Re: 2014 UN271: cometary activity


Sam Deen
 

Hi all,

A quick elaboration: The reason for occultations being inaccurate in the past is that Occult cannot predict/model orbit perturbations, which this object has quite a few of. For these reasons, I had to simulate occultations a few months at a time with different epoch orbits just to be accurate to a couple thousand kilometers. I have now done a finer pass with the epoch given as the two predicted occultation events to determine exactly where they will appear:

2021 Sep 18 event: https://i.imgur.com/Lkq6oo5.png (Tasmania, with 1-sigma lines passing over most of Australia's eastern coast. In reality these 0.033" lines will be much smaller, because the uncertainty is mostly in the direction of motion, not perpindicular as depicted here. With that in mind, I think only observers in Tasmania and the Australian coast have a chance of observing it.)

2023 Sep 20 event: https://i.imgur.com/yRlUW83.png (passes over Antarctica and pretty much nothing else, making this event a no-go. Again, the uncertainty is smaller in reality than it appears here.)

It looks like the 2021 event is the only event in the next >2 years we have any chance at all of observing. Perhaps at least theoretically thinking of the logistics of an observation campaign in Tasmania/Melbourne/Sydney?

~Sam

On Wednesday, June 30, 2021, 4:15:52 PM PDT, Sam Deen via groups.io <planetaryscience@...> wrote:


Hi all,

I agree entirely that it's premature to predict occultations more than a year or two in advance now - I've just made an optimized orbit with some more specific formal uncertainties for each observation to reduce the position uncertainty - the uncertainty at the current moment is around +/- 0.022 arcseconds (320 kilometers) - about 4 times its nominal radius of 85 kilometers (A=0.05). It will peak around +/- 0.044'' (620 km) in December of this year, before actually reaching an even lower minimum of +/- 0.014'' (~200 km) by April 2022. For meaningful predictions in the near future I would consider 0.030'' an upper limit - between 390 and 440 km / 4.6-5.2 radii - giving the average 1-sigma observer a ~20% chance of spotting an occultation.

With this in mind, I've manually derived a formal list of upcoming appulses, with associated uncertainties, maps, circumstances, and other assorted info. All of these were manually validated:

TYPE          DATE                                    STAR                             STAR MAG       PATH DETAILS                                                           STAR VISIBLE FROM                                                                     CHART
APPULSE: 2021/07/10 07:55            |     UCAC4 191-002484   |     V=13.1     |     closest approach: 0.82 (+/- 0.023) arcseconds     |     visible: South America                                                                |    https://i.imgur.com/VcMxRma.png
APPULSE: 2021/08/10 00:43            |     UCAC4 183-002452   |     V=12.8     |     closest approach: 0.55 (+/- 0.025) arcseconds     |     visible: Sub-Saharan Africa, far southern Argentina/Chile          |    https://i.imgur.com/IG6GC8w.png
APPULSE: 2022/04/24 21:12            |     TYC 8484-00451-1     |     V=10.9     |     closest approach: 1.97 (+/- 0.014) arcseconds     |     visible: Argentina, Southern Brazil, Western Australia               |    https://i.imgur.com/vIoLz9l.png
APPULSE: 2023/03/28 10:28            |     UCAC4 162-002342   |     V=15.4     |     closest approach: 0.79 (+/- 0.012) arcseconds     |     visible: Australia, New Zealand, far southern Argentina/Chile    |    https://i.imgur.com/KBC3FQe.png
APPULSE: 2023/05/19 05:32            |     UCAC4 164-002766   |     V=13.9     |     closest approach: 0.26 (+/- 0.027) arcseconds     |     visible: New Zealand, far southern Argentina/Chile                    |    https://i.imgur.com/9x4lXer.png

Unfortunately there are no predicted occultations in these timespans when the uncertainty is less than 30 mas - and the closest appulse (2023) happens during astronomical twilight for the only place that can see it at a high altitude. However! There IS one occultation opportunity in the next couple years - across western Australia - where the uncertainty is higher, but should be easy to narrow down in the coming couple of months:

