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September 2009 Astronomical Calendar

Dave Mitsky

Note: All times in UTC (EST + 5)

The zodiacal light, or the false dawn, is visible about two hours before sunrise from a dark site during the latter part of September.

A minor meteor shower, the Alpha Aurigids (5 per hour), peaks on the morning of September 1.

The Moon is 11.6 days old and is located in Capricornus on September 1 at 0:00 UT. The Moon occults Mars on September 13 and the first-magnitude star Antares on September 24. Browse http://www.lunar-occultations.com/iota/ for additional information on these occultations. The Lunar X occurs on September 26 at approximately 358 degrees co-longitude and the Curtiss Cross on September 12 at approximately 194 degrees co-longitude. The Moon is at its greatest northern declination on September 12 (26.3 degrees) and its greatest southern declination on September 25 (-26.2 degrees). Longitudinal libration is at a maximum of 6.5 degrees on September 22 and a minimum of -5.5 degrees on September 9. Latitudinal libration is at a maximum of 6.6 degrees on September 21 and a minimum of -6.7 degrees on September 8. Visit http://www.astronomyblogs.com/member/saberscorpx/?xjMsgID=50821 for tips on spotting extreme crescent Moons. Times and dates for the lunar light rays predicted to occur this month are available at http://www.lunar-occultations.com/rlo/rays/rays.htm

The Sun is located in Leo on September 1.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on September 1: Mercury (0.4 magnitude, 8.3", 40% illuminated, 0.81 a.u., Virgo), Venus (-3.9 magnitude, 12.5", 83% illuminated, 1.33 a.u., Cancer), Mars (1.0 magnitude, 5.8", 89% illuminated, 1.60 a.u., Gemini), Jupiter (-2.8 magnitude, 48.4", 100% illuminated, 4.07 a.u., Capricornus), Saturn (1.1 magnitude, 16.0", 100% illuminated, 10.41 a.u., Leo), Uranus (5.7 magnitude, 3.7", 100% illuminated, 19.09 a.u., Pisces), Neptune (7.8 magnitude, 2.3", 100% illuminated, 29.14 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.56 a.u., Sagittarius)

This month Jupiter is located in the southeast and Uranus in the east during the evening. Jupiter and Uranus lie in the southern sky at midnight. Mercury, Venus, Mars, Saturn, and Uranus are in the east in the morning.

At month's end, Mercury is visible during morning twilight. This apparition favors observers in the southern hemisphere.

Venus rises at 4:00 a.m. EDT. Venus passes 1.5 degrees south of M44 on September 2 and 0.5 degree north of the first-magnitude star Regulus on September 20. Venus continues to increase in phase from 83% to 90% but decreases in apparent size from 13 arc minutes to 11 arc minutes during September.

Mars rises at 1:00 a.m. EDT. Mars passes 1.1 degrees north of the third-magnitude star Mu Geminorum on September 3 and 0.8 degree north of the fourth-magnitude star Delta Geminorum on September 25. The Red Planet forms a "red triangle" with the first-magnitude stars Aldebaran in Taurus and Betelgeuse in Orion in the early morning.

Jupiter decreases in apparent size by some 5% this month. The gas giant subtends 47 arc seconds, culminates at 10:48 p.m. EDT, and sets around 4:00 a.m. EDT on September 15. Jupiter is less than a third of a degree north of the fourth-magnitude star Iota Capricorni from September 20 to September 24. It may be possible to see Jupiter (magnitude -2.7) without optical aid during daylight on September 29 when it is about 3 degrees south of the gibbous Moon. None of Jupiter's four Galilean satellites are visible from 12:43 a.m. EDT to 2:29 a.m. EDT on September 3, a situation that won't occur again until 2019. E. E. Barnard discovered Jupiter's fifth satellite, Amalthea, using the 36-inch refractor at the Lick Observatory on September 9, 1892. Browse http://skyandtelescope.com/observing/objects/planets/article_107_1.asp to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://skytonight.com/observing/objects/javascript/3307071.html#

On September 4, Saturn's rings are edge-on as seen from Earth but the planet is only 11 degrees from the Sun at the time. Saturn is in conjunction with the Sun on September 17.

