Post by Dave Mitsky on May 1, 2016 3:44:58 GMT
May Celestial Calendar by Dave Mitsky
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
5/1 May Day or Beltane, a cross-quarter day
5/2 Neptune is 1.6 degrees south-southeast of the Moon at 11:00; asteroid 18 Melpomene is 1.4 degrees north-northwest of the Moon at 12:00
5/3 The Moon is at the descending node at 1:28
5/5 Uranus is 2.1 degrees north-northwest of the Moon at 4:00; the peak of the Eta Aquarid meteor shower (20 per hour for northern observers) occurs at 20:00
5/6 The Moon is at perigee, subtending 33' 23'' from a distance of 357,827 kilometers (222,344 miles), at 4:00; New Moon (lunation 1155) occurs at 19:30
5/7 A double Galilean satellite shadow transit begins at 4:39
5/8 The Moon is 0.47 degree north-northwest of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation occurring in Japan, China, Russia, the Middle East, southern Europe, and northern and northeastern Africa, at 9:00
5/9 Mercury is at the descending node at 8:00; Mercury begins to transit the Sun at 11:12; Mercury is in inferior conjunction at 15:00; the Moon is 5.9 degrees south of the bright open star cluster M35 in Gemini at 21:00; Jupiter is stationary in right ascension at 23:00
5/12 The Moon is 4.7 degrees south of the bright open star cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 12:00
5/13 First Quarter Moon occurs at 17:02; Mercury is 0.38 degree south-southeast of Venus at 18:00; the Sun enters the constellation of Taurus at 19:00
5/14 The Lunar X (also known as the Werner or Purbach Cross), an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to begin at 1:02; the Moon is 2.2 degrees south-southwest of the first-magnitude star Regulus (Alpha Leonis) at 6:00
5/15 Jupiter is 1.9 degrees north-northeast of the Moon at 8:00; the Moon is at the ascending node at 20:41
5/18 The Moon is 4.9 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 18:00; the Moon is at apogee, subtending 29' 26'' from a distance of 405,933 kilometers (252,235 miles), at 22:00
5/19 Mercury is at aphelion (0.4667 astronomical units from the Sun) at 17:00
5/21 Full Moon, known as the Milk or Planting Moon, occurs at 21:14; Mercury is stationary in right ascension at 22:00; Mars is 5.9 degrees south of the Moon at 22:00
5/22 Mars (apparent size 18.4'', magnitude -2.05) is at opposition at 11:17; the Moon is 9.5 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 14:00; Saturn is 3.2 degrees south of the Moon at 22:00
5/23 Asteroid 4 Vesta is in conjunction with the Sun at 19:00
5/24 Venus is 4.6 degrees south-southeast of the bright open star cluster M45 (the Pleiades or Subaru) in Taurus at 16:00
5/25 Pluto is 3.0 degrees north of the Moon at 15:00
5/29 Last Quarter Moon occurs at 12:12; asteroid 7 Iris (magnitude +9.2) is at opposition at 18:00; Neptune is 1.4 degrees south-southeast of the Moon at 18:00
5/30 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to begin at 4:10; the Moon is at the descending node at 4:46; asteroid 18 Melpomene is 1.4 degrees north-northwest of the Moon at 21:00; Mars is closest to the Earth (75,280,000 kilometers or 46,777,000 miles) at 21:34
Nicolas Lacaille (1713-1762) and Joseph Lockyer (1836-1920) were born this month.
Nereid, Neptune’s third-largest satellite, was discovered on May 1, 1949 by Gerard Kuiper.
The peak of the Eta Aquarid meteor shower on the afternoon of May 5th occurs near New Moon so meteor watching should be almost equally good on the mornings of May 5th and May 6th. Southern hemisphere observers are favored. Eta Aquarid meteors are debris from the famous periodic comet 1P/Halley.
