333P - MPC coordinates far off
I am currently doing some work on older images and noticed a large difference
in coordinates of 333P between MPC and JPL. While the latter are very close to
the position of the comet in the image the former are off by almost 1 degree.
In addition to the wrong position the web form
does return a completely wrong motion vector as well.
Could anybody check this?
Thanks
Thomas
|
Re: Comets with similar orbits
Hi Adrien and all!
There's the beautiful Theory of Probability playing amazing tricks here and there! The initial assumption of Adrien's calculation was as follows:
On Tue, Nov 26, 2024 at 9:17?PM Adrien Coffinet wrote:
Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to have so similar angles at random.
Let's assume we have a set of 1846 items and 180*360*360 (23.328 Mln) cages in 3D space, each having 1*1*1 degree. What do you think is the expected number of two items falling in one cage? 1846/23328000, or ~1/12600? Nope! It's 924 times more, or ~1/14. Simply because we have N*(N-1)/2 pairs of items. In case of N=1846 random comets there are 1846*1845/2 = 1?702?935 chances to have orbital elements falling into one cage, or in one cubic degree in the 3-D orbital parameters space.
Here's the personal story that amazed me so much about forty years ago. (Not astronomy or comets related, so sorry for the off-topic!) At school I was collecting "lucky tickets" from trams, buses and trolleybuses. Tickets had 6-figure numbers from 000001 to 999999 plus alphanumeric series. By definition, the ticket is considered lucky, if the sum of the first three digits is equal to that of three last digits (a+b+c=d+e+f). For example, I had a ticket with the number 100100 in my collection! Instead of eating them, I glued them to the pieces of cardboard, 4 rows with 13 tickets in each row. :-) Imagine my amusement when after 5 full sets of 52 tickets I have found two tickets (one from bus, the other from tram) with the *exactly* same 6 figures! Yes, the same 6 figures in the same order!
There are 55251 possible "lucky numbers" in the total set of 999999 (so, every 18th is lucky). Thinking linearly, one would expect to have a matching pair after some 25-30 *thousand* items. But I got the matching pair after 250 or 300 tickets in my collection! A hundred times earlier, that is. Of course, this is because the chance to have two items in one cage (or two comets in one cubic degree in 3-dimension orbital parameters space) is growing proportional to the number of items squared. Simply because of the N*(N-1)/2 formula above.
One picture is worth a thousand words. Here is the picture showing the expected number of matching lucky numbers: One can see that you should expect the first match around 300 tickets. I had my luck a bit earlier.
Best regards,
Denis
|
Re: Comets with similar orbits
All,
these might be interesting to read:
L. Kresak: A Strange Anomaly in the Occurence Rate of Old Comets
l. Kresak: On the Reality and Genetic Association of Comet Groups and Pairs
Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________
*** @skymorph.bsky.social
|
Comet 333P/LINEAR now in SWAN
Hi All.
Just for information. Recent moderate bright comet 333P/LINEAR now is visible in the last SWAN images with X-Y position (0,0 - upper left): 25/11 342-239. Brightness in the level of +12m based on UV appearience.
Vladimir.
|
Re: Comets with similar orbits
After looking a bit deeper, I found this paper which identified the relevant comet cluster, although it doesn't identify an obvious candidate stellar flyby:
They found a strong overdensity in radiant (aphelion) direction to be centered at ecliptic (lon, lat) of (111 deg, +17 deg), while C/2020 N2 is at (105 deg, +9 deg) and C/2021 T4 is at (107 deg, +10 deg). With a lot of comets coming from that direction (constraining 2 degrees of freedom), a pair of comets from the cluster then just needs to line up in the remaining 1 degree of angular freedom to have full sets of very similar angular elements. That doesn't rule out some of these comets could actually have been split from each other (perhaps even before they first approached the Sun), but that's a more complicated analysis.
Qicheng
On Tuesday, November 26, 2024 at 04:09:26 p.m. MST, planetaryscience via groups.io <planetaryscience@...> wrote:
Hi Qicheng,
HD 7977 is the only (currently known) star that might have produced currently-observable influence on the Oort Cloud during its approach to 30,200 +6600 -4900 AU, 2.76 million years ago. The accuracy of this solution is a little questionable but assuming the nominal orbit it would have caused a surge of comets around 900,000 years ago.
On Tuesday, November 26, 2024 at 01:36:42 PM PST, Qicheng Zhang via groups.io <qzalaska@...> wrote:
First, a few minor notes that probably don't change the overall problem but matter if you want to calculate a proper expectation value:
1. The difference between any two sets of node/peri can't be more than 180 degrees apart. 2. The distribution of inclination differences for isotropic orbits is highly non-uniform (there are much fewer orbits near 0 & 180 degrees. Also if one orbit is near 90 deg, the other can't be more than ~90 deg away). 3. You'd need another factor of 4 to scale the modal case (approx. mean case) to 0.5*number of objects. Otherwise, you could imagine just increasing the number of parameters and the probability dropping toward zero even for any unremarkable pair.
