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July 2009 Celestial Calendar

Dave Mitsky

Note: All times in UTC (EST + 5)

A minor meteor shower, the Southern Delta Aquarids, takes place during the last week of the month.

The Moon is 8.2 days old and is located in Virgo on July 1 at 0:00 UT. The first-magnitude star Antares is occulted by the Moon twice this month, on July 4 and July 31. See http://www.lunar-occultations.com/iota/iotandx.htm for further information. A very minor penumbral lunar eclipse takes place on July 7. An occultation of M45 is visible from Europe on July 18. The Moon reaches its farthest apogee of 2009 on July 7 and its closest perigee of 2009 on July 21. The Moon is at its greatest northern declination of +26.5 degrees on July 19 and its greatest southern declination of -26.5 degrees on July 5. Longitudinal libration is at a maximum of +7.6 degrees on July 28 and a minimum of -7.5 degrees on July 15. Latitudinal libration is at a maximum of +6.9 degrees on July 28 and a minimum of -6.8 degrees on July 15. 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 in June are available at http://www.lunar-occultations.com/rlo/rays/rays.htm

The Sun is located in Gemini on July 1. The Earth is farthest from the Sun on July 3, when it is 3.3% more distant than it was at perihelion. On July 22, the longest solar eclipse of the century (6 minutes and 38.9 seconds) takes place in India, China, and a number of islands in the Pacific Ocean. It is the 37th member of saros number 136. For additional information on this eclipse, see http://eclipse.gsfc.nasa.gov/SEmono/TSE2009/TSE2009.html

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on July 1: Mercury (-1.0 magnitude, 5.7", 80% illuminated, 1.18 a.u., Taurus), Venus (-4.2 magnitude, 18.5", 62% illuminated, 0.90 a.u., Taurus), Mars (1.1 magnitude, 4.9", 92% illuminated, 1.89 a.u., Aries), Jupiter (-2.7 magnitude, 45.7", 99% illuminated, 4.31 a.u., Capricornus), Saturn (1.0 magnitude, 17.0", 100% illuminated, 9.77 a.u., Leo), Uranus (5.8 magnitude, 3.6", 100% illuminated, 19.62 a.u., Pisces), Neptune (7.8 magnitude, 2.3", 100% illuminated, 29.16 a.u., Capricornus), and Pluto (13.9 magnitude, 0.1", 100% illuminated, 30.74 a.u., Sagittarius).

On July evenings, Saturn is located in the west. At midnight, Jupiter is in the southeast and Uranus in the east. In the morning, Mercury lies in the northeast, Venus and Mars in the east, Jupiter in the southwest, and Uranus in the south.

On July 14, Mercury is in superior conjunction. It shines at magnitude -1.2 and is nine degrees from the Sun during the total solar eclipse on July 22. Mercury is barely visible a half hour after sunset just above the west-northwestern horizon during the last week of the month.

Venus rises at approximately 3:00 a.m. EDT at mid-month. The planet is very prominent this month, since Venus is heading northwards as the Sun travels in the opposite direction. Venus passes just eight arc minutes north of the third-magnitude star Epsilon Tauri in the northern section of the Hyades star cluster on July 13 and near the supernova remnant M1 (the Crab Nebula) on July 27. During July, Venus decreases in apparent size from 19 to 15 arc seconds and increases in phase from 62 to 73%.

Mars rises at 2:00 a.m. EDT in mid-July. The Red Planet leaves Aries and enters Taurus on July 2. Mars (magnitude 1.1) and Venus (magnitude -4.1) are about four degrees apart at the start of the month but that distance increases to sixteen degrees by the end of July. The two planets pass close to both the Pleiades and the Hyades during the course of the month. From July 17 to July 20, Mars, Venus, and the waning crescent Moon form picturesque groupings with the two bright open clusters.

