has moving focus the non‑gravitational acceleration may be unnecessary to explain that “the observed orbital arc cannot be fit in its entirety by a trajectory governed solely by gravitational forces due to the Sun, the eight planets, the Moon, Pluto, the 16 biggest bodies in the asteroid main belt, and relativistic effects” [5]. This is corroborated by the lack of coma.

We have also discovered that even the smallest error on the position and velocity of the Sun is enough to create an unexpected gap. Indeed, the distance used to reproduce the unexpected gap is only 12% of the radius of the Sun. So, the position and velocity of the Sun and the data of ‘Oumuamua must be precisely set.

On the other hand, our hypothesis must be checked again and again before being validated. Indeed, other value was given to this gap, for example, in the article « THIS INTERSTELLAR ASTEROID IS ACCELERATING » [18], 100 000 km has been given to the gap rather than 40 000 km. Obviously, there are several different predicted trajectories for ‘Oumuamua with different results. The correct theoretical trajectory for ‘Oumuamua must give Gap = 0 and our method can help for finding it.

We have proposed to check our hypothesis using the SOHO satellite in real time to find new alien asteroids and comets, work out their orbits for observing them later. It will be interesting to search for alien asteroids and comets in the archives of SOHO, which I have done partly.

For more detail of this study please read the complete paper here:
« Trajectory of 'Oumuamua and wandering Sun, alien asteroids and comets detected by SOHO »
https://www.academia.edu/100818112/Trajectory_of_Oumuamua_and_wandering_Sun_alien_asteroids_and_comets_detected_by_SOHO

On Thursday, April 27, 2023 at 4:27:13 AM UTC+10, PengKuan Em wrote:
> The apparent non‑gravitational acceleration the extra-solar-system ‘Oumuamua exhibits is puzzling. We find that when the position and velocity of the Sun is correctly set in computing the predicted orbit, ‘Oumuamua’s trajectory can be explained with gravity and we have reproduced the unexpected gap by computation. We also propose to search for new extra-solar-system high speed asteroids with SOHO to check our method with their trajectories.
>
> 1. ‘Oumuamua’s acceleration
>
> ‘Oumuamua, formally designated 1I/2017 U1, is an interstellar object passing through the Solar System which was first detected by Robert Weryk using the Pan-STARRS telescope on 19 October 2017 [1][2][3]. It seems to exhibit non‑gravitational acceleration, making it go further than expected [3][4][5][6][7][8].
>
> In the article « Our Solar System's First Known Interstellar Object Gets Unexpected Speed Boost » June 27, 2018 [9], it was reported that “'Oumuamua had been boosted by 25,000 miles (40,000 kilometers) compared to where it would have been if only gravitational forces were affecting its motion”, see Figure 1 and Figure 2 which are screenshots of the animation in this article and show the predicted orbit and the unexpected gap of 40 000 kilometers between the last observation of ‘Oumuamua and the predicted spot.

I'm sorry. A laudable effort, but misguided.

First off, instead of getting data from a magazine article where numbers are rounded to 1000s of km, you could
get the "real" numbers from Horizons at JPL.
They already calculate the relative speeds with the earth and sun for you and usu check their calculation of "deldot" against dopler radar on the object.

I think you might have a problem anyway with your thesis that seems to imagine an organization that has 17,000 science and engineering phds on the staff do not know something fundamental like the
difference between the postion of the sun and the barycenter of the solar system.
Horizons knows the positon of the sun to a few meters at any moment with respect to any given reference coodinate system.
NASA after all gets probes into orbit around distant objects like planets, the moons of planets, and even the odd asteroid,
after travelling for decades. So we might assume they know a couple basic things and can do things fairly accurately.

>
> Although “the Canada-France-Hawaii Telescope (CFHT) and, in the following days, the ESO Very Large Telescope (VLT) and the Gemini South Telescope, both8-meter-class facilities, found no sign of coma despite optimal seeing conditions”, the authors still “find outgassing to be the most physically plausible explanation” [5].
>
> However, because of the lack of coma we think that the boost of 'Oumuamua can still be attributed to some overlooked effects. For example, what if the Sun is moving in the solar system? What if, due to the motion, the Sun is not exactly at the focus of the predicted hyperbolic orbit?