I'd expect the closeness to still be statistically significant, albeit not quite at that level (probably easiest with Monte Carlo sampling). The explanation is most likely that there's actually considerable anisotropy in the orbital distribution of comets coming from the Oort cloud, since the main driver of comets coming to the inner solar system is the galactic tide, followed by the gravity of individual nearby stars. The latter, in particular, can create clusters of comets approaching from a fairly common direction, but spread over a wide range of rotations and perihelion distances, which could make it far more likely for any two to have similar angular elements since that's just one extra degree of freedom they have to match in.
This particular case reminded me of the closely aligned pair of sungrazers C/2012 S1 & C/1680 V1 that could not have been broken apart from a prior apparition, given one was dynamically new. As it turn out, both of these also have orbits aligned closely with C/2020 N2 & C/2021 T4 (but significantly rotated along the line of apsides), and it could well be all of these (and probably many more) were sent in by the same star passing through the Oort cloud. Many other sungrazing/sunskirting also approach from a similar direction, including the Kreutz and C/1962 C1, and these could be associated as well, though I haven't done the analysis to verify the clustering remains significant after accounting for the galactic tide. I vaguely recall reading a paper that looked into recent stellar passages through the Oort cloud that claimed to have identified a potential cluster of comets associated with a past encounter with a certain star, but I can't find that paper at the moment, and don't remember if these comets matched that stellar passage (or if even if that paper used/stood up to Gaia data).
Qicheng
On Tuesday, November 26, 2024 at 11:59:35 a.m. MST, Adrien Coffinet via groups.io <adrien.coffinet2@...> wrote:
Hi Maik,
Thank you, interesting.
Adrien
Hello Adrien,
> My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles
> (i, peri, node), the main difference being their perihelion distance.
>
> If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the
> relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will
> remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably
> different, right?
>
> So, could such pairs of comets be related?
>
> Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
>
> Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the
> sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to
> have so similar angles at random.
But it is a much better chance than winning the lottery! :-)
I usually dismiss those cases as chance coincidences.
However, I can not really answer your question whether it is possible. However, I just want to mention Zdenek Sekanina's
model of cascading fragmentation for the Kreutz group where non-tidal break-up's occur usually far from the sun (even
centuries from perihelion) but still the perihelion distances are rather similar. The separation velocity only account
for the temporal distribution of the fragments, not the perihelion distance. Of course, the Kreutz group is a special case.
But he also writes
"At distances exceeding 100 AU, the acquired extra momentum causes only a minor perturbation of the orbital period,
thus accounting for fragments subsequently arriving at the Sun nearly simultaneously, but exerts a major effect on both
the angular orbital elements and perihelion distance, thus accounting for the orientation diversity of the orbital
planes and perihelion distances of fragments."
So, for the Kreutz group we speak of differences in the perihelion distance of, say, 0.005 au vs 0.008 au, and not 0.3
au as for your example. Also, in your example, the periods differ by a large amount, ~1000 years vs 4 million years!,
while Sekanina says that it should have no effect on q.
But again, I am no expert here, just my 2 cents.
Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________
*** @skymorph.bsky.social
|
Re: Comets with similar orbits
Hi Qicheng,
HD 7977 is the only (currently known) star that might have produced currently-observable influence on the Oort Cloud during its approach to 30,200 +6600 -4900 AU, 2.76 million years ago. The accuracy of this solution is a little questionable but assuming the nominal orbit it would have caused a surge of comets around 900,000 years ago.
On Tuesday, November 26, 2024 at 01:36:42 PM PST, Qicheng Zhang via groups.io <qzalaska@...> wrote:
First, a few minor notes that probably don't change the overall problem but matter if you want to calculate a proper expectation value:
1. The difference between any two sets of node/peri can't be more than 180 degrees apart. 2. The distribution of inclination differences for isotropic orbits is highly non-uniform (there are much fewer orbits near 0 & 180 degrees. Also if one orbit is near 90 deg, the other can't be more than ~90 deg away). 3. You'd need another factor of 4 to scale the modal case (approx. mean case) to 0.5*number of objects. Otherwise, you could imagine just increasing the number of parameters and the probability dropping toward zero even for any unremarkable pair.
I'd expect the closeness to still be statistically significant, albeit not quite at that level (probably easiest with Monte Carlo sampling). The explanation is most likely that there's actually considerable anisotropy in the orbital distribution of comets coming from the Oort cloud, since the main driver of comets coming to the inner solar system is the galactic tide, followed by the gravity of individual nearby stars. The latter, in particular, can create clusters of comets approaching from a fairly common direction, but spread over a wide range of rotations and perihelion distances, which could make it far more likely for any two to have similar angular elements since that's just one extra degree of freedom they have to match in.
