To the reader:
The Skywatcher's Diary for December 1999 has been prepared by Robert C.
Victor. 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 December issue, please send
a long, self-addressed stamped envelope to:
December 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/
Planet Summary for December Evening: Jupiter at mag. -2.7 is
brightest evening "star," in ESE at dusk early in month, drifting to high
in SE by month's end. Saturn, at mag. 0, is the bright object 16
to 15 degrees to Jupiter's lower left at dusk. Mars appears as a
reddish "star" of first magnitude in SSW to SW at dusk. Watch lineup
of bright outer planets, Mars-Jupiter-Saturn, shrink, from 97 degrees
long on Dec. 1, to 73 degrees on Dec. 31. Mars will pass the giant planets
on April 5 and 15 of the year 2000, before they disappear into the western
evening twilight glow. Our Sky Calendar will illustrate them frequently
until then. Morning: Venus at mag -4 is brilliant in SE at dawn.
Mercury,
brighter than mag 0, appears farthest from Sun, 20 degrees, on Dec. 2 and
3. On Dec. 3-7, Mercury lingers 23 degrees lower left of Venus, and remains
in excellent view first half of month. Odds 'n' ends: Moon near
planets mornings of Dec. 3-6, and evenings of Dec. 11, 12, and 17-19; Geminid
meteor shower nights of Dec. 13 and 14; Moon shines with rare brilliance
on nights of Dec. 21 & 22.
Skywatcher's Diary: December 1999
Please note: in Skywatcher's Diary, morning events are described on the
previous date.
Wednesday, December 1
At nightfall, about 1-1/2 hours after sunset, locate Mars in SSW to SW.
Note 3rd-mag. star Beta in Capricornus 6 degrees upper right of Mars, and
the close double star Alpha Cap another 2.4 degrees upper right of Beta
Cap. (Binoculars easily show Alpha as a double star, and split the closer
pair Beta as well.) Mars, Beta, and Alpha lie in a straight line this evening.
Using binoculars, look for 4th-mag. Theta Cap 9.5 degrees upper left of
Mars, and 6th-mag. Uranus 20' (arcminutes) or 1/3 degree lower right of
Theta. Watch for changes in positions of Mars and Uranus as they move toward
Theta by about 3/4 degree and 2' per day.
On Thursday about an hour before sunrise, the waning crescent Moon is
high in SE, with brilliant Venus 16 degrees lower left. Spica is within
5 degrees right of Venus, and Mercury is low in ESE, 24 degrees to Venus'
lower left. On Thursday and Friday mornings, Mercury appears farthest from
Sun this time around its orbit, 20 degrees.
Thursday, December 2
An hour before sunrise on Friday, look in SE for pretty grouping of crescent
Moon, brilliant Venus, and Spica a few degrees to their right. Low in ESE,
Mercury lingers 23 degrees lower left of Venus Friday through Tuesday December
7, and remains in excellent view through mid-December.
Friday, December 3
In the southeastern sky an hour before sunrise on Saturday, the old crescent
Moon is accompanied to its upper right by brilliant Venus and the blue-white
star Spica. Mercury is unusually easy to spot, low in ESE about 17 degrees
to Moon's lower left.
Season of Light continues at Abrams Planetarium. Showtimes are
Fridays and Saturdays at 8:00 p.m., and Sundays at 4:00 p.m., through December
19. For more information, call our recorded showline at (517) 355-4672.
Saturday, December 4
On Sunday an hour before sunrise, a beautiful thin old crescent Moon, with
earthshine on its dark side, is low in ESE about 18 degrees lower left
of Venus. Mercury twinkles about 6 degrees below Moon and 23 degrees lower
left of Venus. Spica is 7 degrees to Venus' upper right.
Sunday, December 5
Our family show, Bear Tales and Other Grizzly Stories, is presented
today at Abrams Planetarium. Shows are presented Sundays at 2:30 p.m. through
December 19.
Last chance for the thin old crescent Moon: An hour before sunrise on
Monday, locate brilliant Venus in SE with Mercury 23 degrees to its lower
left. The hairline thin old crescent is very low in ESE about 5 degrees
lower left of Mercury. An hour before sunup in mid-lower Michigan, it is
nearly 35 hours until New Moon.
