Galaxy of the Month in Ophiuchus

• NGC 6368 in Ophiuchus

  July 2024 - Galaxy of the Month

  I apologise that the GOM is going to be rather short this month as there is a shortage of galaxies in the twilit summer skies. Our challenge this month may also be tricky on account of its faintness.

  The galaxy NGC 6368 in Ophiuchus was missed by William Herschel and was discovered in 1863 by Albert Marth using William Lassell’s 48” speculum metal mirror telescope in Malta. Marth was a prolific observer of faint nebulae and discovered 583 new objects that made it into the NGC, along with one that made it into the IC.

  As an aside many years ago Alan Dowdell wrote a paper in the Webb Quarterly Journal about Marth’s observations, and at that time it was very difficult to get access to the original paper whereas now it is freely downloadable.

  NGC 6368 itself appears to be a nearly edge on spiral galaxy of type Sb lying at a distance of perhaps 32 Mpc. NGC 6368 appears to be an isolated field galaxy and as far as I can see not much research has been done on it. SIMBAD suggests that it may be a candidate for having an AGN. There are also suggestions that it may be part of an outlying galaxy filament of the Virgo cluster. NGC 6368 is a relatively small galaxy with a calculated diameter of only 49,000 light-years.

  NGC 6368 lies very near the border with Hercules so it does rise pretty high as seen from the UK, this may help when observing it. I note that it can be seen from the UK with 40cm but is not described as terribly impressive, although it is not clear under what circumstances that observation was made. My suspicion is that probably only the central part of the galaxy was seen. Perhaps unsurprisingly NGC 6368 does not feature in any of the standard observation guides so any observations of it are of interest.

  Owen Brazell - Galaxy Section Director

• NGC 6384 in Ophiuchus

  July 2022 - Galaxy of the Month

  I must admit that every summer I ask myself if it is worth doing a GOM for the months of June and July as it never gets dark in the northern latitudes of the UK, and this year (2022) even if it had got dark we seem to have had perennial cloud cover, except of course during the full moon period! However just to keep the sequence running I have chosen the galaxy NGC 6384 in the northern part of Ophiuchus as this month’s challenge.

  Much to my surprise Ophiuchus is littered with faint galaxies with maybe 9 from the NGC catalogue alone. NGC 6384 is a bright galaxy that was missed by William Herschel and was subsequently discovered by Marth in 1866 from Malta using William Lassell’s 48” speculum metal mirror telescope and then independently by d’Arrest and Stephan a few years later. Marth described it as pretty bright.

  The bright nuclear region, which is all that I suspect most people will see, is because the object is a LINER, a form of low luminosity AGN. It is regarded as a weakly barred system about 80 million light-years from us and was host to SN 1971L, which despite occurring in the spiral arms was probably a type Ia. It was also home to SN 2017drh. If it is at this distance then it is perhaps 150,000 light-years across, so slightly larger than our own Milky Way galaxy. NGC 6384 is regarded as probably very similar to what our Milky Way might look like. Hubble imaged the central core of this galaxy in 2011. NGC 6384 appears to be a field galaxy, not associated with any others. GALEX images in the UV part of the spectrum show that NGC 6384’s spiral arms are marked out by very active star forming regions which indicate that the galaxy is currently undergoing a lot of star formation. There is also a fine amateur image at the Capella Observatory.

  Luginbuhl & Skiff (L&S) suggest that NGC 6384 is barely visible in 15cm and shows as a faint patch in 25cm, remember however these observations were from a high dry site so don’t expect to see much with such a small telescope from the UK. The Night Sky Observer's Guide (NSOG) Vol. 2 has NGC 6384 covered as the only galaxy in Ophiuchus. It again suggests that 25cm telescopes should show the core and 40-50cm will show a faint haze surrounding a bright core but are not going to show any spiral structure. Steve Gottlieb notes that there is some structure in the outer haze as seen with his 24”. Observations from the UK with a 35cm suggest that it is not too impressive and only the core is seen. NGC 6384 also has an entry in The Cambridge Photographic Atlas of Galaxies.

  Owen Brazell - Galaxy Section Director