Uranus reaches opposition on the night of September 17 and can be seen without optical aid from a dark site. It lies to the west of the sixth-magnitude star 20 Piscium, about five degrees south of the fourth-magnitude star Lambda Piscium, the southeastern-most member of the Circlet of Pisces.

At the beginning of the September, Neptune is approximately 1.5 degrees east of the fifth-magnitude star 42 Capricorni. By the end of the month, Neptune has moved to within one degree of 42 Capricorni.

Finder charts for Uranus and Neptune appear on page 59 of the September 2009 issue of Sky & Telescope and are posted online at http://www.skyandtelescope.com/observing/highlights/41561382.html

The dwarf planet Pluto is located in the northwestern portion of Sagittarius. A finder chart is available on page 53 of the June 2009 issue of Sky & Telescope.

During September, the tenth-magnitude comet 22P/Kopff continues to pass southwestward through the constellation of Aquarius, passing a few degrees to the north of the large planetary nebula NGC 7293 (the Helix Nebula). Comet C/2006 W3 (Christensen) in Aquila is an even brighter target. Browse http://www.aerith.net/comet/future-n.html for additional information on these and other visible comets.

Asteroid 3 Juno, the tenth largest of the "minor planets", shines unusually bright at magnitude 7.7 when it reaches opposition on September 21. Other asteroids coming to opposition this month include 20 Massalia (magnitude 9.3), 42 Isis (magnitude 9.5), 44 Nysa (magnitude 10.3), 89 Julia (magnitude 9.3), and 106 Elektra (magnitude 11.0). Information on asteroid occultations of stars can be found at http://www.poyntsource.com/New/Global.htm

Binary and Multiple Stars for September

12 Aquarii, Struve 2809, Struve 2838 (Aquarius); Alpha Capricorni, Sigma Capricorni, Nu Capricorni, Beta Capricorni, Pi Capricorni, Rho Capricorni, Omicron Capricorni, h2973, h2975, Struve 2699, h2995, 24 Capricorni, Xi Capricorni, Epsilon Capricorni, 41 Capricorni, h3065 (Capricornus); Kappa Cephei, Struve 2751, Beta Cephei, Struve 2816, Struve 2819, Struve 2836, Otto Struve 451, Struve 2840, Struve 2873 (Cepheus); Otto Struve 394, 26 Cygni, h1470, h1471, Omicron Cygni, Struve 2657, 29 Cygni, 49 Cygni, 52 Cygni, 59 Cygni, 60 Cygni, 61 Cygni, Struve 2762 (Cygnus); Struve 2665, Struve 2673, Struve 2679, Kappa Delphini, Struve 2715, Struve 2718, Struve 2721, Struve 2722, Struve 2725 (in the same field as Gamma Delphini), Gamma Delphini, 13 Delphini, Struve 2730, 16 Delphini, Struve 2735, Struve 2736, Struve 2738 (Delphinus); 65 Draconis, Struve 2640 (Draco); Epsilon Equulei, Lambda Equulei, Struve 2765, Struve 2786, Struve 2793 (Equuleus); 1 Pegasi, Struve 2797, h1647, Struve 2804, Struve 3112, 3 Pegasi, 4 Pegasi, Kappa Pegasi, h947, Struve 2841, Struve 2848 (Pegasus); h1462, Struve 2653, Burnham 441, Struve 2655, Struve 2769 (Vulpecula)

Challenge binary star for September: 1 Delphini

Notable carbon star for September: LW Cygni

Top ten binocular deep-sky objects for September: IC 1396, LDN 906, M2, M15, M29, M30, M39, NGC 6939, NGC 6871, NGC 7000

Top ten deep-sky objects for September: IC 1396, M2, M15, M30, NGC 6888, NGC 6946, NGC 6960, NGC 6992, NGC 7000, NGC 7009

Challenge deep-sky object for September: Abell 78 (Cygnus)