The local prediction time and circumstances for main body (miss) for Chews Ridge. Ring contact times not given here
This is a do-able event, if we get lucky and the Ring #1 has dense areas for our position. The main body does not occult for us, or anyone - it's in daylight in the Arctic, but the denser ring #1 looks to be occulted by this target star. Favorably, the incidence is a grazing angle, which means any opaque ring segment will get extended time in front of the target star, making detection easier. We know ring #1 has at least some areas of high density and opacity, but we have too few occultations to say much more than that. After analysis of the June 12 event and inclusion in his predictions, John Irwin (UCLA Astronomy & Astrophysics) finds the duration in ring Q1R at MIRA Chews Ridge looks to be nominally about 45 seconds, This is a good long figure; about the same as if it were an occultation for the main body.
The local prediction time and circumstances for main body (miss) for Chews Ridge. Ring contact times not given here |
The other conceivable observer(s) are at Lick Observatory on Mt. Hamilton, but I've been unsuccessful in getting that to happen. Alas, the 40" Nickel telescope is not available to us. A better 30" scope farther north than MIRA is Fremont Peak, but it still gets only part of the outside of the Q1R ring, and again I've been unsuccessful in getting response on having one of my team or all of our team, at this telescope. Farther north is better. I've not heard any response from Chris Angelos on possible observation at FPO. Ted Swift in Davis likely gets all of ring Q1R, but as far as I know, only has access to a small personal scope. He's had thoughts of engaging a local community college with a larger scope for important events, but I'm not aware that is going to happen for this event.
BEFORE the June 12 Quaoar Occultation Analysis by LuckyStar et al. ...
The table of images panel and comments immediately below show sky plane predictions by John Irwin; but before the analysis of the June 12 success at Mauna Kea, Hawaii and by David Dunham's AZ team indicated a 27 km south shift. So the actual tracks are now predicted to be a little farther up (deeper into the ring) than shown immediately below. I keep these here for completeness only...
Sky plane predictions for Chews Ridge. Barely touches the outer edge of the Q1R ring |
For Bonny Doon; still most of the ring is not occulted. Would be slightly worse for Fremont Peak Observatory |
Prediction for Ted Swift in Davis, CA. |
The SF / Monterey Bay area gets grazing incidence on the denser Q1R ring. My own calculated tracks are shown here, based on measurements on Google Earth and John Irwin's prediction. |
AFTER the June 12 Analysis;
How long and how deep will the Q1R ring occultation be? We're not sure of the opacity distribution around the ring. The dense part of the ring may be only 20 or 30% of the circumference of the ring, more or less. We don't know yet. There is certainly a dense ring arc and there is certainly azimuths on Q1R that are very low opacity and would not be detectable by our gear. But the occultation of Aug 9, 2021 shows the dense arc in ring Q1R would take ~4-5 seconds to cross the star for a non-grazing typical incidence angle. The dense arc that was seen, would take at least 3 or 4 seconds. Our chord will be grazing through the ring. So if we can get a good detection of the star with 1-second integrations, that should, with luck, reveal the ring if dense. 1.2s integrations correspond to 64x setting on the Watec 910hx. The target star should be plenty bright enough to get a good detection of even shallower depths for 64x. The star should look 3.27 magnitudes brighter than in our 8SE scopes, although will be spread over more pixels. If separation is good enough, we may want to insert the 0.5x reducer to get higher flux per pixel. 3.27 magnitudes means that the 14.57 star will look like a 11.3 star familiar in our 8SE scopes, at comparable light per pixel. This strongly suggests we will get good data on the 36" with much quicker cadence; 16x or 8x even.
The original Q1R ring discovery is published here (Morgada et al. 2021), and figures below are from the analysis of the Aug 2021 occultation, which included timings on the main body by Kirk Bender in Bonny Doon and myself at UCSC respectively, but not the rings.
