To the reader:
The Skywatcher's Diary for May 2001 has been prepared by
David Batch. Credit to the author and to
Abrams Planetarium,
Department of Physics and Astronomy at
Michigan State University, and mention of
our
Sky Calendar, would be
appreciated.
A sample issue of the Sky Calendar is available over the Internet. It
can be viewed via the World-Wide Web at
http://www.pa.msu.edu/abrams/SkyCalendar/Index.html
If you would like a printed sample of the May issue, please send a long,
self-addressed stamped envelope to:
May Sky Calendar
Abrams Planetarium
Michigan State University
East Lansing, MI 48824
Each month, the Department of Physics and Astronomy at Michigan State
University makes the Skywatcher's Diary available over the Internet. It can
be accessed at
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Diary.html
Current and back-issues of the Skywatcher's Diary are available in our
archives
at
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ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: May 2001
Our May Day celebration is the remnant of an ancient Celtic festival known as Beltaine. It was one of the "cross-quarter" days -- halfway between the equinox and solstice -- marking the approximate time of mid-spring, or, in some circles, the beginning of summer. The theme of the celebration was rebirth and fertility, as the earth reawakened and life was renewed.
This evening the waxing gibbous Moon, two days past first quarter, is a bit more than halfway up in the SSE. Through binoculars and telescope the beautiful crater Copernicus stands out just to the right of the terminator (the light-dark boundary) and slightly above center. It makes an easy target because it is well-formed and sits in an area devoid of other large craters.
Look for Mercury early this evening -- 45 minutes after sundown. You'll need a flat WNW horizon since the planet is only 3 degrees (6 moon diameters) up. Binoculars are useful for finding the planet in twilight. Fainter Saturn is 7 degrees to Mercury's upper left, and bright Jupiter is another 13 degrees to the upper left of Saturn.
Today Venus attains magnitude -4.5, its greatest brilliancy for this current morning apparition. The event is of little practical significance since Venus will continue to be the brightest planet visible, even after it fades to -3.9 in November. To find the planet look low in the east an hour and a half before sunrise.
Watch Mercury every clear evening as it parades past Saturn, then Jupiter, over the next week. Tonight Mercury slides by Saturn, 4 degrees (almost half a fist width) to the Ringed Planet's right. Catch the event low in the WNW about 45 minutes after sunset.
This evening Mercury is 4 degrees to the upper right of Saturn. Mercury is the brighter of the pair. With binoculars you may be able to detect the Pleiades star cluster 3 degrees to the lower right of Mercury.
Full Moon occurs at 9:52 a.m. You will not be able to witness the exact moment since it occurs about 3 hours after the Moon sets this morning and 11 hours before it rises this evening. But, then, you won't be bothered by werewolves, either. The Full Moon of May was known by American colonists as the Planting or Milk Moon.
Mercury perches 4 degrees overtop Saturn early this evening, as it climbs toward Jupiter, the brighter planet, 10 degrees (a fist width) to Mercury's upper left.
The Moon rises about 1 1/2 hours after sunset. Several hours later the reddish object you see below the Moon is not Mars, but the star Antares, heart of Scorpius.
Trivia question: What two planets are on opposite sides of the solar system today? One recently disappeared from the evening sky and the other rises around midnight. Answer: Saturn and Mars.
At first light tomorrow morning Mars sits 5 1/2 degrees (11 moon diameters) to the left of the Moon.
This morning the Moon was to the right (west) of Mars. As dawn begins tomorrow, the Moon is 7 degrees to the left of the Red Planet. If you prefer to do your Mars-watching in the evening, the planet rises in the SE just before midnight. The Moon makes its appearance 20 minutes later.
For the last 23 months Mars has merrily glided eastward against the background starfield. Today it hesitates, then begins traveling westward for the next two months, in what is termed "retrograde motion." While observing Mars, scan 2 degrees to the left with binoculars and look for the faint Lagoon Nebula, a huge star-forming region of gas and dust well-known to amateur astronomers.
The great winter constellation Orion finally makes his exit, stage west. The "belt" stars set due west an hour after sunset. Betelgeuse, the right shoulder of the giant, follows 40 minutes later. Twenty degrees (2 fists) to the right, Jupiter and Mercury set almost simultaneously with Betelgeuse.
As the winter stars disappear over the western horizon, the summer stars begin climbing the eastern sky. Bright Vega, in Lyra the Harp, sits 15 degrees up in the NE an hour after sunset. Its Summer Triangle companion, Deneb, is 25 degrees to Vega's lower left, only 6 degrees above the horizon. The third member of the triangle, Altair, doesn't rise until just before midnight.
Jupiter and Mercury are now side-by-side low in the WNW an hour after sundown. Jupiter is by far the brighter of the pair. Mercury is 3 degrees to the right. Watch Mercury continue to climb every night, although dimming, while Jupiter slowly settles into the twilight over the next two weeks.
Last Quarter Moon occurs at 6:11 a.m. EDT. The Moon does not rise until about 3 a.m. and sets in early afternoon. Watch for it after sunrise during the next several mornings in the S to SW. If the sky is hazy, look carefully, since the Moon's contrast against the background will be minimal.
