Astronomy

Leo

A Quest for Galaxies Amongst the Stars of the Lion

Whilst Orion and Monoceros are constellations synonymous with the clear, frosty skies of winter, these are now starting to slip towards the eastern horizon in the evening. Replacing them is Leo the Lion, harbinger of spring and all things warm(ish) and flowery (and possibly bird flu).

After the striding figure of Orion, and the instantly recognisable Plough shape of Ursa Major, the sickle shape of Leo's mane is one of the northern skies most famous asterisms. The backward question mark is now high in the south eastern sky late in the evening, with the bright star Regulus shining at the bottom.

Leo's mythology dates back to Ancient Grecian times when he got himself tangled up in the twelve tasks of Hercules. Hercules, famous already for such might feats as impregnating all 50 of King Thespius' daughters in one night, was made by his jealous semi-Mother-Aunt-in-law Hera (wife and sister of Zeus who was father of Hercules through Queen Alcmene) to carry out 12 years of labour for King Eurystheus.

The Kings first request was for Hercules to slay a lion that had been terrorising the Nemeans. As proof of his victory Hercules was to bring back the lion's skin. The skin of the lion was impenetrable to all weapons and eventually Hercules had to wrestle the beast with his bare hands and only managed to kill it by thrusting his fist down its throat thus strangling the poor creature. Eventually, after some handy divine advice, Hercules used the lions own claw to skin it and returned triumphant to the king. The king, it is said, was so frightened by Hercules dressed in the skin of a lion that he hid in a bronze jar and would only communicate through a herald.

The fearsome lion was rewarded for his pains by a place in the heavens so that Hercules could pursue him for evermore into eternity.

Leo is also the name of the Metro-Goldwyn-Mayer lion who roars at the start of so many classic films.

Stellar Sights

Alpha Leonis, or Regulus, is the 21st brightest star in the sky (magnitude 1.23) and lies at the bottom of the sickle. A certain author named JK Rowling is creating mythology based on this star - the brother of Harry's godfather, Sirius, is called Regulus Black. It is a triple system with the two main stars an easy split in any scope. The companion star is much dimmer than the primary at magnitude 8 and is in itself a double, but this cannot be split with a small telescope.

Two stars up the sickle from Regulus can be found Algieba, or Gamma Leonis. This is a double star, with the two components more balanced in magnitude and showing rich gold colouring. This is also the radiant of the Leonids meteor shower which happens in November.

Two other interesting stellar targets are iota Leonis, a tight double which may be a challenge to split, and R Leonis, a variable red star that goes from magnitude 4.4 to magnitude 11.3 with a period of 312 days.

Gliese 436, a faint star in Leo about 33 light years away from the Sun, is orbited by one of the smallest extrasolar planets ever found.

Into the Deep

Because it lies away from the Milky Way, Leo lacks in the more usual deep sky features such as globular and open clusters. However, it more than makes up for this with the number of galaxies and galaxy groups that it holds. There aren't too many of these which are suitable for the small to medium telescope but I will highlight the best of the bunch.

The Leo I Group of Galaxies

The Leo I Group is a group of approximately 10 galaxies lying around 38 million light years away from us here in the Local Group.

The three main galaxies were all catalogued by Charles Messier and are designated M96, M95 and M105 in order of brightness.

At magnitude 9.2, M96 is the brightest galaxy in the group and is the one most easily seen under urban conditions. It was discovered by Pierre Méchain in 1781 and is a spiral (type Sb) galaxy with a bright central core like our own. Long exposure photography can bring out the delicate spiral arms but our own views will be limited to the bright fuzz of the core.

M95 is slightly dimmer than its close neighbour, but at magnitude 9.7 should still be visible in the scope. M95 is a barred spiral with nearly circular arms giving it a TIE Fighter sort of appearance.

M105 is, at magnitude 9.3, the brightest elliptical galaxy in the Leo I group of galaxies. For some reason it was not originally catalogued by Messier and was only put into the catalogue in 1947 by the delightfully named Helen Hogg. She was a Canadian astrophysicist interested in globular clusters who discovered a letter written by the Pierre Méchain describing the discoveries of many of the Galaxies in the Leo area including what was to become M105.

The Leo Triplett Group

Further down the Lion is another group of galaxies. The Leo Triplett or M66 group is located at a distance of about 35 million light years and may well be part of the same supercluster which includes the Leo I Group described above.

At magnitude 8.9 M66 (bottom right in the image) is the brightest member of the group. It is a spiral galaxy although encounters with its neighbours have left the spiral arms distorted. M65 (top right), another spiral galaxy is slightly dimmer at magnitude 9.3. The third member of the group, NGC 3628 (left), is a spiral galaxy albeit one which we see edge on. This will make it a more challenging target.

NGC 2903

Our final target is back near the sickle. NGC 2903 is one of the brightest non-Messier galaxies. It is fairly large and bright, located 20.5 million light years away and is a spiral galaxy seen at an oblique angle. With a visual magnitude of 8.9 and good surface brightness it is one of the few galaxies that can stand up to high magnifications thus allowing for slightly more detailed observation.

"Galaxies, they flood the street"

Although galaxies and galaxy clusters may not form the most stunning of sights in a small telescope it is important to remember what we are looking at and how far the light has had to travel to reach our eyes. All of the galaxies described in this article along with thousands of others, including the members of our own Local Group are a part of the Virgo Supercluster. This is then only part of a grouping of Superclusters which form one tiny clump of the visible universe. Enjoying the sight of a galaxy is to enjoy appreciating our own tiny place in the vast wonder of the universe which is out there.

Clear Skies

Nick Bramhall