This particular case reminded me of the closely aligned pair of sungrazers C/2012 S1 & C/1680 V1 that could not have been broken apart from a prior apparition, given one was dynamically new. As it turn out, both of these also have orbits aligned closely with C/2020 N2 & C/2021 T4 (but significantly rotated along the line of apsides), and it could well be all of these (and probably many more) were sent in by the same star passing through the Oort cloud. Many other sungrazing/sunskirting also approach from a similar direction, including the Kreutz and C/1962 C1, and these could be associated as well, though I haven't done the analysis to verify the clustering remains significant after accounting for the galactic tide. I vaguely recall reading a paper that looked into recent stellar passages through the Oort cloud that claimed to have identified a potential cluster of comets associated with a past encounter with a certain star, but I can't find that paper at the moment, and don't remember if these comets matched that stellar passage (or if even if that paper used/stood up to Gaia data).
Qicheng
On Tuesday, November 26, 2024 at 11:59:35 a.m. MST, Adrien Coffinet via groups.io <adrien.coffinet2@...> wrote:
Hi Maik,
Thank you, interesting.
Adrien
Hello Adrien,
> My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles
> (i, peri, node), the main difference being their perihelion distance.
>
> If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the
> relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will
> remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably
> different, right?
>
> So, could such pairs of comets be related?
>
> Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
>
> Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the
> sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to
> have so similar angles at random.
But it is a much better chance than winning the lottery! :-)
I usually dismiss those cases as chance coincidences.
However, I can not really answer your question whether it is possible. However, I just want to mention Zdenek Sekanina's
model of cascading fragmentation for the Kreutz group where non-tidal break-up's occur usually far from the sun (even
centuries from perihelion) but still the perihelion distances are rather similar. The separation velocity only account
for the temporal distribution of the fragments, not the perihelion distance. Of course, the Kreutz group is a special case.
But he also writes
"At distances exceeding 100 AU, the acquired extra momentum causes only a minor perturbation of the orbital period,
thus accounting for fragments subsequently arriving at the Sun nearly simultaneously, but exerts a major effect on both
the angular orbital elements and perihelion distance, thus accounting for the orientation diversity of the orbital
planes and perihelion distances of fragments."
So, for the Kreutz group we speak of differences in the perihelion distance of, say, 0.005 au vs 0.008 au, and not 0.3
au as for your example. Also, in your example, the periods differ by a large amount, ~1000 years vs 4 million years!,
while Sekanina says that it should have no effect on q.
But again, I am no expert here, just my 2 cents.
Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________
*** @skymorph.bsky.social
|
Re: C/2024 G3 and it further behavior
To follow up about the prospects for comet 2024 G3 ATLAS, I made the same kind of tail simulations as for comet Tsuchinshan-ATLAS. Besides what has already been said about the unfavorable viewing geometry, comet C/2024 G3 ATLAS seems to have some potential for showing a low-brightness dust tail for a few days after perihelion for observers located near the equator and south of it. This depends a lot on the actual magnitude that the comet will reach at perihelion.
The current extrapolation range for perihelion brightness is extremely wide, with last observations of the comet around magnitude 12 in early November to negative magnitudes at perihelion, ie around 15magnitude = one million-fold increase of brightness. Needless to say that with such a range of extrapolation, the perihelion magnitude remains very uncertain, and could easily be anywhere between magnitude -1 and -6.
Assuming a perihelion brightness around magnitude -3.5, the best window of opportunity for capturing the dust tail would be between January 19th?and 23rd, when the dust tail could possibly reach between 15¡ã and 20¡ã, with about 10¡ã of the tip of tail visible with the comet head located below the horizon.
More detailed analysis on my website?