TYPE          DATE                                    STAR                             STAR MAG                                  PATH DETAILS                                                                                             STAR VISIBLE FROM                                                                     CHART
OCCULTATION: 2021/09/18 16:46    |     UCAC4 172-002357   |    V=15.9      |    PATH: northwestern Australia, West Papua (+/- 0.033 arcseconds / 464 km)    |    visible: Australia, New Zealand, Indonesia                                  |    https://i.imgur.com/tRkO2Rm.png

The maximum duration will be 6.2 seconds (depending on diameter) - the main problem is that the target star is magnitude 15.9, so would not be small-telescope accessible at all. To add to this, the part of australia it passes over isn't particularly densely populated, and most of the +1 sigma would be unobservable over sea, unless there are large telescope observers in Timor, Sumba, Flores, or the Maluku Islands.

Very uncertain occultations:
TYPE          DATE                                    STAR                             STAR MAG                                  PATH DETAILS                                                                                             STAR VISIBLE FROM                                                                     CHART
OCCULTATION: 2023/09/20 04:59    |     UCAC4 132-003086   |    V=16.0      |    PATH: Chile, Argentina, Brazil (+/- 0.100 arcseconds / 1227 km)                       |    visible: South America, western Africa                                        |    https://i.imgur.com/y8Fdc5I.png

Beyond this point the uncertainty grows too large to be practical to predict. These are the only two possible occultations before then - I invite others to double check these events for themselves as well to confirm or disprove the accuracy of my solutions. Below is attached the existing observations list with the associated uncertainties I used added on - a combination of formal uncertainties, and assumed "worst case scenario" ones.