It will not be. Asteroids do not orbit the sun -- they orbit the
sum total of all the matter in the interior solar system along the lines of Gauss' Theorem (an idealised case of spherical symmetry). Since 2017U1 came from outside it will have been
orbiting a point close if not identical to the system barycenter
for a lot of its time under observation.

>In these cases, the real trajectory of 'Oumuamua will not fit the predicted one.
>
> We know that the Sun is not exactly at the barycenter of the solar system and moves relative to it, as shown by Figure 3 [11] in which the Sun is the central point and the barycenter wanders around it. But in reality the solar system is an isolated system the center of which is its barycenter. The frame of the barycenter is inertial, in this frame the barycenter is fixed and the Sun wanders around it. So, the Sun is always at a distance from the barycenter and moves at nonzero velocity.
>
> Pursuing this direction we propose this hypothesis: the unexpected gap could be the consequence of erroneous position and velocity of the Sun with which the predicted orbit was computed.
>
> For checking this hypothesis we will compute the trajectory of ‘Oumuamua by adjusting the position and velocity of the Sun such as to reproduce approximately the gap of 40 000 km.
>
> 2. Static and shifting orbits
>
> The basic parameters of the predicted orbit for ‘Oumuamua are published by JPL / NASA in the page 'Oumuamua (A/2017 U1) [12]. The eccentricity , the semi-major axis a, the orbital elements [15] and the standard gravitational parameter of the Sun GM☉ [13] are given in Table 1. The semi-latus rectum l and specific relative angular momentum h are computed in (2) and (3). The predicted orbit is a hyperbolic orbit which is expressed by equation (1) [14].
>
> Just for the purpose of checking our hypothesis, we put the focus of the predicted orbit at the barycenter of the solar system. This orbit is static and we call it the static orbit. The orbit of 'Oumuamua is a hyperbola the focus of which is the moving Sun. So this orbit shifts in the frame of the barycenter and is called shifting orbit.
>
> …
>
> 3. Search for high speed asteroids near the Sun
>
> Beside of computing the trajectory of ‘Oumuamua, a better way to check our hypothesis is by experiment, that is, by observing new high speed asteroids and compare their trajectory with prediction. However, recorded asteroids and comets coming into the solar system from the outside are scarce. But I think that in reality such objects are not so rare, only that far from the Sun they are too faint to be detected. When they are near the Sun they become very bright and can be detected by Sun gazing satellites such as SOHO (Solar and Heliospheric Observatory).
>
> Many such alien asteroids and comets are already recorded by SOHO and are dormant in great number in the archives of SOHO. Thanks to NASA Goddard’s YouTube Movie “Decades of Sun from ESA & NASA’s SOHO” [19], which is a video made with all the photos taken by LASCO/C3 between 1998/01/06 and 2020/10/23, I have found several high speed asteroids and comets in it.
>
> For example, the asteroid that was recorded from 2004/02/26 to 2004/02/28.. I have computed its visual velocity which is the velocity of the dot on the image and got 160 km/s, see Figure 7. The comet recorded from 2015/02/18 to 2015/02/21 is measured at 182 km/s, see Figure 8. For comparison, the speed of ‘Oumuamua at perihelion is 87.71 km/s [8]. I used the diameter of the view field of LASCO/C3 which equals 30 radii of the Sun [20] and the time printed on the images to compute its visual velocity. As the actual trajectories make an angle with the plane of the image, their real velocity are forcefully bigger. Only objects coming from the outside of the solar system can be as speedy.
>
> I have made a clip of the asteroid and put it here: Super-fast alien asteroid (160 km/s), taken by SOHO in 2004, https://youtu.be/GTGuEKndNIc
>
> The alien asteroids and comets in the archives of SOHO are interesting. We can count their number, mapping their direction and measure their record breaking speed and size. On the other hand, we can monitor in real time the appearance of new alien asteroids and comets, work out their orbits for observing them later.
>
> In searching asteroids in the Movie “Decades of Sun from ESA & NASA’s SOHO” [19], the background stars and the streaks left by space particles are very dizzying which makes the researcher miss interesting asteroids and comets. So, I suggest that the background stars and streaks be removed for this research.
>
> For those who are interested in seeing the asteroids and comets that I have found I have put in the appendices the links that point to the frames of the Movie “Decades of Sun from ESA & NASA’s SOHO” [19] where they appear. I have seen more comets because they are brighter and easy to see. I have also put the few visual velocities that I have computed, which show that some comets are very fast and could have come from the outside of the solar system.
>
> 4. Discussion
>
> The analysis above shows that the unexpected gap can be well explained by the gravity of the Sun provided that the position and velocity of the Sun be correctly set in computing the predicted orbit. What matters is that the position and velocity of ‘Oumuamua be given with respect to the Sun’s actual position and velocity. If ‘Oumuamua were located with respect to the barycenter of the solar system while the Sun is not there, the predicted orbit would be wrong.
>
> We have shown that because the combined trajectory is not a hyperbola and has moving focus the non‑gravitational acceleration may be unnecessary to explain that “the observed orbital arc cannot be fit in its entirety by a trajectory governed solely by gravitational forces due to the Sun, the eight planets, the Moon, Pluto, the 16 biggest bodies in the asteroid main belt, and relativistic effects” [5]. This is corroborated by the lack of coma.
>
> We have also discovered that even the smallest error on the position and velocity of the Sun is enough to create an unexpected gap. Indeed, the distance used to reproduce the unexpected gap is only 12% of the radius of the Sun. So, the position and velocity of the Sun and the data of ‘Oumuamua must be precisely set.
>
> On the other hand, our hypothesis must be checked again and again before being validated. Indeed, other value was given to this gap, for example, in the article « THIS INTERSTELLAR ASTEROID IS ACCELERATING » [18], 100 000 km has been given to the gap rather than 40 000 km. Obviously, there are several different predicted trajectories for ‘Oumuamua with different results. The correct theoretical trajectory for ‘Oumuamua must give Gap = 0 and our method can help for finding it.
>
> We have proposed to check our hypothesis using the SOHO satellite in real time to find new alien asteroids and comets, work out their orbits for observing them later. It will be interesting to search for alien asteroids and comets in the archives of SOHO, which I have done partly.
>
> For more detail of this study please read the complete paper here:
> « Trajectory of 'Oumuamua and wandering Sun, alien asteroids and comets detected by SOHO »
> https://www.academia.edu/100818112/Trajectory_of_Oumuamua_and_wandering_Sun_alien_asteroids_and_comets_detected_by_SOHO