Regards
Nicolas
Le?jeu. 21 nov. 2024 ¨¤?22:48, Michael Mattiazzo via <mmatti= [email protected]> a ¨¦crit?: FYI This is a photo of C/2024 G3 I captured on Nov 4th. Details on image Cheers, Michael ? ? Dear Alexander, all, ? Since no one else seems to have answered this, I¡¯ll chime in. ? Yes, the calculations suggest that this is a dynamically ¡°old¡± comet (according to the most recent MPC orbit, 1/a(orig) = +0.000337? ¨¤ most recent return 160,000 years ago, taking things at face value). The fact that this comet has survived a previous perihelion passage and is ¡°broken in,¡± so to speak, is potentially good news, but that may or may not mean very much. ? The Bortle survival limit ¨C which I remind everyone is strictly an empirical determination and not any kind of natural ¡°law¡± ¨C for a comet with this one¡¯s perihelion distance is H_10 = 7.6. The most recent brightness reports (late October/early November) of m1 ~12 suggest an H_10 ~ 7.0, which is above that threshold, although not by very much. So, the news again is good, albeit not great, and I¡¯m not sure one should put much stock in it. ? The comet was just recently in conjunction with the sun and is now emerging into the southern hemisphere¡¯s morning sky, albeit at a small elongation (currently 22 degrees, and decreasing). If it brightens sufficiently the observers there may be able to pick it up within the near future and perhaps follow it into early January. And while I will leave this part of the discussion to those with more expertise in these instruments, it may be detectable with SWAN and/or HI1A sometime during this period. For about three days centered around the time of perihelion passage it will be visible in LASCO C3. ? If it does brighten and survive perihelion, the observers in the southern hemisphere should be able to get some reasonably decent observations of it. Those of us in the northern hemipshere are significantly less fortunate: our best opportunity may actually be during daylight right around the time of perihelion, provided, of course, that the comet becomes very bright. (For what it¡¯s worth, around this time it reaches a maximum phase angle of 116 degrees, so there may possibly be some modest brightness enhancement due to forward scattering.) ?In that case it might then be visible very low in evening twilight for a handful of days shortly after perihelion before it heads south and (presumably) fades pretty rapidly. I don¡¯t believe I would bet much money on that particular scenario happening . . . but I guess one never knows. ? ? Sincerely, Alan ? Hello all
As it turns out, C/2024 G3 is actually a dynamically old comet (e=1.0000142, epoch 15 Sep; e=0.999997, epoch 1 Jan 2022. Calculated by find_orb)
Until early November it followed H=5, 2.5n=17. Is this likely to persist to perihelion? Or should we expect similar to c/2002 v1 deceleration to n=~3.5?
|
Re: Comets with similar orbits
First, a few minor notes that probably don't change the overall problem but matter if you want to calculate a proper expectation value:
1. The difference between any two sets of node/peri can't be more than 180 degrees apart. 2. The distribution of inclination differences for isotropic orbits is highly non-uniform (there are much fewer orbits near 0 & 180 degrees. Also if one orbit is near 90 deg, the other can't be more than ~90 deg away). 3. You'd need another factor of 4 to scale the modal case (approx. mean case) to 0.5*number of objects. Otherwise, you could imagine just increasing the number of parameters and the probability dropping toward zero even for any unremarkable pair.
I'd expect the closeness to still be statistically significant, albeit not quite at that level (probably easiest with Monte Carlo sampling). The explanation is most likely that there's actually considerable anisotropy in the orbital distribution of comets coming from the Oort cloud, since the main driver of comets coming to the inner solar system is the galactic tide, followed by the gravity of individual nearby stars. The latter, in particular, can create clusters of comets approaching from a fairly common direction, but spread over a wide range of rotations and perihelion distances, which could make it far more likely for any two to have similar angular elements since that's just one extra degree of freedom they have to match in.
This particular case reminded me of the closely aligned pair of sungrazers C/2012 S1 & C/1680 V1 that could not have been broken apart from a prior apparition, given one was dynamically new. As it turn out, both of these also have orbits aligned closely with C/2020 N2 & C/2021 T4 (but significantly rotated along the line of apsides), and it could well be all of these (and probably many more) were sent in by the same star passing through the Oort cloud. Many other sungrazing/sunskirting also approach from a similar direction, including the Kreutz and C/1962 C1, and these could be associated as well, though I haven't done the analysis to verify the clustering remains significant after accounting for the galactic tide. I vaguely recall reading a paper that looked into recent stellar passages through the Oort cloud that claimed to have identified a potential cluster of comets associated with a past encounter with a certain star, but I can't find that paper at the moment, and don't remember if these comets matched that stellar passage (or if even if that paper used/stood up to Gaia data).
Qicheng
On Tuesday, November 26, 2024 at 11:59:35 a.m. MST, Adrien Coffinet via groups.io <adrien.coffinet2@...> wrote:
Hi Maik,
Thank you, interesting.
Adrien
Hello Adrien,
> My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles
> (i, peri, node), the main difference being their perihelion distance.
>
> If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the
> relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will
> remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably
> different, right?
>
> So, could such pairs of comets be related?
>
> Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
>
> Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the
> sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to
> have so similar angles at random.
But it is a much better chance than winning the lottery! :-)
I usually dismiss those cases as chance coincidences.
However, I can not really answer your question whether it is possible. However, I just want to mention Zdenek Sekanina's
model of cascading fragmentation for the Kreutz group where non-tidal break-up's occur usually far from the sun (even
centuries from perihelion) but still the perihelion distances are rather similar. The separation velocity only account
for the temporal distribution of the fragments, not the perihelion distance. Of course, the Kreutz group is a special case.
But he also writes
"At distances exceeding 100 AU, the acquired extra momentum causes only a minor perturbation of the orbital period,
thus accounting for fragments subsequently arriving at the Sun nearly simultaneously, but exerts a major effect on both
the angular orbital elements and perihelion distance, thus accounting for the orientation diversity of the orbital
planes and perihelion distances of fragments."