~Sam

    CK14UR1N KC2014 08 14.59978001 42 23.996-35 36 37.600.13 0.1322.58GVEM083F51
    CK14UR1N OC2014 08 28.60113601 41 25.15 -36 02 11.8 0.07 0.0722.1 rVEM083568
    CK14UR1N OC2014 08 28.60381801 41 25.15 -36 02 12.2 0.18 0.1823.6 uVEM083568
    CK14UR1N OC2014 08 28.60641901 41 25.11 -36 02 12.4 0.07 0.0723.0 gVEM083568
    CK14UR1N OC2014 08 28.60906401 41 25.10 -36 02 12.6 0.07 0.0721.7 iVEM083568
    CK14UR1N OC2014 08 28.61174301 41 25.09 -36 02 13.0 0.07 0.0722.2 rVEM083568
    CK14UR1N*-C2014 10 20.29435 01 34 35.019-37 14 46.140.07 0.0722.49rVEM083W84
    CK14UR1N -C2014 11 04.12204 01 32 21.029-37 23 21.140.07 0.0721.97zVEM083W84
    CK14UR1N -C2014 11 15.25191 01 30 47.039-37 25 39.200.07 0.0722.43zVEM083W84
    CK14UR1N -C2014 11 18.23559 01 30 23.425-37 25 40.010.07 0.0722.12rVEM083W84
    CK14UR1N -C2014 11 18.23835 01 30 23.407-37 25 39.980.07 0.0722.15iVEM083W84
    CK14UR1N -C2014 11 27.22148 01 29 17.583-37 24 12.510.07 0.0722.71gVEM083W84
    CK14UR1N -C2014 12 11.11568 01 27 54.830-37 17 49.640.07 0.0721.94iVEM083W84
    CK14UR1N -C2015 01 09.10701 01 26 35.324-36 51 38.750.07 0.0722.80zVEM083W84
    CK14UR1N KC2015 08 11.61298001 47 05.427-37 26 12.910.13 0.1321.87GVEM083F51
    CK14UR1N -C2015 08 17.35747 01 46 47.505-37 37 39.810.07 0.0722.23rVEM083W84
    CK14UR1N -C2015 08 17.35883 01 46 47.517-37 37 39.890.07 0.0722.55gVEM083W84
    CK14UR1N -C2015 08 24.34452 01 46 18.605-37 51 28.610.07 0.0722.62gVEM083W84
    CK14UR1N -C2015 09 02.37787 01 45 30.196-38 08 52.300.07 0.0722.21YVEM083W84
    CK14UR1N -C2015 09 13.39051 01 44 15.863-38 28 51.620.07 0.0721.95iVEM083W84
    CK14UR1N -C2015 10 06.27435 01 40 59.774-39 03 19.840.07 0.0722.01zVEM083W84
    CK14UR1N -C2015 11 20.22851 01 33 55.078-39 29 32.570.07 0.0722.33zVEM083W84
    CK14UR1N -C2015 11 20.23556 01 33 55.010-39 29 32.480.07 0.0722.13iVEM083W84
    CK14UR1N -C2016 01 11.09386 01 29 57.738-38 50 26.060.07 0.0722.13rVEM083W84
    CK14UR1N -C2016 01 11.09524 01 29 57.729-38 50 25.960.07 0.0722.89gVEM083W84
    CK14UR1N  C2016 08 09.58536001 52 24.356-39 29 37.720.13 0.1322.16GVEM083F51
    CK14UR1N  C2016 08 09.59528201 52 24.325-39 29 39.110.13 0.1322.13GVEM083F51
    CK14UR1N -C2016 10 01.29899 01 46 40.180-41 11 31.780.07 0.0721.65rVEM083W84
    CK14UR1N -C2016 10 01.30036 01 46 40.173-41 11 32.000.07 0.0721.96gVEM083W84
    CK14UR1N -C2016 10 03.31546 01 46 20.177-41 14 24.530.07 0.0721.91rVEM083W84
    CK14UR1N -C2016 10 03.31682 01 46 20.167-41 14 24.590.07 0.0722.56gVEM083W84
    CK14UR1N KC2017 08 13.57144901 58 27.697-41 56 20.770.13 0.1321.81GVEM083F51
    CK14UR1N KC2017 08 14.58512301 58 24.711-41 58 44.070.13 0.1321.49GVEM083F51
    CK14UR1N KC2017 09 08.55424701 56 09.883-42 55 16.280.13 0.1321.76GVEM083F51
    CK14UR1N KC2017 09 30.42187801 52 49.635-43 36 32.720.13 0.1322.02GVEM083F51
    CK14UR1N -C2017 10 15.27208 01 50 05.746-43 57 07.300.07 0.0721.97gVEM083W84
    CK14UR1N -C2017 10 15.33777 01 50 04.988-43 57 11.800.07 0.0721.23zVEM083W84
    CK14UR1N -C2017 10 15.33915 01 50 04.970-43 57 11.890.07 0.0721.63rVEM083W84
    CK14UR1N KC2017 10 29.35825001 47 22.733-44 09 45.250.13 0.1321.54GVEM083F51
    CK14UR1N KC2017 11 06.33049701 45 51.862-44 13 42.340.13 0.1322.08GVEM083F51
    CK14UR1N KC2017 12 11.25003001 40 25.195-44 04 24.940.13 0.1321.53GVEM083F51
    CK14UR1N -C2017 12 15.18042 01 39 59.837-44 00 56.400.07 0.0722.04rVEM083W84
    CK14UR1N -C2017 12 15.18181 01 39 59.824-44 00 56.380.07 0.0722.44gVEM083W84
    CK14UR1N -C2018 10 21.24337 01 55 54.039-46 47 14.940.07 0.0721.60YVEM083W84
    CK14UR1N -C2018 10 27.17859 01 54 38.204-46 52 42.840.07 0.0721.43zVEM083W84
    CK14UR1N -C2018 11 08.23513 01 52 05.914-46 59 29.070.07 0.0721.63rVEM083W84
    CK14UR1N -C2018 11 08.23651 01 52 05.899-46 59 29.100.07 0.0721.57iVEM083W84
    CK14UR1N -C2018 11 08.23789 01 52 05.884-46 59 29.050.07 0.0722.22gVEM083W84
    CK14UR1N KC2019 08 19.59829602 14 55.242-47 31 52.430.13 0.1320.30GVEM083F51
    CK14UR1N  C2019 08 29.56986902 14 08.352-47 59 21.630.13 0.1320.58GVEM083F51
    CK14UR1N  C2019 08 29.58523402 14 08.234-47 59 24.180.13 0.1320.66GVEM083F51
    CK14UR1N  C2019 08 29.59292102 14 08.226-47 59 25.210.13 0.1320.52GVEM083F51
    CK14UR1N KC2021 06 22.13538 02 35 28.86 -51 07 43.1 0.10 0.10      VEM083L81
    CK14UR1N KC2021 06 22.16834 02 35 29.32 -51 07 47.8 0.10 0.1019.6 GVEM083L81
    CK14UR1N  C2021 06 22.16880502 35 29.32 -51 07 47.7 0.18 0.1819.8 GVEM083K93
    CK14UR1N  C2021 06 22.17258202 35 29.36 -51 07 48.5 0.18 0.1819.9 GVEM083K93
    CK14UR1N  C2021 06 22.17636102 35 29.38 -51 07 48.9 0.18 0.1819.9 GVEM083K93
    CK14UR1N  C2021 06 22.18014202 35 29.47 -51 07 49.2 0.18 0.1819.6 GVEM083K93
On Tuesday, June 29, 2021, 8:16:52 PM PDT, Marshall Eubanks <tme@...> wrote:


On 2021-06-29 11:32, Bill J. Gray wrote:
> Agreed on the unlikeliness of getting measurable non-gravs.
> (With caveats below.)
>
>    Carlos' list is extremely unlikely to prove specifically
> correct.  But it does suggest that we'll get a decent number of
> occultation opportunities over the coming years (just not of
> those specific stars).  We don't know _which_ stars yet or
> where the paths will be on the earth,  but we should get
> roughly the number of opportunities shown in his list.

If there is to be a mission to UN271, the best rendezvous time for a
flyby is  near the time of ecliptic passage, August 8, 2033, out at 11.9
AU at

Minimum energy orbits for a direct trajectories to UN271 exist, with one
launch window per year for the rest of this decade. These minimum energy
trajectories for launches up through 2029 _all_ flyby UN271
within 2 weeks of the time of its passage through the ecliptic plane. 
All of these opportunities from 2022-2029 have characteristic energies
(C_{3})  < 150 km^2/s^2, substantially less than the C_{3} of 170
km^2/s^2 required for the New Horizons probe to Pluto.

Based on a series of discussions with people who might actually launch
such a probe, I think that the 2026 window (which peaks on 2026-10-07)
is likely to be the earliest launch opportunity.

If such a mission goes forward, it would obviously be good if there were
occultation estimates of the orbit and object size and shape from  the
2024/2025 period. That (unfortunately for Northern Hemisphere observers)
will be at declinations of ~ -70 degrees.

