To the reader:
The Skywatcher's Diary for October 2003 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 October issue, please send a long,
self-addressed stamped envelope to:
October 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: October 2003
An hour after sunset this evening the stout crescent Moon perches relatively low in
the south-southwestern sky. Although the Moon technically lies within the
boundaries of Sagittarius, it is situation between the brighter stars of that
constellation and Scorpius. The spot is within a couple degrees of the direction
toward the center of the Milky Way galaxy. The Moon is a foreground object, of
course, lying about 1.2 light seconds from us. (That's how long it takes light to
reach us from the Moon.) Our galaxy's center is some 30,000 light years beyond.
The Moon passes First Quarter phase this afternoon at 3:09 p.m. EDT. Tonight
can you detect that the Moon is slightly larger than half? Luna sits among the
stars of the "teapot's handle," as that part of the constellation Sagittarius is often
called. Second-magnitude Nunki, the brightest of the four handle stars, lies 1 1/2
degrees (3 moon diameters) above the Moon. The other three stars are 2
degrees to the upper right, 3 degrees to the lower left, and 3 degrees to the left of
Luna. Binoculars can help pick them out from the moonlight.
If you've yearned for a glimpse of those magnificent rings of Saturn, the planet is
slowly working its way back into the evening sky. It now rises before midnight and
reaches its highest point due south about sunrise, so it's well placed for early
dawn viewing. Early risers can find the planet about 20 degrees (2 fists) to the
upper left of Orion's famous shoulder star, Betelgeuse, and smack in the middle
of the constellation Gemini.
Jupiter is now high enough in the dawn sky to be conspicuous to anyone with an
uncluttered view to the east. An hour before sunrise it stands 19 degrees (2 fists)
above the horizon. Fainter Regulus, heart of Leo, perches 8 degrees to the
planet's upper right. See if you can spot Mercury, about a magnitude fainter than
Jupiter, 16 degrees to the brighter planet's lower left and 3 degrees above the
horizon.
The gibbous Moon sits 8 degrees to the right of Mars. Tomorrow night look for it 5
degrees to the planet's lower left. Uranus is in the vicinity of Mars, about 4
degrees above. To locate the faint planet use binoculars and a finder chart, such
as the one found at http://www.pa.msu.edu/abrams/Oct503.pdf. Wait until the
Moon has moved out of the region and try to detect Uranus without optical aid
from a dark location away from city lights.
How soon after sunset can you spot Capella? The star rises in the north-
northeast about the time the sun sets. By the end of twilight it perches 7 degrees
above the horizon. Sometime between those two moments the star will become
distinguishable, first with binoculars, then with unaided eye. Looking for objects
as they first become visible is good training for the eye and makes you aware of
the subtleties of the sky. It also provides challenge and reward.
The Big Dipper is sliding low in the northwestern sky. Some Native American
legends hold that the bowl of the Dipper symbolizes a great bear being chased by
three hunters (the handle stars). About this time every year the lead hunter pulls
back his bow and fires an arrow that strikes the bear. Blood from the wound drips
onto the trees, producing the vibrant red leaves we marvel at each autumn. The
bear is immortal. He rests the winter months near the northern horizon and by
spring begins climbing the northeastern sky, where the hunt begins anew.
Since around the time of its closest approach near the end of August, Mars has
remained a brilliant evening object. Even though the Red Planet's luminosity
diminishes below the brightest star, Sirius, by month's end, it's still quite a show
to unaided eye. Telescopically, Mars definitely wanes as November approaches.
The growing distance between Earth and Mars shrinks the planet to the point that
little detail is visible in moderate telescopes. The extraordinary opportunity for
backyard amateurs is coming to a close.
To the casual observer the Moon will look Full this evening, although the exact
moment of the phase doesn't occur until 3:27 a.m. EDT tomorrow morning. Once
the Moon climbs above the trees, an hour or two after sunset, carefully inspect its
lower left edge. Compare it to the Moon's upper right side. Does the left appear
slightly more ragged? Use binoculars or a telescope, if you have them. Tomorrow
night again compare the two edges. The effect should be reversed.
The Full Moon that officially occurred early this morning is traditionally known as
the Hunter's Moon. The astronomical effect usually associated with last month's
Harvest Moon is also evident with the Hunter's Moon. That is, for several nights
around the time of Full Moon, Luna rises each night only slightly later than the
night before -- significantly less than the year's average. This month, instead of
providing light to gather crops, the quick-rising Moon is said to make it easier for
hunters to stalk their prey.
