The July Sky

Paul Curtin

Event Alerts: On July 4th the long-lived storm system known as “The Great Red Spot” may collide with a smaller storm. Observers should start watching the red spot now so that post collision effects can be described. Drawings, photographs or measurements need to be carefully documented, and precise timing records should be kept. [Readers: Please send your reports on this event here. Editor.] Gupta has information on the timing of red spot transits. Observers in Europe can watch the moon occult Mars on July 27.

Northern summer is the season of the Milky Way, and thus a time of dense star clouds, bright and dark gaseous nebulae, planetary nebulae and a huge number of multiple and variable stars. We begin east of Hercules with the compact, distinct form of Lyra. Near Vega, the dazzling alpha Lyrae, we find the famous “double-double” of epsilon Lyrae. The first split can be made with binoculars; good conditions allow you to further split each of these stars with a small telescope. Nestled between the southern stars of the parallelogram of Lyra is M57, the Ring Nebula. This ghostly doughnut, although tricky to find due to its tiny apparent diameter, is a must see for observers. Take time to locate the globular cluster M56 by following the line formed by beta and gamma Lyrae to the east.

We will deal with Cygnus and Aquila next month. For now let us concentrate on the western edge of the Milky Way and head south to Serpens Cauda, the western half of Serpens, the only modern constellation with noncontiguous sections. Whereas the head of the serpent is solidly in the realm of galaxies, the tail is host to more local attractions. The most famous object in this region is M16, the Eagle Nebula. The interior of this nebula is perhaps best known from the series of photo taken by the Hubble Space Telescope. Its fingerlike structure is unmistakable. Apart from this object there are a number of globular clusters and star fields in this constellation. The star fields are reduced as a result of obscuring dust in our line of view.

Last month we discussed western Scorpius, July is a good time to become acquainted with the rest of this fascinating constellation. In addition to bright-red Antares, Scorpius boasts relatively bright stars, a distinct form, and a host of deep-sky objects and bright star clouds. The area around the stinger is one of my favorite fields in binoculars. Kepple and Sanner have finder charts for all the objects of interest. Don’t neglect the clusters near Antares, of which M4 is the most impressive.

Observers in the south get their best view of Ara, Triangulum Australe, Apus and Octans this month. Of these the most interesting is Triangulum A., which has a wide range of Milky Way objects. NGC 6025, an open cluster, is the most striking deep-sky object in this constellation.

The planets in July

Mercury is in the evening dusk at month’s end for southern observers.

Venus is in the early morning sky and might still be too low for most northern observers.

Mars begins to slip behind the sun and will be difficult to locate in the evening twilight.

Jupiter stands out clearly in the south. Keep watching the dance of its brightest satellites and get to know the atmospheric details prior to the clash of the cyclones predicted to occur July 4.

Saturn will be lost in evening glare for most observers this month.

Uranus and Neptune can be located midmonth as the moon passes just south of them. See Gupta for details


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.