Regards
Marshall


>
>    The first few will probably require the traditional IOTA
> method of saying "the uncertainty is several times the width
> of the ground track,  so let's get a heck of a lot of observers
> and/or put down temporary remote stations and figure that
> somebody will be in the right place."  As Brian says,  we
> might see some interesting photometric results as the star
> passes through the coma,  so even the near-miss stations might
> tell us something.
>
>    While we can't say much about specific occultations in 2028
> (start of Carlos' list),  we could make a multiple path width
> prediction for a "near-term" occultation,  much as was done
> for (486958) Arrokoth = 2014 MU69 = Ultima Thule before New
> Horizons visited it.  As with that object,  we'd quite likely
> have a failed effort or two before getting lucky.  (Though
> maybe not.  This object is about three times bigger than
> Arrokoth and half as far away.)
>
>    Depending on when it happened,  an occultation by a 100-km
> nucleus would last a minimum of about three seconds.  So
> it'd be long enough to get a decent size estimate.
>
>    The other value of occultations would be to really nail down
> the position of the object : "it was over the following star
> at exactly the following time,  and we know exactly where that
> star was because we have Gaia astrometry for it."  This has
> a couple of knock-on effects.  Give me a few such data points,
> and we'll have a much better orbit so that further occultation
> predictions will _not_ have multi-path-width uncertainties.
> And we might end up with a good enough orbit (very good
> astrometry over a couple of decades) so that very subtle
> effects,  such as non-gravs,  really _could_ be determined,
> even for such an enormous object.  In which case,  we might get
> a decent mass measurement after all.
>
>    For Arrokoth,  we started from Hubble astrometry... which,
> sadly,  may not happen this time.  But perhaps Gaia can get
> some data.
>
> -- Bill
>
> On 6/29/21 9:57 AM, Marshall Eubanks wrote:
>> On 2021-06-28 21:01, P. Clay Sherrod wrote:
>>> Personally it is my opinion that this far out, with so many unknown
>>> parameters still considered as variable factors for this unusual
>>> object, predicting occultations – unless in the immediate time frame
>>> – is unreliable and meaningless.  I believe that we are going to see
>>> some changes in orbital parameters of 2014 UN271 from both
>>> gravitational and non-gravitational forces in coming  months as the
>>> objects covers more space.  There is no reason for any of us to be
>>> planning occultation observations predicted for 2028 and 2029 at this
>>> time.
>>
>>
>> I fully agree. After July of 2024 the current UN271 ephemeris error
>> exceeds 1 Earth diameter, and there is clearly no reason to plan
>> anything at present for that period or after.
>>
>> The real question to me for now is, should money be raised to support
>> an occultation campaign in the Southern hemisphere in the next few
>> years?
>>
>> I would be very surprised if a 100 km body shows non-gravitational
>> forces visible with conventional optical astrometry. A 100 km body
>> will have 100 times the mass/area ratio of a 1 km body of the same
>> density.
>>
>> The highest mass determined from NG forcing in
>> https://academic.oup.com/mnras/article/393/1/192/1083616
>> is 4 x 10^14 kg or 1000 times smaller than the mass predicted for
>> UN271 with a 100 km diameter and a density of 0.4 gm/cm^3.
>>
>> However, if NG motions could be detected by occultation at the mas
>> level, I think that there _would_ be a decent chance of determining
>> the mass of UN271 from its NG forcing.
>>
>> Regards
>> Marshall
>>
>>>
>>> Dr. Clay
>>> Arkansas Sky Observatories
>>> www.arksky.org
>>> Petit Jean Mountain
>>> MPC H41 / MPC H43 / MPC H45
>>> .....serving astronomical sciences since 1971
>>>
>>> -----------------
>>>
>>> From: Sam Deen via groups.io
>>> Sent: Monday, June 28, 2021 7:53 PM
>>> To: mpml@groups.io ; Carlos Perelló
>>> Subject: Re: {MPML} 2014 UN271: cometary activity
>>>
>>> Hi Carlos,
>>>
>>> I'm not sure those are particularly accurate - at least, not enough
>>> for a particularly meaningful prediction. I think that this is more
>>> of
>>> a problem with occult than the orbit uncertainty, but for instance on
