Brian Jones: The Celestial Hare
Visible below the conspicuous constellation Orion, Lepus is a comparatively small but distinct pattern of stars seen over the southern horizon during the winter months. Part of the Orion group, containing the bright star Rigel, is shown here (see last month’s blog) and acts as a good pointer to Lepus, which can be difficult to make out if there is mist or street light glow over the horizon, so a pair of binoculars will be of help in your search.
The origins of Lepus are somewhat uncertain although the most popular story comes from Sicily. In early times there was a great deal of crop devastation wrought by the local hare population. The Greeks who inhabited the island placed the animal up in the sky quite close to the mighty hunter Orion, presumably so that he could keep their numbers under control! Arabic astronomers likened the group to a herd of thirst-slaking camels who were drinking from the nearby Milky Way whilst to the Egyptians the stars in Lepus represented the legendary Boat of Osiris, the powerful Egyptian god whose form was depicted by the nearby group of stars we now know as Orion.
The brightest star in Lepus is Arneb, a yellow-white object shining from a distance of around 900 light years. Arneb is very luminous, its actual brightness being around 6,000 times that of our own Sun. Slightly fainter than Arneb is Nihal, which is also a great deal closer to us, its light having taken only 115 years to reach our eyes. Nihal has a yellowish tint and a true luminosity of around 70 times that of our Sun. Although its actual brightness is considerably less than that or Arneb, it appears to be of roughly the same brightness simply because it is so much closer.
Gamma is another yellowish-white star and shines from a distance of only 29 light years. Gamma has a companion star with a distinctly orange tint which can be seen through a good pair of binoculars with a magnification of at least 12x, provided that you can hold them really steady. When seen together the pair form a pretty colour contrast.
Binoculars will also reveal the globular cluster M79, discovered by the French astronomer Pierre Francois Andre Mechain in 1780. It can be detected as a hazy star like object lying roughly on a line from Arneb, through Nihal, and projected for approximately the same distance again. Although visible in binoculars, strong moonlight or any horizon mist or glow will tend to hide it from view. A good dark viewing site will help you to track this cluster down.
There are two types of star cluster. Open (or galactic) clusters are relatively loose collections of stars with no distinctive shape. They can have up to several hundred members and are found along the main plane of our Milky Way Galaxy. Globular clusters, on the other hand, are found outside the Galaxy and, as their name suggests, are vast spherical collections of stars, and can contain many tens of thousands of individual members. M79 is quite a good example of a globular cluster, although from our latitude it is situated fairly low over the southern horizon and is not seen to its best effect.
Measurements have shown that M79 lies at a distance of around 50,000 light years. If the sky is really dark and clear, try to find it in binoculars, which will show it as a fuzzy star like object. If you do manage to pick it out then you can definitely give yourself a pat on the back!
Lepus the Hare is one of the most southerly star groups visible from our latitudes although it is well worth seeking out as it tries to escape the attentions of the mighty hunter Orion. Arm yourself with a warm coat, gloves and a pair of binoculars and watch out for the celestial hare skipping along the rooftops during the cold winter evenings. Happy stargazing!