It is generally known that the Big Dipper can help locate Polaris, the North Star,
but which Dipper stars to use is frequently forgotten. The Pointers, as they are
often called, are the two stars at the end of the bowl. Merak (MEE rak) is currently
the lower of the two stars and Dubhe (DUBB ee) the upper. Their separation is 5
degrees. Because the North Star is 25 degrees away, an imaginary line drawn 5
times as long as the distance between the Pointers takes your eye to Polaris.
Don't make the common error of expecting Polaris to be brilliant. It's the same
brightness as the Pointers.
The star names Merak and Dubhe have Arabic origins, both referring to parts of a
bear. Merak translates as "loin," and the position of that star in the classical figure
of Ursa Major, the Great Bear, fits that description. Similarly, Dubhe is placed in
the pattern to mark the "back of the bear," which roughly equates to its ancient
Arabic meaning.
The Moon lies between the Hyades and Pleiades star clusters tonight. The
Pleiades, or Seven Sisters, is easily recognized as a cluster. If you have difficulty
doing so, try again once the Moon leaves its proximity. The Hyades is a more
diffuse collection of stars, so its identity as a cluster is much less obvious. The
Hyades is more often thought of as the "face" of Taurus. Its stars include those
that form the familiar "V" shape. The bright beauty Aldebaran is a foreground
object that's not part of the group.
The Moon rises a couple hours after sunset tonight. Once it's above the tree line,
look for Aldebaran, the eye of Taurus, 8 degrees (approx. a fist) to Luna's right
and slightly lower. By dawn tomorrow the lunar scene shifts to high in the west-
southwestern sky, and the orientation is noticeably different, too. Aldebaran then
appears 11 degrees below and slightly to the left of the Moon.
Tonight the Moon rises about 3 hours after sunset. If you have the opportunity to
watch moonrise, notice how far north of due east Luna comes up. It's only a few
degrees to the south of northeast. Tomorrow night the Moon rises about 50
minutes later and peeks above the horizon a degree still farther north -- the
northernmost rise point for this cycle of phases. The following night (17th) the
rising point will be the same as tonight. Thereafter it drifts southward each night.
Tomorrow morning, before sunrise, look for the Moon perching high in the sky,
nearly overhead. The bright object 5 degrees (10 moon diameters) below it (to the
south) is Saturn. As dawn approaches try to continue to track the planet. Use the
Moon as a guide when bright twilight makes Saturn difficult to spot. Binoculars
coupled with the Moon serving as a pointer may allow you to sight the planet until
almost sunrise, or later!
Before sunrise tomorrow, while the sky is still dark, notice the two stars to the
upper right of the Moon, high in the south-southeast. They are the Gemini twins.
Pollux is the closest, about 2 1/2 degrees (5 moon diameters), and Castor is
another 5 degrees beyond Pollux. Saturn is the brighter object 13 degrees to the
lower right. The Moon passes Last Quarter phase at 8:31 a.m. EDT tomorrow
morning. Although the exact moment occurs after sunrise, the Moon will still be
easily visible at that time, provided the sky is clear. Look for it very high up.
Tomorrow morning, a couple hours before sunrise, the Moon sits halfway
between Saturn, about 24 degrees (2 1/2 fists) to the upper right, and the star
Regulus in Leo, to the lower left. You will notice that the Moon is not directly
aligned with the two objects but slightly to the upper left. Three to 4 degrees south
(lower right) of Luna lies the Beehive star cluster. To examine it with binoculars,
place the Moon outside the field of view so that the moonlight will be less
bothersome.
Tomorrow morning the Moon enters the constellation boundary of Leo. It sits to
the right of the lion's head (about even with his nose) and 11 degrees (a fist)
above Regulus, the beast's heart. Jupiter is the brilliant object 22 degrees below
and slightly left. The following morning (Tuesday), the waning crescent hangs 5
degrees to the left of Regulus and 9 degrees above Jupiter, in the lion's belly.
The Orionid meteor shower makes its annual appearance over the next three
mornings. The thinning Moon provides only slight interference. The shower is
best viewed before dawn and from a dark location. Expect to see not more than
one meteor every 3 minutes, on average. Perhaps most intriguing about the
Orionids: the dust particles that produce the streaks of light are from Halley's
Comet, sloughed off when the famous comet passed close to the sun.
The waning crescent Moon -- only 3 days before New -- makes a lovely
companion to brilliant Jupiter in tomorrow's dawn sky. The pair sits about 30
degrees up (3 fists) in the east an hour before sunrise. Planet and Moon are
separated by 7 degrees. With sunup occurring later, many of us will have the
opportunity to catch Luna and Jupiter on our way to work, provided we remember
to look!
