Galaxies in Leo Minor

2015 March 22

Callum Potter

Leo Minor is another poorly observed constellation, which is a pity as it contains a large number of interesting galaxies. The Spring is a good time to view it, as it rides high in the sky, but it is another of these rather indistinct constellations without a good asterism, or any bright stars.

There are so many galaxies in the area that it’s difficult to choose some highlights. A good star atlas or charting programme will give plenty of targets. Amongst the brightest are NGC 3344 (mag 10), 3486 (mag 10), and 3504 (mag 11).

NGC 3395 and 3396 make up Arp 270, and there is an interesting grouping of galaxies around them – NGC 3413, 3423, and 3430, with 3442 nearby. Other interesting Arp Catalogue objects are Arp 107 (UGC 5984), Arp 162 (NGC 3414) and Arp 206 (NGC 3432) – and also Arp 21 and 267, which are rather faint.

Many of these galaxies are within range of medium telescopes under good conditions, though the fainter will need something large. There are interesting challenges for all in Leo Minor.

But perhaps the most famous object in Leo Minor, only discovered in 2007, is Hanny’s Voorwerp (‘Hanny’s Object’). Hanny Van Arkel, a school teacher in the Netherlands, discovered it while analysing images as part of the Galaxy Zoo project. It seemed to appear as a blue ‘blob’ in the foreground of the galaxy IC 2497. It does seem to be associated with IC 2497, and may be remnants of a galaxy which were illuminated by a quasar or active galactic nucleus inside it. Confusingly, however, the source of the illumination is nowhere to be seen.

Hanny’s Voorwerp is rather faint (around mag 19) and IC 2497 is itself only 16th magnitude. I am not aware of any observations of it from the UK – however, there are amateur images elsewhere, so it’s not impossible. Perhaps one of our members would like to take up the challenge!

Callum Potter, Director, Deep Sky Section