NGC 2648 in Cancer

February 2025 - Galaxy of the Month

This interactive image of the NGC 2648 in Cancer was provided by the Sloan Digital Sky Survey (SDSS) using Aladin Sky Atlas. We also have a finder chart should help you locate this galaxy, as will this link for NGC 2648 on the Stellarium Web planetarium.

Our object this month is the galaxy NGC 2648, also known as Arp 89, in Cancer. NGC 2648 was first discovered by William Herschel in 1784 and is paired with the galaxy PGC 24469, also known as MCG +02-22-006, which is a part of Arp 89. NGC 2468 is one of the brighter galaxies in Cancer, which however is not saying much! R.J. Mitchell observing with the 72” at Birr did actually find PGC 24469 in 1857 but it was not included in the final copy of Lord Rosse’s monograph and hence did not make it into the NGC. The full story can be found on Harold Corwin's website.

NGC 2468 and PGC 24469 are physically interacting. NGC 2648 is thought to be a retired galaxy, one in which star formation has ceased. The pair lie at about 112 million light-years from us. Arp classified it in his group Spiral galaxy with large high surface brightness companion on arm. If they are at this distance then the pair would be about 150,000 light-years across.

Both NGC 2648 and PGC 24469 shows signs of tidal interactions with one of the spiral arms of NGC 2468 being pulled towards its companion and tidal tails coming out of PGC 24469. PGC 24469 is also suggested to be a WR (Wolf-Rayet) galaxy which suggests a lot of star formation going on as it contains a lot of short lived massive Wolf-Rayet stars. The star formation could have been triggered by the interaction with NGC 2648. NGC 2648 although classified as a spiral shows no signs of star formation going on and its colours are rather yellow, not dissimilar to a lenticular however the pair are quite isolated and there is no nearby cluster for it to have formed in the usual way as a lenticular. Interestingly despite it appearing in Arp’s catalogue it did not make it into the original VV catalogue of interacting galaxies but was added in the extended version as VV 1239.

Steve Gottleib did not note the faint companion PGC 24469 when observing with his 17.5” but did see it as faint with the 24”. Victor van Wulfen suggested he saw both with his 14” in mountain skies. Perhaps surprisingly as an Arp object it does not appear in the The Night Sky Observer's Guide. Alvin Huey in his Arp Observing guide says that both galaxies were clearly seen at high power in his 22”.

Owen Brazell - Galaxy Section Director

If you'd like to try out the Clear Skies Observing Guides (CSOG), you can download observing guide for the current Galaxy of the Month without the need to register. CSOG are not associated with the Webb Deep-Sky Society but the work of Victor van Wulfen.