Information on Iridium flares and passes of the ISS, the Tiangong-1, the USAF’s X-37B, the HST, and other satellites can be found at www.heavens-above.com/
The Moon is 23.5 days old, is illuminated 40.9%, subtends 31.2 arc minutes, and is located in Capricornus on May 1st at 0:00 UT. The Moon occults Uranus from western and central Africa and central South America on May 15th. The Moon is at its greatest northern declination on May 10th (+18.4 degrees). The Moon is at its greatest its greatest southern declination on May 24th (-18.4 degrees). Longitudinal libration is at maximum (+7.5 degrees) on May 12th and at minimum (-6.4 degrees) on May 28th. Latitudinal libration is at maximum (+6.6 degrees) on May 9th and at minimum (-6.6 degrees) on May 23rd. New Moon occurs on May 6th. Large tides will take place on May 6h through May 9th. The Moon occults the fourth-magnitude star Theta Virginis for North American observers on the night of May 17th-May 18th. Consult www.lunar-occultations.com/iota/bstar/0518zc1891.htm for more on this event. The Full Moon forms a rectangle with Mars, Saturn, and Antares on the night of May 21st. Visit 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 www.lunar-occultations.com/rlo/rays/rays.htm
The Sun is located in Aries on May 1st.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on May 1st: Mercury (magnitude +3.0, 10.8", 7% illuminated, 0.63 a.u., Aries), Venus (magnitude -3.9, 9.8", 99% illuminated, 1.70 a.u., Aries), Mars (magnitude -1.5, 16.1", 98% illuminated, 0.58 a.u., Scorpius), Jupiter (magnitude -2.3, 40.8", 99% illuminated, 4.83 a.u., Leo), Saturn (magnitude +0.2, 18.1", 100% illuminated, 9.18 a.u., Ophiuchus), Uranus on May 16th (magnitude +5.9, 3.4", 100% illuminated, 20.80 a.u., Pisces), Neptune on May 16th (magnitude +7.9, 2.3", 100% illuminated, 30.22 a.u., Aquarius), and Pluto on May 16th (magnitude +14.2, 0.1", 100% illuminated, 32.46 a.u., Sagittarius).
In the evening, Mars is in the southeast and Jupiter in the south. Mars is located in the southeast, Jupiter in the west, and Saturn in the southeast at midnight. Mercury can be seen in the east, Mars in the southwest, Saturn in the southwest, Uranus in the east, and Neptune in the southeast at dawn.
At midmonth, Mercury is visible in morning twilight, Mars is visible for the entire night, Jupiter transits the meridian at 8:00 p.m. and sets at 3:00 a.m. local daylight time, and Saturn rises at 9:00 p.m. and transits the meridian at 2:00 a.m. local daylight time for observers at latitude 40 degrees north.
Mercury transits the Sun on May 9th. This relatively rare event, the first one since 2006, is visible in its entirety from eastern North and South America, the Atlantic Ocean, and western Europe. At least part of the transit can be seen from most of the world. Telescopes equipped with proper solar filters and working at magnifications of 50 to 100x will provide the best views of tiny Mercury (apparent size 12 arc seconds) during the transit. First contact takes place geocentrically at 11:12:19 UT (7:12:19 EDT), greatest transit (when Mercury passes closest - 319 arc seconds - to the center of the Sun) at 14:57:26 UT (10:57:26 EDT), and fourth (final) contact at 18:42:26 UT (2:42:26 EDT). For more on the transit, see eclipsewise.com/oh/tm2016.html or pages 62 and 63 of the May issue of Astronomy and pages 48 and 49 of the May issue of Sky & Telescope. Inferior conjunction takes place on May 9th and aphelion on May 19th.
Venus is not observable this month.
