The April Sky

Paul Curtin

Noteworthy Events this Month

For observers in the northeastern U. S. and Canada, the crescent moon will pass in front of the Pleiades in the early evening hours of 1 April. (See Gupta for timings and locations.)

If you have never observed an occultation, this will be a fantastic first view. The sight of a single star blinking out gives new meaning
to the concept of ‘instantaneous.’ A string of Pleiades disappearing will be truly amazing.

In order to create a useful record of the occultation, one needs a reliable source of universal time. One method is to play a short-wave timekeeping station while verbally marking the disappearance and reappearance of the star. Record this on two (or more) tape machines to avoid the heartache of equipment malfunction. Record your latitude, longitude and altitude as accurately as possible.

The April Sky

The Milky Way is out of sight in the north this month. While our own galaxy hides, we have the opportunity to view huge clusters and superclusters of distant galaxies.

Galaxies are sprinkled from the bowl of the big dipper west and north to Camelopardalis and Ursa Minor. More galaxies lurk north of the handle near the border with Draco. South of this is Leo. To the east of the sickle that stands on bright Regulus is the triangle shape of eastern Leo. Among the many galaxies in this area look for M65 and M66 just south of the triangle.

Western Virgo is festooned with galaxies, the most famous of which is M104, the Sombrero, found on the Virgo/Corvus border. Kepple and Sanner have excellent finder charts for such objects. Virgo is shaped somewhat like a “Y” on its side, open to the northwest. The star at the nexus of the Y, gamma Virginis, is a beautiful double.

Corvus is a box-shaped constellation hovering over Hydra. Hydra meanders from the late January sky well into June. The segment that we see this month boasts both galaxies, of which M83 is the most prominent, as well as an impressive globular cluster, M68.

Southern observers can find the famed radio source Centaurus A, which is associated with the galaxy NGC 5128. A brighter object in this region is the globular cluster NGC 5139, so bright that it is also given a stellar designation, omega Centauri. Centaurus is an amazing constellation as it contains impressive objects of all classes. Galaxies in the north are replaced by globular, planetary, and open clusters as one sweeps south towards the Milky Way.

The Planets in April

Mercury can best be viewed by southern observers. It will hover between Aquarius and Pisces in the morning twilight.

Venus is also a morning object, moving swiftly from Capricornus into Aquarius by month’s end.

Mars still stands out on the Taurus/Gemini border. It is a nice naked-eye object in the west at dusk.

Jupiter is the morning planet this month. After a session observing Saturn, one can turn to Jupiter for a view of its satellites and cloud belts.

Saturn remains in Cancer. Now is the last chance for some time to view it in dark skies.

Bibliography

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

Gupta, R. (ed.), Observers Handbook 2006. Toronto: University of Toronto Press, 2005.

Kepple, G. R., Sanner, G. W., The Night Sky Observers 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.