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The lander trajectory is being significantly affected by the propellant leak. My astrometry of it tonight (Jan 10) is around 2 arcmins from where it should be assuming a ballistic trajectory. The spacecraft is around mag 18 tonight. The Centaur is much better behaved and quite bright (mag 14). We should be able to follow that for quite some time as it goes off in a heliocentric orbit. I’ve attached an ephemeris for the Centaur in case you want to have a go.
Gennady Borisov has found the Centaur too and this was briefly listed as gb00471 on the NEOCP. I’ve just imaged it and it is around 12 deg SW of the spacecraft and quite a bit brighter at 14th mag.
This is a good summary of the angular momentum misalignment and some of the theories put forward to explain it:
https://iopscience.iop.org/article/10.3847/0004-6256/152/5/126
Short answer, as Dominic says this is a coincidence. Longer answer as follows…
I assume that the tilt you mention is the apparent position angle of the sun’s rotation axis in equatorial coordinates. This is a function of the sun’s axial tilt with respect to the ecliptic (around 7.3 degrees), the Earth’s axial tilt (around 23.5 degrees) the orientation of the two spin axes in space and where we are in our annual orbit around the Sun. In the short term the rotation axes of the Sun and Earth and the plane of the Earth’s orbit have a fixed orientation so as we travel around the Sun the relative geometry changes on an annual cycle.
Our view of this tilt depends on the coordinate system we use.
In ecliptic coordinates (i.e. not including the Earth’s axial tilt) you would see the rotation axis nodding from side to side in a simple sinewave over 12 months going through a minimum in March when we see the south pole tilted towards us and in September when we see the north pole. In between it reaches its maximum tilt of 7.3 degrees tilted left or right. When you look in the equatorial coordinate system you have to add in the effects due to the Earth’s axial tilt as well. This makes the geometry more complex since you have two sinewaves adding together but, as you have noted, the tilt is around 0 in early January and reaches around 26 degrees in early April.
The orientation of the Earth’s perihelion in its orbit is completely unrelated to the orientation of the rotation axes and, as Dominic noted, precession affects the Earth’s axis orientation and the perihelion orientation over the long term so this “coincidence” will not last forever.
The thing that is surprising, following up on Dominic’s comment, is why there is a such a large angle between the Sun’s rotation axis and the normal to the Solar System’s invariable plane (essentially the perpendicular to Jupiter’s orbit plane). Since the Sun and its planetary system formed out of the same rotating cloud of material you would expect them to have the same angular momentum orientation. The fact that the planets now move in a plane tilted at around 6 degrees to the Sun’s equator is a bit surprising. There are some quite inventive theories out there to explain this.
It was cloudy in Chelmsford but here it is from my SW pointing camera.
https://nickdjames.com/meteor/2023/202312/UK004F_20231230_020727_ndj.mp4
This thread has wandered way off topic.
Grant – I think that those mince pies have clouded your judgement! Don’t fall for the pro-Pluto propaganda. The term is loose but the possible criteria for “orbit clearing” are strong. One of the best was actually proposed by Alan Stern himself. In this scheme even Mars is five orders of magnitude above Pluto:
https://en.wikipedia.org/wiki/Clearing_the_neighbourhood
Have a great Christmas everyone.
I suspect that Gary’s cocoa comment (and Jeremy’s Horlicks follow-up) were tongue in cheek.
I really don’t see why we need to “honour” the fact that somebody, mainly through luck and age, has reached the milestone of 50 continuous years membership. As Grant says, we have awards for achievement and it would be good if we got more nominations for those.
This is an interesting discussion and I need to declare an interest since I’m coming up to my 50th year of membership.
I’m strongly in favour of scrapping this tier of membership for the following reasons:
1) I don’t think it is fair that older (and usually more wealthy) members are subsidised by the rest of the membership.
2) I don’t think you need to be “honoured” for being a member for 50 years. Surely you’re a member because you want to be and you get something out of membership. It is not an ordeal that needs some kind of prize after 50 years.