The apparent brightness of Mars exceeds magnitude -1.50 on May 1st. Mars rises around 10:00 p.m. local daylight time on that date. It passes 1.2 degrees north of the globular cluster M80 on May 6th and 1.0 degree north of the second-magnitude star Delta Scorpii on May 19th. By May 19th, Mars exceeds magnitude -2.00. The best Martian opposition in eleven years takes place on May 22nd. Mars subtends 18.4 arc seconds and shines at magnitude -2.05 on that date and reaches a maximum brightness of magnitude -2.06 the next day. The Martian north pole is inclined 12 degrees toward the Earth at opposition. Since it is late summer on Mars, the southern polar cap may be more visible than the northern one. On May 28th, the Red Planet leaves Scorpius and enters Libra as it progresses on its retrograde opposition loop. When it makes its closest approach to the Earth (0.50321 astronomical units or 4.19 light-minutes) on May 30th, Mars subtends 18.6 arc seconds and is 21 degrees south of the celestial equator. An article on observing Mars appears on pages 58 and 59 of the May issue of Astronomy. Martian surface features can be identified using the map posted at www.bluewaterastronomy.info/resources/MapsCharts/Mars-map-ALPO_color.jpg or the Sky & Telescope Mars Profiler at www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Jupiter decreases in brightness from magnitude -2.3 to magnitude -2.1 and shrinks in angular diameter from 40.8 arc seconds to 37.4 arc seconds during May. Jupiter sets around 4:00 a.m. local daylight time on May 1st and 2:00 a.m. local daylight time on May 31st. A double Galilean satellite shadow transit involving Callisto and Io occurs on May 7th. Jupiter completes its retrograde loop on May 9th and begins to move eastward through southern Leo. The waxing gibbous Moon passes 1.9 degrees south of Jupiter on May 15th. Browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/ or www.projectpluto.com/jeve_grs.htm in order to determine transit times of Jupiter’s central meridian by the Great Red Spot (GRS). GRS transit information also appears on page 50 of the May issue of Sky & Telescope. Data on the Galilean satellite events is available at www.skyandtelescope.com/observing/interactive-sky-watching-tools/ and www.projectpluto.com/jevent.htm
At mid-month, Saturn shines at magnitude +0.1 and has an apparent equatorial diameter of 18.3 arc seconds. Its rings are inclined by 26 degrees and subtend 41.6 arc seconds. Eighth-magnitude Titan is positioned north of the planet on May 5th and May 21st and south of it on May 13th and May 29th. Saturn’s variably bright moon Iapetus passes two arc minutes south of Saturn on May 31st-June 1st. For further information on Saturn’s satellites, browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Uranus is lost in morning twilight until late May.
Neptune lies within one half of a degree of the fourth-magnitude star Lambda Aquarii this month.
Pluto lies in northern Sagittarius and transits the meridian before dawn.
For more on the planets and how to locate them, browse www.nakedeyeplanets.com/
Comet C/2013 X1 (PanSTARRS) travels southwestward through Aquarius during May. It can be seen low in the east before dawn. The periodic comet 9P/Tempel heads southeastward through Leo. It lies about one degree southwest of the second-magnitude star Denebola on May 21st. Visit cometchasing.skyhound.com/ and www.aerith.net/comet/weekly/current.html for information on comets visible this month.
Asteroid 6 Hebe (magnitude +10.5) glides southeastward through Leo this month. It passes just southeast of the twelfth-magnitude spiral galaxy NGC 3801 on May 1st and very close to Comet 9P/Tempel on May 11th. By the end of May, 6 Hebe is about two degrees northwest of Denebola. Some of the brighter asteroids reaching opposition this month include 23 Thalia (magnitude +10.4) on May 22th, 432 Pythia (magnitude +10.9) on May 26th, 7 Iris (magnitude +9.2) on May 29th, and 516 Amherstia (magnitude +10.6) on May 31th. Information on asteroid occultations taking place this month is available at www.asteroidoccultation.com/2016_05_si.htm
