C/2023 A3 Tsuchinshan-ATLAS

Closest to Sun on 2024 September 27 at 0.39AU.
Closest to Earth on 2024 October 12 at 0.47AU.
Maximum magnitude 0-3 in October 2024
Orbital period: N/A (Dynamically new)



Comet C/2023 A3 Tsuchinshan-ATLAS was discovered by the ATLAS survey (located in South Africa) on 2023 February 22,
and later connected to earlier observations reported by Purple Mountain (Tsuchinshan) Observatory on 2023 January 9.
This comet has potential to reach bright naked eye visibility during October 2024.
At discovery, the comet shone at 18th magnitude and situated 7.3AU from the Sun.
Calculations indicate that the orbital geometry of the Sun-Earth encounter will be very favourable.
The comet will arrive at perihelion on 2024 September 28, at 0.39AU (58 million km) from the Sun.
Two weeks later, on 2024 October 12, the comet will be closest to the Earth at 0.47AU. (70 million kms)
A conservative approach to its rate of brightening will see the comet reach 3rd magnitude at this time,
but a peak of 0 magnitude is not out of the question.
Also, the comet will be seen at a very high phase angle during the first 2 weeks of October, peaking on October 9-10.
i.e. it will be situated nearly directly between the Sun and the Earth.
A process known as “forward scattering” of sunlight by dust particles could cause a significant surge in the comets brightness,
but this requires the nucleus to release a large amount of dust for this effect to be noticeable, and it will be brief
(a few days either side of October 9-10).
The comet will also need to be large enough to survive its solar encounter and not fizzle out.
We have seen this so many times before, with first time Oort cloud comets fizzing out and causing big disappointment.
A famous example was the much anticipated "comet of the century" Comet Kohoutek in 1973 that fizzled.
The good news is that C/2023 A3 appears to be large enough.
It has an absolute magnitude of 6 (ie would appear magnitude 6 if situated 1AU from Earth and Sun),
hich translates to an object of about 10kms across.

It also appears strongly condensed, which is a good indicator of a large, active, dusty nucleus.
As the comet is dynamically new, they tend to brighten more slowly than a periodic comet,
typically a rate of 8 log r, where r is the distance to the Sun.
Thus, the most likely outcome is a baseline peak brightness of magnitude 2,
with a potential brief surge on October 9 to magnitude -4 due to effect of forward scattering,
however this will be offset by its close proximity to the Sun.

Viewing will favour Southern Hemisphere observers in the morning sky
when the comet is at perihelion in late September 2024.

Viewing will then favour Northern Hemisphere observers when the comet passes Earth during mid October 2024
and enters evening skies, but southerners will still get the chance to see it, albeit low on the horizon.

 
C/2023 A3 Tsuchinshan-ATLAS Observing Guide

January 2024
the comet is best observed in the hour before dawn, in the constellation of Libra, brightening from magnitude 14.0 to 13.5.
On January 1, the comet is situated 9’ north of magnitude 12 galaxy NGC5812.
The best period of visibility is between January 10 to 24.

February 202
the comet is best observed in the hour before dawn, in the constellation of Libra, brightening from magnitude 13.5 to 12.5.
It remains situated about 2 degrees north east of Zuben Elschemali (Beta Librae) during the first half of the month.
The best period of visibility is between February 7 to 22.

March 2024
the comet is best observed in the hour before dawn, as it treks westerly through the constellations of Libra and Virgo,
brightening from magnitude 12.5 to 11.5.
The best period of visibility is between March 6 to 23.
On March 24-27, the comet is within 30’ of Mu Virginis.

April 2024,
the comet is now visible in late evening skies but best observed after midnight, as it continues its westerly trek
through the constellation of Virgo, reaching opposition mid-month and brightening from magnitude 11.5 to 10.5.
The best period of visibility is between April 1 to 19, then from April 27.
On April 10-11, it will be 30’ south of magnitude 12 galaxy NGC 5506.
On April 27, it will be a degree south of Zeta Virginis.

