• Astronomical Calendar
• Binary/Multiple Star List
• DSO Lists

April 2009 Celestial Calendar

Dave Mitsky

Note: All times in UTC (EST + 5)

The usually minor Lyrid meteor shower peaks during the morning of April 22. However, outbursts of up to 90 meteors per hour have occurred in some years. At the end of the month, some early Eta Aquarid meteors may be visible.

The zodiacal light is visible from a dark site in the early evening during the first week of April.

The Moon is 5.3 days old at 0:00 UT on April 1. It's at its greatest southern declination of -26.7 degrees on April 14 and its greatest northern declinations of +26.8 degrees on April 1and +26.6 degrees on April 28. Latitudinal libration is at a maximum of +6.6 degrees on April 10 and a minimum of -6.5 degrees on April 25. Longitudinal libration is at a maximum of +4.6 degrees on April 10 and a minimum of -6.2 degrees on April 22. 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 Pisces on April 1. The first photograph of the Sun was taken on April 2, 1845.

Brightness, apparent size, illumination, distance from the Earth in astronomical units, and location data for the planets and Pluto on April 1: Mercury (-2.1 magnitude, 5.0", 100% illuminated, 1.34 a.u., Pisces), Venus (-4.2 magnitude, 58.6", 2% illuminated, 0.28 a.u., Pisces), Mars (1.2 magnitude, 4.3", 97% illuminated, 2.18 a.u., Aquarius), Jupiter (-2.1 magnitude, 35.0", 99% illuminated, 5.63 a.u., Capricornus), Saturn (0.6 magnitude, 19.6", 100% illuminated, 8.48 a.u., Leo), Uranus (5.9 magnitude, 3.4", 100% illuminated, 20.95 a.u., Pisces), Neptune (7.9 magnitude, 2.2", 100% illuminated, 30.52 a.u., Capricornus), and Pluto (14.0 magnitude, 0.1", 100% illuminated, 31.23 a.u., Sagittarius).

During April, Mercury is located in the west and Saturn is in the southeast during the evening. Saturn is in the southwest at midnight. Venus and Mars can be seen in the east, Jupiter in the southeast, and Uranus in the east in the morning. All five of the bright planets are easy targets by the end of April.

This month Mercury undergoes its best evening apparition of the year for observers in the northern hemisphere. On April 9, Mercury sets 50 minutes after sunset and is as bright as Sirius. From April 16 to April 24, Mercury is at least ten degrees above the horizon and shines at least zero magnitude. On April 26, when the planet is at greatest eastern elongation, Mercury, the Pleiades, and a thin crescent Moon form a tight group, with the Moon situated less than two degrees to the north of the Pleiades and Mercury less than three degrees to the south. By April 29, a rapidly fading Mercury has moved northward to within a degree and a half of the cluster. Mercury decreases in illumination from 90% to 27% over the course of the month.

Venus is a "morning star" this month. Like Mercury, Venus undergoes dramatic changes during April, gaining half a magnitude in brightness, increasing in illumination from 2% to 24%, and decreasing in apparent size from 58.6 arc seconds to 39.9 arc seconds. It is occulted by a 17% illuminated crescent Moon on April 22. For information on this daylight occultation, see http://www.lunar-occultations.com/iota/pleiades/pleiades.htm

On April 15, Mars departs Aquarius and enters Pisces. The Red Planet passes 0.5 degree south of Uranus on the same day. Three days later Venus passes 5.5 degrees north of Mars. The visibility of Mars improves as the month ends.