On Thursday, April 27, 2023 at 6:42:46 AM UTC+10, Kym Horsell wrote:
> On Thursday, April 27, 2023 at 4:27:13 AM UTC+10, PengKuan Em wrote:
> > The apparent non‑gravitational acceleration the extra-solar-system ‘Oumuamua exhibits is puzzling. We find that when the position and velocity of the Sun is correctly set in computing the predicted orbit, ‘Oumuamua’s trajectory can be explained with gravity and we have reproduced the unexpected gap by computation. We also propose to search for new extra-solar-system high speed asteroids with SOHO to check our method with their trajectories.
....

I was looking at 2017 U1 in the past few weeks so have some of the
data handy after uploading from Horizons.

The r and rdot data from 2017 upto today (daily) is at
<kym.massbus.org/U1>.

The graphs show the data as observed and the "s" graphs try to measure the discrepency between what was orbserved an the
expected orbit given the positions of all the relevant planets and sun.

The data at JPL is only what they saw and -- from some recent date -- what they predict given the model Micheli at el (2018) came up with to handle the non-gravity movement.

You can see from some of the plots there seems
to be a yuge difference between observation and expectation, esp as it gets near the sun and even moreso when it is leaving.

Looking at the night sky in the past couple years you would notice all the planets in a row. I.e. the solar system
is as lop-sided as it gets. I did some calcs for some other project
and it seems early 2022 showed the SSB (barycenter) about 1.4 mn km away from the centre of the sun.

Even in 2017 when Oumuamua was spotted the sun was ~1 mn km away from the barycenter. But that was taken into account when determining the "discrepency" in its motion.