A wealth of current information on solar system celestial bodies is posted at www.curtrenz.com/astronomy.html and nineplanets.org/
A free star map for May can be downloaded at www.skymaps.com/downloads.html and www.telescope.com/content.jsp?pageName=Monthly-Star-Chart
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from 2.1 to 3.4, on May 3rd, 6th, 9th, 12th, 15th, 18th, 20th, 23rd, 26th, and 29th. For more on Algol, see stars.astro.illinois.edu/sow/Algol.html and www.solstation.com/stars2/algol3.htm
Eighty binary and multiple stars for May: 1 Bootis, Struve 1782, Tau Bootis, Struve 1785, Struve 1812 (Bootes); 2 Canum Venaticorum, Struve 1624, Struve 1632, Struve 1642, Struve 1645, 7 Canum Venaticorum, Alpha Canum Venaticorum (Cor Caroli), h2639, Struve 1723, 17 Canum Venaticorum, Otto Struve 261, Struve 1730, Struve 1555, h1234, 25 Canum Venaticorum, Struve 1769, Struve 1783, h1244 (Canes Venatici); 2 Comae Berenices, Struve 1615, Otto Struve 245, Struve 1633, 12 Comae Berenices, Struve 1639, 24 Comae Berenices, Otto Struve 253, Struve 1678, 30 Comae Berenices, Struve 1684, Struve 1685, 35 Comae Berenices, Burnham 112, h220, Struve 1722, Beta Comae Berenices, Burnham 800, Otto Struve 266, Struve 1748 (Coma Berenices); h4481, h4489, Struve 1604, Delta Corvi, Burnham 28, h1218, Struve 1669 (Corvus); H N 69, h4556 (Hydra); Otto Struve 244, Struve 1600, Struve 1695, Zeta Ursae Majoris (Mizar), Struve 1770, Struve 1795, Struve 1831 (Ursa Major); Struve 1616, Struve 1627, 17 Virginis, Struve 1648, Struve 1658, Struve 1677, Struve 1682, Struve 1689, Struve 1690, 44 Virginis, Struve 1719, Theta Virginis, 54 Virginis, Struve 1738, Struve 1740, Struve 1751, 81 Virginis, Struve 1764, Struve 1775, 84 Virginis, Struve 1788 (Virgo)
Notable carbon star for May: SS Virginis
One hundred and sixty-five deep-sky objects for May: NGC 5248 (Bootes); M3, M51, M63, M94, M106, NGC 4111, NGC 4138, NGC 4143, NGC 4151, NGC 4214, NGC 4217, NGC 4244, NGC 4346, NGC 4369, NGC 4449, NGC 4485, NGC 4490, NGC 4618, NGC 4631, NGC 4656, NGC 4868, NGC 5005, NGC 5033, NGC 5297, NGC 5353, NGC 5354, Up 1 (Canes Venatici); Mel 111, M53, M64, M85, M88, M91, M98, M99, M100, NGC 4064, NGC 4150, NGC 4203, NGC 4212, NGC 4251, NGC 4274, NGC 4278, NGC 4293, NGC 4298, NGC 4302, NGC 4314, NGC 4350, NGC 4414, NGC 4419, NGC 4448, NGC 4450, NGC 4459, NGC 4473, NGC 4474, NGC 4494, NGC 4559, NGC 4565, NGC 4651, NGC 4689, NGC 4710, NGC 4725, NGC 4874, NGC 5053 (Coma Berenices); NGC 4027, NGC 4038-9, NGC 4361 (Corvus); M68, M83, NGC 4105, NGC 4106, NGC 5061, NGC 5101, NGC 5135 (Hydra); M40, NGC 4036, NGC 4041, NGC 4051, NGC 4062, NGC 4085, NGC 4088, NGC 4096, NGC 4100, NGC 4144, NGC 4157, NGC 4605, NGC 5308, NGC 5322 (Ursa Major); M49, M58, M59, M60, M61, M84, M86, M87, M89, M90, M104, NGC 4030, NGC 4073, NGC 4168, NGC 4179, NGC 4206, NGC 4215, NGC 4216, NGC 4224, NGC 4235, NGC 4260, NGC 4261, NGC 4267, NGC 4281, NGC 4339, NGC 4343, NGC 4365, NGC 4371, NGC 4378, NGC 4380, NGC 4387, NGC 4388, NGC 4402, NGC 4429, NGC 4435, NGC 4438, NGC 4517, NGC 4526, NGC 4535, NGC 4536, NGC 4546, NGC 4550, NGC 4551, NGC 4567, NGC 4568, NGC 4570, NGC 4593, NGC 4596, NGC 4636, NGC 4638, NGC 4639, NGC 4643, NGC 4654, NGC 4666, NGC 4697, NGC 4698, NGC 4699, NGC 4753, NGC 4754, NGC 4760, NGC 4762, NGC 4866, NGC 4900, NGC 4958, NGC 5044, NGC 5054, NGC 5068, NGC 5077, NGC 5084, NGC 5087, NGC 5147, NGC 5170, NGC 5247, NGC 5363, NGC 5364 (Virgo)
Top ten deep-sky objects for May: M3, M51, M63, M64, M83, M87, M104, M106, NGC 4449, NGC 4565
Top ten deep-sky binocular objects for May: M3, M51, M63, M64, M84, M86, M87, M104, M106, Mel 111
Challenge deep-sky object for May: 3C 273 (Virgo)
The objects listed above are located between 12:00 and 14:00 hours of right ascension.
