Out-of-this-world series

Natural History, Oct, 1998 by Joe Roo

The Great Square of Pegasus, high in the south on October evenings, is a conspicuous landmark in the autumn sky. The constellation is also an excellent example of the extremes to which ancient astronomers went to find images of gods and monsters in random star patterns. For a modern stargazer, visualizing an upside-down half of a flying horse is a big stretch.

We can, however, project our own interests onto the same Great Square. What could be more timely for this World Series month than a celestial baseball field? The star Scheat can represent home plate; Alpheratz, first base; Algenib, second; and Markab, third. The pitcher can be represented either by fifth-magnitude Upsilon Pegasi ([Upsilon]) or by Tau Pegasi ([Tau]), which are both near the center of the square. Eta ([Eta]) can be the catcher.

An imaginative stargazer can visualize various plays, drafting stars from nearby Aries, Pisces, Aquarius, and Piscis Austrinus as outfielders. In the last constellation, for instance, the first-magnitude star Fomalhaut can be seen as a left-fielder chasing a long ball and running up against the foul pole (the western edge of the Great Square points almost exactly to that star). To complete the scene, Mu ([Mu]) and Lambda ([Lambda]--just southwest of Scheat) can be the manager and umpire.

The star Alpheratz is actually "borrowed" from Andromeda. Until the constellation boundaries were officially delineated in 1930, astronomers spoke of this star as being common to both patterns. Today, every star belongs to only one constellation.

The Sky in October

Mercury, which was at superior conjunction (beyond the Sun as seen from Earth) last month, is not visible to observers in most of the U.S.

Venus arrives at superior conjunction on October 30 and is not visible.

Mars, in Leo, rises near 3:30 A.M., EDT, and is high in the east as morning twilight begins. The planet makes a close approach to the star Regulus, less than one degree to the north, on the morning of October 7. Mars s yellow-orange color contrasts sharply with Regulus's brighter, blue-white light. A waning crescent Moon is near Mars on the morning of October 16.

Jupiter, in Aquarius, is prominent in the southeast at dusk and outshines every other point of light by at least one and a half magnitudes. It sets in the west between 3:30 A.M. and 5:30 A.M., EDT A waxing gibbous Moon is near Jupiter on the morning of October 4 and on Halloween night.

Saturn, rivaling the star Arcturus at-0.2 magnitude, is at its brightest since 1989. In addition, Saturn's distance from Earth is "only" 771 million miles, and its rings are tilted about 160 to our line of sight. These are very favorable conditions for viewing the golden-hued planet. The Moon--brilliant and just past full--is near Saturn on the evening of October 6. The planet reaches an excellent opposition on October 23, rising at sunset and setting at sunrise.

The Moon is full for the first time since the autumnal equinox. This "harvest Moon" occurs on October 5 at 4:11 P.M., EDT; last quarter comes on the 12th at 7:10 A.M., EDT; new Moon is on the 20th at 6:09 A.M., EDT; and first quarter is on the 28th at 6:46 A.M., EST.

Meteors shed by the Giacobini-Zinner comet may be visible in the northwest sky soon after sunset on October 8. Called the Giacobinids, they were seen by the thousands in 1933 and 1946 and by the hundreds in 1985. The comet is due to return to the Sun's vicinity later next month, but the odds are against your seeing more than a few "falling stars" per hour.

Move clocks back one hour on October 25, from daylight saving time to standard time.