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Prediction for MIRA Chews Ridge. If central event (miss) time is 6:58:47 UT, then the ring passage looks to be before that, I'm guessing by about 1 minute. We can tentatively plan on 8 total minutes of data, centered on 6:58:00 UT, is my guess until further notice |
Target star magnitudes and coordinates. The target is a red star, shown on the Aladin image on LuckyStar. (Quaoar is far fainter and will not be visible)
Target Star UCAC4 376-136839 at mag=15.46 in C2A but 14.93 in OWc
Neighbor UCAC4 376- 136847 at mag=15.96 in C2A
BP=16.1 (B=16.09 in OWc)
G=14.9 (V=14.93 in OWc)
RP=13.9
J=12.2
J2000
RA= 18h 41' 28.6s
Dec=-14 53 33"
Coords on date
RA=18h 42 57.4s
Dec=-14 52' 06"
I've ID'd the target star from the Aladin photograph image on the LuckyStar page; on both my 333 frame test data in dark Bonny Doon using PyMovie Fourier Finder crop zoom, and on C2A. We will not want to use the f/3.3 finder on an 8SE! We will want no focal reduction in our 8SE scopes, nor other scopes if possible. It's a very crowded field. Contamination of the aperture masks with fainter neighbors is a strong danger without great care, except on the full f/10 focal length of the 36" telescope, where we get sub-arcsec per pixel resolution, easily. I may want to use the 0.5x reducer at the 36" f/10 scope at MIRA, if helpful (see below - I did not use the reducer).
If we take photometric B = BP and G = V as an approximation, that would make the Watec 910hx W magnitude = 14.9 - .315(1.2) = 14.5. But RP=13.9, which is much brighter still. This star looks to be at least 1.2 magnitude brighter than the difficult June 12 target star, and in a moonless dark sky. It should be do-able for even the 10" of Bernard, and even perhaps the 8SE scopes of Karl and Ted Swift, if the ring is dense enough where we sample it.
Alt=34, Az=152, in Scutum. Time=11:58:47pm +-4.4 seconds at Chews Ridge.
The 27 km south shift of the shadow paths, together with our tests of the visibility of the target on our 8SE scopes, make MIRA Chews Ridge the clear choice to stay with, given Lick Observatory cannot accomodate us. The 36" telescope is now back up and being readied for use for our observing time by Dan Cotton. The team looks to be only me and hopefully Kirk Bender, although I've invited Will Glass to join and he could help do the 14" Planewave telescope observing if Kirk is called away by remote work. In case we lose Kirk, I will have to borrow back Kirk's OccBox, or else get a new OccBox readied (tough) for the 14" Planewave. I will mount my PAL Watec on the 36". I never got a response from either Sandy or Bernard and took them out of the loop. I see Bernard is signed up on OWc for his home. I hope he gives it a good go, but fog will almost certainly ruin chances from his location in Santa Cruz proper.
Kirk Bender got test footage of the target star after the Shimizu asteroid event in a dark sky, w/o the f/3.3 reducer on his 8SE scope. Not analyzed yet. Our need is high FL to get the target separated from two troublesome nearby dimmer but still annoyingly bright neighbor stars. The 8SE scopes' small FL is difficult in that regard, which also helped decide me that the high FL of the 36" at MIRA was more valuable than being deeper into the ring crossing at, say, Mt Diablo but with our small scopes.
I am working to assemble the pieces of a new OccBox #4 for us, which will use the Startec cable and other Watec 910hx PAL. But it will take more time to complete and won't be available. In any case, we definitely will be ready with the existing OccBox of mine on the main 36" scope. I will try to see if I can get up and running on Startec/Lenovo recording, but that too is iffy. The chord for MIRA should penetrate, slightly, the best calculated boundary of the Q1R ring, and could be more given the uncertaintly in the co-planarity and direction of the triaxial pole of Quaoar, based on occultations. It is even still possible there would be a miss. It is also possible our track might penetrate through the entire ring width but also unlikely. The target star is brighter than last year's ring occultation attempt and we're in a dark moonless sky with distant urban lights under fog. I'm optimistic we'll get quite useful data.