All times, unless otherwise noted, are UT (subtract four hours and, when appropriate, one calendar day for EDT)
5/1 May Day or Beltane, a cross-quarter day
5/2 Neptune is 1.6 degrees south-southeast of the Moon at 11:00; asteroid 18 Melpomene is 1.4 degrees north-northwest of the Moon at 12:00
5/3 The Moon is at the descending node at 1:28
5/5 Uranus is 2.1 degrees north-northwest of the Moon at 4:00; the peak of the Eta Aquarid meteor shower (20 per hour for northern observers) occurs at 20:00
5/6 The Moon is at perigee, subtending 33' 23'' from a distance of 357,827 kilometers (222,344 miles), at 4:00; New Moon (lunation 1155) occurs at 19:30
5/7 A double Galilean satellite shadow transit begins at 4:39
5/8 The Moon is 0.47 degree north-northwest of the first-magnitude star Aldebaran (Alpha Tauri), with an occultation occurring in Japan, China, Russia, the Middle East, southern Europe, and northern and northeastern Africa, at 9:00
5/9 Mercury is at the descending node at 8:00; Mercury begins to transit the Sun at 11:12; Mercury is in inferior conjunction at 15:00; the Moon is 5.9 degrees south of the bright open star cluster M35 in Gemini at 21:00; Jupiter is stationary in right ascension at 23:00
5/12 The Moon is 4.7 degrees south of the bright open star cluster M44 (the Beehive Cluster or Praesepe) in Cancer at 12:00
5/13 First Quarter Moon occurs at 17:02; Mercury is 0.38 degree south-southeast of Venus at 18:00; the Sun enters the constellation of Taurus at 19:00
5/14 The Lunar X (also known as the Werner or Purbach Cross), an X-shaped illumination effect involving various rims and ridges between the craters La Caille, Blanchinus, and Purbach, is predicted to begin at 1:02; the Moon is 2.2 degrees south-southwest of the first-magnitude star Regulus (Alpha Leonis) at 6:00
5/15 Jupiter is 1.9 degrees north-northeast of the Moon at 8:00; the Moon is at the ascending node at 20:41
5/18 The Moon is 4.9 degrees north-northeast of the first-magnitude star Spica (Alpha Virginis) at 18:00; the Moon is at apogee, subtending 29' 26'' from a distance of 405,933 kilometers (252,235 miles), at 22:00
5/19 Mercury is at aphelion (0.4667 astronomical units from the Sun) at 17:00
5/21 Full Moon, known as the Milk or Planting Moon, occurs at 21:14; Mercury is stationary in right ascension at 22:00; Mars is 5.9 degrees south of the Moon at 22:00
5/22 Mars (apparent size 18.4'', magnitude -2.05) is at opposition at 11:17; the Moon is 9.5 degrees north of the first-magnitude star Antares (Alpha Scorpii) at 14:00; Saturn is 3.2 degrees south of the Moon at 22:00
5/23 Asteroid 4 Vesta is in conjunction with the Sun at 19:00
5/24 Venus is 4.6 degrees south-southeast of the bright open star cluster M45 (the Pleiades or Subaru) in Taurus at 16:00
5/25 Pluto is 3.0 degrees north of the Moon at 15:00
5/29 Last Quarter Moon occurs at 12:12; asteroid 7 Iris (magnitude +9.2) is at opposition at 18:00; Neptune is 1.4 degrees south-southeast of the Moon at 18:00
5/30 The Curtiss Cross, an X-shaped illumination effect located between the craters Parry and Gambart, is predicted to begin at 4:10; the Moon is at the descending node at 4:46; asteroid 18 Melpomene is 1.4 degrees north-northwest of the Moon at 21:00; Mars is closest to the Earth (75,280,000 kilometers or 46,777,000 miles) at 21:34
Nicolas Lacaille (1713-1762) and Joseph Lockyer (1836-1920) were born this month.
Nereid, Neptune’s third-largest satellite, was discovered on May 1, 1949 by Gerard Kuiper.
The peak of the Eta Aquarid meteor shower on the afternoon of May 5th occurs near New Moon so meteor watching should be almost equally good on the mornings of May 5th and May 6th. Southern hemisphere observers are favored. Eta Aquarid meteors are debris from the famous periodic comet 1P/Halley.