May 2024
the comet is best observed in evening skies, preferably late evening, as it continues its westerly trek
through the constellation of Virgo, brightening from magnitude 10.5 to 10.0.
The best period of visibility is between May 1 to 17, then from May 26.
On May 8-9, it will be 30’ north of magnitude 12 galaxy NGC 4904.
On May 10, it will be 1 degree south of magnitude 12 galaxy NGC 4845.
On May 15, it will be within 1 degree south of magnitude 11 galaxy NGC 4643.
On May 18-19, it will be within 40’ south of the beautiful magnitude 11 intermediate spiral galaxy NGC 4536.
On May 29, it will be within 30’ south of the 12th magnitude spiral pair NGC 4116/ 4123.
On May 31, it will be within 40’ north of the 12th magnitude galaxy pair NGC 4045/ 4073.

June 2024
the comet is best observed in evening skies, after dusk, as it continues its westerly trek
through the constellations of Virgo and Leo, brightening from magnitude 10.0 to 9.5.
The best period of visibility is between June 1 to 12, then from June 23.
On June 6, the comet is a degree north of Beta Virginis.
On June 21, it will be adjacent to 5th magnitude star Tau Leonis.
On June 26, it will be 20’ south of magnitude 12 galaxy NGC 3640.

July 2024
the comet is best observed in the evening sky after dusk, as it continues its westerly trek through the constellation of Leo,
brightening from magnitude 9.5 to 8.5, and becoming visible through binoculars.
The best period of visibility is between July 1 to 9, and then from July 23.
It will locate about 2 degrees north of the beautiful magnitude 9 spiral galaxy NGC 3521 during the third week of the month,
so wide field rigs will be the choice for photography.

August 2024
the comet is best observed in the evening sky
but the approaching twilight and low elevation will make it increasingly more difficult to see as the month progresses.
It continues its westerly trek through the constellations of Leo and Sextans, brightening from magnitude 8.5 to 6.5,
favouring observers in the southern hemisphere.
The best period of visibility is between August 1 to 6.
By August 20, the comet will be lost in evening twilight at magnitude 7.5 as it approaches solar conjunction late in the month.

September 2024
the comet reappears in morning twilight for southern observers, brightening from magnitude 6.5 to 2.5.
The comet should be recovered by mid-September, very low in the eastern morning twilight,
about 1 hour prior to sunrise, shining at magnitude 4.5, in the constellation of Sextans.
The solar elongation remains low during the month, but this will be offset by the comets rapid brightening.
A clear view of the eastern horizon is required.
Moonlight also interferes with visibility.
On the morning of perihelion, September 27, the magnitude 3.0 comet, now at a maximum solar elongation of 23 degrees west,
should make a fine site with the crescent moon, about an hour prior to sunrise.
By September 30, the now magnitude 2.5 comet is also observable from the northern hemisphere but southerners are still favoured.

October 2024
T
he comet is at its finest and may put on a spectacular display,
however it will remain close to the Sun for the first 2 weeks of the month.
The comet will remain in morning twilight during the first 6 days of October whilst the elongation rapidly decreases.
This may be offset by forward scattering which may see the comet reach negative magnitude.
On October 9-10, it should reach peak brightness, the exact peak will depend on the amount of forward scattering enhancement.
If the comet is dusty, a possible sharp peak of magnitude -4 is possible, which may make the comet observable during daylight at this time.

The comet will be situated some 4 degrees from the Sun and best attempted at midday by experienced observers only.
On October 12, the comet is closest to the Earth (70 million kms) and reappears in the evening twilight, favouring northern hemisphere observers.
On October 15, southern hemisphere observers should get their first views of the comet during evening twilight,
about 1 hour after Sunset. It may appear of 1st magnitude and joins the brighter planet Venus in the evening.
You must have a clear western horizon with no obstructions.
Visibility rapidly improves with each passing night, but moonlight will interfere.
However, the advantage of moonlight is that it will light up the landscape and create excellent opportunities for landscape photography.
On October 16, Earth crosses the orbital plane of the comet, where we will view the dust tail edge-on.
This has the effect of enhancing visibility. The tail should appear as a long narrow spike, with a possible anti-tail pointing towards the sun.