My plan is to pack up Kirk at my place, then drive my RAV4 to get the van at Cabrillo Tue afternoon by 3pm, print paper versions of the charts, and then drive to MIRA and arrive before sunset and get as ready as possible before we do the twilight flat field video, and the scope is then in use by Dan and 2 interns on HIPPI-2 polarimetry observing and check-out work. The scope will be turned back to Quaoar work when needed, maybe by 10:00pm or 10:30pm, before the midnight occultation.
Weather at event time looks good.
Here are the best charts for using at MIRA. The 36" f/10 is FL=360 inches, vs. 8" f/3.3 is FL = 26.4". So, that requires I scale down to only 7.3% of the charts I use on the Celestron 8SE at f/3.3. That means I need a
36" f/10..... rectangle on the sky of 1.88' x 1.39' = (1' 53") x (1' 13.2"). I've programmed this into my C2A under "guide scope" option.
14" f/7..... rectangle on the sky of 6.91' by 5.10' This is the configuration that's best plate scale, I'd discourage use of the 0.5x reducer on this scope.
John Irwin's prediction for the ring passage, "with the revised pole" (? the revised pole actually shows a miss of the ring from MIRA, so I'm not sure which pole this prediction refers to)
"D = 06:57:18, R = 06:58:03, Mid = 06:57:41, Duration = 45 s"
Planned Recording time (as of 24 hr before the event)
6:55:00 UT till 7:00:00 UT (I changed my mind at event time; Actual start 6:54:34 UT, and when an actual occultation 2.4 min before ring Q1R event time, I extended shut down time to 7:03:30 UT)
For the 36" both the eyepiece view and the Watec views below have been left-right reversed, and camera rotated in the 1.25" holder to have the RCA video connector down, instead of "up" as in our straight-through 8SE configuration. The closest bright neighbor and which was partially blended with Kirk's video was UCAC4 376-136847 at G=15.94
This is the alt/az rotation view from C2A with the 8SE square as the big square, and the little square is for the 36" at f/10. |
The small square is the anticipated Watec chip view on the 36" at f/10. That square will be twice as big if I mount the 0.5x reducer. This is an alt/az view, so will be rotated by about 12 degrees or so from the actual view, since Quaoar is not due south in which case "up" and "north" are the same, but instead is at Az=150 in the SE. In the Planewave 14", the Watec chip square will be 3.6x bigger, at f/7. |
This is for the 36" scope only. The inner box is the FOV on the Watec if at f/10. The outer box is if using the 0.5x reducer. Rotate the Watec in the eyepiece holder so the video terminal is DOWN, towards the observer. |
This is for the 14" Planewave, with Watec mounted w/o the 0.5x reducer, and I've shown the "arrow" and "box" asterisms for help. A 0.5x reducer mounted version would be twice the size of this box, and then the neighbor stars will be difficult to remove from the photometry - not advised. |
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Here, below this double line, these charts below are less useful now that we're firmly planning on being at MIRA's 36" and 14" telescopes. If there are other observers elsewhere, they may still be useful... Here's charts for locating the target. Since this event happens at azimuth 152, but the June 12 event at azimuth 182 when N/S and Up/Dn were the same, then this time the tilt of the charts will be different by a perhaps ~15 degrees of tilt. If you're using an equatorial telescope, straight through with no diagonal, and a Watec, then to agree with my C2A charts (made for alt/Az scope) you should twist the Watec inside the 1.25" tube so that the video RCA adapter on the Watec is oriented straight up.
The images below are not the proper orientation if you have 3 mirrors in the system, as I will have for the 36" main scope.
