Lepus - The Celestial Bunny

After all, the presence of Orion and his two hunting dogs Canis Major and Canis Minor nearby do nothing for the little hare’s nerves. Though it must be admitted, Lepus has survived intact to now, whether through sheer luck or unreserved bravery.

Lepus is one of Ptolemy’s 48 constellations, Ptolemy relating Lepus as like Saturn and Mercury. It gives a quick wit, timidity, circumspection, fecundity and defiance. Lepus covers 290 sq° in area and holds 14 stars of 5th magnitude and brighter. The Germans called it Hase, the Portuguese Lebre, the Italians saw it as Lepre and the French as Lievre.

The Arabs imagined the four stars, alpha, beta, gamma and delta as the ‘Chair of the Giant’ or alternatively the ‘Throne of the Jauzah’, in reference to nearby Orion. Al Sufi, the prominent Persian astronomer of the tenth century, referred to these four bright stars as the ‘Thirst-slaking Camels’, apparently because of their position near the Celestial River, the Milky Way.

Early Egyptians related Lepus to the ‘Boat of Osiris’, Osiris being their great God and husband of Isis. He was one of the most widely worshipped deities in Egypt and was the ‘Judge of the Dead’ and the ‘King of the Underworld’.

The Chinese, with practicality though a distinct lack of imagination, called it simply a ‘Shed’.

Lepus has a number of interesting treasures well worth hunting down. There are a few double stars, a small compact globular cluster, the only one in the area, and the remarkable variable star R Leporis. Also included is the wonderful multiple star h3780, catalogued as open cluster NGC 2017 and a small, bright planetary nebula, IC 418.

Alpha Leporis, or Arneb, is the brightest star at magnitude 2.6 and lies near the centre of the constellation. It is a very luminous F0, yellow supergiant star lying 1280 (± 290) light years away. The luminosity is 12000 (± 5500) times that of our Sun. There is also an 11.2 magnitude companion nearby as well as one of magnitude 11.8.

Around 1.6° east of alpha lies the remarkable star group NGC 2017. There are six stars easily seen with two of these close doubles. The magnitudes range from 6.4 to 9.5 and one of 12.4. Hartung describes to these stars a range of colours including yellow, orange and blue.

Around 5° west and north of alpha lies the B9 subgiant star mu Leporis. Moving 33.5’ to the north and slightly west captures the almost face-on galaxy NGC 1832. It appears as a bright, round glow with a brighter central region.

North of mu Leporis, halfway along a line joining mu to Rigel in Orion, lies a small trapezium of early type stars, iota, kappa, nu and lambda. Two of these stars, iota and kappa have companions. Iota is a B8 dwarf star of magnitude 4.4 lying 241.1 (± 9.8) light years away. A dwarf companion of magnitude 9.9 lies 12.7" in PA 337°. The combined luminosity of this system is 75.4 (± 6.1) Suns.

Kappa, a B7 dwarf star, lies to the south of iota but is farther away at 559 (± 57) light years. There is a white B9 dwarf companion of magnitude 7.4 very close to the north.

Just 2° east and slightly north of lambda lies the lovely planetary nebula IC 418. At low power, it appears stellar in form. Boosting the power will show a bright oval and further magnification in a large aperture may show the central star and a bright outer ring. Lying around 1300 light years distant, it was discovered by Fleming in 1891.

Moving south once again, past alpha, we come to magnitude 2.8 Nihal or beta Leporis. Here we have a beautiful yellow G5 bright giant star and a close companion of magnitude 7.5 to the north. The magnitude difference, around 63 times, makes separation difficult in anything but steady atmospheric conditions. There are a further three companions of magnitude 12.0, 10.5 and 10.5 well separated.

Around 1.7° southeast of beta lies NGC 1964, an Sc type spiral galaxy. This faint and large glow has a much brighter stellar nucleus. As a guide, there are three stars, magnitude 10.2, 9.6 and 10.9, just north of the galaxy. A further star of magnitude 10.5 lies west of the galaxy's southern part.

Moving back to beta, we now swing 4.1° to the southeast to capture the yellow dwarf star gamma. This close relation to our Sun is an F7 star, slightly younger and therefore less evolved but still in the immediate neighbourhood. The distance is 29.25 (± 0.11) light years and the luminosity is 2.452 (± 0.019).

An added bonus for double star addicts is a companion of spectral type K2 V. This magnitude 6.1 orange dwarf is well separated from the primary and contrasts beautifully with yellow gamma. This pair lies in a field of many stars and is suitable for any size aperture. Sky Catalogue 2000 also lists another faint member at magnitude 10.9.

Nearby, 36.3’ to be exact, lies 41 Leporis. This G7 giant star of magnitude 5.4 has a companion of magnitude 6.6 close to the east. This companion is of spectral type A7 IV or perhaps A7 V. There is another star, of magnitude 9.1, well separated but this K0 type is an optical companion only.

Finally, I would like to have a look at arguably the best object in Lepus. On the border of Lepus and Eridanus resides the beautiful variable star R Leporis. Ranging from around 10th magnitude through to about 6th at maximum, it is a long period (444 days) red variable of the Mira type. First noticed by J.R. Hind in 1845, it is also commonly called ‘Hind's Crimson Star’. The intensity of this star's colour has captured the imagination of many an observer, notably Hind himself who found it to be:

"...of the most intense crimson, resembling a blood-drop on the background of the sky..."

However, this marvel must be seen before it glows at maximum where it appears a lot paler. Hipparcos measured this carbon star at 820 (± 170) light years distant and the luminosity at 31 (± 13) Suns.

So next time you are sweeping the familiar region of nearby Orion, hop on down to Lepus, the celestial bunny. I'm sure you will be pleasantly surprised.

Clear skies and good hunting.

~CosMos

Credits

Image: M79 copyright "National Optical Astronomy Observatory/Association of Universities for Research in Astronomy/National Science Foundation"