To the reader:
The Skywatcher's Diary for February 2005 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 2005
The bright "star" sitting more than a fist width to the right of the Moon during
twilight this morning is Jupiter. The planet currently resides among the stars of
Virgo. The star between and below Jupiter and Luna is Spica, brightest in that
constellation. Notice the Moon is slightly larger than half -- technically a waning
gibbous. It turns Last Quarter at 2:27 a.m. EST tomorrow morning.
Today, suffering from a severe bout of cabin fever, we look for the shadows cast
by small furry animals in an attempt to divine the number of weeks of winter
weather remaining. This quaint custom is now associated with the notion of mid
winter. In earlier times and in different parts of the world, today would have
marked the start of spring. The equinox then represented the middle of spring
rather than its beginning.
Tomorrow morning an hour before sunrise, an attractive crescent Moon perches
in the south-southeast. Antares, heart of the scorpion, sits 5 degrees (half a fist or
10 moon diameters) to Luna's upper right. The following morning at the same
time, the Moon slips another 14 degrees to the lower left. Then, it rests 5 degrees
to the lower right of Mars. Notice how similar Antares and Mars appear.
Although Comet Machholz has slipped a magnitude off of its brightest, you should
still be able to pick it up with unaided eye from a dark location. Look north, two-
thirds of the way up. Just to the west (left) of due north find the constellation
Cassiopeia, shaped like a letter "M". Its stars are similar in brightness to the Big
Dipper. Tonight the comet sits 7 degrees (less than a fist) to the right of
Cassiopeia. Look at the end of twilight.
Tomorrow morning is the last comfortable opportunity to spot the waning crescent
Moon. Luna rises a little more than an hour before sunrise. Forty-five minutes
before sunup it sits 5 degrees above the southeast point on the horizon. Fifteen
minutes before daybreak, the Moon is 9 degrees up. Venus then appears 21
degrees (2 fists) to the lower left of the Moon but only 3 degrees above the
horizon. If you locate Venus, use it the following morning to help pinpoint Luna, 7
degrees to the planet's right.
This time of year a little reminder of the warm season is often welcome. Look to
the morning sky for a summer preview. The Summer Triangle stars now rise
enough ahead of the sun for you to easily see them in the eastern sky an hour
before sunrise. The scorpion and Sagittarius, other familiar sights of summer,
show up in the southeast.
Pollux and Castor, the bright stars of the constellation Gemini, are often referred
to as the twin stars. Look for them in tonight's sky to the upper left of Orion, along
with brighter Saturn. While at casual glance the stars look alike, closer inspection
reveals differences. Pollux is 1st magnitude, for example, and Castor is a bright
2nd. Pollux is somewhat cooler than our sun and therefore slightly orange
colored, while Castor is hotter and more white.
The Moon turns New tonight at 5:28 p.m. EST, about the time it and the sun set,
as seen from the continental U.S. The Earth, Moon, and sun are lined up then,
more or less. Perfect alignment would mean that a solar eclipse occurs, and
none is visible this month. Astronomers like to refer to the alignment of several
astronomical bodies as a "syzygy" (SIH zih gee) What a great word, don't you
think? Syzygy. Work it into a conversation and watch your friend's expression.
The Islamic New Year 1426 begins tonight around sunset. Its onset is
determined by the first sighting of the young crescent Moon. Luna sets about an
hour after sunset in the U.S. Thirty minutes after sundown the Moon perches 5
degrees (half a fist) above the west-southwest horizon, 4 degrees south (left) of
the sunset point. Because the Moon is so young and delicate, binoculars will be
helpful.
Tonight the slender crescent Moon is a treat for the eye. The natural beauty of this
phase makes it the moon shape most often replicated in artwork and symbolism.
Luna sits by itself low in the west-southwestern sky during dusk. No bright
planets or stars are in its vicinity. As the sky darkens, notice the earthshine, the
dim gray portion of the Moon that fills in the crescent and completes the sphere.
The Equation of Time, the difference between time told by a properly set clock and
an accurate sundial, is at a minimum today. The sun is about 14 minutes behind
the clock. Another way of thinking about it is the sun runs 14 minutes behind its
average position. This variability in Sol's position occurs because the Earth's orbit
is oval rather than perfectly circular, and its rotation axis is not precisely
perpendicular to the orbit.
Sundials are usually considered to be decorative rather than serious
timekeepers. That's because most sundials available to the average person are
strictly ornamental. A well-constructed, properly aligned sundial can be made to
tell time within seconds. In addition, sundials embody a rich history of culture,
science, and art. To further explore the topic, start with the North American Sundial
Society website, http://sundials.org/registry/.
The Moon hangs to the lower left of Aries, the Ram, tonight, 11 degrees (a fist)
from the constellation's brightest star Hamal. Shining at only 2nd magnitude,
Hamal may not be obvious with moonlight so near. The constellation is faint
overall. Its distinction comes from its placement in the zodiac. Tomorrow night the
noticeably larger crescent Moon perches 11 degrees to the left side of Hamal.
Today Mercury sits in its orbit on the far side of the sun what astronomers call
superior conjunction. Later this month the fast moving planet emerges in the west
shortly after sunset. This best-of-the-year evening appearance of Mercury peaks
in early March. If you have never seen Mercury, then will be the time to check it off
your life list. Keep following our sky watching tips and we will pinpoint it for you.
