To the reader:
The Skywatcher's Diary for February 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 February issue, please send a long,
self-addressed stamped envelope to:
February 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: February 2004
The waxing gibbous Moon sits between the "bull's horns" this evening. The bull
is, of course, Taurus, and the stars to either side of the Moon are often pictured as
the horn tips. Beta, or Alnath, will be easiest to see -- it's almost 1st magnitude.
Look for that star 3 degrees (6 moon diameters) to the upper left of Luna. Fainter
Zeta (3rd magnitude) is 5 degrees to the Moon's lower right. The face of the bull is
marked by 1st-magnitude Aldebaran, 16 degrees (1 1/2 fist widths) to the Moon's
right.
The bright "star" 4 degrees (half a fist) below and slightly right of the Moon this
evening is Saturn. Groundhog Day is our version of an older feast day known as
Candlemas, when candles were brought to church to be blessed by the priest.
Like a number of Christian holidays, the event replaced an earlier pagan
celebration. Candlemas is the first of the four cross-quarter days that mark the
approximate midpoints of the seasons. In some older cultures it indicated the
beginning of spring rather than the middle of winter.
This evening the Moon approaches the heads of the Gemini Twins, distinguished
by the bright stars Pollux, 6 degrees (half a fist) to Luna's lower left, and Castor, 6
degrees to the upper left. By tomorrow night, the Moon slides 7 degrees to the
lower left of Pollux. Between these two times, the Moon passes directly below the
Twin stars, but this occurs about mid morning, when the Moon is out of sight of
the U.S.
Try your hand at capturing four planets at once. Jupiter now rises just before
Venus sets, so if you time it just right and have unobstructed eastern and western
horizons, these brightest planets will be visible simultaneously. Saturn and Mars
sit between the two extremes. The time to catch the show is about 3 1/2 hours
after sunset. Each night Venus sets later and Jupiter rises earlier, so as more
days pass, it becomes easier to snag all four planets.
The Moon turns Full overnight -- the precise moment is 3:47 a.m. EST tomorrow
morning. To the casual observer, the Moon appears Full a day or two on both
sides of the exact date. Using binoculars, see if you can distinguish a difference
between tonight's and tomorrow night's Moon. The Full Moon this time of year has
been called the Snow, Hunger, or Wolf Moon, among other designations, all
evoking the harshness of mid winter.
Tonight the Moon rises shortly after sunset. Where would you expect it to come
up? In the east, to the north of east, or to the south of east? Think about what
direction the sun sets this time of year, and remember that the Full (or nearly Full)
Moon appears opposite the sun in the sky. After the Moon rises, look for Regulus,
the brightest star in Leo, 6 degrees (12 moon diameters) below and slightly right
of Luna. Try to pick out 3rd-magnitude Eta, 2 degrees to the lower left of the Moon.
With moonlight glare, binoculars may be necessary to locate the fainter star. By
dawn tomorrow morning, look for Eta 3 degrees to the Moon's right.
Watch for the Moon to rise tonight in the eastern sky about 1 1/2 hours after
sunset. Jupiter follows Luna across the horizon less than an hour later. The two
objects are separated by 8 degrees (almost a fist width). By dawn tomorrow
morning, the pair travels to the west, and the Moon creeps within 3 degrees of
Jupiter. You'll also notice the orientation is significantly different. The Moon is to
the right and slightly above the planet.
Jupiter and the Moon reverse roles from last evening. The planet rises first, a little
more than 2 hours after sunset. Luna follows about 30 minutes later. Try to spot
the 4th-magnitude star Sigma, in Leo, 2 degrees below and slightly left of Jupiter.
Over the next several months you can watch Jupiter separate from this star, as the
planet retrogrades toward the west (right). The spread between planet and star
reaches a maximum of 10 degrees in early May. Jupiter then resumes direct
(eastward) motion and passes less than a degree below Sigma in early August.
Venus is spectacular. If you've been outdoors during evening twilight, you have
probably already marveled at the "evening star." It's blazing 4.0 magnitude is
almost 2 magnitudes brighter than Jupiter, the next brightest planet. It dominates
the western sky for three hours after sunset. The planet will line up with the east
(left) side of the Great Square of Pegasus in the next few days. Try to determine by
observation when that alignment occurs.
