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[Chicago Astronomer - Astro Joe]

April 2007
Astronomical Calendar of Events

4/1 Pluto is stationary at 0:00; Mercury is 1.6 degrees south of
Uranus at 7:00; a minimum lunar libration of 2.4 degrees occurs at
15:00

4/2 Full Moon, known as the Egg or Grass Moon and the smallest one of
2007, occurs at 17:15

4/3 The Moon is at apogee, subtending 29'24" from a distance of
406,329 km, at 9:00; the Moon is 1.3 degrees south of the first
magnitude star Spica (alpha Virginis) at 17:00

4/5 A double Galilean shadow transit (Europa's shadow is followed by
Ganymede's) begins at 20:07

4/6 Jupiter is stationary at 2:00

4/7 The Moon is 0.6 degree south of the first magnitude star Antares
(alpha Scorpii), with an occultation taking place in southern South
America, western Antarctica, New Zealand, and eastern Australia, at
13:00

4/8 Jupiter is 6 degrees north of the Moon at 9:00

4/9 A maximum lunar libration of 9.6 degrees occurs at 16:00

4/10 Asteroid 3 Juno (magnitude 9.7) is at opposition; Last Quarter
Moon occurs at 18:04

4/11 Venus is 3 degrees south of the bright open cluster M45 (the
Pleiades) in Taurus

4/13 A double Galilean shadow transit (Europa's shadow is followed by
Ganymede's) begins at 0:05

4/14 Mars is 0.5 degree south of the Moon, with an occultation taking
place in southern and eastern Asia, India, and eastern Africa, at
2:00; Uranus is 1.0 degree south of the Moon, with an occultation
taking place in northwestern Canada, Alaska, Japan, and eastern
Siberia, at 20:00

4/15 Mercury is at its greatest heliocentric latitude south today

4/16 A minimum lunar libration of 3.5 degrees occurs at 7:00

4/17 The Moon is at perigee, the second closest of 2007, subtending 33'27" from a distance of 357,135 km, at 6:00; New Moon (lunation 1043) occurs at 11:36

4/18 Asteroid 4 Vesta is stationary today

4/19 Venus is at perihelion today; the Moon is 0.9 degree north of
M45 at 16:00

4/20 Saturn is stationary at 1:00; Venus is 3 degrees south of the Moon at 8:00

4/21 Venus is 7 degrees north of the first magnitude star Aldebaran (alpha Tauri) at 12:00

4/22 A maximum lunar libration of 9.6 degrees occurs at 7:00; the
peak of the Lyrid meteor shower (20/hour) occurs at 16:00

4/24 First Quarter Moon occurs at 6:36; the Moon is 1.7 degrees north of the bright open cluster M44 (the Beehive Cluster) in Cancer at 13:00

4/25 Saturn is 1.1 degrees south of the Moon, with an occultation
taking place in northern Greenland, northwestern Canada, Alaska, and eastern Siberia, at 10:00

4/26 Mercury is 3.5 degrees south-southeast of the Moon at 6:00; the Moon is 1.0 degree north of the first magnitude star Regulus (alpha Leonis), with an occultation taking place in northwestern North America and the Arctic, at 10:00

4/28 Mars is 0.7 degree south of Uranus at 19:00

4/29 A minimum lunar libration of 3.1 degrees occurs at 7:00

4/30 The Moon is at apogee, subtending 29'25" from a distance of 406,209 km, at 11:00; the Moon is 1.3 degrees south of Spica at 23:00

The Moon is at its greatest southern declination of -29 degrees on April 8 and its greatest northern declination of +29 degrees on April 21. It is 12.9 days old at 0:00 UT on April 1. Times and dates for the lunar light rays predicted to occur this month are available at www.lunar-occultations.com/rlo/rays/rays.htm

Brightness, apparent size, illumination, distance from the Earth in
astronomical units, and location data for the planets and Pluto on
April 1: Mercury (0.0 magnitude, 16.4", 67% illuminated, 1.1 a.u.,
Aquarius), Venus (-4.0 magnitude, 13.6", 79% illuminated, 1.2 a.u., Aries), Mars (1.1 magnitude, 4.9", 93% illuminated, 1.9 a.u.,
Capricornus), Jupiter (-2.3 magnitude, 40.3", 99% illuminated, 4.9
a.u., Ophiuchus), Saturn (0.2 magnitude, 19.4", 100% illuminated, 8.6 a.u., Leo), Uranus (5.9 magnitude, 3.4", 100% illuminated, 20.9 a.u., Aquarius), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.5 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.9 a.u., Sagittarius).

This month Mercury is not well placed for northern hemisphere
observers.

Venus lies just a bit more than two degrees to the south of the
Pleiades on the evening of April 11 and is less than a degree
northwest of the northern section of the Hyades on April 18. It
passes 1/3 degree north of the 4.4 magnitude star 37 Tauri on April 14. At sunset, Venus is nearly 40 degrees above the horizon for observers at our latitude of 40 degrees north.

Mars moves into Aquarius on April 2. It rises in east-southeast in
the early morning. On April 28, Mars and Uranus are in close
conjunction with the fourth magnitude star Phi Aquarii half-way
between the two planets.

Jupiter begins to retrograde on April 6. It rises around 11:00 p.m.
by the end of April. Click on
skyandtelescope.com/observing...icle_107_1.asp to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at
skytonight.com/observing/obje...t/3307071.html

At the middle of the month, Saturn culminates at approximately 8:00 p.m. EDT and sets in the west-northwest prior to 3:00 a.m. Titan (magnitude 8.6) passes north of the planet on the nights of April 9 and April 24 and south of Saturn on the night of April 16. During April, Rhea shines at a magnitude of 10.0, Tethys at 10.5, and Dione at 10.5. Iapetus shines at magnitude 10.1 when it's at greatest western elongation on April 13. It is due west of Saturn by the listed separations on the following dates: April 2 (21"), April 6 (30"), April 10 (36"), April 16 (38"), April 20 (34"), April 24
(26"), and April 30 (11"). On the night of April 12, Iapetus is about
3 times farther west from Saturn than is Titan. For further
information on Saturn's satellites, browse
skytonight.com/observing/obje...t/3308506.html

Uranus is a difficult morning sky target.

This month Neptune is lost in morning twilight.

Pluto is located in northwestern Sagittarius.