The model NASA/JPL use for prediction is:

Asteroid non-gravitational force model (AMRAT= m^2/kg;A1,A2,A3=au/d^2;R0
AMRAT= 0.
A1= 2.790193367004E-7 A2= 1.441264152527E-8 A3= 1.573922634125E-8
Non-standard or simulated/proxy model:
ALN= .04083733261 NK= 2.6 NM= 2. NN= 3. R0= 5.
NOTE:
This orbit solution includes non-gravitational perturbations as describe
Micheli et al. (2018): http://dx.doi.org/10.1038/s41586-018-0254-4

The behavior of these accelerations outside the observed data arc from
2017 October 14 to 2018 January 2 can only be assumed. Predictions outside
this time interval, especially prior to October 2017, could be much more
uncertain than reported here.

You can get the orbital elements for 2017U1 from Horizons. Instead of a steady stream of the same value around 2017 the orbit is constantly changing, sometimes with some jumps.

If you look at the eccentricity there are some big bumps where it changes from a closed orbit to a parabolic then hyperbolic.

Kinda unusual. :)

FOr those interesting in that kind of thing it seems the motion of Oumuamua does match up with
some "activity" reported over N America at the time.
Even the little bumps in its motion seem to predict
certain activity to some extent. But not as closely as
the motion of some other bodies.

I've posted elsewhere you could interpret that as certain objects
perhaps living someplace else but passing by
Oumuamua maybe to welcome it to the neighbourhood, give it a once-over, or maybe to tell it
"all full up here keep moving".

On Friday, April 28, 2023 at 11:24:50 AM UTC+10, Kym Horsell wrote:
> On Thursday, April 27, 2023 at 6:42:46 AM UTC+10, Kym Horsell wrote:
> > On Thursday, April 27, 2023 at 4:27:13 AM UTC+10, PengKuan Em wrote:
> > > The apparent non‑gravitational acceleration the extra-solar-system ....

OK. Another lil update. You know when you go to bed
and then wake up totally awake after only 2 hours and you
just HAVE to look at something on the computer or
you know somthing in your head its gunna bust?

Like that.

I downloaded the elements for 2017 U1 for 2017 with respect to the Sun and the SSB (barycenter). These are the "wld" files in the U1 dir mentioned before.

I also plotted out the EC for U1 over the 365 days of 2017. You can see a "glitch" in each coordinate system with the barycenter having the biggest. While the perihelion of U1 was maybe 2.5 AU it seems there is quite a diff between the 2 coordinate systems when it comes to caculating just the eccentricity of the thing.

But the main point is -- there was a glitch. It did something unusual that seems independent of where you measure it from. While I would expect (ideally) the eccentricy measured in one frame of ref to be exactly the same as in another it seems Mr Correlated Noise has reared its interesting head making calculations in
one frame of ref blow up the glitch.

Le vendredi 28 avril 2023 à 03:24:50 UTC+2, Kym Horsell a écrit :
> On Thursday, April 27, 2023 at 6:42:46 AM UTC+10, Kym Horsell wrote:
> > On Thursday, April 27, 2023 at 4:27:13 AM UTC+10, PengKuan Em wrote:
> > > The apparent non‑gravitational acceleration the extra-solar-system ‘Oumuamua exhibits is puzzling. We find that when the position and velocity of the Sun is correctly set in computing the predicted orbit, ‘Oumuamua’s trajectory can be explained with gravity and we have reproduced the unexpected gap by computation. We also propose to search for new extra-solar-system high speed asteroids with SOHO to check our method with their trajectories.
> ...
>
> I was looking at 2017 U1 in the past few weeks so have some of the
> data handy after uploading from Horizons.
>
> The r and rdot data from 2017 upto today (daily) is at
> <kym.massbus.org/U1>.
>
> The graphs show the data as observed and the "s" graphs try to measure the discrepency between what was orbserved an the
> expected orbit given the positions of all the relevant planets and sun.
>
> The data at JPL is only what they saw and -- from some recent date -- what they predict given the model Micheli at el (2018) came up with to handle the non-gravity movement.
>
> You can see from some of the plots there seems
> to be a yuge difference between observation and expectation, esp as it gets near the sun and even moreso when it is leaving.
>
> Looking at the night sky in the past couple years you would notice all the planets in a row. I.e. the solar system
> is as lop-sided as it gets. I did some calcs for some other project
> and it seems early 2022 showed the SSB (barycenter) about 1.4 mn km away from the centre of the sun.
>
> Even in 2017 when Oumuamua was spotted the sun was ~1 mn km away from the barycenter. But that was taken into account when determining the "discrepency" in its motion.
>
> The model NASA/JPL use for prediction is:
>
> Asteroid non-gravitational force model (AMRAT= m^2/kg;A1,A2,A3=au/d^2;R0
> AMRAT= 0.
> A1= 2.790193367004E-7 A2= 1.441264152527E-8 A3= 1.573922634125E-8
> Non-standard or simulated/proxy model:
> ALN= .04083733261 NK= 2.6 NM= 2. NN= 3. R0= 5.
>
> NOTE:
> This orbit solution includes non-gravitational perturbations as describe
> Micheli et al. (2018): http://dx.doi.org/10.1038/s41586-018-0254-4
>
> The behavior of these accelerations outside the observed data arc from
> 2017 October 14 to 2018 January 2 can only be assumed. Predictions outside
> this time interval, especially prior to October 2017, could be much more
> uncertain than reported here.
>
> You can get the orbital elements for 2017U1 from Horizons. Instead of a steady stream of the same value around 2017 the orbit is constantly changing, sometimes with some jumps.
>
> If you look at the eccentricity there are some big bumps where it changes from a closed orbit to a parabolic then hyperbolic.
>
> Kinda unusual. :)
>
> FOr those interesting in that kind of thing it seems the motion of Oumuamua does match up with
> some "activity" reported over N America at the time.
> Even the little bumps in its motion seem to predict
> certain activity to some extent. But not as closely as
> the motion of some other bodies.
>
> I've posted elsewhere you could interpret that as certain objects
> perhaps living someplace else but passing by
> Oumuamua maybe to welcome it to the neighbourhood, give it a once-over, or maybe to tell it
> "all full up here keep moving".