The Moon now rises 5 hours after sunset, so it can be more properly thought of
as a morning object. Tomorrow morning, early risers will find the waning gibbous
Moon perched high in the southwestern sky. It's among the stars of the
constellation Virgo. You can confirm that by noticing Spica, the brightest star in
that constellation, sitting 3 degrees (6 moon diameters) to the lower right of the
Moon.
The Equation of Time reaches its minimum for the year, -14 minutes. Sundial
enthusiasts recognize the term as a way to describe the difference between clock
time, known as mean solar time, and what a sundial registers, or apparent solar
time. If you were to examine a properly mounted sundial at exactly 12 noon today
(according to your watch), the sundial would read 11:46 a.m. We say the sun is
currently 14 minutes "slow."
Some night soon, as twilight falls, look to the north-northeast. There you will find
the Big Dipper, part of Ursa Major, the Great Bear. During winter evenings the
Dipper sits low, hard to see near the northern horizon. Now the celestial bear is
stirring out of hibernation and begins its climb up the northeastern sky. Watch the
ascent continue throughout spring evenings. It's a sure sign that summer is on
the way.
The Moon passed Last Quarter phase at 8:40 a.m. EST. You might have noticed
the "half" Moon this morning after sunrise. It's also paraskevidekatriaphobia day.
Some people consider the day particularly unlucky due to the alignment of two
ancient superstitions, one regarding the number 13 and the other concerning
Fridays. If you are looking for bad luck today, or any day, you're likely to find it.
Over the next several mornings the Moon passes through a part of the zodiac
that's familiar territory to summer stargazers. The constellations of Scorpius and
Sagittarius are well placed in the southern evening skies during the warm
months. Furthermore, they are rich in fascinating objects -- star cluster and gas
clouds -- that are favorites to scan with unaided eye, binoculars, and telescope.
Before dawn today, the Moon stands 3 degrees (6 moon diameters) to the upper
right of Antares, the bright star that marks the heart of the scorpion. Tomorrow
morning look for Luna above the tail of Scorpius.
Tomorrow morning before sunrise, the waning crescent Moon sits amidst the
stars that mark the "lid" of the teapot pattern that is often associated with
Sagittarius. Notice the triangle of 3rd-magnitude stars surrounding the Moon, each
star approximately 3 degrees (6 moon diameters) from Luna. The following
morning the Moon slips 8 degrees to the lower left of the teapot's handle. That
morning offers the last easy chance to spot the old crescent Moon before it turns
New.
Although certainly no match for its brilliance last summer, Mars is still 1st
magnitude and easy to spot because it's situated in a relatively faint patch of sky.
An hour after sunset you'll find it hanging nearly two-thirds of the way up in the
southwest. The planet is within the boundary of the constellation Aries, the Ram.
The brightest star in the constellation is 2nd-magnitude Hamal, or Alpha. It sits 9
degrees (a fist) to the upper right of Mars.
The hairline crescent Moon presents a challenge to observers tomorrow morning.
Although Luna is 25 degrees (2 1/2 fists) away from the sun, for mid northern
latitudes it rises only about 30 minutes ahead of sunrise. The reason is that the
Moon's orbit currently is tilted at a shallow angle with respect to the southeastern
horizon. The farther south you are, the steeper the angle becomes, and the easier
it is to sight the Moon. Observers in the southern states have the best hope of
capturing Luna low in the east-southeast tomorrow morning.
Venus and Mars are now 28 degrees (3 fists) apart. These two planets pull within
6 degrees of each other in late April. Venus and Saturn currently span 85
degrees. In early May their separation decreases to 15 degrees. Mars and Saturn
also cozy up. They pass within 2 degrees of each other in late May. You have an
invitation to the planetary party this spring.
The magnificent region of the sky that contains Orion and related bright
constellations is at its best in early evening this time of the year. Look toward the
south. Even if you know none of the constellations, you'll still be impressed with
the number of stars that appear in that area. You owe it to yourself and your
children to acquire a simple star map and learn/teach the principal constellations
(and stars) of winter: Orion (Betelgeuse and Rigel), Canis Major (Sirius), Canis
Minor (Procyon), Gemini (Pollux and Castor), Auriga (Capella), and Taurus
(Aldebaran).
