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August 28th 2024 was a day I gave little thought to thanks to warm cloud tops and issues with convective depth, however a deeper look at the models showed a classic post-frontal air mass low CAPE high shear day. In fact, with 40 knots 0-2km shear and 40 knots 0-6km shear cells would be low topped but very organized with a chance of rotation, funnels and structure. The day turned out better than expected with two local chases, I captured a distant thunderstorm which was dropping c-gs over Portglenone which even had a small rope funnel. The highlight was one of two structured cells over Tyrone with well formed rain free bases, tilted updraughts, strongly vented precip and vaults, all traits of highly sheared storms, in essence these were almost 'mini supercell' structures which I felt were worth documenting on here. One page report with 12 images and 1 video clip. - REPORT.
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August 11th 2024 brought a much welcomed thunderstorm outbreak when an elevated plume engaged with an active cold front producing hours of night time lightning. A rare event from Ireland which brought the entire Summer thunder drought to an end. I spent the entire night with Colleen Webb on Benbradagh and the back roads of the west watching hours of distant lightning, beautiful orange c-gs, glimpses of a planet conjunction, Perseid fireballs, a surprise aurora, the loudest thunder in a long time and a beautiful G2 aurora the following night. Despite much frustration and not getting the photo opps I wanted seeing all these phenomena at the same time was a very special experience. One page report with 14 images. - REPORT.
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On August 8th 2024 I headed out on a ship chasing adventure to catch an exceptional vessel called the MPI Adventure, a famous off-shore supply vessel and wind turbine installation ship. She was anchored on Drains Bay near Larne so I did the two hour drive and arrived on location during the late evening before sunset where I filmed her with my drone. This ship uses six 60m tall legs to jack herself up out of the water to undertake her operations with greater stability at off-shore wind farms making her an exceptional vessel. My last aerial flight took place in twilight with the MPI lit up with lights when she made for a spectacular scene on the tranquil bay. One page report with 12 images and 2 video clips. - REPORT.
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(Above) C/2023 A3 on July 28th by Gerald Rhemann from Namibia showing healthy dust and gas formations.
It's about time I posted about C/2023 A3 Tsuchinshan-ATLAS again. For those who don't know this comet has been on the radar of both amateur and professional Astronomers since it was first discovered last year. Orbital calculations showed that this comet was making its way into the inner solar system from the Oort Cloud making this the comet's first visit around the sun since it formed 4.5 billion years ago. However, to make matters more interesting the comet's parabolic orbit will bring the comet as close to the Sun as planet Mercury followed by a swing by Earth after perihelion. These parameters all indicated that a potentially bright comet was on the way.
Experts were quick to note that the Earth-Sun-Comet geometry during and after perihelion passage would be greatly affected by forward scattering, this meant the comet could surge in brightness during this time, perhaps making it visible in daylight for trained observers before slowly fading as it moved back into the outer solar system. The climax of this much anticipated apparition would take place in the evening sky around mid October 2024 when the comet with an impressive tail could put on a show in the W-SW twilight arch. Magnitude predictions varied wildly with reports of mag+1 to 0 at perihelion with forward scattering boosting the magnitude to -3 or -4 (almost as bright as Venus) so hopes were high that this could be the comet we have all been waiting for.
If only Mother nature was as easy to predict. There were a few issues which needed to be addressed, first of all this was the comet's first trip towards the Sun. These 'fresh' or 'new' Oort Cloud comets can be highly unpredictable and can lead to unrealistic expectations as they have a tendency to brighten early giving Astronomers false hopes about their future, more often than not the comet's rate of brightening slows down and under performs leading to disappointment. Not all new Oort cloud comets do this, but many have displayed this behavior in the past so this sobering aspect of A3 needed to be accepted, even anticipated.
Meanwhile everyone was quietly optimistic about the comet's performance when suddenly during the Summer the magnitude of A3 began to slow down, and even stalled at +10 to +10.5 for almost two months. The comet clearly wasn't brightening further which gave the negative skeptics much voice as they trumpeted loudly that the comet was doomed, as they expected. Around this time a damning paper was released by a highly respected comet scientist which stated that the comet would fall apart, however not only that but it was already falling apart and in the process of actually becoming a boulder field. The author stated many reasons for this conclusion. It looked like our dreams of a bright comet were once again over for observers in the northern hemisphere.
Then the tables turned, optimistic voices emerged from the dark to boldly challenge this respected paper. In fact, many long time comet experts completely disagreed with the prediction and provided logical counter arguments which debunked the debunkers. As it turned out the brightness slow down and stall was completely normal, it was a direct result of phase angle effects and scattering, as the comet approached then receded from Earth in its orbit, and if this was the case then the comet should begin to brighten rapidly once more by late Summer. All CCD images showed that the comet is currently in a healthy state and most certainly not breaking up, in addition to this healthy coma A3 is also producing a long gas tail in conjunction with the classic dust tail, something a disintegrating comet wouldn't do. As it stands as I write this during early August the comet is looking good and still promising for a nice show in October.
