The sky in May

A "celestial summit meeting." Belgian astronomer Jean Meeus has called the appearance of three planets within a circle 5 [degrees] or less in diameter a "planetary trio." In early May, just such a trio is readily visible low in the west-northwestern sky for about two hours after sunset. The three planets--dazzling, silvery Venus (magnitude -3.9), medium-bright Saturn (+0.1), and dim, orange Mars (+1.6) appear within a 5 [degrees] circle from May 3 to May 10. On the 6th, they fit into the smallest circle (2.7 [degrees]). Separate planetary conjunctions also occur during this interval: between Mars and Saturn (2.2 [degrees] apart on the 4th), Venus and Saturn (2.4 [degrees] apart on the 7th), and Venus and Mars (just 0.3 [degrees] apart on the 10th). All of this takes place in central Taurus, just north of the orange first-magnitude star Aldebaran and the Hyades star cluster. Amazingly, a fourth planet--Mercury--is not far away. Having passed just south of the Pleiades on April 29, Mercury arrives on May 4 at 21 [degrees] east of the Sun, a very favorable elongation, and sits roughly 8 [degrees] below and to the right of the planetary trio on May 6, shining at magnitude +0.8. Lastly, a skinny crescent Moon--the icing on this cosmic cake--passes through the same part of the sky on the evenings of the 13th and 14th.

Thereafter, Mercury slides into invisibility, overwhelmed by the bright evening twilight. Venus and Mars continue to plod eastward. Both pass from Taurus into Gemini--Venus on the 20th and Mars on the 28th. Toward the end of May, both planets approach Jupiter.

Jupiter is the only one of the five bright planets visible to the naked eye that is not involved in the extraordinary clustering of celestial bodies mentioned above. Nonetheless, it shines brilliantly this month at magnitude -1.9 in the middle of the constellation Gemini, well up in the western sky at dusk. The planet sets at approximately 12:30 A.M. local daylight time at the start of May and at about 11:00 P.M. by month's end. The Moon sweeps past Jupiter at midmonth: on the evening of the 15th it's well below and to the right of Jupiter, and by the next night it has moved well above and to the left of the planet. During the final week of May, Venus draws noticeably closer to Jupiter.

The Moon wanes to last quarter on May 4 at 3:16 A.M. and is new on the 12th at 6:45 A.M. First quarter is on May 19 at 3:42 P.M., and the Moon waxes full on the 26th at 7:51 A.M.

A penumbral lunar eclipse is visible on May 26 over nearly all of the Pacific Ocean, including Hawaii, Australia, and New Zealand. The event is rather uninspiring, however. Even at its darkest phase, which occurs at 2:04 A.M. local time in Hawaii, the Moon's lower limb will appear only very slightly shaded by Earth's faint outer shadow.

Unless otherwise noted, all times are given in Eastern Daylight Time.

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