Post orbital crossing, the dust tail will start to broaden quite rapidly.
From October 19, moonlight no longer interferes, and the now fully developed magnitude 3.0 comet will now be seen in a dark sky.
Rural skies and a clear western horizon are a must have to observe the magnificent splendour of the comet and its dust and ion tails.
On October 20, the now magnitude 3.5 comet can be seen near 4th magnitude Lambda Ophiuchii,
about 10 degrees above the horizon at end of astronomical twilight.
On October 26, the now magnitude 4.5 comet can be seen near Sigma Oph, of similar brightness.
On October 28, the now magnitude 5.0 comet can be seen a degree south of Beta Oph.
By the end of October, the comet has faded to magnitude 5.5

November 2024
the comet is best observed in evening skies, after dusk, as it continues its easterly trek
through the constellations of Ophiuchus, Serpens and Aquila fading from magnitude 5.5 to 8.5.
Best viewing occurs early in the month as moonlight interferes from November 4 to 16.
On November 22-23, the now magnitude 8.0 comet is situated near Theta 1,2 Serpens
and by this time, southerners will lose sight of it due to increasing twilight.
Henceforth the comet will remain a northern object until the end of the year as it approaches solar conjunction,
reappearing for them in February at magnitude 12.

 

C/2023 A3 Tsuchinshan-ATLAS Observations


Image of C/2023 A3 Tsuchinshan-ATLAS on 2023 September 3. Note the small highly condensed nature.