Here are a few more positive facts...
1) Measurements indicate C/2023 A3 has a nucleus approximately 2km in diameter. Although this isn't as large as NEOWISE (5km) or Hale-Bopp (40 to 70km) it is larger than the average comet nucleus and is of a size which greatly reduces its chance of disintegration. However the composition is still unknown to anyone.
2) These measurements also indicate the comet is releasing large amounts of dust and the dust particles themselves are of large size. There are suggestions that a large surface area of the nucleus is also very active. In a nutshell an active nucleus means more dust release and the latter reflects sunlight, so if this dust production keeps up it will aid with the naked eye visibility of any Type II tail phenomena after perihelion.
3) As of early August the brightness stall has ceased and the comet has come back to life once more and appears to be brightening rapidly. Chris Wyatt from Australia estimates the comet's magnitude at +8.9. We expect the comet's magnitude to reach +8 to +7 by the end of the month, if so then the comet isn't far off track from its predicted light curve.
The window is now small to observe this comet, in fact, it's completely gone for northern hemisphere observers so only our southern comet lovers can keep an eye on its progress in the meantime, but even they will loose the comet from view soon as it approaches solar conjunction. Then we will all have to wait and see what happens in October. So what could the comet look like? this leads us next to a fascinating glimpse of the future.
Comet Dust Tail Simulations
Let me introduce this fantastic work by Nicolas Lefaudeux who took time to create a computer simulation showing the expected dust and gas tail geometry based on the comet's orbit and from work on other comets from the past. The results are very interesting and indicate two areas of interest for observers and photographers. The first takes place between Sept 28th and Oct 2nd when the comet will be visible extremely low on the horizon before sunrise. The comet could display a dust tail 10-15 degrees long visible in the sky well before the comet's head actually rises, the gas tail could be longer still. Please keep in mind that observers near the Equator will be best positioned for this part of the apparition.
The main event will be in the SW evening sky for the northern hemisphere during and after mid October. After sunset and during twilight the comet will display a short stubby and possibly curved dust tail with a developing straight anti-tail pointing towards the Sun. As the elongation improves the anti-tail will become edge-on and much better defined. The author notes the similarity with Arend-Roland of 1957 which had the greatest anti-tail of all time. Lefaudeux confidently states that the anti-tail on C/2023 A3 could be brighter and longer given the comet's larger dust particle size. However please keep in mind that Arend-Roland was viewed against a dark sky background while A3's appearance will be against twilight. This sharp anti-tail will peak on Oct 14th for several days.
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(Above) Dust tail simulation showing the post-perihelion dust tail and anti-tail by Nicolas Lefaudeux
Then the main dust tail was will become longer, possibly 15 degrees and still sporting some degree of anti-tail as the comet increases elongation higher into a darker sky while gradually fading from view coinciding with a waning moon and increasing dark sky window in the evening. It should be clearly noted that these are photographic measurements in degrees so the visual tail lengths could be slightly less.
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Overall it looks like we still have a very interesting comet to observe this October. I expect C/2023 A3 to be a very impressive sight in binoculars and rich field telescopes and a superb object for astrophotographers. Just how bright the comet will be is still largely unknown, the chance of this being a great comet are now small, estimates range from +4 to +2 (Polaris) to somewhere in the range of NEOWISE (+1) which I think would make most people happy enough. There remains a low chance that with forward scattering and active dust production and with any outbursts the comet still could take us by surprise. I'm currently very much looking forward to seeing it and hope we get treated to an impressive show with two weeks of clear skies during its best performance. I urge you to read Nicolas Lefaudeux's full simulation here...
https://hdr-astrophotography.com/comet-tails-simulations/
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The 2024 storm season has been the worst on record however on July 15th I got treated to a shocking surprise during a funnel hunt with very low expectations. With weak CAPE but notable surface convergence we knew we had a chance of seeing something so I met up with Colleen Webb on Benbradagh Mountain for a day of sky watching. I had just arrived and within a few minutes a funnel cloud appeared from nowhere which took us completely by surprise. It was far away to the NW and looked massive in size and even had that tornadic look, we took images of the funnel despite battling haze and obscuring precip curtains. We soon learned it had been rotating near Letterkenny in Co. Donegal over 25 miles away from our location. This was an impressive vortex and suspected landspout tornado event which was accompanied by second funnel at the same time. One page report with 11 images. - REPORT.
