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June 2012 Celestial Calendar

Dave Mitsky

Note: All times in UTC (EST + 5)

Giovanni Cassini (1625-1712), Charles Messier (1730-1817), and George Ellery Hale (1868-1938) were born this month.

The normally very minor Boötid meteor shower peaks on the night of the First Quarter Moon, June 27.

The Moon is 11.0 days old and is located in Virgo on June 1 at 0:00 UT. Large tides will take place from June 3 through June 6. A partial lunar eclipse occurs from 9:59 to 12:06 UT on June 4. The Moon is at its greatest northern declination of +21.7 degrees on June 18 and its greatest southern declination of -21.7 degrees on June 4. Longitudinal libration is at a maximum of +7.3 degrees on June 9 and a minimum of -6.2 degrees on June 24. Latitudinal libration is at a maximum of +6.8 degrees on June 24 and a minimum of -6.9 degrees on June 10. See http://www.lunar-occultations.com/iota/iotandx.htm for information on lunar occultations. Visit http://saberdoesthestars.wordpress.com/2011/07/05/saber-does-the-stars/ 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 Taurus on June 1. The Sun reaches its farthest position north for the year on June 20, the longest day of the year in the northern hemisphere. There are 15 hours and one minute of daylight at latitude 40 degrees north.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on June 1: Mercury (magnitude -1.8, 5.2", 97% illuminated, 1.30 a.u., Taurus), Venus (magnitude -4.1, 57.0", 1% illuminated, 0.29 a.u., Taurus), Mars (magnitude 0.5, 7.9", 89% illuminated, 1.19 a.u., Aries), Jupiter (magnitude -2.0, 32.9", 100% illuminated, 5.98 a.u., Taurus), Saturn (magnitude 0.5, 18.4", 100% illuminated, 9.02 a.u., Virgo), Uranus (magnitude 5.9, 3.5", 100% illuminated, 20.52 a.u., Cetus), Neptune (magnitude 7.9, 2.3", 100% illuminated, 29.84 a.u., Aquarius), and Pluto (magnitude 14.0, 0.1", 100% illuminated, 31.34 a.u., Sagittarius).

Mercury is in the northwest, Mars is in the southwest, and Saturn is in the south in the evening sky. At midnight, Mars is located in the west and Saturn in the southwest. Venus and Jupiter can be found in the east and Uranus and Neptune in the southeast at dawn.

At midmonth, Mercury is visible during evening twilight, Venus rises at 5:00 a.m., Mars sets at 1:00 a.m., Jupiter rises at 4:00 a.m., and Saturn transits the meridian at 9:00 p.m. and sets at 3:00 a.m. local time for observers at latitude 40 degrees north.

Mercury reappears in the evening sky by the second week of the month. It's situated between Pollux and a waxing crescent Moon on the evening of June 21. The speediest planet reaches a greatest eastern elongation of 26 degrees on the night of June 30 (July 1 UT). At that time, Mercury is 42% illuminated, subtends 7.9 arc seconds, and shines at magnitude 0.4.

Venus is in inferior conjunction with the Sun on the evening of June 5. An extremely rare transit of the Sun by Venus, the last until 2117, takes place on that date. The transit lasts for 6 hours and 30 minutes but won't be visible in its entirety from the contiguous United States. First contact for North America occurs within two minutes of 22:05 UT (6:05 p.m. EDT). (The geocentric time is 22:10 UT.) Second contact takes place about 18 minutes later. At 1:30 UT geocentric time, Venus is 9.4 arc minutes from the center of the Sun. The geocentric time of third contact is 4:32 UT, with Venus exiting the solar disk 18 minutes later. Venus subtends 58 arc seconds, almost a full arc minute, and is 0.289 astronomical units or 2.4 light-minutes from the Earth at the time of the transit. Venus reappears in the dawn sky by the second half of June. On the morning of June 27, Venus is three degrees above Aldebaran and five degrees below Jupiter. By the end of the month, Venus has decreased in apparent size to 45 arc seconds, increased in illumination to 16%, and brightened to magnitude -4.6.