Information on Iridium flares and passes of the ISS, the Tiangong-1, the USAF’s X-37B, the HST, and other satellites can be found at www.heavens-above.com/
The Moon is 23.5 days old, is illuminated 40.9%, subtends 31.2 arc minutes, and is located in Capricornus on May 1st at 0:00 UT. The Moon occults Uranus from western and central Africa and central South America on May 15th. The Moon is at its greatest northern declination on May 10th (+18.4 degrees). The Moon is at its greatest its greatest southern declination on May 24th (-18.4 degrees). Longitudinal libration is at maximum (+7.5 degrees) on May 12th and at minimum (-6.4 degrees) on May 28th. Latitudinal libration is at maximum (+6.6 degrees) on May 9th and at minimum (-6.6 degrees) on May 23rd. New Moon occurs on May 6th. Large tides will take place on May 6h through May 9th. The Moon occults the fourth-magnitude star Theta Virginis for North American observers on the night of May 17th-May 18th. Consult www.lunar-occultations.com/iota/bstar/0518zc1891.htm for more on this event. The Full Moon forms a rectangle with Mars, Saturn, and Antares on the night of May 21st. Visit 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 www.lunar-occultations.com/rlo/rays/rays.htm
The Sun is located in Aries on May 1st.
Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on May 1st: Mercury (magnitude +3.0, 10.8", 7% illuminated, 0.63 a.u., Aries), Venus (magnitude -3.9, 9.8", 99% illuminated, 1.70 a.u., Aries), Mars (magnitude -1.5, 16.1", 98% illuminated, 0.58 a.u., Scorpius), Jupiter (magnitude -2.3, 40.8", 99% illuminated, 4.83 a.u., Leo), Saturn (magnitude +0.2, 18.1", 100% illuminated, 9.18 a.u., Ophiuchus), Uranus on May 16th (magnitude +5.9, 3.4", 100% illuminated, 20.80 a.u., Pisces), Neptune on May 16th (magnitude +7.9, 2.3", 100% illuminated, 30.22 a.u., Aquarius), and Pluto on May 16th (magnitude +14.2, 0.1", 100% illuminated, 32.46 a.u., Sagittarius).
In the evening, Mars is in the southeast and Jupiter in the south. Mars is located in the southeast, Jupiter in the west, and Saturn in the southeast at midnight. Mercury can be seen in the east, Mars in the southwest, Saturn in the southwest, Uranus in the east, and Neptune in the southeast at dawn.
At midmonth, Mercury is visible in morning twilight, Mars is visible for the entire night, Jupiter transits the meridian at 8:00 p.m. and sets at 3:00 a.m. local daylight time, and Saturn rises at 9:00 p.m. and transits the meridian at 2:00 a.m. local daylight time for observers at latitude 40 degrees north.
Mercury transits the Sun on May 9th. This relatively rare event, the first one since 2006, is visible in its entirety from eastern North and South America, the Atlantic Ocean, and western Europe. At least part of the transit can be seen from most of the world. Telescopes equipped with proper solar filters and working at magnifications of 50 to 100x will provide the best views of tiny Mercury (apparent size 12 arc seconds) during the transit. First contact takes place geocentrically at 11:12:19 UT (7:12:19 EDT), greatest transit (when Mercury passes closest - 319 arc seconds - to the center of the Sun) at 14:57:26 UT (10:57:26 EDT), and fourth (final) contact at 18:42:26 UT (2:42:26 EDT). For more on the transit, see eclipsewise.com/oh/tm2016.html or pages 62 and 63 of the May issue of Astronomy and pages 48 and 49 of the May issue of Sky & Telescope. Inferior conjunction takes place on May 9th and aphelion on May 19th.
Venus is not observable this month.