This is the 5 arcmin SDSS photo of the target area, and is oriented North up/East left. This is about 15 degrees tilted from the Watec charts which are done for an Alt/Az telescope, and shown in the panels at right... |
Here's the Aladin photo image at scale=11' FOV, roughly like our Watec LCD images w/o the f/3.3 reducer. But, the 36" MIRA scope w/ diagonal will be left-right reversed from this image |
C2A eyepiece chart for Q70 eyepiece, with coordinates 'of date' for GoTo, |
C2A chart for Watec 910hx field of view, with coords "of date" for GoTo. |
This is a close up of my 333 frame PyMovie "finder" from my 128x video on my 8SE telescope. I've labelled asterisms that will help guide you, and for Watec users, this is the "finder chart" to use, since the star brightness vary, sometimes by a lot, between C2A and Aladin and the Watec 910hx. In particular, the bottom star in the "box" is rather bright, and especially bright on the Aladin chart, but small and dim on C2A. |
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I observed on the MIRA OOS 36" telescope, using my Watec 910hx PAL camera. I used the native f/10 focus, no focal reducers in the optical train. For the first time in my occultation career, I used the IOTA Video Capture software, version 2.4, and Startech cable, together with the Lenovo mini-laptop gifted to me by Ted Blank. The display of the star and field on the screen was a major improvement over that on my small 7" monitor, and even smaller camcorder flip-out monitor. The sky looked very dark gray. The seeing was quite good, 1 arcsec or less, and the target star remained very isolated from the two neighboring stars so obvious on the Aladin field. I used a 3.2px aperture box in PyMovie and dynamic masks on all stars because the stars were typically elongated diagonally. The histogram of values was quite truncated at zero value, with stars standing out in a black background sky. The S/N on the target and ref stars was very good, only around 10-15% scatter. The aerosol count was higher than typical at MIRA OOS, but well within tolerance, and the sky looked to the eye to be very clean and black. Nevertheless, one can see some variable transparency at the level of about 20% during the 9 minutes of the recording, and which affected both ref and target stars; and so was easily calibrated out of the data. The measured (off my video) seeing at the 36" was 1.0".
I recorded at 16x integrations, the stars were sometimes tight bright circular, and sometimes a little smeared and pixel values lower. I used the default values in PyMovie for mask threshold. I could have easily done 8X integration, but I wanted to have less noise point-to-point to assess variable ring opacity and so wanted to keep pixel values high. I did not anticipate that high time resolution at the 1/10s time level would be important for ring Q1R. There were no saturated pixels in any stars. I left Watec settings at Gamma=1, Sharpness=4, Gain=41 (maximum). I also did a BPC correction before the recording, eliminating hot pixels. I also did a thorough air bulb cleaning of the Watec chip window.
In PyMovie, unlike in past uses, the field order was reversed from usual. It was the top field that was earlier in chrono sequence. This was seen by PyMovie software, but in the past it has been bottom field first. The other field did get read. But the output CSV file had no time stamps, so I had to do a manual time stamp entry. I chose two frames 70 seconds apart, using the earlier field time to associate with that frame, and straddling the clear occultation, and PyOTE accepted these time stamps as valid, finding no dropped frames. Most likely the digits are not recorded precisly in the same place as when using the miniDV camcorder as the recording device. I will want to do a new OCR training session before reducing later events with this setup. There were no dropped frames.
Manual Time Stamps for PyOTE
frame 250 = 6:54:41.6011 UT
frame 2000 = 6:55:51.6007 UT
This occultation detection of 1.23 seconds was abrupt and complete to zero, no evident variable opacity. Kirk Bender's data on the 14" Planewave on the same telescope mount showed the same PyOTE time solutions to within our differing (PAL for me vs. EIA for Kirk) output cadence and accuracy. D and R for us was the same, to within 0.02s. I solved for the event times by giving PyOTE "min=3, max=6" points for the duration of the event. The solution met the NIE test with a very large 181 standard deviations significance. Below is from the PyOTE log file...