Jupiter rises by 5:00 a.m. EDT on the first day of the month and about 3:30 a.m. EDT by the end of April. On April 19, the Moon is two degrees north of Jupiter (magnitude -2.2), providing a chance for a daytime naked-eye view of the planet. The star 44 Capricorni (magnitude 5.9) lies between Jupiter and Ganymede on the morning of April 26. Click on http://skyandtelescope.com/observing/objects/planets/article_107_1.asp to determine transits of the central meridian by the Great Red Spot. Data on the Galilean satellites is available at http://www.skyandtelescope.com/observing/objects/javascript/3307071.html

Saturn still dominates the constellation of Leo, shining almost twice as bright as Regulus. The ring tilt angle on April 1 is 3.4 degrees and on April 15 is 3.8 degrees. The shadow of eighth-magnitude Titan, Saturn's brightest satellite, transits the planet's disk on April 13, from 3:22 to 7:51 a.m. EDT. A second shadow transit of Titan takes place on April 29, from 2:22 to 7:16 a.m. EDT. Titan will be eclipsed by Saturn on 5:10 a.m. EDT on April 5 and at 3:50 a.m. EDT on April 21. Saturn's odd moon Iapetus is at its brightest, a magnitude of 10.1, when it reaches greatest eastern elongation on April 2.

For further information on Saturn's satellites, browse http://www.skyandtelescope.com/observing/objects/javascript/3308506.html

Observing Uranus is rather difficult this month.

During April, Neptune is located near the fifth-magnitude star Mu Capricorni. Jupiter passes 4.5 degrees to the west of Neptune on April 1 and 2.5 degrees to the west of it on April 30.

The dwarf planet Pluto is located to the southwest of the bright open cluster M18 in northwestern Sagittarius.

Comet C/2007 N3 (Lulin) continues westward through Gemini until April 21, when it is a few degrees to the east of the third-magnitude star Mu Geminorum. On that date, the fading comet is stationary and then begins to retrograde.

Asteroid 1 Ceres heads southward through Leo Minor this month. The magnitude 7.5 dwarf planet lies to the west of 40 and 41 Leonis Minoris and to the east of the bright binary star Gamma Leonis in the Sickle of Leo. Asteroids reaching opposition this month include 8 Flora (magnitude 9.8), 14 Irene (magnitude 8.9), 15 Eunomia (magnitude 9.8), and 187 Lamberta (magnitude 10.2).

Binary and Multiple Stars for April

h4481 (Corvus); Aitken 1774, Gamma Crateris, Jacob 16, Struve 3072, h4456, Burnham 1078 (Crater); h4311, Burnham 219, N Hydrae, h4455, h4465 (Hydra); 31 Leonis, Alpha Leonis (Regulus), h2520, Struve 1417, 39 Leonis, Struve 1421, Gamma Leonis (Algieba), Otto Struve 216, 45 Leonis, Struve 1442, Struve 1447, 49 Leonis, Struve 1482, 54 Leonis, Struve 1506, Chi Leonis, 65 Leonis, Struve 1521, Struve 1527, Struve 1529, Iota Leonis, 81 Leonis, 83 Leonis, Tau Leonis, 88 Leonis, 90 Leonis, Struve 1565, Struve 1566, 93 Leonis, h1201, S Leonis (Leo); h2517, Struve 1405, Struve 1432, 33 Leo Minoris, Struve 1459, 40 Leo Minoris, Struve 1492 (Leo Minor); Struve 1401, Struve 1441, Struve 1456, Struve 1464, 35 Sextantis, 40 Sextantis, 41 Sextantis (Sextans); Struve 1402, Struve 1415, Struve 1427, Struve 1462, Struve 1486, Struve 1495, Struve 1510, Struve 1520, Xi Ursae Majoris, Nu Ursae Majoris, Struve 1541, 57 Ursae Majoris, Struve 1544, Struve 1553, Struve 1561, Struve 1563, 65 Ursae Majoris, Otto Struve 241 (Ursa Major)

Challenge binary star for April: Gamma Sextantis

Notable variable star for April: S Ursae Majoris (Ursa Major)

Notable carbon star for April: V Hydrae (Hydra)

Challenge deep-sky object for April: Leo I (Leo)

Top ten deep-sky objects for April: M65, M66, M95, M96, M97, M105, M108, NGC 3115, NGC 3242, NGC 3628

Top ten binocular deep-sky objects for April: M65, M66, M95, M96, M97, M105, M108, M109, NGC 3115, NGC 3242