Galaxies Section

Welcome to the Galaxies Section of the Webb Deep-Sky Society. Our role is to promote visual observation and scientific imaging of galaxies by amateur astronomers.

Galaxy of the Month

Below is our current Galaxy of the Month. These are galaxies that we feel are particular worthy of your precious observing time. We have an archive of these articles that stretch back to the beginning of 2011. You can browse them, or search for specific objects and constellations in the Galaxy of the Month archives.

Your observations (sketches, images or observing notes) of any of these objects are very welcome.

Skytools users

There is a Skytools plan created for all the Galaxy of the Month pieces from 2011 onwards to make it easier to find the galaxies we have covered so far. These will be updated as new GOM’s are added.

February 2017 - Galaxy of the Month

NGC 3801 Group in Leo

This interactive image of the NGC 3801 group was provided by the Sloan Digital Sky Survey using Aladin Sky Atlas. We also have a finder chart should help you locate these galaxies.

Writing the galaxy of the month article is always a challenge, especially coming up with new targets so I am grateful this month for the suggestion from Andrew Robertson to have the small group of galaxies associated with NGC 3801 as the challenge.

The group has quite a chequered discovery history, and the usual naming challenges. The brightest galaxy in the group is NGC 3801 and it was discovered by William Herschel, along with NGC 3790. Even the NGC sleuths seem to disagree about who discovered NGC 3806. This could have been either William Herschel or, more probably, John Herschel.

Although NGC 3806 was bright enough to be seen by William at the time he was using his 18.7” reflector in Newtonian mode rather than in front view mode and Wolfgang Steinicke suggests the extra light loss may have contributed to him not seeing it.

Some confusion has also reined over NGC 3806 being numbered as NGC 3807 but this is actually a star seen by the team at Birr. They did however discover the other two galaxies in the field, NGC 3802 and NGC 3803. Some software, for instance Megastar 5, still plots NGC 3806 as NGC 3807.

The group is regarded as a physical system, or at least some of them are, and have been given the designation WBL 347, which lists 5 galaxies in the group. The group is also in the LGG catalogue as number 246, which lists 17 galaxies in the group, an interesting discrepancy. If this is true it would mean that this little group of galaxies covers over 3 degrees on the sky as the LGG survey also includes NGC 3800 and 3853 along with NGC 3768 as part of the group.

NGC 3801 is classified as a S0 (lenticular galaxy) but as the attached Hubble image shows it has some very strange dust clouds in it which would be unusual for a S0 galaxy including one at right angles to the main axis.

Hubble Space Telescope (HST) image of NGC3801 showing dust clouds
Hubble Space Telescope (HST) image of NGC3801 showing dust clouds. Courtesy the Hubble Legacy Archive (STScI/ST-ECF/CADC)

All of this suggests some form of interaction/merger, indeed in the UV NGC 3801 shows an intriguing S shape which suggests the merger hypothesis is the more likely. This is also borne out by looking closely at the SDSS image which shows evidence for shells or streams about the galaxy. It also has a radio jet and this is suggestive of an AGN.

The SkyTools chart attached also does not mark NGC 3803, it is the fuzzy galaxy above NGC 3802. It is regarded as too faint to mark at this scale.

Most of the galaxies here are regarded as lenticulars except for NGC 3806 which is a face on spiral.

Interestingly none of these galaxies appear in Night Sky Observers' Guide (NSOG) or other popular resources, although it is in the AL Galaxy groups and clusters list.

Owen Brazell - Galaxy Section Director

We've received some excellent observations of this group of galaxies already!