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Solar maximum is a time when NLCs are expected to wane in activity with the prospects of a good display being a rare event. On June 25th/26th 2024 I walked outside to check the sky and was shocked to see a vast type 5 NLC display covering the NW to NE sky sectors and directly overhead. In a panic I drove to Lough Fea where I spent the night observing what I can only describe as an epic display which rivaled the best I had ever seen back in 2009. The NLCs exhibited insane structure in the form of large whirls, knots and herringbone waves all moving in real time while casting shadows on the ground and bathing my dog and I in eerie blue light. This was a spectacular experience and to make things more interesting scientists reckon the 2022 Hunga Tonga undersea volcano seeded the Mesosphere with water droplets causing this NLC storm. One page report with 23 images and 1 video clip. - REPORT.
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May 21st 2024 - I teamed up with convective forecaster Owain Rice to intercept thunderstorms on a convergence zone near Omagh. After hours of waiting we got thunder however the storms became outflow dominant and unphotogenic. We chased E back into clear air and strong solar heating intercepting a new cell with a menacing base. Later in the day random events had conspired to bring us to Ballyronan Marina along with Nigel McFarland and Colleen Webb. Within min's of our arrival a stunning thunderstorm erupted after 5pm taking full advantage of over 1000j/kg of CAPE, the storm developed a stunning overhead anvil like a volcanic plume with anvil thunder, in fact, the storm produced thunder for an hour with over 340 discharges. We got to enjoy this spectacular photogenic storm in sunshine with the anvil back-lit by the sun with crepuscular rays fanning through the thunderheads, what a day this was! One page report with 16 images and 1 video clip. - REPORT.
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May 10th 2024 - Mega sunspot group unfurling six CMEs and a violent impact at 800km/sec with a Bz of -50, the result was the most severe geomagnetic storm since 2003 and we had perfect clear skies. I was located in a field at Beaghmore in Co. Tyrone beside the famous fairy tree alongside a television film crew. As twilight deepened a truly spectacular aurora manifested covering the entire sky 360 degrees. Pink, green, blue, crimson and purple rays and streamers astonished us while overhead a remarkable corona dominated the sky. This corona took on the forms of birds and even a giant Angel, the display washed most of the stars from the sky and even appeared on the southern horizon. I observed it all night long and obtained my finest astro time lapse of my life. This was easily within my top five aurora experiences ever and a night never to be forgotten! One page report with 34 images and 1 video clip. - REPORT.
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Skywatchers be on high alert for an extremely rare event which might happen in 2024, in fact, it could happen tonight! I urge you to check the constellation of Corona Borealis 'The Northern Crown' every clear night, even several times a night. Located at the SE (lower left corner) of the star Epsilon is a faint star called T Coronae Borealis or TCrB for short. This famous star, sometimes called 'The Blaze Star' is in fact a dramatic example of a reverse Nova, normally this star sits around mag +10 and can only be seen in large binoculars or small telescopes, however at periodic intervals spanning roughly 80 years this star suddenly flares in brilliance and becomes a naked eye Nova peaking at mag+2 breaking up the familiar pattern of the Northern Crown.
Previous outbursts occured during May 1866 and February 1946 with historical records highly indicative of earlier eruptions in ancient times also. The consensus is that this star is ready to erupt again at any moment. Predicitons favour Spring 2024 give or take several months but in truth no one knows for sure when it will happen, however based on previous eruptions the next one is imminent, if this happens we willl be witnessing a truly rare event and the brightest Nova in our sky since 1975.
To the naked eye a Nova looks like a new star has suddenly appeared in the sky but what we are are actually seeing is an old star going into outburst. This typically happens in binary star systems when we get a red giant with a smaller white dwarf companion orbiting around the parent star. Over time the smaller star captures material from the host star, if we could see it happening it would look like a tear drop of sellar atmosphere connecting one star to the other. Eventually a threshold is reached and a thermonuclear eruption takes place causing the white dwarf to increase in magnitude making it visible to the unaided eye.
The rise to mag +2 (Polaris) can happen extremely fast, over several hours, so it's possible the event could happen in the course of a single night where it will peak at its brightest before a slow decline sets in, so in order of having a chance of catching it in the act observers will need to be dedicated and vigilant. Corona Borealis will be well placed for the rest of the year, all one has to do is check the lower left corner with your naked eye any night the sky is clear and get in the habit of doing this often, you never know, you could be the one who witnesses this Nova as it takes to the stage, what an experience that would be.
If you are not familiar with variable stars and novae then google the subject, or better still read Leslie Peltier's Starlight Nights, he has a wonderful chapter dedicated to these stars and to his quest to see TCrB erupt, it's well worth reading. I wish you all clear skies and happy hunting. Check out the chart above from Sky & Telescope.
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Astronomy is not the only subject I'm interested in, check out my N. Ireland Storm Chasing section and view the chase reports and images which detail not only storms but other phenomena such as a moonbows, noctilucent clouds, aurora displays and exciting nature related photo shoots.
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Martin McKenna
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