5 day Ephemeris


Tsuchinshan-ATLAS (C/2023 A3)
   Date        RA           declination   r      delta  mag Elong Phase Con
-------------------------------------------------------------------------
 1 Aug 2023 12 14h03m20.81s +01 59' 58.2" 5.8377 5.9346 16.5 79.6 9.8 Vir
 6 Aug 2023 12 14h03m01.77s +01 44' 17.9" 5.7890 5.9684 16.5 75.0 9.7 Vir
11 Aug 2023 12 14h02m58.05s +01 27' 38.8" 5.7400 6.0003 16.5 70.4 9.6 Vir
16 Aug 2023 12 14h03m09.23s +01 10' 06.5" 5.6909 6.0297 16.5 65.8 9.3 Vir
21 Aug 2023 12 14h03m34.75s +00 51' 47.2" 5.6416 6.0561 16.4 61.4 9.1 Vir
26 Aug 2023 12 14h04m13.92s +00 32' 47.2" 5.5920 6.0790 16.4 56.9 8.7 Vir
31 Aug 2023 12 14h05m06.05s +00 13' 12.5" 5.5423 6.0980 16.4 52.5 8.3 Vir
 5 Sep 2023 12 14h06m10.47s -00 06' 51.9" 5.4924 6.1126 16.3 48.2 7.9 Vir
10 Sep 2023 12 14h07m26.60s -00 27' 21.6" 5.4422 6.1226 16.3 43.9 7.4 Vir
15 Sep 2023 12 14h08m53.80s -00 48' 11.7" 5.3918 6.1275 16.3 39.7 6.8 Vir
20 Sep 2023 12 14h10m31.34s -01 09' 16.8" 5.3412 6.1270 16.2 35.5 6.3 Vir
25 Sep 2023 12 14h12m18.46s -01 30' 31.9" 5.2904 6.1208 16.2 31.4 5.7 Vir
30 Sep 2023 12 14h14m14.42s -01 51' 52.3" 5.2394 6.1087 16.1 27.4 5.0 Vir
 5 Oct 2023 12 14h16m18.57s -02 13' 14.2" 5.1881 6.0906 16.1 23.4 4.4 Vir
10 Oct 2023 12 14h18m30.29s -02 34' 33.8" 5.1366 6.0661 16.0 19.7 3.8 Vir
15 Oct 2023 12 14h20m48.88s -02 55' 46.6" 5.0849 6.0352 16.0 16.2 3.1 Vir
20 Oct 2023 12 14h23m13.56s -03 16' 47.9" 5.0329 5.9978 15.9 13.1 2.6 Vir
25 Oct 2023 12 14h25m43.54s -03 37' 33.3" 4.9807 5.9536 15.8 10.9 2.2 Vir
30 Oct 2023 12 14h28m18.07s -03 57' 59.1" 4.9282 5.9028 15.8 10.1 2.0 Vir
 4 Nov 2023 12 14h30m56.48s -04 18' 01.8" 4.8755 5.8453 15.7 11.0 2.2 Vir
 9 Nov 2023 12 14h33m38.05s -04 37' 37.7" 4.8225 5.7811 15.6 13.3 2.7 Vir
14 Nov 2023 12 14h36m21.95s -04 56' 42.4" 4.7692 5.7102 15.6 16.4 3.4 Vir
19 Nov 2023 12 14h39m07.27s -05 15' 11.2" 4.7157 5.6326 15.5 20.0 4.1 Vir
24 Nov 2023 12 14h41m53.07s -05 33' 00.2" 4.6619 5.5486 15.4 23.7 4.9 Vir
29 Nov 2023 12 14h44m38.49s -05 50' 06.0" 4.6078 5.4583 15.3 27.7 5.7 Vir
 4 Dec 2023 12 14h47m22.66s -06 06' 25.0" 4.5534 5.3619 15.2 31.8 6.5 Lib
 9 Dec 2023 12 14h50m04.56s -06 21' 52.9" 4.4987 5.2595 15.1 35.9 7.4 Lib
14 Dec 2023 12 14h52m43.05s -06 36' 25.1" 4.4438 5.1513 15.0 40.1 8.2 Lib
19 Dec 2023 12 14h55m16.85s -06 49' 56.8" 4.3885 5.0376 14.9 44.4 9.0 Lib
24 Dec 2023 12 14h57m44.69s -07 02' 24.1" 4.3329 4.9188 14.8 48.7 9.8 Lib
29 Dec 2023 12 15h00m05.32s -07 13' 43.1" 4.2769 4.7952 14.7 53.1 10.6 Lib
 3 Jan 2024 12 15h02m17.33s -07 23' 49.5" 4.2207 4.6671 14.6 57.5 11.3 Lib
 8 Jan 2024 12 15h04m19.09s -07 32' 37.9" 4.1641 4.5348 14.5 62.0 12.0 Lib
