May Sky chart; Northern Hemisphere gazer's guide
All month: Months when the planets are at or close to opposition from the sun are particularly good for planet-watchers, and this is one. Saturn is at opposition on the 3rd and Mars on the 11th, and Jupiter arrives at its opposition in late June. Near opposition, the planets are with us virtually all night long, part of the early evening sky, then highest around midnight, and still with us at dawn. Though technically changing from morning to evening stars , they give us the best of both. This is because both in the evening and in the morning they are best placed opposite the twilight glow, where the sky is darkest and the planets appear brightest.
In May, Saturn and Mars are just rising in the east at sundown. About two hours later, they will be found easily above the eastern horizon, in line with and lower than the bright star Spica, in Virgo. Spica leads them out of the horizon and across the sky, Saturn following. At midnight, the same objects are high up in the south to the southeast. They stretch across the sky from Spica on the right, past Saturn, then Mars, and finally Jupiter, now clearly the brightest. Just before dawn, the string of bright objects descends from the south down toward the west. Begin with Jupiter, highest and brightest, then Mars , Saturn, and Spica lowest.
The best time of the month to see them is from the 14th to the 20th, when the nearly full moon passes them one by one.
(The events described in the calendar below are given in local time unless indicated otherwise.)
May 1: No moon tonight. It was new about an hour before midnight on Monday night, and tonight the crescent is too slim and sets too early to be seen as it drifts from Aries into Taurus.
May 2-3: The new crescent moon could be visible soon after sundown on Wednesday, and should clearly be visible on Thursday. It's in Taurus both nights , but twilight will overpower the Bull's stars. Saturn deserts the morning sky. Opposite the sun at about 3 a.m. Eastern standard time on the 3rd, it rises virtually at sundown and sets at sunrise both days, and technically becomes an evening star on the 3rd.
May 7: Look above the moon on the 7th for ''the sickle,'' the circular group of stars with bright Regulus at the end of the sickle's handle. These same stars are the head (the circle) and heart (Regulus) of Leo the Lion, and a triangle of three stars above them forms Leo's hindquarters and tail.
May 8: The moon is at first quarter at 6:50 a.m., EST. It's just above and to the right of Regulus late today.
May 10-11: You've surely seen that bright yellowish object brightening and rising earlier in the eastern sky each night. It's Mars, at opposition from the sun (at 4 a.m., EST on the 11th) as Earth passes between it and the sun. The gibbous moon, high in the south and well to the right of Mars, is at perigee (nearest earth) at about 10 p.m., EST, on the 11th.
May 12: The bright star near the moon tonight is Spica, in Virgo. To the left and lower you can find Saturn and Mars, with Mars by far the brighter. Then, after Jupiter rises about 11 p.m., it becomes the brightest.
May 14: The moon passes both Saturn and Mars today, Saturn about 3 a.m. (occulted by the moon in the Southern Hemisphere), and Mars about 2 p.m., EST. An hour before midnight, the moon is full and a penumbral lunar eclipse takes place. What's it going to be like tonight? Take a look and see! The big, bright, full moon casts so much light that the only objects visible near it are Mars and Saturn, to the moon's right. The penumbral eclipse (from about 9:42 p.m. to 1:38 a.m. EST) will be slightly darker than usual, but not noticeably so.
May 17: The gibbous moon rises about 10 p.m. in Sagittarius, right at the top of the ''teapot'' group of its stars. Very bright Jupiter rises about an hour later. Compare its brightness with that of Mars (Jupiter is half again as bright). At favorable oppositions, Mars can be much brighter than Jupiter!
May 19: Mars is closest to the earth today, 79.5 million kilometers (49.37 million miles) distant.
May 20: Mercury is at its greatest distance from the sun in the morning sky (greatest westerly elongation). The planet can be found low in the east northeast after dawn until obscured by the twilight for about a week.
May 28: Mercury is in conjunction with the moon at about 1 p.m., EST, and the moon covers the planet over Alaska and northern Canada.
May 30: The eclipse of the decade (for North America, at least) occurs today, an annular solar eclipse in a narrow path across Mexico and the Southeastern United States, with a partial solar eclipse everywhere except Alaska. Solar eclipse of May 30
When the new moon casts its long, slender shadow toward Earth on May 30, a solar eclipse occurs throughout North America (except Alaska) during the morning or early afternoon. The eclipse is partial in most places; that is, part of the sun is covered by the moon. But an annular eclipse occurs along a narrow path in Mexico and the Southeastern US, where the moon passes centrally across the sun. During this eclipse, the moon's distance is slightly greater than its shadow length, so the shadow doesn't quite reach Earth's surface. Therefore, at mid-eclipse, along the central line and for a short distance on either side, a thin ring (annulus) of the sun remains visible.
An annular eclipse may not have the scientific appeal of a total solar eclipse, but it can be equally interesting to observe, especially when the moon's shadow comes so close to touching Earth as it does on May 30. The ring of sun visible at mid-eclipse will be exceptionally thin, broken in places by the moon's mountains from some locations. Unfortunately, for the same reason, this will be a very short annular eclipse (7 to 14 seconds in the United States) and the annular path very narrow (3 to 6 miles wide).
Care must be taken to avoid eye damage when observing a solar eclipse. The risk is acute, because we may be tempted to look by the unusual nature of the event. The light from even a small area of the sun can be damaging if looked at without protection. Black and white film, opened to daylight and then fully developed, in several layers as necessary, can be used as a filter with caution.