magDrop report: percentDrop: 99.9 magDrop: 7.140 +/- 3.626 (0.95 ci)
DNR: 6.81
D time: [06:55:20.6315]
D: 0.6800 containment intervals: {+/- 0.0224} seconds
D: 0.9500 containment intervals: {+/- 0.0583} seconds
D: 0.9973 containment intervals: {+/- 0.1092} seconds
R time: [06:55:21.8706]
R: 0.6800 containment intervals: {+/- 0.0224} seconds
R: 0.9500 containment intervals: {+/- 0.0583} seconds
R: 0.9973 containment intervals: {+/- 0.1092} seconds
Duration (R - D): 1.2390 seconds
Duration: 0.6800 containment intervals: {+/- 0.0336} seconds
Duration: 0.9500 containment intervals: {+/- 0.0765} seconds
Duration: 0.9973 containment intervals: {+/- 0.1319} seconds
This shows the target clearly far separated from the "bright neighbor" to its left. The "dim neighbor" is faint at upper left of the pair. Also well separated. |
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The minimum metric for flatness was met at a smoothing length of only 4 points. Quite unusual. And no offset in time. Why? Because, visually, watching the video one sees the star goes back and forth between integrations from sharp and small to blurrier and elongated. A dynamic mask was the right choice. The other cause, was that the distribution of pixel values was nearly all at close to zero. Nowhere near Gaussian as is assumed in PyMOvie. The long FL and moonless high altitude sky with fog-covered distant city lights led to very black skies. |
Close up of the occultation. Kirk's and my data both agree on a 1.24s duration event to within the 1-sigma confidence range, as we'd hoped. Note the tight error spreads on the D and R from PyOTE. This fit is assuming the PyOTE 'Square Wave' model. If it's due to a moonlet, then Fresnel diffraction could play a role, except at 16x time resolution, (0.32s per integration) fringes would very likely be lost within each integration of frames. |
Noise test: This is the highest NIE sigma separation I've yet seen in any of my occcultation work. Despite being a W=14.5 magnitude star, there is a 181 sigma (!) separation in distributions of values with, and without, the occultation. |
PyOTE gave me a 1.2 sec event from the MIRA 14" without a focal reducer, at 16x. I didn't see any other obvious events in the light curve. Target was very close to another star, so I used a small size 11 static aperture in PyMovie and turned off re-centering so it wouldn't jump to that other star during the event, I watched it and it didn't. I smoothed on a tracking star. I went to the Lucky Star Occultation Portal to upload my data but they apparently don't have an entry in their calendar to join yet, I did email Bruno and the others with the timings and cc'ed you, but here's other plots for your records.
A positive 1.2 second event was found in my recording centered on 6:55:21 UT. I recorded for 9 minutes total, synched to your live instructions on starting and ending together at the scopes. No other obvious events.
I was using the 14" f/7.2 PlaneWave CDK telescope and Watec 910HX NTSC camera, with a diagonal and without a focal reducer. I used a Watec integration of x16, or 16/60 = .26s per integration. R. Nolthenius was simultaneously recording on the 36" f/10 Cassegrain on the same mount so our GPS positions were the same and he observed an event at the same time. This was a Lucky Star event prediction:https://lesia.obspm.fr/lucky-star/occobs.php?p=145787&lon=-122&lat=37 I have uploaded my recording and data to the Lucky Star Occultation portal, including these attached IOTA report and files. The Occult Watcher cloud prediction:https://cloud.occultwatcher.net/event/1636-50000-264591-647066-U136839# for my location was 6:58:47, but that was for the main body, and being far south of the path of the main body, we were looking for occultations by the rings of Quaoar. However, the timing for the event we found was much earlier than predicted for the Q1R ring.
The target star was very close to another star. I used a small size 11 px static aperture, with re-centering off so it wouldn't jump to the other star during an event. I used two other stars with static apertures for reference and tracking. After block integration in PyOTE I normalized the target against reference star tracking1.
I used a min/max setting of 2/30 points for PyOTE to find the event. Other settings and information can be found in the attached PyMovie .csv and PyOTE log files. Let me know if you need more information or my .avi movie file.