13 Jan 2024 12 15h06m08.74s -07 40' 02.5" 4.1071 4.3989 14.4 66.5 12.7 Lib
18 Jan 2024 12 15h07m44.28s -07 45' 57.8" 4.0498 4.2598 14.2 71.1 13.3 Lib
23 Jan 2024 12 15h09m03.67s -07 50' 18.7" 3.9921 4.1180 14.1 75.8 13.8 Lib
28 Jan 2024 12 15h10m04.70s -07 52' 59.7" 3.9341 3.9740 13.9 80.6 14.3 Lib
 2 Feb 2024 12 15h10m44.86s -07 53' 53.7" 3.8757 3.8283 13.8 85.4 14.7 Lib
 7 Feb 2024 12 15h11m01.26s -07 52' 52.5" 3.8169 3.6815 13.6 90.3 15.0 Lib
12 Feb 2024 12 15h10m50.65s -07 49' 47.6" 3.7576 3.5342 13.5 95.4 15.2 Lib
17 Feb 2024 12 15h10m09.62s -07 44' 30.5" 3.6980 3.3872 13.3 100.5 15.2 Lib
22 Feb 2024 12 15h08m54.62s -07 36' 52.4" 3.6379 3.2412 13.2 105.8 15.2 Lib
27 Feb 2024 12 15h07m01.72s -07 26' 43.2" 3.5774 3.0969 13.0 111.3 14.9 Lib
 3 Mar 2024 12 15h04m26.56s -07 13' 50.7" 3.5165 2.9550 12.8 116.9 14.6 Lib
 8 Mar 2024 12 15h01m04.43s -06 58' 02.0" 3.4551 2.8165 12.6 122.7 14.0 Lib
13 Mar 2024 12 14h56m50.51s -06 39' 04.8" 3.3932 2.6823 12.4 128.6 13.2 Lib
18 Mar 2024 12 14h51m40.27s -06 16' 48.9" 3.3308 2.5534 12.3 134.8 12.2 Lib
23 Mar 2024 12 14h45m29.52s -05 51' 05.5" 3.2679 2.4308 12.1 141.2 11.0 Vir
28 Mar 2024 12 14h38m14.59s -05 21' 47.2" 3.2044 2.3155 11.9 147.8 9.6 Vir
 2 Apr 2024 12 14h29m52.71s -04 48' 51.8" 3.1405 2.2085 11.7 154.5 7.9 Vir
 7 Apr 2024 12 14h20m22.80s -04 12' 25.2" 3.0759 2.1111 11.5 161.2 6.0 Vir
12 Apr 2024 12 14h09m46.39s -03 32' 46.9" 3.0108 2.0242 11.3 167.5 4.1 Vir
17 Apr 2024 12 13h58m08.27s -02 50' 30.9" 2.9451 1.9487 11.1 171.3 3.0 Vir
22 Apr 2024 12 13h45m36.43s -02 06' 24.7" 2.8787 1.8854 11.0 169.1 3.8 Vir
27 Apr 2024 12 13h32m22.06s -01 21' 28.8" 2.8118 1.8346 10.8 162.7 6.1 Vir
 2 May 2024 12 13h18m39.36s -00 36' 55.1" 2.7441 1.7964 10.7 155.2 8.9 Vir
 7 May 2024 12 13h04m44.86s +00 05' 56.6" 2.6757 1.7708 10.5 147.2 11.8 Vir
12 May 2024 12 12h50m56.23s +00 45' 47.5" 2.6066 1.7571 10.4 139.2 14.7 Vir
17 May 2024 12 12h37m30.22s +01 21' 30.1" 2.5367 1.7542 10.3 131.2 17.5 Vir
22 May 2024 12 12h24m41.04s +01 52' 15.5" 2.4661 1.7608 10.1 123.3 20.1 Vir
27 May 2024 12 12h12m39.73s +02 17' 33.7" 2.3946 1.7756 10.0 115.6 22.4 Vir
 1 Jun 2024 12 12h01m34.02s +02 37' 10.7" 2.3222 1.7969 9.9 108.2 24.5 Vir
 6 Jun 2024 12 11h51m28.55s +02 51' 05.3" 2.2490 1.8231 9.8 101.0 26.3 Vir
11 Jun 2024 12 11h42m24.93s +02 59' 28.1" 2.1748 1.8526 9.7 94.1 27.8 Vir
16 Jun 2024 12 11h34m21.96s +03 02' 39.0" 2.0995 1.8837 9.6 87.4 28.9 Leo
21 Jun 2024 12 11h27m16.60s +03 01' 02.7" 2.0233 1.9151 9.5 81.0 29.7 Leo
26 Jun 2024 12 11h21m04.71s +02 55' 03.9" 1.9459 1.9454 9.3 74.9 30.3 Leo
 1 Jul 2024 12 11h15m41.77s +02 45' 04.0" 1.8674 1.9735 9.2 69.0 30.5 Leo