The Moon turns New this morning at 4:18 a.m. EST. Folks in Hawaii have a rare
chance to spot the ultra thin crescent -- less than 20 hours old -- just after
sunset tonight. For those of us on the continent, the Moon is just too young. We'll
have to wait until the following evening to catch a glimpse. By then it becomes
relatively easy to find. Look near the horizon between west and west-southwest,
beginning 30 minutes after sunset. Eventually you are certain to see the Moon. It
sets about 1 1/2 hours after the sun.
First sight of the crescent Moon this evening marks the beginning of the Islamic
New Year 1425 A.H. Look for it between west and west-southwest. The three
"belt" stars of Orion are easy to find and to show others. From left to right (east to
west) the stars are Alnitak (al-nee-TAK), Alnilam (al-nee-LAM), and Mintaka (min-
TAAK-ka). Take time to learn to pronounce their names and impress your family,
friends, and acquaintances of the opposite sex. Astronomy nerds are considered
desirable, aren't they?
The Moon is lovely to behold in the west-southwestern evening sky. The delicate
bright arc frames the ashen gray disk in what has been poetically referred to as
"the old moon in the new moon's arms." The dim portion of the Moon is often
called earthshine because that's what illuminates it. Sunlight bouncing off the
Earth hits the Moon and reflects back to us. If you were standing on the Moon
looking back at Earth, our planet would have the complementary phase, that is, it
would appear gibbous rather than crescent.
Celestial Scenery Alert! The Moon and Venus team up to produce an impressive
display this evening. The two brightest nighttime objects sit 3 degrees (6 moon
diameters) apart in the western sky. The proximity of Venus and the Moon
provides an excellent opportunity to view a planet in daylight. Simply find Luna
while the sun is up and use it to pinpoint Venus. Binoculars will help you initially
find Venus, but once located, the planet should be visible with normal eyesight.
The challenge is easier just before sunset (technically still daylight), but you may
wish to try earlier. Venus is to the upper right of the Moon.
On Shrove Tuesday the crescent Moon hovers between Venus and Mars, about a
fist width from either planet, although slightly closer to Venus. The Red Planet,
coincidentally, is in heliocentric opposition with Pluto today, too. That's an
astronomer's way of saying that the two planets are on opposite sides of the sun
as seen from a viewpoint far above the solar system. The alignment has no
particular significance. It's merely a shorthand way of describing the planets'
positions.
The Moon appears 2 degrees (4 moon diameters) below Mars during early
twilight. As the night progresses Luna inches to within a degree of the Red
Planet. Closest approach occurs about 4 hours after sundown. The Moon slides
even closer for some locations in the southern hemisphere. Off the coast of Chile,
it occults or passes completely in front of Mars.
The scene we now witness in early morning, just before dawn, is full of the stars
that we associate with summer. Scorpius and Sagittarius are low in the
southeast. The Summer Triangle is halfway up in the east. The "summer" Milky
Way flows across the eastern sky. So, if you'd like a preview of the constellations
of June evenings, observe some morning before first light.
The Moon reaches First Quarter at 10:24 p.m. EST. It resides in the constellation
of Taurus. The bull's eye, bright star Aldebaran, appears 8 degrees (a fist) to
Luna's lower left, while the famous Pleiades star cluster sits the same distance
to the lower right. Use binoculars for a good view. Tomorrow night look for the
Moon above and to the left of its current position, but still within Taurus. Notice
how high in the sky the Moon passes. It's near the position that the sun occupies
in late spring.
Once darkness falls, look carefully at Jupiter in the east. The Giant Planet passes
within a tenth degree of the 5th-magnitude star Chi, in Leo. You may be able to
pick out the star with binoculars that are held steady or mounted on a tripod. If you
have access to a telescope, use this as an excuse to view Jupiter. The star
appears not that different than the bright moons of Jupiter. Chi is the point of light
about 3 Jupiter diameters to the lower right (south).
It's Leap Day, the point in time we find it necessary to fiddle with our calendar in
order to remain aligned with the universe, so to speak. If we didn't make this
periodic adjustment, eventually we'd have spring occurring in June. The current
scheme, which we call the Gregorian calendar, produces a year with an average
length of 365.2425 days. The true length turns out to be 365.2422, so we're still a
little off. The error amounts to one day every 3,300 years, which suffices for most
of us.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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