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June 2010 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 minor Boötid meteor shower peaks on the night of June 23 but is compromised by a gibbous Moon. A possibility exists that the Boötids may be more active than usual this year.

The Moon is 17.9 days old and is located in Capricornus on June 1 at 0:00 UT. A partial lunar eclipse favoring observers in the western part of North America takes place on the morning of June 26. Observers in the Pacific can see the entire eclipse, which belongs to Saros 120. At 7:38 a.m. EDT, 54% of the Moon will be covered by the umbra. The Moon is 17.9 days old and is located in Capricornus on June 1 at 0:00 UT. The Moon is at its greatest northern declination of +25.0 degrees on June 12 and its greatest southern declination of -25.0 degrees on June 25. Longitudinal libration is at a maximum of +5.5 degrees on June 23 and a minimum of -5.7 degrees on June 9. Latitudinal libration is at a maximum of +6.9 degrees on June 20 and a minimum of -6.8 degrees on June 7. 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 Taurus on June 1. It reaches its farthest position north for the year on June 21, the day of the summer solstice, 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 0.1, 7.3", 50% illuminated, 0.92 a.u., Aries), Venus (magnitude -3.9, 13.0", 81% illuminated, 1.29 a.u., Gemini), Mars (magnitude 1.1, 6.0", 90% illuminated, 1.56 a.u., Leo), Jupiter (magnitude -2.3, 37.9", 99% illuminated, 5.21 a.u., Pisces), Saturn (magnitude 1.0, 18.1", 100% illuminated, 9.17 a.u., Virgo), Uranus (magnitude 5.9, 3.4", 100% illuminated, 20.41 a.u., Pisces), Neptune (magnitude 7.9, 2.3", 100% illuminated, 29.79 a.u., Aquarius), and Pluto (magnitude 14.0, 0.1", 100% illuminated, 30.92 a.u., Sagittarius).

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

At midmonth, Mercury is visible during morning twilight, Venus sets at 11:00 p.m. EDT, Mars sets at 1:00 a.m. EDT, Jupiter rises at 2:00 a.m. EDT, and Saturn sets at 2:00 a.m. EDT for observers at latitude 40 degrees north.

Mercury increases in brightness from magnitude 0.1 to magnitude -0.6 during the first tens days of the month. However, dawns are long during June and Mercury will be difficult to locate with the naked eye. Observers in the southern hemisphere are favored during this month's morning apparition.

During June, Venus shines at magnitude -4.0 and attains its highest altitude after sunset for the year. Browse http://www.curtrenz.com/1024o.html to see a graphic created by Curt Renz that illustrates the position of Venus with respect to the horizon. On June 1, Venus, Mars, and Saturn form a nearly straight line spanning more than 70 degrees. The first-magnitude stars Castor and Pollux form a straight line some ten degrees in length with Venus on June 11. Venus enters Cancer on June 12 and glides past the third-magnitude open cluster M44 on the nights of June 19 and June 20.

Mars and Regulus are separated by less than two degrees on June 3. Mars is 50 arc minutes from Regulus on June 6. The separation is one degree the following night. Mars, Regulus, and the crescent Moon form a triangle on the night of June 16. By the end of June, Mars is 13 degrees from Regulus, sets before midnight, and subtends only five arc seconds.

Jupiter is 1.3 degrees south of the point of the vernal equinox on June 2. Jupiter is at western quadrature on June 23. Click on http://skyandtelescope.com/observing/objects/planets/article_107_1.asp 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

Saturn reaches eastern quadrature on June 19. Saturn's rings are inclined by 1.7 degrees in the early part of the month and by 2.1 degrees at the end of June (see the graphic at http://www.curtrenz.com/1024q.html). On the night of June 9, eighth-magnitude Titan and tenth-magnitude Rhea come within four arc minutes of each other. Saturn occults Rhea at 12:45 a.m. EDT and Titan at 2:40 a.m. EDT on June 10. Iapetus shines at twelfth-magnitude when it reaches greatest eastern elongation on June 16. For further information on Saturn's satellites, browse http://skytonight.com/observing/objects/javascript/3308506.html

Uranus and Jupiter are less than one degree apart during the first half of the month. The two gas giants are in conjunction in ecliptic longitude on June 8, when Uranus (magnitude 5.9) is just 26 arc minutes north of Jupiter (magnitude -2.3). Uranus and Jupiter remain less than half a degree apart through June 10. Uranus is at western quadrature on June 22.

Neptune is located approximately half-way between the fifth-magnitude stars Mu Capricorni and 38 Aquarii, nearly the same position it was at 164 years ago when the German astronomer Johann Galle discovered the planet. Retrograde motion commences on June 1.

Finder charts for Uranus and Neptune are posted at http://media.skyandtelescope.com/documents/Uranus_Neptune_2010.pdf

Pluto reaches opposition on June 25. This month the dwarf planet travels through M24 (the Small Sagittarius Star Cloud) in northwestern Sagittarius. A finder chart is available at http://www.skyandtelescope.com/skytel/beyondthepage/89002802.html

Comet C/2009 R1 (McNaught) may be visible to the naked-eye as it travels northeastward through Perseus and into Auriga this month. On the morning of June 5, the comet crosses just north of the large, fifth-magnitude open cluster NGC 752. The next two mornings finds it within two degrees of the colorful, second-magnitude binary star Gamma Andromedae. On June 8, the comet passes close to the tenth-magnitude, edge-on spiral galaxy NGC 891. Comet McNaught is approximately one degree north of the fifth-magnitude open cluster M34 on June 10. It passes just south of the third-magnitude star Delta Persei on June 15 and north of the first-magnitude star Capella (Alpha Aurigae) on June 21. Browse http://www.aerith.net/comet/future-n.html for additional information on this comet.

Asteroid 1 Ceres takes a southwestward course through Sagittarius this month. The dwarf planet passes just south of the bright emission nebula M8 in early June. Ceres reaches opposition on June 18. This month, asteroid 4 Vesta heads southeastward through the central portion of Leo. The 515-kilometer-wide minor planet shines at magnitude 7.7 as it passes between two seventh-magnitude stars in Leo on the nights of June 2 and June 3.

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)

Challenge binary star for June: Gamma Coronae Borealis

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