 6 Jul 2024 12 11h11m02.96s +02 31' 21.7" 1.7876 1.9981 9.0 63.2 30.5 Leo
11 Jul 2024 12 11h07m03.04s +02 14' 15.0" 1.7065 2.0183 8.8 57.7 30.2 Leo
16 Jul 2024 12 11h03m36.58s +01 54' 00.8" 1.6240 2.0329 8.6 52.3 29.7 Leo
21 Jul 2024 12 11h00m38.28s +01 30' 53.3" 1.5401 2.0413 8.4 47.0 28.9 Leo
26 Jul 2024 12 10h58m03.16s +01 05' 02.9" 1.4547 2.0424 8.2 41.9 27.8 Leo
31 Jul 2024 12 10h55m46.54s +00 36' 35.6" 1.3676 2.0355 7.9 36.9 26.5 Leo
 5 Aug 2024 12 10h53m43.61s +00 05' 36.2" 1.2789 2.0197 7.6 32.1 24.9 Leo
10 Aug 2024 12 10h51m49.26s -00 27' 49.8" 1.1884 1.9939 7.2 27.3 23.1 Leo
15 Aug 2024 12 10h49m58.18s -01 03' 37.0" 1.0961 1.9572 6.9 22.8 21.0 Sex
20 Aug 2024 12 10h48m05.08s -01 41' 39.3" 1.0020 1.9085 6.4 18.5 18.7 Sex
25 Aug 2024 12 10h46m04.90s -02 21' 50.0" 0.9064 1.8463 5.9 14.8 16.5 Sex
30 Aug 2024 12 10h43m52.97s -03 03' 56.0" 0.8096 1.7688 5.3 12.1 15.1 Sex
 4 Sep 2024 12 10h41m26.10s -03 47' 25.8" 0.7124 1.6738 4.6 11.3 16.0 Sex
 9 Sep 2024 12 10h38m46.77s -04 31' 09.4" 0.6169 1.5579 3.9 12.7 21.1 Sex
14 Sep 2024 12 10h36m15.26s -05 12' 39.9" 0.5269 1.4172 3.0 15.9 31.4 Sex
19 Sep 2024 12 10h35m03.33s -05 46' 59.2" 0.4505 1.2472 2.0 19.5 48.2 Sex
24 Sep 2024 12 10h38m36.13s -06 05' 08.4" 0.4012 1.0473 1.1 22.4 72.6 Sex
29 Sep 2024 12 10h54m43.94s -05 54' 20.4" 0.3945 0.8301 0.6 22.5 104.0 Leo
 4 Oct 2024 12 11h36m49.77s -04 58' 30.2" 0.4329 0.6299 0.4 16.2 139.8 Leo
 9 Oct 2024 12 12h59m05.52s -02 53' 19.7" 0.5033 0.4973 0.5 3.5 172.9 Vir
14 Oct 2024 12 14h48m36.03s +00 03' 43.0" 0.5905 0.4812 1.1 23.9 136.8 Vir
19 Oct 2024 12 16h17m53.63s +02 12' 08.0" 0.6850 0.5738 2.2 41.8 104.2 Ser
24 Oct 2024 12 17h13m22.07s +03 12' 03.2" 0.7819 0.7224 3.2 51.2 82.7 Oph
29 Oct 2024 12 17h47m21.97s +03 37' 25.7" 0.8789 0.8915 4.2 55.3 68.3 Oph
 3 Nov 2024 12 18h09m48.90s +03 49' 01.6" 0.9749 1.0658 5.0 56.4 58.0 Oph
 8 Nov 2024 12 18h25m53.77s +03 55' 42.4" 1.0694 1.2391 5.8 56.0 50.2 Oph
13 Nov 2024 12 18h38m14.75s +04 01' 14.0" 1.1621 1.4086 6.4 54.7 44.0 Ser
18 Nov 2024 12 18h48m16.53s +04 07' 16.7" 1.2531 1.5732 7.0 52.8 38.9 Ser
23 Nov 2024 12 18h56m47.42s +04 14' 39.3" 1.3424 1.7320 7.5 50.6 34.6 Ser
28 Nov 2024 12 19h04m16.23s +04 23' 49.0" 1.4299 1.8848 7.9 48.2 30.9 Aql
 3 Dec 2024 12 19h11m00.66s +04 35' 00.5" 1.5158 2.0312 8.3 45.6 27.7 Aql
 8 Dec 2024 12 19h17m11.88s +04 48' 20.7" 1.6001 2.1710 8.7 43.1 24.9 Aql
13 Dec 2024 12 19h22m57.14s +05 03' 50.7" 1.6830 2.3041 9.1 40.6 22.4 Aql
18 Dec 2024 12 19h28m21.48s +05 21' 29.2" 1.7644 2.4304 9.4 38.1 20.1 Aql
23 Dec 2024 12 19h33m28.51s +05 41' 15.9" 1.8446 2.5498 9.7 35.8 18.2 Aql
28 Dec 2024 12 19h38m20.56s +06 03' 11.2" 1.9234 2.6623 10.0 33.7 16.5 Aql