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On April 1st Michael Mattiazzo reported a probable comet in SWAN data with a position in Pegasus. I performed a search around the rough position on the morning of April 2 but didn’t find anything. Subsequently Qicheng Zhang found the comet in images he had taken using a 40mm refractor on April 2.51. This allowed Bill Gray to compute an ephemeris and Mattazzio then found a precovery image from March 30.22.
For now, this comet doesn’t have an official designation but you can get an ephemeris from here:
https://www.projectpluto.com/swan.htm
I imaged it this morning from Chelmsford in bright twilight as it cleared the roof of my house. Image attached.
Michael Jaeger reports a total magnitude of 10.0.
Attachments:
Nice coverage, Nick.
This is core Comet section work.
I see your astrometry (along with D15 and A71) extends the observational arc to about 7½ days.
Will it reach about 10th mag or similar?Richard
Thanks Richard. Tracking it down was a good team effort. It is currently on the PCCP but it is most definitely a comet!
It is well placed for us to follow from the UK. It is moving north but the elongation is decreasing as the Sun moves north too. The current orbit is based on astrometry from March 26 – April 3 and it may change a bit. The orbit is parabolic and the comet reaches perihelion on May 1 at a distance of 0.33 au. For us it moves slowly northwards in the morning sky, passing under the pole in late April and then becoming an evening object. It should brighten by a couple of magnitudes from where it is at the moment.
I imaged the comet from Chelmsford again this morning (April 6) and it was considerably brighter than yesterday. I get the following total magnitudes and coma diameters with comphot using a 51mm, f/4.9 refr. + ASI2600MC. Green channel vs Gaia G DR3:
2025 April 5.157 9.6 2.3′
2025 April 6.150 8.0 3.8′Transparency was probably a bit better this morning but conditions and time were similar.
Interesting behaviour so please observe this comet if you can and submit magnitude estimates. It is still on the PCCP so no official designation yet but there is now pre-discovery astrometry from Panstarrs going back to early September.
Will do. Was up this morning at 4am to observe, but there was a lot of cloud from the N to E. Of course it had all cleared by 9am…David
The ephemeris in the third post above is still pretty good but while the comet is on the PCCP you can get an ephemeris from:
https://www.minorplanetcenter.net/iau/NEO/pccp_tabular.html
Just select SWAN25F.
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