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The formation of dust is the usual reason for these sudden dips, and that is consistent with the reddening as shown in the recent photometry, but what about the big humps when it was bright? Is that dust related too or is it an actual brightening of the disc? V1405 Cas has these humps too whereas other novae (V1674 Her for instance) don’t.
Novae are such fascinating things!
I suspect that this particular flare was caused by DirecTV 7S. It was boosted to the graveyard orbit at the start of 2021 (see here) which is why it is around 370km higher than the other two. It would have been passivated and would not be under control which would explain the odd geometry for this glint.
Here is what one of those GEO flares looks like in real time. The attached is a still from a meteor camera video which you can see here. The video starts at 2021-11-03 01:09:45 UTC and the flare reaches around 2nd mag at 01:09:56 and lasts for around 15s. The potential candidates within 0.1 deg of the estimated position are:
2021-11-03 01:09:56.000000 UTC TOPO 28238 143.17 24.40 0.07 39494.87 -0.009 DIRECTV 7S
2021-11-03 01:09:56.000000 UTC TOPO 38741 143.07 24.34 0.07 39129.06 -0.000 HYLAS 2
2021-11-03 01:09:56.000000 UTC TOPO 47306 143.17 24.36 0.08 39122.74 0.000 TURKSAT 5AThe solar phase angle at the time of this flare was 125 deg so nowhere near opposition.
I don’t know whether there is a website which allows you to search for satellites which are in a particular direction at a given time but I computed these directly using TLEs downloaded from here.
That is a very interesting video. I’ve estimated the time of the brightest one as 2021-10-11 00:26 and its position as azimuth 177, alt 29. If you search within 2 deg of that for Kelling you get this list of satellites (This is a bit of a mess but I can’t attach a text file since it is not one of the permitted file types:
UTC ID Az Alt Ofs Rg (km) RR (km/s)
===========================================================================================================
2021-10-11 00:26:00.000000 UTC TOPO 24748 175.99 28.87 1.16 39039.51 -0.070 DIRECTV 6 (TEMPO 2)
2021-10-11 00:26:00.000000 UTC TOPO 32299 175.37 29.43 1.91 38664.80 -0.000 ASTRA 4A (SIRIUS 4)
2021-10-11 00:26:00.000000 UTC TOPO 33414 175.84 28.30 1.50 39268.93 0.004 VENESAT-1
2021-10-11 00:26:00.000000 UTC TOPO 36831 177.75 29.53 1.01 38670.19 0.000 RASCOM QAF 1R
2021-10-11 00:26:00.000000 UTC TOPO 39773 177.53 29.57 0.84 38665.08 -0.001 EUTE 3BMy guess is that the bright one is Eutelsat 3B. It has large solar panels (around 70 m^2) and could certainly flare to negative magnitudes if the geometry was right.
If you do the calculations it is not that surprising if it is a specular reflection from the solar panels. Around opposition these are pointing straight back at us and they are quite large. A quick order of magnitude calculation follows. Please check!
The sun has an apparent area of around 1E-4 rad^2. A 1m^2 mirror at 40,000 km is around 1E-15 rad^2. Assuming the mirror is a perfect reflector it will have the same surface brightness as the sun so will be 2.5 log10(1E-11) fainter so around 28 mags. The sun is mag -27 so the 1m^2 mirror in GEO could be around mag 1. GEO satellites have solar arrays of 50m^2 or more so a bright NE glint is certainly possible.
A lot of that is down to the IoP’s AV technician who did a fantastic job supporting us before and during the meeting.
Livestream is here: https://www.youtube.com/watch?v=pYFNWAlu6uw
David – That is a really interesting story. V476 Cyg is sitting at around 18.0 tonight. I think you’d need a pretty big telescope and dark skies to get the shell.
Yes, the flash triggered all of my cameras (UFO and RMS). My SE recorded it but behind thick cloud. My all sky showed that the sky was completely cloudy in Chelmsford at the time. Steve Bosley and Stan Armstrong both had clear skies and have nice images of it.
There can’t be many 0.8m telescopes on LP: https://www.astrosysteme.com/references/asa-az800-in-spain/.
There is a high res map of the lava flow here. You are a little way off the top of the frame.
Alex. I’ll pass on your request and I’ll see if we can make it as dark as Headingly on a mid-summer’s day.
Eeek. A bit close! At least we don’t have to worry about volcanic dust clouds when observing from the UK. There is some quite spectacular footage on the Reuters site here. The pictures from El Paso and Los Llanos look very familiar.
The reason for the pre-booking is that the IoP have decided to restrict the numbers in the lecture theatre to around 70 and this helps us assess how many people are likely to come. I doubt if that will be a problem for the AGM but it will be potentially more of a problem for Christmas. As with everything Covid-related things can change quickly but I hope that this meeting can go ahead since I am really looking forward to getting back to face-to-face meetings after a long break.
In the last few months I’ve been to many crowded events and have managed to survive but I know that some people will prefer to stay away, or are just too far away for convenient travel, so we will be livestreaming the meeting on Youtube. The IoP have been very helpful with this and it will probably become a permanent feature.