So, for the Kreutz group we speak of differences in the perihelion distance of, say, 0.005 au vs 0.008 au, and not 0.3
au as for your example. Also, in your example, the periods differ by a large amount, ~1000 years vs 4 million years!,
while Sekanina says that it should have no effect on q.
But again, I am no expert here, just my 2 cents.
Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________
*** @skymorph.bsky.social
|
Re: Comets with similar orbits
Hi Maik,
Thank you, interesting.
Adrien
Hello Adrien,
> My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles
> (i, peri, node), the main difference being their perihelion distance.
>
> If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the
> relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will
> remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably
> different, right?
>
> So, could such pairs of comets be related?
>
> Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
>
> Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the
> sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to
> have so similar angles at random.
But it is a much better chance than winning the lottery! :-)
I usually dismiss those cases as chance coincidences.
However, I can not really answer your question whether it is possible. However, I just want to mention Zdenek Sekanina's
model of cascading fragmentation for the Kreutz group where non-tidal break-up's occur usually far from the sun (even
centuries from perihelion) but still the perihelion distances are rather similar. The separation velocity only account
for the temporal distribution of the fragments, not the perihelion distance. Of course, the Kreutz group is a special case.
But he also writes
"At distances exceeding 100 AU, the acquired extra momentum causes only a minor perturbation of the orbital period,
thus accounting for fragments subsequently arriving at the Sun nearly simultaneously, but exerts a major effect on both
the angular orbital elements and perihelion distance, thus accounting for the orientation diversity of the orbital
planes and perihelion distances of fragments."
So, for the Kreutz group we speak of differences in the perihelion distance of, say, 0.005 au vs 0.008 au, and not 0.3
au as for your example. Also, in your example, the periods differ by a large amount, ~1000 years vs 4 million years!,
while Sekanina says that it should have no effect on q.
But again, I am no expert here, just my 2 cents.
Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________
*** @skymorph.bsky.social
|
Re: Comets with similar orbits
Hello Adrien, My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles (i, peri, node), the main difference being their perihelion distance.
If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably different, right?
So, could such pairs of comets be related?
Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to have so similar angles at random. But it is a much better chance than winning the lottery! :-) I usually dismiss those cases as chance coincidences. However, I can not really answer your question whether it is possible. However, I just want to mention Zdenek Sekanina's model of cascading fragmentation for the Kreutz group where non-tidal break-up's occur usually far from the sun (even centuries from perihelion) but still the perihelion distances are rather similar. The separation velocity only account for the temporal distribution of the fragments, not the perihelion distance. Of course, the Kreutz group is a special case. But he also writes "At distances exceeding 100 AU, the acquired extra momentum causes only a minor perturbation of the orbital period, thus accounting for fragments subsequently arriving at the Sun nearly simultaneously, but exerts a major effect on both the angular orbital elements and perihelion distance, thus accounting for the orientation diversity of the orbital planes and perihelion distances of fragments." So, for the Kreutz group we speak of differences in the perihelion distance of, say, 0.005 au vs 0.008 au, and not 0.3 au as for your example. Also, in your example, the periods differ by a large amount, ~1000 years vs 4 million years!, while Sekanina says that it should have no effect on q. But again, I am no expert here, just my 2 cents. Maik -- "One cannot discover comets lying in bed." * Lewis Swift ________________________________________________________________________ *** @skymorph.bsky.social
|
Comets with similar orbits
Hi all,
My question may be stupid, but I have found a few pairs of quasi-parabolic comets with nearly exactly the same angles (i, peri, node), the main difference being their perihelion distance.
If, for whatever reason, a body with a near-parabolic orbit split quite far from the Sun (at a distance where the relative velocity of the two fragments is not negligible compared to their heliocentric velocity), the angles will remain essentially the same, but we could end up with two fragments whose perihelion distances could be noticeably different, right?
So, could such pairs of comets be related?
Examples: C/2020 N2 (ATLAS) vs. C/2021 T4 (Lemmon)
Assuming isotropy for all three angles, and knowing that my initial sample (e > 0.9, and q > 0.05 au to exclude the sungrazers) contains 1846 objects, this pair has a probability of 1846*(?i/180)*(?node/360)*(?peri/360) = ~1/38000 to have so similar angles at random.
Thank you in advance for your answers.
Adrien
|
Re: Viewing geometry for comet ATLAS, war Re: C/2024 G3 and it further behavior
If Comet C/2023 A3 (Tsuchinshan-ATLAS) had actually been magnitude -3 as seen from "Earth" on October 10 it would have been very easy to see given that the comet set well after the Sun set, it would have been like looking at Venus. So much nonsense in all of this reporting.
|
Re: Viewing geometry for comet ATLAS, war Re: C/2024 G3 and it further behavior
Hello all
Is it possible, that the comet could observe at the daylight, if it survives?
