Stars over Sisters

Nearly overhead by nightfall in September, Vulpecula, the celestial fox, can be found directly south of Cygnus the swan. But because there are no bright stars in this constellation, locating it will be no easy feat.

The arrangement of dim stars that give Vulpecula its shape have an east-west orientation and, perhaps not surprisingly, bears absolutely no resemblance to the animal it's supposed to represent. The constellation's brightest star, Alpha Vulpeculae, is located about 4 degrees south of the famous double star Albireo in Cygnus.

Unlike most of the other 88 constellations that populate the celestial sphere, Vulpecula didn't come on the scene until fairly recently. It was the creation of astronomer Johannes Hevelius in the late seventeenth century. As a result, the constellation has no link to ancient mythology. It was originally known as Vulpecula et Anser (the little fox and the goose), and was illustrated with a goose in the jaws of a fox. Today, only the fox is recognized, but the goose is remembered by the name given to the star Alpha Vulpeculae, Anser.

Besides Cygnus, its neighbor to the north, Vulpecula is bordered to the west by Hercules, to the south by Sagitta and Delphinus, and to the east by Pegasus.

Although relatively small and inconspicuous, Vulpecula contains two well-known deep-sky objects.

The most prominent of these is M27, an object discovered by French astronomer Charles Messier in 1764.

M27 is one of the finest examples of a class of objects known as planetary nebulae, a label coined by the late eighteenth and early nineteenth century British astronomer William Herschel.

To Herschel these bodies resembled the ghostly appearance of the planet Uranus - which, by the way, he discovered in 1781.

By the mid-20th century, improvements in technology revealed that these bodies have nothing to do with planets at all, but instead are old, medium-to-low mass stars that have blown off their outer atmospheres into space, producing a spherical shell.

It is believed that as the sun nears the end of its life, it too will produce a planetary nebula.

M27, also known as the Dumbbell or Apple Core Nebula, is located at a distance of 1,360 light-years from Earth. The other object of interest in Vulpecula is an unusual grouping of stars called Brocchi's Cluster. In the 1920s Dalmero Francis Brocchi, amateur astronomer and chart-maker for the American Association of Variable Star Observers, created a map of this object for use in calibrating photometers. The cluster is also known as "the Coathanger" because of its distinctive star pattern when viewed with binoculars or at low power through a telescope. It is located in the southern part of Vulpecula, near the border of Sagitta.

At 7:29 p.m. PDT on September 22, the sun will stand directly above the earth's equator on its southward journey toward the Tropic of Capricorn (the winter solstice). This event is called the autumnal equinox and signals the start of the fall season in the Northern Hemisphere. At that time the earth's axis of rotation is tilted neither toward nor away from the sun, resulting in days and nights that are of nearly equal length at most locations.

Although Mercury will distance itself from the sun by a full 26 degrees on September 21, the speedy orb will languish in the sun's twilight, hovering just three degrees above the western horizon for most of the month.

During the past few months Mars has appeared west of Saturn in the evening sky. But in August the faster moving Red Planet caught up to Saturn and this month it lies east of the ringed planet, very near the reddish star Antares in Scorpius. Look for them in the southwest sky.

Jupiter and Venus are morning objects this month as both draw nearer the sun. Slow-plodding Jupiter rises at about 4 a.m. at the beginning of the month. Venus is closing in on the sun much more quickly, rising at 5 a.m. Both planets are very bright and easy to see.

A waxing moon moves through first quarter on September 2 on its way to becoming the Full Harvest Moon on September 8. Thereafter, the moon dims, fading to last quarter on September 15, darkening to new on September 23.

To learn more about the night sky, all are invited to attend the Stars over Sisters star watch on Saturday, September 27, at the Sisters Park & Recreation District building beginning at 7:30 p.m. Following a brief presentation, visitors will have the opportunity to view celestial objects through telescopes provided by members of the Sisters Astronomy Club. The event is free.