magDrop report: percentDrop: 95.9 magDrop: 3.463 +/- 2.859 (0.95 ci)
DNR: 2.91
D time: [06:55:20.6546]
D: 0.6800 containment intervals: {+/- 0.0630} seconds
D: 0.9500 containment intervals: {+/- 0.1793} seconds
D: 0.9973 containment intervals: {+/- 0.3707} seconds
R time: [06:55:21.8636]
R: 0.6800 containment intervals: {+/- 0.0630} seconds
R: 0.9500 containment intervals: {+/- 0.1793} seconds
R: 0.9973 containment intervals: {+/- 0.3707} seconds
Duration (R - D): 1.2090 seconds
Duration: 0.6800 containment intervals: {+/- 0.0950} seconds
Duration: 0.9500 containment intervals: {+/- 0.2220} seconds
Duration: 0.9973 containment intervals: {+/- 0.4449} seconds
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This deep occultation 2.3 minutes before the predicted Q1R ring contact was clearly real and I can find no credible explanation that it might be a local anomaly (flying bird, airplane, drone, power glitch, interloper asteroid, bad pixels, etc. I've used the final sky plane prediction for MIRA from John Irwin, and scaled the location of our event using the path parallel through Quaoar itself as 45 seconds. The location clearly is too far to be due to ring Q1R, and its profile looks more consistent with a new satellite. This was corroborated by John Irwin who soon thereafter sent to me a sky plane prediction which included our occultation.
The actual closest approach of our chord to ring Q1R shows no evidence of opacity in the high S/N photometry data from the 36", nor the 14" telescopes.
Dismissing Alternate Explanations, other than a real occulting object around Quaoar
1. A large bird? No, a bird would have had to cover both telescopes for a long 1.23s; both the 14" and the 36" scopes. Such a bird would need a very fat wing and long wingspan of 6 feet or more. The only bird that might be able to do that is a California Condor. But condors do not fly at midnight; only in the day, and their occultation flight would also not give precisely the same D and R timings as Kirk and I saw on separate telescopes.
2. A drone? MIRA OOS is very isolated. There are no inhabited places for a dozen miles, and none that concievably would be flying a drone. Consumer drones also do not have sizes capable of covering both telescopes. Drones are also not opaque, but only partially opaque. Yet my occultation went to zero and stayed there for a full second. Not possible with a drone unless a large one secretly launched by authorities with access to such large drones
3. An airplane? No. Airplanes are required to have lights, especially at night. There is no light traces on our recordings
4. An Earth orbiting artificial satellite? Would cross the star with a duration of 0.1s or less. Far too short to account for our event.
5. A power glitch? No. KIrk's and my power sources were completely independent - Kirk used DC batteries of his own, I used my own DC battery and also AC Observatory power for the laptop. And a glitch would affect not just a single star that happened to be the target star.
6. An interloper asteroid from the Main Belt which just happened to occult the target during the passage through the Quaoar system? Extremely unlikely. An occultation of 1.2s is long, these days. Here's a list of recent asteroid predictions with comparable occultation duration:
(1089) Tama 6/5/25 Dur=1.5s, D=1.5 AU, G=15.1
(3382) Cassidy 6/20/25 Dur=1.1s, D=1.04 AU, G=15.3
(7747) Michalowsky 6/21/25, Dur=0.9s, D=0.76 AU, G=14.9
(22440) Bangsgaard 6/26/25, Dur=0.9s, D=2.56 AU, G=18.2
(1219) Britta 6/29/25, Dur=1.0s, D= 1.48 AU, G=15.0
(41080) 1999VX45, 7/2/25, Dur=1.4s, D=1.90 AU, G=17.6
(3888) Hoyt, 7/3/25 Dur=1.2s, D=0.93 AU, G=15.2
(45583) 2000 CK87, 7/7/25, Dur=1.0s, D=1.91 AU, G=17.7
These fall in the range 15th to 17th magnitude. Such an asteroid would give a significant mid-occultation signal in my recording on the 36". Even more so since most stars in this area are red, and our red-sensitive Watec 910hx would give stronger signals. At 17.5 magnitude by a fortuitous occultation by an unknown Main Belt asteroid would produce a brightness drop of 94%; i.e. from 100% brightness down to 6% brightness. In fact, the observed drop at the 36" was not 94% but 99.9% (Kirk Bender's data is not useful for this question because his short focal length and smaller aperture left the target partially contaminated by light from one of two fainter neighboring stars).
The remaining hypotheses are that it was caused by a new Quaoar satellite, or else a dense portion of a new, 3rd ring.