Greetings Anja Verh?fen
Alexander Balashov via <skywatcher422= [email protected]> schrieb am Mo., 25. Nov. 2024, 12:31:
[Edited Message Follows]
Coma c/2024 g3 is likely to be more condensed than coma c/2023 a3, because c/2024 g3 will be further from Earth and mag -3 will be reached by close approach to the Sun rather than by forward scattering. I think is better to compare visibility condition with C/2006 P1 (was visible with similar conditions with -4 mag)
Alexander Balashov
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Re: Viewing geometry for comet ATLAS, war Re: C/2024 G3 and it further behavior
Coma c/2024 g3 is likely to be more condensed than coma c/2023 a3, because c/2024 g3 will be further from Earth and mag -3 will be reached by close approach to the Sun rather than by forward scattering. I think is better to compare visibility condition with C/2006 P1 (was visible with similar conditions with -4 mag)
Alexander Balashov
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Viewing geometry for comet ATLAS, war Re: C/2024 G3 and it further behavior
Can we predict the (non-)visibility of C/2024 G3 around peak brightness in strong twilight from the recent experience with C/2023 A3's around its solar conjunction? The following assumes a) that G3 follows the brightness slope used by JPL Horizons right now all the way to perihelion and back, b) that the offset of actual observations in COBS from what Horizons predicts remains constant, i.e. that the comet is ~1.7 mag. brighter (no change of slope and no significant scattering effects), and c) that the degree of condensation and thus strength to make it through a severely brightened sky is similar. Here is what I get, for my place in Germany (Bochum at 51.5¡ã North) and Johannesburg at 26¡ã South:
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Jan. 07 | +2.0 mag. | Elongation 14¡ã | vertical Delta for GER 4¡ã | vertical Delta for RSA 12¡ã
Jan. 08 | +1.2 mag. | Elongation 13¡ã | vertical Delta for GER 4¡ã | vertical Delta for RSA 10¡ã
Jan. 09 | +0.5 mag. | Elongation 12¡ã | vertical Delta for GER 5¡ã | vertical Delta for RSA 10¡ã
Jan. 10 | -0.5 mag. | Elongation 10¡ã | vertical Delta for GER 5¡ã | vertical Delta for RSA 7¡ã
Jan. 11 | -1.7 mag. | Elongation 09¡ã | vertical Delta for GER 5¡ã | vertical Delta for RSA 5¡ã
Jan. 12 | -2.9 mag. | Elongation 07¡ã | vertical Delta for GER 5¡ã | vertical Delta for RSA 1¡ã
Jan. 13 | -3.8 mag. | Elongation 05¡ã | vertical Delta for GER 3¡ã | invisible in the RSA
Jan. 14 | -2.9 mag. | Elongation 06¡ã | vertical Delta for GER 4¡ã | vertical Delta for RSA 2¡ã
Jan. 15 | -1.6 mag. | Elongation 09¡ã | vertical Delta for GER 4¡ã | vertical Delta for RSA 6¡ã
Jan. 16 | -0.5 mag. | Elongation 11¡ã | vertical Delta for GER 4¡ã | vertical Delta for RSA 9¡ã
Jan. 17 | +0.5 mag. | Elongation 13¡ã | vertical Delta for GER 3¡ã | vertical Delta for RSA 11¡ã
Jan. 18 | +1.2 mag. | Elongation 15¡ã | vertical Delta for GER 2¡ã | vertical Delta for RSA 13¡ã
Jan. 19 | +2.0 mag. | Elongation 16¡ã | vertical Delta for GER 2¡ã | vertical Delta for RSA 16¡ã
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Note that this applies to the morning only until Jan. 12, for the morning and evening about equally on Jan. 13 (perihelion is near noon in Europe and Africa) and to the evening only from Jan. 14. "Vertical Delta" means the actual difference in altitude of the comet and the Sun at any given time rising or setting, respectively, and it is always smaller than or (when the comet sits straight above the Sun) equal to the elongation. E.g. with a Delta of 12¡ã you can have the comet 6¡ã above and the Sun 6¡ã below the horizon or the comet 3¡ã above and the Sun 9¡ã below the horizon etc.
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This Delta had the greatest effect on the visibility of comet Tsuchinshan-ATLAS in the days before and after solar conjunction, more so even than the brightness: from what I gather from the (few!) reports in https://cobs.si/obs_list?id=2410 (page 4 by now) as well as my own observations (quoting a Delta for Europe here) from Oct. 11 to 14 this comet was
- invisible at twilight on Oct. 10 with a Delta of 6¡ã while at roughly -3 mag.,
- visible with great difficulty on Oct. 11 with a Delta of 10¡ã while at roughly -1 mag.,
- easy, esp. with binoculars, on Oct. 12 with a Delta of 14¡ã at about +0.3 mag.,
- pretty easy with long tail on Oct. 13 with a Delta of 18¡ã at about +1.3 mag.,
- spectacular with a long tail on Oct. 14 with a Delta of 21¡ã at about +1.7 mag.
