The April Sky

Paul Curtin


Special Event this month: Viewers in northeastern Canada and parts of  Scandinavia will be able to see the moon pass in front of Mars on the evening of 12 April.

Few forms in the northern sky are as readily recognizable as that of  the Big Dipper. Its seven stars, roughly equal in color and magnitude, stand out sharply in the otherwise timid circumpolar region. The middle star of the handle, Mizar, is a fine double even in small telescopes. The Dipper, although distinct, does not comprise the whole of Ursa Major, however, and observers should take the time to learn
the fainter guide stars of this constellation as there are some wonderful objects awaiting the prepared eye.

Spring is a time of galaxies, and the great bear does not disappoint. M81 and 82 can be found by sweeping from alpha past 35 on a line towards 24. M108 hovers near beta, the nearby planetary nebula M 97, the Owl Nebula, comes as a bonus. In all, there are more than fifty galaxies in Ursa Major that can be captured in reasonably sized amateur telescopes. Patience, practice, dark skies and good star charts are all needed here.

Patience will also come in handy when searching for the form of Canes Venatici, a faint constellation south of the handle of the Big Dipper. The brightest star here is the double Cor Caroli. Use this star as the starting point to hop to the galaxies M94 and 63 (the Sunflower galaxy). M51, the Whirlpool galaxy, is on a line from Cor Caroli to eta Ursae Majoris at the end of the Dipper's handle. An initial sweep 
with binoculars may help you locate M51. In addition to a number of other interesting galaxies, Canes Venatici boasts one of the first globular clusters of the season, M3, in the extreme southeast of the constellation.

In dark skies the region to the east of Leo seems to shimmer like a diffuse cluster or an errant portion of the Milky Way. It is in fact the constellation Coma Berenices, a delightful area for binoculars as well as larger telescopes. The delicate star field centered on 12 Comae Berenices is in fact the open cluster Melotte 111. The southern portion of Coma hosts the galaxies M 64, 85, 88, 91, 98, 99, 100, as 
well as the globular cluster M53.

South of Coma is a form that resembles a “Y” tumbling headfirst to the west. This is the constellation Virgo. Its brightest star is Spica, which at first magnitude stands out starkly in this sector of the sky. The northwest part of Virgo contains a huge number of galaxies, twelve of them included in Messier's catalogue. See Kepple and Sanner or the Webb Society Handbooks for details and finder tips.

Riding on Hydra's back is the goblet shaped form of Crater. East of this is the small box shape of Corvus. Distinct as these little constellations are, they hold little of interest to the observer save a
handful of double stars and some faint galaxies.

Southern observers are treated to the superb star fields and dark clouds of Crux. Crux and Musca also contain a number of multiple stars 
worth seeking.

Planets in April

Mercury is difficult to find this month.

Venus is likewise a challenge to find for most of April.

Mars remains in Gemini this month.

Jupiter is still a morning object.

Saturn is in Leo. It is in the evening sky not far from Regulus.


Bibliography

Burnham, Robert Jr., Burnham's Celestial Handbook, New York: Dover, 1978.

Jones, K. G. (ed.), Webb Society Deep-Sky Observer's Handbook, Volume 4, Galaxies. Hillside, NJ: Enslow Publishers, 1981.

Kelly, P. (ed.), Observers Handbook 2007. Toronto: University of Toronto Press, 2006.

Kepple, G. R., Sanner, G. W., The Night Sky Ob servers Guide, Richmond, Virginia: Willman-Bell, 1999.

Tirion, W., Rappaport, B., Remaklus, W., Uranometria Deep Sky Atlas, Richmond, Virginia: Willman-Bell, 2000.

Webb, T. W., Celestial Objects for Common Telescopes, New York: Dover, 1962.