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A new diagram just before the occultation night, from John Irwin, and a snippet of his thoughts... John Irwin: "I've also determined and displayed a circular orbit that matches the star position. It has a radius of 5762 km. The shading on each side of the orbit shows the variation due to the 1-sigma AL uncertainty in the relative position of the star (±15 s). Do not mistake it for a ring, even though the cause of the occultation may in fact be ring material, rather than an unknown satellite. If not of terrestrial origin, I would favour the latter." (RN: I, too, favor the moonlet hypothesis, although I hope LuckyStar people will do a deep look at my photometry around the time of the possible 2nd "ring" crossing at 6:59:38 UT).
There's a new paper by Proudfoot et al. on the Planetary Science Journal (https://iopscience.iop.org/article/10.3847/PSJ/addd02) that says an even better orbit for Weywot is forthcoming. Hopefully that will be helpful.
The "x" marks the location inferred for our occultation observed. |
John Irwin's reconstruction of best prediction with our occultation position shown, and if caused by a ring, the width shown is the width of prediction uncertainties, not the width of a putative 3rd ring itself. |
My light curve from 36" data, shows a dip of ~25% near the corresponding moment of 2nd "ring" contact (if occultation was ring-caused). It is not statistically significant, but perhaps keeps the hypothesis of a 3rd ring still alive. |
Weywot path with its tight error limits. Clearly this was not the source of the occultation at MIRA. |
Ben Proudfoot (https://iopscience.iop.org/article/10.3847/PSJ/addd02) provided this image of his analysis of the JWST occultation trace at the inferred distance of a putative 3rd ring inferred by our occultation here. Despite the high S/N and small rms magnitude rms of only 0.15, there is no detection of a ring on either side. |
The just published paper by Proudfoot et al. (Proudfoot et al. 2025) uses a JWST observed 18th magnitude stellar occultation to measure the rings and gets 3 detections out of 4 contacts, and a pole that is 1.9 degrees different than past ground-based occultation determinations of Quaoar's pole. No clear resolution with pole direction from past work is made, and hypotheses they examined are mostly disfavored, although the presence of shepherd satellite moons to stabilize the rings is still a good possibility. They urge more efforts in setting up observer fences when occultations are predicted. Not mentioned is the fact that Quaoar right now is in the Scutum Star Cloud - one of the very densest star concentrations in the sky. Stellar occultation bounty for just a very few years! We should make every effort to make use of the current higher occurance rate of Quaoar occultations to figure out this system. As Proudfoot et al. pointed out, the theory of small-body rings is "in its infancy", but has significant implications for the long term evolution of objects in the solar system. Such ring systems were not predicted - but now they're here and real, and the challenge is to understand them.
My own guess, pending more data, is that this occultation was more likely due to an unknown satellite, only because I assume a ring would already have been discovered. but a new moon could be missed. But that assumption might be false if data taking for most occultations did not include a wide enough time band, or if the region of observable opacity is small enough to make that argument moot. The wide enough time band issue is quite unlikely to be a problem for the large CFHT and Mauna Kea observations, which are not about to economize on data taking time, after the initial investment in time and effort.
July 1
Jerry Bardecker did a re-reduction of his initial "miss" report and PyOTE found a possible wide shallow 55s (+-24s 2-sigma confidence interval) occultation centered 9s after our event. But looking at the Irwin sky plane, if JB's event is real and associated with a ring that also produced our occultation, and if our occultation corresponded to the center of his putative ring, it should have been centered before our event, not after, both because of the path direction (roughly 20s offset for this reason) and also because his chord was farther north and deeper into the ring, and the ring would be hit sooner (roughly by another 15s). Could his shallow dip instead be due to the known Q1R ring? Could it instead by a ring and our occultation was a condensation at the outside edge of his ring? But the story deepens...
