COTM: Fornax

Steve Crouch

Given that its brightest star is only magnitude 4, Fornax could hardly be called a conspicuous constellation. It makes up for this, however, by having one of the best collections of galaxies in the sky with one of my principal deep sky references indicating something like 275 of magnitude 15 or brighter. Most of the brighter ones are concentrated in the Fornax galaxy cluster, which is easily found on the Fornax-Eridanus border just to the east of a prominent triangle of 4th magnitude stars, f,g and h Eridani. Included in the galaxies is the Fornax dwarf galaxy, the only one of these local group objects known to possess globular clusters, one of which can be viewed in 15cm. Fornax also has a bright planetary nebula and some interesting double stars which, as usual, come first.

Double Stars

Omega For (RA 02h 33.8m, Dec. -28 deg. 14') is a bright unequal double (5.0, 7.9, 10" separation). Alpha For (03 12.1, -28 59) is a similar somewhat more impressive object (4.0, 7.0, 4.2"). Both are easily split in small apertures.

Planetary Nebulae

Fornax has only one planetary, which is not all that surprising given its distance from the galactic plane. NGC 1360 (03 33.3, -25 51) is a fairly bright object that is visible in a large finder scope under a dark sky. The C11 shows it as a large bright oval haze, elongated NE-SW, with a prominent central star. An OIII filter brightens the nebulosity but does not increase its overall extent.

Galaxies

As stated before, Fornax has far too many galaxies for a column such as this to give a comprehensive treatment, so I will confine myself to identifying the highlights, with perhaps one or two challenging ones thrown in. ESO 356-G4 (02 39.9, -34 32) is the Fornax dwarf galaxy. At magnitude 7.5 it sounds as if it should be an easy object, but this is definitely not the case because the diameter of 20' means it has an extremely low surface brightness. If you have a rich field telescope with excellent high contrast optics and an extremely dark sky you might have a chance, but don't even think about it from within Canberra. The globular clusters associated with the Fornax dwarf are a different matter, however, and several are visible in amateur telescopes. The secret to observing these objects is to remember that they are small, and need a reasonable amount of magnification. The two brightest are NGC 1049 (02 39.7, -34 17) and ESO 356-SC08 (2 42.4, -34 06), both appearing as slightly nebulous stellar points at 127x.

The barred spiral NGC 1097 (02 46.3, -30 17) is, by contrast to the Fornax dwarf, one of the best galaxies in Fornax. In the C11, the central bar and the distinctly oval core are very prominent and I had some suspicion of the spiral arms as well. A satellite galaxy, NGC 1097A, is a bright hazy spot about 3.5' away.

The next galaxy that I picked, ESO 299-G020 (02 49.6, -38 46), is a far more difficult proposition at magnitude 13.8, but can still be seen without too many problems with some use of averted vision.

With NGC 1316 (03 22.7, -37 12) we enter the Fornax cluster. This galaxy is generally classified as the brightest member and is a quite featureless elliptical haze with NGC 1317 apparent 6'.5 to the north. The Fornax cluster is obviously a great area for galaxy hunting and I won't go into too much detail about it. A good place to start is to centre your telescope at approximately RA 3h 35m, -35d 40m dec. An eyepiece of one degree field at this position will show at least nine galaxies in a 15cm telescope (NGC 1374, 1379, 1380, 1381, 1387, 1399 and 1404). NGC 1381 is a rather good example of an edge-on galaxy.

Perhaps the finest galaxy in Fornax, NGC 1365 (03 33.6, -36 08), lies almost exactly 10o due south from NGC 1360. This barred spiral is not the brightest galaxy in the constellation, but is a particular favourite of mine because of the amount of structure visible in relatively small telescopes. The central bar and spiral arms are clearly seen under a dark sky in a 20 cm telescope and may be visible with even smaller apertures. This galaxy, in common with NGC 1316, is traditionally regarded as a member of the Fornax cluster, but it may in fact be a foreground object.