The apparent brightness of Mars exceeds magnitude -1.50 on May 1st. Mars rises around 10:00 p.m. local daylight time on that date. It passes 1.2 degrees north of the globular cluster M80 on May 6th and 1.0 degree north of the second-magnitude star Delta Scorpii on May 19th. By May 19th, Mars exceeds magnitude -2.00. The best Martian opposition in eleven years takes place on May 22nd. Mars subtends 18.4 arc seconds and shines at magnitude -2.05 on that date and reaches a maximum brightness of magnitude -2.06 the next day. The Martian north pole is inclined 12 degrees toward the Earth at opposition. Since it is late summer on Mars, the southern polar cap may be more visible than the northern one. On May 28th, the Red Planet leaves Scorpius and enters Libra as it progresses on its retrograde opposition loop. When it makes its closest approach to the Earth (0.50321 astronomical units or 4.19 light-minutes) on May 30th, Mars subtends 18.6 arc seconds and is 21 degrees south of the celestial equator. An article on observing Mars appears on pages 58 and 59 of the May issue of Astronomy. Martian surface features can be identified using the map posted at www.bluewaterastronomy.info/resources/MapsCharts/Mars-map-ALPO_color.jpg or the Sky & Telescope Mars Profiler at www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Jupiter decreases in brightness from magnitude -2.3 to magnitude -2.1 and shrinks in angular diameter from 40.8 arc seconds to 37.4 arc seconds during May. Jupiter sets around 4:00 a.m. local daylight time on May 1st and 2:00 a.m. local daylight time on May 31st. A double Galilean satellite shadow transit involving Callisto and Io occurs on May 7th. Jupiter completes its retrograde loop on May 9th and begins to move eastward through southern Leo. The waxing gibbous Moon passes 1.9 degrees south of Jupiter on May 15th. Browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/ or www.projectpluto.com/jeve_grs.htm in order to determine transit times of Jupiter’s central meridian by the Great Red Spot (GRS). GRS transit information also appears on page 50 of the May issue of Sky & Telescope. Data on the Galilean satellite events is available at www.skyandtelescope.com/observing/interactive-sky-watching-tools/ and www.projectpluto.com/jevent.htm
At mid-month, Saturn shines at magnitude +0.1 and has an apparent equatorial diameter of 18.3 arc seconds. Its rings are inclined by 26 degrees and subtend 41.6 arc seconds. Eighth-magnitude Titan is positioned north of the planet on May 5th and May 21st and south of it on May 13th and May 29th. Saturn’s variably bright moon Iapetus passes two arc minutes south of Saturn on May 31st-June 1st. For further information on Saturn’s satellites, browse www.skyandtelescope.com/observing/interactive-sky-watching-tools/
Uranus is lost in morning twilight until late May.
Neptune lies within one half of a degree of the fourth-magnitude star Lambda Aquarii this month.
Pluto lies in northern Sagittarius and transits the meridian before dawn.
For more on the planets and how to locate them, browse www.nakedeyeplanets.com/
Comet C/2013 X1 (PanSTARRS) travels southwestward through Aquarius during May. It can be seen low in the east before dawn. The periodic comet 9P/Tempel heads southeastward through Leo. It lies about one degree southwest of the second-magnitude star Denebola on May 21st. Visit cometchasing.skyhound.com/ and www.aerith.net/comet/weekly/current.html for information on comets visible this month.
Asteroid 6 Hebe (magnitude +10.5) glides southeastward through Leo this month. It passes just southeast of the twelfth-magnitude spiral galaxy NGC 3801 on May 1st and very close to Comet 9P/Tempel on May 11th. By the end of May, 6 Hebe is about two degrees northwest of Denebola. Some of the brighter asteroids reaching opposition this month include 23 Thalia (magnitude +10.4) on May 22th, 432 Pythia (magnitude +10.9) on May 26th, 7 Iris (magnitude +9.2) on May 29th, and 516 Amherstia (magnitude +10.6) on May 31th. Information on asteroid occultations taking place this month is available at www.asteroidoccultation.com/2016_05_si.htm
