To the reader:
The Skywatcher's Diary for May 2004 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
http://www.pa.msu.edu/abrams/SkyWatchersDiary/Archives.html
ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: May 2004
May Day is considered one of the four "cross-quarter" days, the points halfway
between the equinoxes and solstices. Nowadays we typically think of the equinox
and solstice dates as the beginning of the seasons, but in earlier times they were
considered the midpoints. That alternative viewpoint makes some since from an
astronomical perspective, particularly for the solstices. The sun would then be
highest in the middle of summer and lowest in mid winter. Under that scheme,
today should be the first day of summer.
Venus officially reaches its greatest brilliancy today, a blazing magnitude 4.5.
Practically speaking, though, the planet remains within a tenth magnitude of that
figure from mid April through mid May. Most observers won't detect much
difference until the end of this month when Venus dims about 11/2 times in
brilliance. If you haven't already tried to detect the crescent phase of Venus using
binoculars, make an attempt. Observe the planet in bright twilight or before
sunset in order to reduce the glare.
Venus passes within 1 degree of 2nd-magnitude Elnath, or Beta, in Taurus. The
star is to the right and slightly higher than Venus. You may need binoculars.
Elnath marks the brighter of the two horns of the bull. The star is a background
object, of course, lying about 130 light years beyond the planet. Take another
glimpse at Venus and Elnath tomorrow night, if it's clear, and notice how far
Venus has moved.
The Moon reaches Full phase at 4:33 p.m. EDT. In colonial times the Full Moon of
May was known as the Milk Moon or Corn Planting Moon. The first lunar eclipse of
the year, a total one, occurs today. It's best seen from Eastern Europe, eastern
Africa, and western Asia. Alas, none of it is visible from North America. We get our
turn in about half a year, on October 28.
The Eta Aquarid meteor shower reaches its peak before dawn this morning.
Although the shower produces a respectable 50 or so meteors per hour, its
radiant (the spot in the sky from which the meteors seem to come) is not well
placed for mid northern latitudes. This year the nearly Full Moon further hampers
the event.
Comet NEAT passes closest to Earth today, about 30 million miles or a third of
the distance to the sun. The comet should also be near to its greatest predicted
brightness of 2nd to 3rd magnitude. Tonight the comet stands about 10 degrees (a
fist width) to the upper left of the bright star Sirius, low in the west-southwest
toward the end of twilight. Use binoculars. The comet is rapidly climbing
northward, so it will be higher each night. But look soon, since it's also fading. For
a chart showing the comet's position, download the map from this website:
http://www.pa.msu.edu/abrams/SkyCalendar
Venus, Mars, and Saturn line up in the western evening sky. The two endpoints,
Venus and Saturn, are easy to spot at 4.5 and 0.1 magnitudes, respectively.
Mars, only 1.7, is easy to overlook. Currently it's slightly closer to Venus than
Saturn, but that configuration continually transforms. Venus and Mars separate a
little more each night, while Saturn and Mars draw closer together. Watch nightly
to observe the change.
Jupiter, the second brightest planet, is due south in early evening twilight. It also
perches high -- about two-thirds of the way toward overhead. The giant planet is
within the boundary of Leo. That constellation's brightest star, 1st-magnitude
Regulus, sits 9 degrees (a fist) to the upper right of the planet. Because Jupiter
outshines the star by more than 25 times, you should be able to pick the planet
out of the bright dusk at least 30 minutes before you can spot Regulus.
The belt stars of Orion set a little more than an hour after sunset. About all that
you will find of the gallant hunter is his shoulder star Betelgeuse, due west and
about 10 degrees up, around an hour after sunset. Orion's fading marks the
beginning of the end of the winter constellations. Crawling up the eastern sky are
the summer replacements. Leading the foray is the star Vega, the sparkling
beauty 15 degrees above the northeastern horizon.
Tonight Mars lies halfway between Venus, 8 degrees to its lower right, and
Saturn, to its upper left. The Red Planet is advancing on Saturn and passes less
than 2 degrees to the upper right of that planet on the 24th of this month.
Thereafter, Saturn continues to drift downward and is eventually overwhelmed by
the twilight glow about mid June. Mars maintains the fight for another few weeks
before succumbing.