July 2
Alas, a new plot from Jerry makes a strong case that the 55s dip he saw in the target was actually due to a spurious rise in the reference star's partially smoothed light curve of this duration. The striking mirror image of the two light curves; ref star and target star, show that if the ref star had truly been flat, the target star's light curve would have been flat too. The ref star may have wandered upward during a period of poorer seeing and inclusion of a fainter neighbor star in the mask for the ref star, and no such event in the target star. His screen capture of the PyMovie screen shows his target star, but also inside the target star mask is the worrisome neighbor (visible to lower left of the target) dimmer but only 8 arc-sec away. A light curve which used a ref star with cleaner separation from neighbors and did not show an anomalous rise, would give a more reliable target light curve. The target star dip seen below doesn't align with a putative 3rd ring from the MIRA occultation, nor rings Q1R nor Q2R.
No one has proposed an explanation how the ref star could remain higher brightness for this long above it's longer term average w/o it being caused by contamination into the mask from a neighbor star. Height is only 0.2 mag, so it would not take a bright obvious neighbor to do this. |
The entire field is crowded for small FL small telescopes. Especially true for the target. Note the "bright neighbor" is inside JB's mask aperture in this screen capture of his PyMovie screen, submitted by JB. This is problematic. |
Here is the Aladin photograph zoomed to show the close neighbors. However in the Watec bandpass, the "bright neighbor" is clearly the brighter vs. the dimmer neighbor up/left of it. This brightness difference is much less in this Aladin photo. |
July 9
An independent exam of Jerry Bardecker's CSV file by PyMovie / PyOTE author Bob Anderson agrees that the putative event is very likely spurious, and for the reasons I described earlier: contamination from neighbor star(s) over a period of time, and JB's chosen smoothing length (short) will conspire to force the target curve downward erroneously. While JB had carefully avoided claiming he has a definite event, the case for any credible event in his data has not yet been made. This is as things stands at the time of submission of the announcement CBET. JB's initial OWc submission result was "Miss".
Publications
Dan Green at the MPC recommended we submit the paper to a larger journal, which we did, after adding 5 figures and some more detail. The paper was published in the Research Notes of the AAS (Nolthenius et al. 2025). Now indexed in ADS:
https://ui.adsabs.harvard.edu/abs/2025RNAAS...9..226N/abstract
and also Google Scholar, e.g.:
And popular-level articles are now appearing...
IFL Science
"Distant Dwarf Planet Quaoar Might Have More Moons Than We Thought – Or Yet Another 'Impossible' Ring" by Dr. Alfredo Carpineti – 1 September 2025
https://www.iflscience.com/distant-dwarf-planet-quaoar-might-have-more-moons-than-we-thought-or-yet-another-impossible-ring-80626
Orbital Today
"Astronomers Saw a Star Blink – Did They Just Find a New Moon at Quaoar?" By Matthew Gover – 12 September 2025
https://orbitaltoday.com/2025/09/12/occultation-points-to-possible-moon-around-quaoar/
Phys.Org
Discovery of New Moon or Ring System Orbiting Mysterious Distant Planet Quaoar" by Paul Arnold – 11 September 2025
https://phys.org/news/2025-09-discovery-moon-orbiting-mysterious-distant.html
Space.com
"The Weird Ringed Dwarf Planet Quaoar May Have an Extra Moon, Astronomers Discover" by Nola Taylor Tillman – 9 September 2025
https://www.space.com/astronomy/dwarf-planets/the-weird-ringed-dwarf-planet-quaoar-may-have-an-extra-moon-astronomers-discover
Universe Magazine (Space Tech)
"Scientists Have Discovered a New Moon or Ring System Orbiting the Dwarf Planet Quaoar" by Oleksandr Burlaka – 12 September 2025
https://universemagazine.com/en/scientists-have-discovered-a-new-moon-or-ring-system-orbiting-the-dwarf-planet-quaoar/
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A theoretical "Paper I" focused on resonances around irregular objects is already published, and is available at: https://www.aanda.org/articles/aa/full_html/2025/12/aa56950-25/aa56950-25.html> and followed now by...
"Rings around irregular bodies. II. Numerical simulations of the 1/3 spin-orbit resonance confinement and applications to Chariklo" by Salo & Sicardy 2026
<https://arxiv.org/abs/2601.06975>