Luna reaches First Quarter at 7:16 p.m. EST. The Pleiades star cluster sits 3
degrees (6 moon diameters) to the Moon's upper left. Use binoculars to examine
both the Pleiades and the Moon. At this phase, Luna is particularly pleasing under
magnification. Well-defined craters line the terminator (the boundary between day
and night), and darker oval basins known as Maria, or seas, dominate the Moon's
western (right) side.
The bright star 9 degrees (a fist width at arm's length) below and slightly left of the
Moon is Aldebaran, eye of Taurus. The star's name derives from ancient Arabic
meaning "the Follower," denoting that the star trails the Pleiades cluster across
the sky. In early contexts the term referred to the group of stars around Aldebaran
as well. We now know that star concentration as the Hyades, a cluster similar to
the Pleiades.
Jupiter dominates the morning sky. In dawn twilight it sits a third of the way up in
the southwest, among the stars of Virgo. Spica is the bright star 6 degrees (half a
fist) to the planet's lower left. Jupiter is currently retrograding, so it's pulling away
from Spica and moving toward 3rd-magnitude Gamma in Virgo, now 8 degrees to
the planet's right. In early May Jupiter passes a little more than a degree below
Gamma.
Jupiter rises about 4 hours after sunset. That's near 9:30 p.m. local time, so it's
becoming observable at a reasonable evening hour. Once Jupiter clears the thick,
unsteady lower atmosphere, it and Saturn -- the two best planets for small
amateur telescopes -- are both available for perusal. Jupiter's four bright moons
make an easy target, while its cloud bands provide more of a challenge.
The waxing gibbous Moon perches 7 degrees (14 moon diameters) above Saturn
this evening and 8 degrees to the planet's lower left tomorrow night. Through the
telescope, Saturn's rings are always pleasing, even to the pure neophyte. Titan,
that mysterious large moon of Saturn that the Huygens spacecraft successfully
landed on last month, appears 3 to 4 ring diameters to the west of the planet
tonight.
Tonight the Moon is left of Saturn and below the Gemini Twins, Pollux and Castor.
Because we so often refer to the two stars in the same breath, there's a tendency
to image that they are together in space, but such is not the case. Pollux lies 34
light years from Earth while Castor is 52 light years distant, about half again
farther than Pollux.
Jupiter passes a quarter degree below (south of) the 4th-magnitude star Theta in
Virgo. You will need binoculars or a telescope to find the star. Don't confuse it with
Jupiter's moons. The star is similar in brightness but the moons lie along the
equator of the planet, parallel to the cloud bands. Theta appears nearly
perpendicular to that plane.
Castor, the fainter of the Gemini Twins, is the more intriguing star. Amateurs
know it as a double star, where both components are visible in their telescopes. A
much fainter third star is also part of the same group. But the real fascination
comes when the light of these three stars is analyzed. Their spectra reveal that
each of the stars is also double. Castor is, in fact, a sextuplet system.
The Moon becomes Full at 11:54 p.m. EST. It rises near sunset in the east-
northeast. Once the sky becomes dark enough, notice the bright star Regulus 6
degrees (12 moon diameters) to Luna's upper right. Regulus represents the
heart of Leo, the Lion. The Full Moon of February in colonial times was known
variously as the Snow, Hunger, and Wolf moon.
One-and-a-half hours before sunrise Mars appears 10 degrees (a fist) above the
southeastern horizon. Tomorrow morning the planet lies 3 degrees to the upper
left of Nunki, the brightest star in the handle of the "teapot" figure of Sagittarius.
Coincidentally, the planet and constellation have an ancient connection. The
Babylonian name for Mars, the god of war, was Nergal, who also was thought to
rule Sagittarius.
If you wish to be among the first to spot Mercury at the start of its evening
apparition, look tonight 30 minutes after sunset. The elusive planet sits 2 degrees
above the horizon between west and west-southwest. Mercury's now near its
brightest but still low enough to be a challenge to find. Over the next two weeks it
will dim somewhat but climb higher. The net result is the planet becomes easier
to locate.
The waning gibbous Moon rises less than 3 hours after sunset. Shortly after Luna
appears, Jupiter follows, 5 degrees (10 moon diameters) to the lower left.
Throughout the night the pair drifts toward the western horizon and the planets
slide closer together. During dawn tomorrow the two bodies lie 2 degrees apart,
with Jupiter above the Moon. From parts of Australia, the Moon passes in front of
Jupiter.
The Big Dipper begins its annual climb up the northeastern sky. Toward the end
of dusk find it there standing on its handle. Some say it looks more like a kite in
this position, rather than the familiar long-handled cup. Because the constellation
is rotating around the North Star, as it rises higher it also turns upside down,
eventually pouring out its imaginary contents.
With the Moon now rising late, the time is ideal to observe the elusive zodiacal
light. This subtle glow, created by sunlight reflecting off interplanetary dust, is best
seen from mid northern latitudes at the end of evening twilight during moonless
nights in February, March, and April. Look toward the west for a cone-shaped wisp
of light, tilted slightly to the south. In order to avoid confusing it with the last
glimmer of twilight, be sure to observe at the end of astronomical twilight, about
1 1/2 hours after sunset.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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