So in a nutshell for Germany the Delta never exceeds 5¡ã when the comet is brighter than +2 mag., which - applying the Tsuchinshan-ATLAS experience - means that we are completely screwed ... unless something really wild happens in the last few days before perihelion and the brightness rises several magnitudes above the already optimistic brightness model here. (Or the tail's length and esp. surface brightness comes to the rescue, but that would probably require West-/Lovejoy-style nucleus damage at precisely the right instant ...)
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75¡ã further south the situatiion is worse on perihelion day +/- one day but better before and especially a few days after perihelion: around Jan. 18-20 ATLAS, performing to plan or better, may actually briefly approach the interesting visibility of Tsuchinshan-ATLAS on Oct. 12-13. But a view approaching the latter's best performance - on Oct. 14 - is mathematically impossible even in the Southern hemisphere as the elongation doesn't rise fast enough while the coma brightness fades. Again, though, a fine tail performance may help to some degree.
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Daniel
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Re: Comets 37P/Forbes and C/2023 C2 (ATLAS) Conjunction
Hi David,
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I routinely image comets brighter than magnitude 15 that are visible from Tucson, Arizona to calculate the magnitudes of these comets. I started imaging 37P and C/2023 C2 in early September and when I got back from farming at the end of October, I noticed that the 2 comets were fairly close using Guide and appeared to be on a collision course, a little investigation concluded that they would have a near conjunction on 2024 November 19 UT as observed from Tucson. Unfortunately, it did not get dark here until a couple hours after the conjunction. The answer to your question is that I take time to investigate any interesting things that might happen in the near future using the Guide software and then hope the weather cooperates. What was interesting about this conjunction was that I expected to find 2 comets that were about the same magnitude 14, I was surprised to find 37P so bright, magnitude prediction curves and observations suggested that 37P should be about magnitude 14 but instead was magnitude 12.5. I had not observed it since November 1 when I calculated the magnitude at 14.5, the ATLAS project had it at magnitude 13.8 on October 31. The comet was suppose to start getting fainter in November not brighter so evidently there was a brightening event that happen in the past several weeks. Of interest, Thomas Lehmann reported 37P at magnitude 12.3 a few hours earlier than my calculation on November 1, Thomas used an aperture diameter of 3.3' and I used an aperture diameter of 1' for both of my magnitude calculations on November 1 and 20. If anyone observed 37P during the first 3 weeks of November it would be interesting to hear what you observed.
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Re: Comets 37P/Forbes and C/2023 C2 (ATLAS) Conjunction
Very nice work Mike!
Where did you discover this conjunction may I ask?
Running JPLHorizons I find the time of closest approach (GEOCENTRIC) was 5.64 arcseconds on Nov.19d 23:32UT
( I think parallax is about 4 arsec for nearest of the two meaning an occultation might have been visible from somewhere on Earth!?)
On Thursday 21 November 2024 at 22:14:49 GMT, Mike Olason via groups.io <molason@...> wrote:
Astrometrica software used several hundred stars in the FOV to determine that my old eyes using only a few stars did not do a very good job of estimating the comets magnitude in the animation above. On 2024, November 20, UT 37P/Forbes was magnitude G=12.5 and C/2023 C2 (ATLAS) was magnitude G=14.1 as calculated from 18x10 second images in an aperture diameter of 1' and 0.7' respectively. The comets were 2.1' apart at 0202UT when these calculations were made. Yes, I forgot to flip the animation images horizontally to take into account the camera sits at the front lens of the RASA telescope.
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Re: Comets 37P/Forbes and C/2023 C2 (ATLAS) Conjunction
Astrometrica software used several hundred stars in the FOV to determine that my old eyes using only a few stars did not do a very good job of estimating the comets magnitude in the animation above. On 2024, November 20, UT 37P/Forbes was magnitude G=12.5 and C/2023 C2 (ATLAS) was magnitude G=14.1 as calculated from 18x10 second images in an aperture diameter of 1' and 0.7' respectively. The comets were 2.1' apart at 0202UT when these calculations were made. Yes, I forgot to flip the animation images horizontally to take into account the camera sits at the front lens of the RASA telescope.
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Re: C/2024 G3 and it further behavior
FYI This is a photo of C/2024 G3 I captured on Nov 4th. Details on image Cheers, Michael ?