Thank you so much. I really did not expect you to give such information. I will study it.

On Saturday, April 29, 2023 at 1:48:01 AM UTC+10, PengKuan Em wrote:
> Le vendredi 28 avril 2023 à 03:24:50 UTC+2, Kym Horsell a écrit :
....
> Thank you so much. I really did not expect you to give such information. I will study it.

Yes, it's a bit of a puzzler. If it gets Avi Loeb "upset" then
there is likely no simple explanation. :)

I put some more stuff up that also might be of interest.

A "skyplot" shows the path across the sky of the asteroid from 2017 to now. Crazy stuff.
It stars in Vega -- if you're interested in unusual objects seen in the sky then anything coming from Vega sets alarms off -- and wanders down to the ecliptic, gets to RA about -20, then wanders back up to the ecliptic. Even for an extra-solar object it's "unusual". :)

I also put up a plot of the calculation of the inclination of U1. It runs around 122 deg but like other things there is a big glitch as it gets to the inner system.

A couple of the other files are day by day datasets for eclip lat and lon. Just in case you want to calculate a detailed gravitation model to see how much and where U1 deviates from what you would expect.

I'l hacking up a little gravity model and I'll put that up there as well if you grok C/C++ written by a 70yo blind man. :)

I hope just taking into account the position of the sun and Jupiter I can get a good curve for what U1 would have done if it was a dead rock versus what it was observed to do.

Anyway, have fun puzzling it out.

On Saturday, April 29, 2023 at 3:34:19 PM UTC+10, Kym Horsell wrote:
> On Saturday, April 29, 2023 at 1:48:01 AM UTC+10, PengKuan Em wrote:
> > Le vendredi 28 avril 2023 à 03:24:50 UTC+2, Kym Horsell a écrit :
> ...
> > Thank you so much. I really did not expect you to give such information.. I will study it.
> Yes, it's a bit of a puzzler. If it gets Avi Loeb "upset" then
> there is likely no simple explanation. :)
>
> I put some more stuff up that also might be of interest.
>
> A "skyplot" shows the path across the sky of the asteroid from 2017 to now. Crazy stuff.
> It stars in Vega -- if you're interested in unusual objects seen in the sky then anything coming from Vega sets alarms off -- and wanders down to the ecliptic, gets to RA about -20, then wanders back up to the ...

That's DEC -20 of course.

Le vendredi 28 avril 2023 à 03:24:50 UTC+2, Kym Horsell a écrit :
> On Thursday, April 27, 2023 at 6:42:46 AM UTC+10, Kym Horsell wrote:

>Looking at the night sky in the past couple years you would notice all the planets in a row. I.e. the solar system
is as lop-sided as it gets. I did some calcs for some other project
and it seems early 2022 showed the SSB (barycenter) about 1.4 mn km away from the centre of the sun.