Mars travels eastward through Leo this month and enters Virgo on June 20. It passes just to the southeast of the fifth-magnitude binary star Chi Leonis on June 1 and southwest of the fourth-magnitude binary star Beta Virginis on June 27. Mars glows at magnitude 0.8 and subtends less than seven arc seconds by month's end.

Jupiter appears again in early June shortly before dawn. The waning crescent Moon passes just to the north of Jupiter on the morning of June 17. By the end of June, the King of the Planets is located approximately half-way between M45 (the Pleiades) and Aldebaran some two hours prior to sunrise. It shines at magnitude -2.0.

Saturn ends its retrograde motion on June 26, when it is less than five degrees to the north of Spica. The tilt angle of Saturn's rings is 12.5 degrees this month, which is the smallest angle for the year. Eighth-magnitude Titan is due south of Saturn on June 5 and June 21 and due north on June 13 and June 29. On the night of June 11, twelfth-magnitude Enceladus lies due west of Saturn and the tenth-magnitude moons Tethys, Dione, and Rhea are located to the west. Titan is situated about an arc minute to the northwest of Enceladus. For further information on Saturn's satellites, browse http://www.skyandtelescope.com/observing/objects/javascript/3308506.html

Uranus can be found in Cetus about 1.5 degrees to the east-northeast of the sixth-magnitude star 44 Piscium.

During June, Neptune is located approximately three degrees to the south-southeast of the fourth-magnitude star Theta Aquarii. The eighth planet begins retrograde motion on June 5.

Finder charts for Uranus and Neptune can be found at http://media.skyandtelescope.com/documents/Uranus-Neptune-2012.pdf

Pluto is two arc minutes south of the seventh-magnitude star SAO 161635 on June 17. The distant dwarf planet reaches opposition on June 29. A finder chart appears on pages 52 and 53 of the June issue of Sky & Telescope.

Comet C/2009P1 (Garradd) fades from tenth to eleventh magnitude as it travels southeastward through Cancer. It passes roughly parallel to the west of a line joining the fifth-magnitude stars Nu and Xi Cancri.

Asteroid 18 Melpomene shines at magnitude 9.8, as it heads westward through Scutum and into Serpens Cauda. Data on asteroid occultations taking place in June is available at http://www.asteroidoccultation.com/2012_06_si.htm

A free star map for June can be downloaded at http://www.skymaps.com/downloads.html

Binary and Multiple Stars for June

Struve 1812, Kappa Bootis, Otto Struve 279, Iota Bootis, Struve 1825, Struve 1835, Pi Bootis, Epsilon Bootis, Struve 1889, 39 Bootis, Xi Bootis, Struve 1910, Delta Bootis, Mu Bootis (Bootes); Struve 1803 (Canes Venatici); Struve 1932, Struve 1964, Zeta Coronae Borealis, Struve 1973, Otto Struve 302 (Corona Borealis); Struve 1927, Struve 1984, Struve 2054, Eta Draconis, 17-16 Draconis, 17 Draconis (Draco); 54 Hydrae (Hydra); Struve 1919, 5 Serpentis, 6 Serpentis, Struve 1950, Delta Serpentis, Otto Struve 300, Beta Serpentis, Struve 1985 (Serpens Caput); Struve 1831 (Ursa Major); Pi-1 Ursae Minoris (Ursa Minor); Struve 1802, Struve 1833, Phi Virginis (Virgo)

Notable carbon star for June: V Coronae Borealis

Top ten deep-sky objects for June: M5, M101, M102, NGC 5566, NGC 5585, NGC 5689, NGC 5746, NGC 5813, NGC 5838, NGC 5907

Top five deep-sky binocular objects for June: M5, M101, M102, NGC 5466, NGC 5907

Challenge deep-sky object for June: Abell 2065

The objects listed above are located between 14:00 and 16:00 hours of right ascension.