>>> 2028-10-05 14:40.8 find_orb records the comet as being at 10 59
>>> 13.715
>>> -61 58 11.58 which is several arcminutes from where this supposed
>>> occultation takes place. While I maintain that occultations are
>>> practically visible (and admittedly don't understand Larry's interest
>>> in discounting them unconditionally) I don't think they will be
>>> practical to predict with such an unusual orbit with Occult.
>>>
>>> ~Sam
>>>
>>> On Monday, June 28, 2021, 5:48:36 PM PDT, Carlos Perelló
>>> <rigilk436@...> wrote:
>>>
>>> I forgot to say the list is filtered by StarMag <12.6. Obviously at
>>> this time the predictions are very preliminary.
>>> Literally from the Help File of Occult: Note that the diameter is
>>> arbitrarily set at 10km, and the positional uncertainty is set at 3".
>>>
>>> Regards,
>>> Carlos
>>>
>>> El 24/06/2021 a las 13:11, Carlos Perelló escribió:
>>>
>>>>
>>>
>>> Using Occult, these are the occultations calculated until 2035:
>>>
>>>      Global summary of events - sorted by Date
>>>
>>>      Date       U.T.    Diameter   Durn  Star  Mag-Drop Elon  %
>>> Star         d Rely        Planet           Min        Moon     § ?
>>>  R.A. (J2000)  Dec.            Rec
>>>    y   m  d    h   m     km   "   sec/m   mag   V    R     o Ill
>>> No.            <1.4     No Name              D   Error Dist ill  ?
>>> h  m   s      o  '   "           #
>>> 2028 Dec  5   14 40.8    10 0.001  0.55s 12.3  8.2  8.6   69    
>>> UCAC4
>>> 140-057616 s 0.85      0 C/2014 UN271 (Be 1.28 ±4.08   89  86      10
>>> 58 27.269 -62  2 45.99         0
>>> 2028 Dec 17    9 15.7    10 0.001  0.62s 12.1  8.5  8.6   74    
>>> UCAC4
>>> 137-051856 s 4.05      0 C/2014 UN271 (Be 0.94 ±4.05   82   2      10
>>> 59 19.973 -62 36 36.98         1
>>> 2029 Jan  1    4 45.9    10 0.001  0.69s 12.6  7.9  8.1   81    
>>> UCAC4
>>> 134-047703 s 0.80      0 C/2014 UN271 (Be 5.14 ±4.00   96 100      10
>>> 58 10.418 -63 14  0.21         2
>>> 2029 Jan 31    4 18.6    10 0.001  0.59s 11.3  9.1  9.4   96     TYC
>>> 8965-01100-1 s 0.75      0 C/2014 UN271 (Be 4.47 ±3.90   75  99
>>> 10 48 24.876 -63 53 48.38         3
>>> 2029 Feb  3   17 51.4    10 0.001  0.56s 12.1  8.4  8.7   98    
>>> UCAC4
>>> 131-040285 s 0.80      0 C/2014 UN271 (Be 6.44 ±3.88   57  74      10
>>> 46 42.995 -63 54  2.93         4
>>>
>>> 2029 Dec 29   10 30.9    10 0.001  0.96s  9.7 10.5 10.3   80    
>>> UCAC4
>>> 193-062412 w 11.1      0 C/2014 UN271 (Be 3.60 ±3.84   43  38      11
>>> 42 34.634 -51 35 50.30         5
>>> 2029 Dec 29   11  7.6    10 0.001  0.94s 11.3  9.0  8.7   80    
>>> UCAC4
>>> 193-062409 w 0.95      0 C/2014 UN271 (Be 3.92 ±3.84   43  38      11
>>> 42 33.976 -51 35 52.60         6
>>> 2030 Jan  1   10  7.4    10 0.001   2.1s 10.7  9.5 10.4   82    
>>> UCAC4
>>> 192-059604 v 1.05      0 C/2014 UN271 (Be 6.15 ±3.83   58  10      11
>>> 42 27.748 -51 41 17.99         7
>>> 2032 Dec  5   20 30.3    10 0.001  0.63s 12.4  8.1  8.3   60    
>>> UCAC4
>>> 384-061530 s 1.05      0 C/2014 UN271 (Be 0.01 ±4.08   98  11      12
>>> 42 35.336 -13 13 18.53         8
>>> 2032 Dec 23    3 55.7    10 0.001  1.03s 12.0  8.4  8.7   77    
>>> UCAC4
>>> 385-061483 s 1.35      0 C/2014 UN271 (Be 0.41 ±3.99   32  66      12
>>> 45  2.980 -13  2 35.43         9
>>>
>>> 2033 Feb  2   22 47.8    10 0.001  0.56s 12.3  8.1  8.4  119    
>>> UCAC4
>>> 391-057575 s 4.20      0 C/2014 UN271 (Be 2.88 ±3.78  162  13      12
>>> 44 16.057 -11 51 12.27        10
>>> 2035 May 17   10 40.8    10 0.001  0.53s 11.0 10.3 10.6  126     TYC
>>> 1449-00435-1 s 1.00      0 C/2014 UN271 (Be 0.47 ±4.41   18  80
>>> 12 48 17.694  15 55 10.51        11
>>>
>>> Regards,
>>> Carlos
>>>
>>> El 24/06/2021 a las 12:41, andrew_j_walker via groups.io escribió:
>>>
>>>>
>>>
>>> Now we have a comet circular
>>> https://www.minorplanetcenter.net/mpec/K21/K21M83.html
>>>
>>> Nice work with the extra observations from F51 and 568, and in the
>>> last few days!
>>> Andrew
>>>
>>>
>>>
>>> Links:
>>> ------
>>> [1] https://groups.io/g/mpml/message/36525
>>> [2] https://groups.io/mt/83710102/2048683
>>> [3] https://groups.io/g/mpml/post
>>> [4] https://groups.io/g/mpml/editsub/2048683
>>> [5] https://groups.io/g/mpml/unsub
>>
>>
>>
>>
>>
>
>
>





Join mpml@groups.io to automatically receive all group messages.