The next two mornings offer excellent views of thin crescent Moons. Tomorrow, an
hour before sunrise, Luna will be easy to find. It perches 16 degrees (a fist and a
half) above the eastern horizon, slightly south of due east. The following morning
at the same time, the Moon pokes only 2 degrees up. If you have difficulty finding it
at first, continue to watch in the general direction and you'll likely snag Luna as it
continues to rise higher. Both mornings notice that the crescent is tilted nearly
horizontal. Compare that to the tilt of the evening crescent you will see in 3 or 4
days.
Autumn is the best time of the year to look for the "zodiacal light" in the predawn
sky. This glow is created as sunlight reflects and scatters off grains of dust and
rock dispersed throughout the plane of our solar system. The dust is exceedingly
tenuous, so the light from these particles reaching Earth is faint -- but visible. To
see it, choose a morning when the Moon is not present and the sky is especially
clear. You must look before morning twilight begins, which now occurs about 1
1/2 hours before sunrise at mid northern latitudes. The zodiacal light appears as
a ghostly pyramid rising out of the east and tilted slightly toward the south.
The Moon reaches New phase tomorrow morning at 8:50 a.m. EDT. It passes
between the sun and us at this phase and so is invisible, except during the rare
occurrence of a solar eclipse. Coincidentally, Mercury is close to alignment with
the sun tomorrow, too. The planet, however, travels on the far side of its orbit
behind the sun. The Moon lies 228,000 miles away from us while Mercury speeds
by at a distance of 132,000,000 miles from Earth, about 600 times farther than the
Moon.
Saturn now rises about 4 hours after sunset, so it's clearly visible in the east-
northeast before midnight. As the night progresses and the planet climbs, it
becomes easier to tell that Saturn appears among the stars of Gemini. The
planet begins retrograde today, that is, its motion relative to those stars will be
westward over the next 4 months. Watch it gradually drift toward the "feet" of the
Twins. Reminder: most places in the U.S. set their clocks back an hour tonight in
order to return to Standard Time tomorrow.
If you've needed an excuse to exert the effort required to locate Venus in the
evening sky, tonight the young crescent Moon may provide the motivation. The two
objects sit within 2 degrees (4 moon diameters) of each other in bright twilight.
Twenty minutes after sunset the pair hangs 4 degrees above the horizon just to
the south of west-southwest. Twenty minutes later the two objects set, so careful
timing is essential.
With the first sighting of the crescent Moon after New, last evening around sunset,
the Islamic holy month of Ramadan began for the continental U.S. and Hawaii.
The time of fasting will continue until the next lunar month begins with another
young crescent sighting. That event should occur on November 24, for the
continental U.S. and Hawaii, but will be a bit more difficult than this month's
sighting.
The crescent Moon, now filling out nicely, continues to hang relatively low above
the southwestern horizon during twilight. Notice how the crescent is tilted more
nearly vertical than usual, and significantly different than the old crescent Moon in
the morning sky 4 or 5 days ago. These evening and morning tilts of the crescent
are characteristic of fall, particularly around the time of the autumnal equinox. Six
months from now the tilts will be reversed, that is, the crescent will appear vertical
in the morning and horizontal at dusk. If you'd like to understand why the change
occurs, look up "seasonal tilt of the ecliptic" in an astronomy textbook or on the
web.
This evening the crescent Moon appears among the stars of the "lid" of the
"teapot," a portion of the constellation Sagittarius. An hour after sunset the two
stars of that pattern that are easiest to spot are Nunki, or Sigma, 5 degrees (half a
fist) to the upper left of the Moon, and Kaus Australis, or Epsilon, 7 degrees below
Luna. Both stars are 2nd magnitude.
Mars is still a handsome object in the evening sky. It remains visible until around
3 a.m., when it sets. Although the planet has lost some of its luster since the
closest passage in August, it is still dramatically bright. It is now slightly less
luminous than the brightest star, Sirius, but verifying that fact by observation could
be tricky, since Sirius rises only two hours before Mars sets.
The Moon turns First Quarter at 11:25 p.m. EST, just before midnight. If we still
observed Daylight Saving on this date rather than Standard time, the phase would
occur an hour later, and therefore the next day, on November 1. Similarly, for the
time zone east of Eastern Standard, known as Atlantic Standard, the date of First
Quarter is the first of November. This shifting of the date occurs somewhere on
the Earth for any celestial event that, like the moon phase, happens at the same
instant worldwide.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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