Last Quarter Moon occurs at 7:04 a.m. EDT. This phase indicates Luna is a
morning object, seen in the last half of darkness and continuing its presence into
early daylight hours. If you know a youngster who has never seen the Moon in the
daytime, now is a good opportunity to introduce him or her. If the sky is reasonably
clear and not hazy or milky blue, the Moon should be visible up to 3 or 4 hours
after sunrise. Look in the south to southwestern sky up until about noon.
The winter stars are fast disappearing into sunset. The summer stars are poised
in the east, ready to take over the stage. Between these two groups lie the spring
constellations. The two most prominent patterns are Leo, to the west (right) of
south and about two-thirds of the way up, and Bootes, to the east. Add Virgo,
below and right of Bootes, and you have all the constellations of spring that
contain 1st-magnitude stars. Can you name the stars? Regulus in Leo, Arcturus in
Bootes, and Spica in Virgo.
Today Jupiter reaches its stationary point relative to the constellations. That is, the
planet halts its retrograde (westward) motion and begins moving direct
(eastward). In four days Venus also becomes momentarily stationary, while it
changes from direct to retrograde. Between these two dates, on the 16th to be
exact, the two planets attain their minimum separation, albeit a rather large 73
degrees.
Today Mercury reaches its greatest western elongation, which means it's at its
greatest angular distance (26 degrees) west of the sun. Normally this
configuration announces the planet's best morning appearance, but not this time,
at least not for the northern hemisphere. We get a poor showing, with Mercury
rising only about 50 minutes before the sun. The farther south you are, the better
the view. The southern hemisphere is ideal.
Comet NEAT has climbed considerably since earlier this month. It now sets five
hours after sunset. If predictions hold, NEAT will be 3rd magnitude. The comet sits
between the Gemini Twins and Leo, within the constellation of Cancer. Use
binoculars to scan along a line between Pollux, in Gemini, and Regulus, in Leo.
The comet is 14 degrees (fist and a half) to the upper left of the former star, and
24 degrees to the lower right of the latter.
This morning and tomorrow morning are the last reasonable opportunities to
catch the waning crescent Moon before it becomes New. And for rising that early,
you get Mercury as a bonus. Optimal observing occurs about 35 minutes before
sunrise both mornings. This morning at that time the Moon is 12 degrees (a fist)
above due east, and Mercury sits 5 degrees to its lower left. Tomorrow morning
the crescent slips 7 degrees to the planet's left, and slightly lower.
As night begins, notice how high the Big Dipper sits. It seems as though the
familiar pattern is perched overhead, although in truth, it's 10 to 15 degrees below
that point. The North Star, recall, can be located by following a line downward from
the pointer stars (those at the end of the Big Dipper's bowl). It's that 2nd-
magnitude star sitting halfway up in the north. To judge the North Star's
brightness, remember that the pointers are also 2nd magnitude.
In addition to guiding us to the North Star, the Big Dipper also points the way to
Arcturus and Spica. By following the Dipper's handle, we first arrive at brilliant
yellow-orange Arcturus and then proceed to bright blue-white Spica. Or, as
generations of sky watchers have recited, we "follow the arc to Arcturus and
speed on to Spica." The stars' respective colors tell us that Spica must be
intrinsically hotter that Arcturus.
New Moon occurs at 12:52 a.m. EDT, or less than an hour after midnight this
morning. Consequently, the Moon will be just short of 21 hours beyond New
phase when it makes a brief appearance after sunset tonight. The sight of a
crescent that's under 24 hours old is a relatively rare and exquisite sight. The
slender curved thread of a moon hangs delicately in the bright twilight. Try to
capture the moment. Look to the west-northwest 30 minutes after sunset The
Moon sits 3 degrees above the horizon and 18 degrees (2 fists) to the lower right
of Venus. Use binoculars.
If you had difficulty seeing the Moon last night, the thin crescent will give you no
trouble tonight, provided you look within an hour of sunset. Brilliant Venus marks
the area. Luna sits 6 degrees (half a fist) to the lower right of Venus. Farther to the
upper left of Venus (13 degrees) is the planet pair Saturn and Mars. Saturn is
brighter and 3 degrees to the upper left of its companion. Notice the fainter star
Epsilon (in Gemini) 11/2 degrees above Mars. Over the next couple nights, Mars
passes between that star and Saturn.