At the end of evening twilight the Big Dipper reaches its highest point in the sky. A casual glance suggests that the pattern is overhead, but it's really only about three-quarters of the way up. The Dipper's handle gently curves toward the SE, drawing the eye to the bright star Arcturus, high in that direction. Arcturus is the brightest star up this evening, although Vega, in the ENE, is close behind.
Watch the waning crescent Moon pass Venus the next three mornings. Tomorrow, about 45 minutes before sunrise, Venus and the Moon are low in the E to ESE, 14 degrees (a fist and a half) apart. Saturday morning the Moon slides 5 degrees to the lower right of the planet. By Sunday the Moon is just above the eastern horizon at dawn, 11 degrees to the lower left of Venus.
At the end of evening twilight the Milky Way "band" lies nearly flat along the horizon. As you look overhead, therefore, you stare straight out of our galaxy toward its "north pole." Notice that few bright stars exist in that direction. Most of the brilliant stars now lie along our horizon.
Mercury is 4 degrees overtop Jupiter early tonight. Look low in the WNW at mid-twilight, or about 45 minutes after sunset. See if you can detect the 2nd-magnitude star Beta, in Taurus, the tip of one of the bull's horns. It is 3 degrees above, and slightly to the right of Mercury. The other horn tip is fainter still, only 3rd-magnitude, located 7 degrees to Mercury's left. In two days Mercury will stand between the horns.
Regulus, the brightest star in Leo, perches halfway up in the WSW near the end of evening twilight. Between it and the horizon, and a bit to the left, is a slightly fainter star, Alphard, brightest member of Hydra, the Water Snake. The star's name comes from ancient Arabic meaning "solitary one." Look around Alphard in the sky and you understand the name's relevance. No other bright stars are nearby.
Mercury sits almost directly between the tips of the horns of Taurus, the Bull. Forty-five minutes after sunset use binoculars to help locate Beta, 3 degrees to the planet's upper right, and fainter Zeta, 4 degrees to the lower left. Coincidentally, Mercury is farthest from the Sun today -- 22 degrees. This angular spread between Mercury and the sun is maximum for the current apparition, an event known to astronomers as "Greatest Elongation."
New Moon occurs at 10:46 p.m. EDT. At that moment the sun and Moon will be about 17 degrees below our northwestern horizon. The term "new moon" indicates that the two bodies are aligned, but not necessarily one in front of the other. The latter circumstance creates a solar eclipse. If you could see below the horizon, the Moon would appear 3 degrees to the lower left of the sun. A line drawn through the center of the two bodies, however, would pass through the sky's north pole (North Star).
Less than 24 hours since New, the Moon returns to our evening skies -- but you need to be quick to catch it. Look very low in the WSW 30 minutes after sunset. Use binoculars. Jupiter is 4 degrees (8 moon diameters) above the Moon, and Mercury is another 7 degrees higher still.
The young Moon is worth adding to your evening agenda. Face WNW. Mercury is 4 degrees due right of Luna, and Jupiter is 10 degrees (a fist width) to the lower right. Look 45 minutes after sunset if you want to grab the giant planet, since it sets shortly thereafter.
The 3-day-old Moon is a magnificent sight tonight. It is perched between the Gemini twins, above, and Mercury and Jupiter below and to the right. Pause long enough to absorb the "earthshine," the faint glow radiating from the dark portion of the Moon. Can you detect any structure in the shadow? Try it with binoculars.
The crescent Moon is nearly aligned with the Gemini Twins tonight. Pollux is the star immediately to the Moon's right, 7 degrees (14 moon diameters) away. Castor, the slightly less luminous brother, is 4 degrees farther right. The fainter sibling is intrinsically a brighter star -- it is just more distant. As you look at them, imagine Castor in the background 1 1/2 times farther away than Pollux.
The Moon resides between Gemini and Leo, among the faint stars of Cancer, the Crab. Since the stars of that constellation are indistinct, to the casual observer Cancer is more a position in the sky rather than a pattern to look for. The constellation is famous for its place in the zodiac -- originally the position of the solstice sun -- which caused a "tropic" to be named for it.
The Moon passes through Leo, the Lion, over the next three nights -- in an astronomical, rather than digestive, sense. Look for Regulus, the heart of the lion, 4 degrees to the Moon's left, and slightly lower. Tomorrow night the Moon is under the lion's midsection, and Wednesday night the Moon is 9 degrees to the lower left of Denebola, the lion's tail.
The Moon reaches First Quarter at 6:09 p.m. EDT. While in this phase, the Moon trails the Earth as we journey around the sun. Try to imagine the scene from above. The Earth travels around the sun counterclockwise in its orbit. The Moon orbits the Earth, also counterclockwise. At the moment of First Quarter, the Moon is behind the Earth, opposite the Earth's direction of motion.
Mars now rises near the end of dusk. Watch it pop up in the SE. Nearing its greatest brilliancy, the Red Planet makes a striking sight. Can you detect an orange tint to the image? Don't mistake it for Antares, the heart of the scorpion, which is also orange-red. The star is in the SE, too, but fainter and 17 degrees to the upper right.
Venus now comes up at the start of morning twilight. Because it is so bright, early risers should have no trouble spotting the planet low in the east during mid-twilight. Mars, the other morning planet, is in the SSW about 20 degrees (two fists) up as dawn breaks.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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