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 584 in Cetus

November 2018 - Galaxy of the Month

First discovered in 1785 by William Herschel, NGC 584 is an elliptical galaxy with a morphological classification of E4 in Cetus. It is accompanied by the spiral galaxy NGC 586, also discovered on the same night by William Herschel.

NGC 584 is also noted as IC 1712 as Barnard found it whilst observing the comet C/1888 R1 – one of his discoveries. He sent a note to Dreyer about it but then realised that it was NGC 584, which he neglected to tell Dreyer so the observation was added in as IC 1712.

Although NGC 584 is classified as an elliptical there is growing evidence that it may in fact be a lenticular, and in fact in the de Vaucouleurs Atlas of Galaxies (CUP) it is given as an example of an SA0-.

NGC 584 is part of a small group of about 8 galaxies catalogued as LGG 27 which also includes the galaxies NGC 586, NGC 596, NGC 600, NGC 615 and NGC 636. Most of the galaxies in this group are ellipticals or lenticulars. It is worth noting that other resources put the number of galaxies in the group as high as 11. William Herschel has the honour of discovering all the NGC galaxies in the group.

The group is only about 20 Mpc away from us and is spread quite widely across the sky with about 2 degrees separating NGC 584 and NGC 636. SIMBAD suggests NGC 584 is part of a pair of galaxies (one assumes with NGC 586). NED does not have this so I guess more work to be done, although NED does reference a paper which does suggest that NGC 586 is the companion. The pair are not obviously interacting. The NGC 584 group is also part of the Cetus II cloud.

Observationally, given that William Herschel found all these galaxies, they should not be that much of a challenge to find. NGC 584 itself is part of the Herschel 400 listing and O’Meara also has it has it as number 6 in his book of Hidden Treasures.

NGC 584, NGC 586, and NGC 596 should all fit in the same field of view of a modern hyperwide eyepiece at a medium power (say 160x). O’Meara suggests they are all visible in a 4” telescope, if you are at 7000’ up a mountain and in pristine skies. O’Meara also carries on the fashion of naming everything by calling NGC 584 the little spindle galaxy. Experienced galaxy observer Mark Stuart finds it only just visible with his 10” SkyWatcher from moderate skies in the UK.

For those who do not feel that NGC 584 is enough of a challenge then there are a number of other fainter galaxies in the area that will be a challenge for larger telescopes, including IC 127 and LEDA 1028168.

Owen Brazell - Galaxy Section Director