Tonight the Moon rests between Venus, 6 degrees to its lower right, and the
Saturn-Mars pair, 8 degrees to the upper left. Comet LINEAR passed closest to
Earth two days ago, coming within 25 million miles of us. It's not visible yet from
the U.S. except perhaps Hawaii and the extreme southern states. By the time it's
high enough to see well, the comet is likely to be only 3rd or 4th magnitude. This
comet becomes the second to grace our evenings. Comet NEAT is currently in
the northern sky between the Big Dipper and Gemini.
The Moon, Saturn, and Mars form a pleasing triangle pattern tonight. Mars lies 5
degrees (10 moon diameters) directly below Luna, and brighter Saturn is 2
degrees to Mars' left. Notice the star that is slightly more than a moon diameter to
the upper right of Mars. The star, Epsilon, in Gemini, is a magnitude fainter than
the planet. Watch Mars' changing position relative to the star and Saturn over the
next several evenings.
Tonight the crescent Moon aligns with the two bright stars of Gemini. Pollux is 3
degrees (6 moon diameters) to Luna's right and Castor sits 41/2 degrees to the
right of Pollux. Tomorrow night the Moon drifts into Cancer, one of the fainter
constellations. It contains no stars brighter than 4th magnitude. Cancer is home to
a nice star cluster, though. Use binoculars to look for the Beehive, or Praesepe,
cluster 3 degrees to the Moon's lower left.
Mars and Saturn arrive at their minimum separation tonight, as the Red Planet
slides 11/2 degrees (3 moon diameters) to the upper right of its brighter sibling.
After tonight Mars continues to separate from Saturn, as both planets slowly drift
lower into the sunset glow. By mid June Mars reaches the vicinity of the bright
Gemini stars, while Saturn is nearly lost in twilight.
The 1st-magnitude star Spica, brightest in the constellation Virgo, crosses due
south about 11/2 hours after sunset. Sky watchers often associate a fainter
constellation, Corvus, the Crow, with this star. Look about 15 degrees (11/2 fists) to
the lower right of Spica. Four 3rd-magnitude stars form a trapezoid about 7
degrees tall. Once spotted, it's easy to recognize. What's the connection with
Spica? The top two stars of Corvus point directly at it.
Tonight the Moon approaches Jupiter and has just passed Regulus. The planet
sits 7 degrees (14 moon diameters) to its left, and the star lies 5 degrees below
and slightly right of Luna. Can you detect that the Moon is just shy of First Quarter
(half shape)? It reaches that phase overnight, at 3:57 a.m. Check tomorrow night
to see that Luna appears slightly greater than half. By then the Moon has traveled
to the other side of Jupiter, 7 degrees to the planet's upper left.
Mars perches almost exactly above Saturn tonight, about 2 degrees away. The
Red Planet is also 11 degrees below the bright Gemini stars, Pollux and Castor,
and nearly equally spaced from them both. Watch these alignments change
nightly. Mars now glows faintly, about 2nd magnitude. Those who observed it when
the planet was spectacularly bright in late summer and early fall of last year
might, with good reason, doubt they are looking at the same object.
Are you still following Venus? A fixture high in the western sky for the last six
months, the planet has recently plummeted toward the horizon. At the beginning
of May it set 31/2 hours after the sun. Now the lag between the sun and Venus is
scarcely an hour. We'll lose it completely sometime in the next week, as it closes
in on the sun. Shortly thereafter, on June 8, Venus passes across our daystar's
face, the first such transit since 1882.
In the next few days Comet LINEAR should become visible to observers at mid
northern latitudes. Tonight, an hour after sunset, the comet sits 9 degrees above
the west-southwestern horizon. It climbs about one degree per night. You will
need binoculars to locate the 4th-magnitude fuzz ball. Don't neglect NEAT, the
other comet, still visible. Although a magnitude fainter than LINEAR, it's much
higher -- between Gemini and the Big Dipper.
The waxing gibbous Moon pauses beside Spica tonight, 4 degrees (8 moon
diameters) to the star's left. Spica, the brightest star in Virgo, is often depicted as
the shaft of wheat in the young maiden's hand. Finding anything resembling the
rest of the woman is likely to be a challenge. The second brightest star of Virgo is
3rd-magnitude Gamma, 15 degrees (11/2 fists) to Spica's upper right.
The bright star sitting low in the west at nightfall is Procyon, of Canis Minor. The
star is well known to most sky watchers but may be hard to identify without its
familiar and easily recognized companions Orion and Sirius, which have now
slipped below the horizon. Similarly, the bright star low in the northwest is
Capella, another member of that wonderful wintertime collection.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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