A wealth of current information on solar system celestial bodies is posted at www.curtrenz.com/astronomy.html and nineplanets.org/
A free star map for May can be downloaded at www.skymaps.com/downloads.html and www.telescope.com/content.jsp?pageName=Monthly-Star-Chart
The famous eclipsing variable star Algol (Beta Persei) is at a minimum, decreasing in magnitude from 2.1 to 3.4, on May 3rd, 6th, 9th, 12th, 15th, 18th, 20th, 23rd, 26th, and 29th. For more on Algol, see stars.astro.illinois.edu/sow/Algol.html and www.solstation.com/stars2/algol3.htm
Eighty binary and multiple stars for May: 1 Bootis, Struve 1782, Tau Bootis, Struve 1785, Struve 1812 (Bootes); 2 Canum Venaticorum, Struve 1624, Struve 1632, Struve 1642, Struve 1645, 7 Canum Venaticorum, Alpha Canum Venaticorum (Cor Caroli), h2639, Struve 1723, 17 Canum Venaticorum, Otto Struve 261, Struve 1730, Struve 1555, h1234, 25 Canum Venaticorum, Struve 1769, Struve 1783, h1244 (Canes Venatici); 2 Comae Berenices, Struve 1615, Otto Struve 245, Struve 1633, 12 Comae Berenices, Struve 1639, 24 Comae Berenices, Otto Struve 253, Struve 1678, 30 Comae Berenices, Struve 1684, Struve 1685, 35 Comae Berenices, Burnham 112, h220, Struve 1722, Beta Comae Berenices, Burnham 800, Otto Struve 266, Struve 1748 (Coma Berenices); h4481, h4489, Struve 1604, Delta Corvi, Burnham 28, h1218, Struve 1669 (Corvus); H N 69, h4556 (Hydra); Otto Struve 244, Struve 1600, Struve 1695, Zeta Ursae Majoris (Mizar), Struve 1770, Struve 1795, Struve 1831 (Ursa Major); Struve 1616, Struve 1627, 17 Virginis, Struve 1648, Struve 1658, Struve 1677, Struve 1682, Struve 1689, Struve 1690, 44 Virginis, Struve 1719, Theta Virginis, 54 Virginis, Struve 1738, Struve 1740, Struve 1751, 81 Virginis, Struve 1764, Struve 1775, 84 Virginis, Struve 1788 (Virgo)
Notable carbon star for May: SS Virginis
One hundred and sixty-five deep-sky objects for May: NGC 5248 (Bootes); M3, M51, M63, M94, M106, NGC 4111, NGC 4138, NGC 4143, NGC 4151, NGC 4214, NGC 4217, NGC 4244, NGC 4346, NGC 4369, NGC 4449, NGC 4485, NGC 4490, NGC 4618, NGC 4631, NGC 4656, NGC 4868, NGC 5005, NGC 5033, NGC 5297, NGC 5353, NGC 5354, Up 1 (Canes Venatici); Mel 111, M53, M64, M85, M88, M91, M98, M99, M100, NGC 4064, NGC 4150, NGC 4203, NGC 4212, NGC 4251, NGC 4274, NGC 4278, NGC 4293, NGC 4298, NGC 4302, NGC 4314, NGC 4350, NGC 4414, NGC 4419, NGC 4448, NGC 4450, NGC 4459, NGC 4473, NGC 4474, NGC 4494, NGC 4559, NGC 4565, NGC 4651, NGC 4689, NGC 4710, NGC 4725, NGC 4874, NGC 5053 (Coma Berenices); NGC 4027, NGC 4038-9, NGC 4361 (Corvus); M68, M83, NGC 4105, NGC 4106, NGC 5061, NGC 5101, NGC 5135 (Hydra); M40, NGC 4036, NGC 4041, NGC 4051, NGC 4062, NGC 4085, NGC 4088, NGC 4096, NGC 4100, NGC 4144, NGC 4157, NGC 4605, NGC 5308, NGC 5322 (Ursa Major); M49, M58, M59, M60, M61, M84, M86, M87, M89, M90, M104, NGC 4030, NGC 4073, NGC 4168, NGC 4179, NGC 4206, NGC 4215, NGC 4216, NGC 4224, NGC 4235, NGC 4260, NGC 4261, NGC 4267, NGC 4281, NGC 4339, NGC 4343, NGC 4365, NGC 4371, NGC 4378, NGC 4380, NGC 4387, NGC 4388, NGC 4402, NGC 4429, NGC 4435, NGC 4438, NGC 4517, NGC 4526, NGC 4535, NGC 4536, NGC 4546, NGC 4550, NGC 4551, NGC 4567, NGC 4568, NGC 4570, NGC 4593, NGC 4596, NGC 4636, NGC 4638, NGC 4639, NGC 4643, NGC 4654, NGC 4666, NGC 4697, NGC 4698, NGC 4699, NGC 4753, NGC 4754, NGC 4760, NGC 4762, NGC 4866, NGC 4900, NGC 4958, NGC 5044, NGC 5054, NGC 5068, NGC 5077, NGC 5084, NGC 5087, NGC 5147, NGC 5170, NGC 5247, NGC 5363, NGC 5364 (Virgo)
Top ten deep-sky objects for May: M3, M51, M63, M64, M83, M87, M104, M106, NGC 4449, NGC 4565
Top ten deep-sky binocular objects for May: M3, M51, M63, M64, M84, M86, M87, M104, M106, Mel 111
Challenge deep-sky object for May: 3C 273 (Virgo)
The objects listed above are located between 12:00 and 14:00 hours of right ascension.