>Even in 2017 when Oumuamua was spotted the sun was ~1 mn km away from the barycenter. But that was taken into account when determining the "discrepency" in its motion.

Thank you to provide this valuable information. First of all, the “the Sun was ~1 mn km away from the barycenter” is very useful. Indeed, In my paper I said that the predicted orbit has its focus on the barycenter. In fact no. So, I have corrected the explanation in my paper and saying that the focus is on a point P in the frame of the barycenter. Then, if the predicted orbit was computed with the focus on the point P while the Sun is not there, then Oumuamua would not fit into the predicted orbit.

In fact, the position of the Sun in Nasa’s Horizon system may be not precisely the point where the Sun really is, since it is a prediction. So, for computing Oumuamua’s orbit, we have to pinpoint the position of Oumuamua but also the Sun. I have found that 80 000 km of error in the 1mn km can make the 40 000 km of unexpected gap. And in 80 days, the Sun travels 80 000 km. Where is the focus of the predicted orbit during these 80 days?

Other question. What is the green line in the plots? The predicted orbit? Does the observed orbit equal the green curve plus the red curve?

KP

On Sunday, April 30, 2023 at 7:02:26 AM UTC+10, PengKuan Em wrote:
> Le vendredi 28 avril 2023 à 03:24:50 UTC+2, Kym Horsell a écrit :
> > On Thursday, April 27, 2023 at 6:42:46 AM UTC+10, Kym Horsell wrote:
>
> >Looking at the night sky in the past couple years you would notice all the planets in a row. I.e. the solar system
> is as lop-sided as it gets. I did some calcs for some other project
> and it seems early 2022 showed the SSB (barycenter) about 1.4 mn km away from the centre of the sun.
>
> >Even in 2017 when Oumuamua was spotted the sun was ~1 mn km away from the barycenter. But that was taken into account when determining the "discrepency" in its motion.
> Thank you to provide this valuable information. First of all, the “the Sun was ~1 mn km away from the barycenter” is very useful. Indeed, In my paper I said that the predicted orbit has its focus on the barycenter. In fact no. So, I have corrected the explanation in my paper and saying that the focus is on a point P in the frame of the barycenter. Then, if the predicted orbit was computed with the focus on the point P while the Sun is not there, then Oumuamua would not fit into the predicted orbit.
>
> In fact, the position of the Sun in Nasa’s Horizon system may be not precisely the point where the Sun really is, since it is a prediction. So, for computing Oumuamua’s orbit, we have to pinpoint the position of Oumuamua but also the Sun. I have found that 80 000 km of error in the 1mn km can make the 40 000 km of unexpected gap. And in 80 days, the Sun travels 80 000 km. Where is the focus of the predicted orbit during these 80 days?
>
> Other question. What is the green line in the plots? The predicted orbit? Does the observed orbit equal the green curve plus the red curve?
....

I think on the plots you are talking about one curve is for "object 10" and one is for "object 0". In the Horizons system 0 == solar system barycenter and 10 == sun.

Supposedly in the Horizons data distance calculations with respect to either coordinate system are good to a few meters. Different asteroids and comets have different specifications but most have "old data" before a given date as "observations" -- probably more accurately thought of as interpolated observations -- and from a certain point on as the output from their solar system model taking other bodies into account.

The solar system moves maybe 20 million km per day around the galaxy. That usually can be ignored because it is an intertial frame (mostly). I think about 300m per day is due to the curve of the sun around the galaxy so that is also taken into account. Trying to get something into orbit around Neptune would fail if it was out 10 km after a decade-long run out there.

I left my little program on the same site. There is something definitely screwy with U1 and gravity. According to a gravity-only sim it is many AU out of position. The JPL data warns only the position inside the limits around Oct 2017 to Jan 2018 are accurate so I squeezed a best fit out of that section of the data and still it would not fit very well.

But that should be expected when the thing started way above the ecliptic, proceeded to move below the ecliptic, but then came back to end up very near lat 0 and seem to stablise around there.

At present I have all the outer planets in the gravity model and they dont help explain the yuge differences between what the gravity track predicts and what the Horizons data shows.