3) When no money is taken each year we have no idea whether the honorary member is alive or dead. We’ve had cases where we have sent Journals and Handbooks to members many years after their membership of life has ended.
As David and Andy have pointed out this isn’t a final decision. It came from the trustees and has been agreed at Council but it could be overturned at the SGM if members wish. I think that would be a mistake since our complex membership tiers definitely need simplification but it is a decision for you.
The Windows/Linux argument is very out of date now. Things have moved on a lot and you can Windows for the ARM architecture so it will run on Raspberry Pis and other similar hardware. It will even run x86 binaries using an emulator. There really is absolutely no need for Windows vs Linux arguments any more. You can run both on the same machine at the same time and select the one that best fits the job in hand.
This is probably not a very helpful reply but I’ve always found NUCs rather pointless and hard to maintain, as you have found with a USB failure writing off the whole box. I run everything in my observatory off a small-form-factor, low-spec, Dell Optiplex 790 which has a mechanical hard disk. It has been sitting out in my damp observatory shed for years with no problem but I do have a stack of replacements in the garage with a disk image ready to go if it does fail. It has the advantage that you can pick them up cheap (£50 a pop from eBay) and they are easy to maintain (you can fit low-profile PCI cards for USB3 etc. and memory strips are dirt cheap). I run two cameras (an ASI6200 and an ASI293) off it plus the mount, scripting software and some other stuff. It is run headless since I do all my observing from inside and seems perfectly capable for image acquisition. It is on a UPS and is left on 24/7 but, when idle, consumes around 40W, so costs around 30p/day and this helps to keep nearby stuff in the shed reasonably dry. Maintenance consists of hoovering it out a couple of times a year to remove spiders and stuff.
Yes, already detected in China a few hours ago: https://www.astronomerstelegram.org/?read=16361
The comet designated as 1862 II is C/1862 N1 (Schmidt) discovered by J Schmidt (Athens) on 1862 July 2.87. See Cometography Vol 2, p305. Apparently just visible to the naked eye on July 7.
Thanks for the reminder about this Paul. I’ll register with the email list and will schedule a few runs on this field each clear night through December. I took the attached tonight. No sign of the nova at the moment!
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This latest outburst was a big one but it has had no detectable effect (so far) on the motion of the very massive nucleus of 12P. This plot shows astrometric residuals from three stations (970, I79 and I81) with an orbit fit that uses positions up to Nov 14. You can see that there is a large temporary displacement of the residuals on Nov 15 and 16. This is due to the biasing of the centroid of the coma by the very bright dust cloud moving NE from the nucleus. As this dust cloud fades the astrometry is returning to normal.
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Robin,
The fact that the total magnitude of the expanding dust coma is constant implies that it must be optically thin, i.e. individual dust grains are not shadowing other dust grains. That tells us that this feature is not a shadow. It is much more likely to be caused by variations in the dust column along our line of sight caused by the outflow dynamics close to the nucleus when the outburst occurred. The outburst itself is a very rapid event where gas and dust leave the nucleus at high velocities and then expand into a vacuum. That process shapes the three dimensional outflows which we then see projected onto a 2D image.
Richard Miles is the real expert on this and this comet and 29P have been giving him a lot of data to work with.
Nick.
Here is a plot of the magnitude of 12P in an approximately 9 arcsec radius photometric aperture. These are all unfiltered vs Gaia G.
While the total magnitude of the comet is constant this is within an expanding aperture, when you restrict the aperture to the region near the nucleus it gives some idea of the amount of dust in that region. The initial rise is incredibly steep. I caught it just after the outburst on Nov 14.75 and it brightened by 1.2 magnitudes in 20 minutes eventually reaching something like mag 9.3. It was 14.2 in this same aperture before the outburst so that is a rise of a factor of 100 in a few hours. That is a lot of dust coming off the nucleus in a very short time.
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And here’s tonight’s. The photocentre is still strong. No sign of any fragmentation but you wouldn’t expect any since this comet has gone through perihelion many times and has a large nucleus. Maybe some big chunks coming off but nothing more than that.
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