Jupiter rises at 10:00 p.m. and transits the meridian at 3:00 a.m. EDT. It is located two degrees north of the third-magnitude star Delta Capricorni in eastern Capricornus. Jupiter's equator is almost edge-on with respect to the Sun and Earth currently, which means that mutual phenomena involving its major satellites can be observed. Ganymede almost entirely eclipses Io beginning at 4:27 a.m. EDT on July 8. On July 30, Io occults Europa for nine minutes starting at 11:21 p.m. EDT. An article on the summertime mutual events of the Galilean satellites appears on pages 50 and 51 of the July 2009 issue of Sky & Telescope. Click on http://www.skyandtelescope.com/observing/objects/planets/3304091.html?page=1&c=y to determine transit times 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

By the middle of July, Saturn sets at 11:00 p.m. EDT. By the end of the month, it's just fifteen degrees above the horizon an hour after sunset. The inclination of Saturn's rings decreases from 3.2 degrees on July 1 to 2.7 degrees on July 15. Saturn dims to an unusually low brightness of magnitude 1.1 this month. On July 31, the inclination is only 1.9 degrees. Saturn passes less than a third of a degree north of the fourth-magnitude star Sigma Leonis from July 25 to July 27. A shadow transit by Titan takes place on July 1 starting at 10:49 p.m. EDT. Saturn eclipses Titan at 11:58 p.m. EDT on July 9, an event that won't be visible from the East Coast. Another shadow transit by Titan occurs on July 17 at 10:00 p.m. EDT.

Uranus rises approximately one hour after Jupiter. The planet that William Herschel discovered in 1780 is located about six degrees southeast of the fourth-magnitude star Lambda Piscium in the Circlet of Pisces and only half a degree to the northwest of fifth-magnitude 20 Piscium.

Neptune and Jupiter undergo their second conjunction of the year. Neptune is 34 arc minutes north-northwest of Jupiter on July 9 and 37 arc minutes north of Jupiter on July 13. During this time, the fifth-magnitude star Mu Capricorni lies between the two planets.

Pluto is more difficult to locate than usual because it lies within a star-rich section of the Milky Way. The dwarf planet is located in the southwestern part of Sagittarius about four degrees northwest of the fourth-magnitude star Mu Sagittarii and is highest around midnight. A finder chart is available on page 53 of the June 2009 issue of Sky & Telescope.

The eight-magnitude periodic comet 22P/Kopff heads southeastward through Aquarius this month. Comet 2006/W3 (Christensen) is located in southeastern Cygnus. Browse http://www.aerith.net/comet/future-n.html for additional information on these comets.

During July, asteroid 1 Ceres travels southeastward through Leo and enters Virgo. At mid-month, it is located due south of the second-magnitude star Denebola. The ninth-magnitude dwarf planet passes less than half a degree to the south of fourth-magnitude star Omicron Virginis on July 28 and July 29. Asteroids 7 Iris (magnitude 8.7), 33 Polyhymnia (magnitude 10.2) , and 140 Siwa (magnitude 10.4) come to opposition this month.

Binary and Multiple Stars for July

Eta Draconis, 17 & 16 Draconis, Mu Draconis, Struve 2273, Nu-1 & Nu-2 Draconis, Psi Draconis (Draco); Kappa Herculis, Gamma Herculis, Struve 2063, 56 Herculis, Struve 2120, Alpha Herculis (Ras Algethi), Delta Herculis, Rho Herculis, Mu Herculis (Hercules); Rho Ophiuchi, Lambda Ophiuchi, 36 Ophiuchi, Omicron Ophiuchi, Burnham 126 (ADS 10405), Struve 2166, 53 Ophiuchi, 61 Ophiuchi (Ophiuchus); h5003 (Sagittarius); Xi Scorpii, Struve 1999, Beta Scorpii, Nu Scorpii, 12 Scorpii, Sigma Scorpii, Alpha Scorpii (Antares), h4926 (Scorpius); Struve 2007, 49 Serpentis, Struve 2031 (Serpens Caput); 53 Serpentis, Struve 2204, h4995, h2814 (Serpens Cauda); Epsilon Ursae Minoris (Ursa Minor)

Challenge binary star for July: 24 Ophiuchi

Challenge deep-sky object for July: NGC 6380 (Scorpius)

Top ten binocular deep-sky objects for July: IC 4665, LDN 1773, M4, M6, M7, M10, M12, M13, M92, NGC 6231

Top ten deep-sky objects for July: M4, M6, M7, M10, M12, M13, M92, NGC 6210, NGC 6231, NGC 6543

The objects listed above are located between 16:00 and 18:00 hours of right ascension.