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From: [email protected] <[email protected]> On Behalf Of Alan Hale
Sent: Friday, 22 November 2024 7:21 AM
To: [email protected]
Subject: Re: [comets-ml] C/2024 G3 and it further behavior? Dear Alexander, all, ? Since no one else seems to have answered this, I¡¯ll chime in. ? Yes, the calculations suggest that this is a dynamically ¡°old¡± comet (according to the most recent MPC orbit, 1/a(orig) = +0.000337? ¨¤ most recent return 160,000 years ago, taking things at face value). The fact that this comet has survived a previous perihelion passage and is ¡°broken in,¡± so to speak, is potentially good news, but that may or may not mean very much. ? The Bortle survival limit ¨C which I remind everyone is strictly an empirical determination and not any kind of natural ¡°law¡± ¨C for a comet with this one¡¯s perihelion distance is H_10 = 7.6. The most recent brightness reports (late October/early November) of m1 ~12 suggest an H_10 ~ 7.0, which is above that threshold, although not by very much. So, the news again is good, albeit not great, and I¡¯m not sure one should put much stock in it. ? The comet was just recently in conjunction with the sun and is now emerging into the southern hemisphere¡¯s morning sky, albeit at a small elongation (currently 22 degrees, and decreasing). If it brightens sufficiently the observers there may be able to pick it up within the near future and perhaps follow it into early January. And while I will leave this part of the discussion to those with more expertise in these instruments, it may be detectable with SWAN and/or HI1A sometime during this period. For about three days centered around the time of perihelion passage it will be visible in LASCO C3. ? If it does brighten and survive perihelion, the observers in the southern hemisphere should be able to get some reasonably decent observations of it. Those of us in the northern hemipshere are significantly less fortunate: our best opportunity may actually be during daylight right around the time of perihelion, provided, of course, that the comet becomes very bright. (For what it¡¯s worth, around this time it reaches a maximum phase angle of 116 degrees, so there may possibly be some modest brightness enhancement due to forward scattering.) ?In that case it might then be visible very low in evening twilight for a handful of days shortly after perihelion before it heads south and (presumably) fades pretty rapidly. I don¡¯t believe I would bet much money on that particular scenario happening . . . but I guess one never knows. ? ? Sincerely, Alan ? Hello all
As it turns out, C/2024 G3 is actually a dynamically old comet (e=1.0000142, epoch 15 Sep; e=0.999997, epoch 1 Jan 2022. Calculated by find_orb)
Until early November it followed H=5, 2.5n=17. Is this likely to persist to perihelion? Or should we expect similar to c/2002 v1 deceleration to n=~3.5?
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Re: C/2024 G3 and it further behavior
Dear Alexander, all, ? Since no one else seems to have answered this, I¡¯ll chime in. ? Yes, the calculations suggest that this is a dynamically ¡°old¡± comet (according to the most recent MPC orbit, 1/a(orig) = +0.000337? ? most recent return 160,000 years ago, taking things at face value). The fact that this comet has survived a previous perihelion passage and is ¡°broken in,¡± so to speak, is potentially good news, but that may or may not mean very much. ? The Bortle survival limit ¨C which I remind everyone is strictly an empirical determination and not any kind of natural ¡°law¡± ¨C for a comet with this one¡¯s perihelion distance is H_10 = 7.6. The most recent brightness reports (late October/early November) of m1 ~12 suggest an H_10 ~ 7.0, which is above that threshold, although not by very much. So, the news again is good, albeit not great, and I¡¯m not sure one should put much stock in it. ? The comet was just recently in conjunction with the sun and is now emerging into the southern hemisphere¡¯s morning sky, albeit at a small elongation (currently 22 degrees, and decreasing). If it brightens sufficiently the observers there may be able to pick it up within the near future and perhaps follow it into early January. And while I will leave this part of the discussion to those with more expertise in these instruments, it may be detectable with SWAN and/or HI1A sometime during this period. For about three days centered around the time of perihelion passage it will be visible in LASCO C3. ? If it does brighten and survive perihelion, the observers in the southern hemisphere should be able to get some reasonably decent observations of it. Those of us in the northern hemipshere are significantly less fortunate: our best opportunity may actually be during daylight right around the time of perihelion, provided, of course, that the comet becomes very bright. (For what it¡¯s worth, around this time it reaches a maximum phase angle of 116 degrees, so there may possibly be some modest brightness enhancement due to forward scattering.) ?In that case it might then be visible very low in evening twilight for a handful of days shortly after perihelion before it heads south and (presumably) fades pretty rapidly. I don¡¯t believe I would bet much money on that particular scenario happening . . . but I guess one never knows. ? ? Sincerely, Alan ? Hello all
As it turns out, C/2024 G3 is actually a dynamically old comet (e=1.0000142, epoch 15 Sep; e=0.999997, epoch 1 Jan 2022. Calculated by find_orb)
Until early November it followed H=5, 2.5n=17. Is this likely to persist to perihelion? Or should we expect similar to c/2002 v1 deceleration to n=~3.5?
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Mike Olason
David Moore(Ireland)