Monday, December 6
An hour after sunset these evenings, zodiac constellations visible, from
west to east, are Sagittarius setting in SW, Capricornus (containing Mars),
Aquarius, Pisces (containing bright Jupiter), Aries (containing Saturn),
and Taurus (containing the beautiful Pleiades and Hyades star clusters
and the first-magnitude star Aldebaran) low in E to ENE.
Tuesday, December 7
The Moon is New at 5:32 p.m. EST today and won't be seen until shortly
after sunset on Wednesday. An hour before sunrise these mornings, the zodiac
constellations visible, in order from west to east, are Taurus setting
in WNW, Gemini (containing Pollux and Castor), Cancer, Leo (containing
Regulus), Virgo (containing Venus and Spica), and Libra (containing Mercury),
just risen in ESE.
Wednesday, December 8
First chance to see the young Moon: Find a place with an unobstructed view
of the horizon between SW and WSW. About 25 minutes after sunset, if the
sky is clear, look for the very slender crescent Moon just a few degrees
above the horizon. The Moon's age (time elapsed since New) is then about
23 hours from New England, 24 hours from Michigan to the Southeast U.S.,
26-27 hours from the West Coast, and 29-30 hours from Hawaii. This evening's
first view of the lunar crescent marks the beginning of the Islamic holy
month of Ramadan. If the young crescent "Hilal" is seen this evening, fasting
begins on Thursday. Within the U.S. this evening, spotting the Moon is
most difficult in Alaska and New England, easier in the Southwest, and
very easy in Hawaii.
Thursday, December 9
The thin 2-day-old crescent Moon is an easy sight early this evening. Half
an hour after sunset, it's low in SW. As sky darkens, but before the Moon
sets, look for Mars in SSW 32 degrees to Moon's upper left. In a dark sky,
the 4th-magnitude star Theta in Capricornus should be visible 3.5 degrees
upper left of Mars. Using binoculars, look for 6th- magnitude Uranus passing
only 0.1 degree lower left of Mars tonight through Saturday.
Friday, December 10
Our feature show Season of Light is presented 8:00 p.m. tonight
and Saturday at Abrams Planetarium, and 4:00 p.m. on Sunday.
An hour after sunset, the 3-day-old crescent Moon is low in SW with
Mars 21 degrees to its upper left. Jupiter gleams well up in ESE, with
Saturn 16 degrees to its lower left. This evening Mars, Jupiter, and Saturn
span 90 degrees of sky. Keep watch until mid-April of 2000, when these
three bright outer planets will fit within a field just 5 degrees across!
Saturday, December 11
An hour after sunset, face SSW to see Mars about 10 degrees upper left
of the crescent Moon. On Sunday for much of eastern U.S., the Moon will
occult or cover Mars during daylight hours. From New York City, Mars will
be covered from 12:34 to 12:51 p.m. EST. For more information on the event,
check the website: http://www.lunar-
occultations.com/iota
By Sunday evening, the crescent will have overtaken Mars and will appear
to the planet's upper left. During the weekend of Dec. 17-19, the waxing
Moon will pass Jupiter and Saturn. Check Moon's position nightly, and watch
it move along the line of planets.
Sunday, December 12
Our family show, Bear Tales and Other Grizzly Stories, is presented
at 2:30 p.m.today at Abrams Planetarium. Our feature show, Season of Light
is presented at 4:00 p.m.
Using binoculars, can you spot Mars just before sunset? From East Lansing,
MI at sunset, Mars is just 1.2 degrees west (lower right) of the sunlit
crescent. The Moon-Mars gap at sunset is narrower from the East Coast,
wider from the West. Check Moon and Mars every half-hour this evening until
they set, and watch the Moon pull away from Mars. Using binoculars, look
for the 4th-mag. star Theta in Capricornus 1.3 degrees upper left of Mars,
and 6th-mag. Uranus 0.1 degree lower left of Theta.
An hour before sunrise these mornings, Venus shines brilliantly in SE.
On Monday Mercury is near the horizon 25 degrees to Venus' lower left.
Binoculars may show the 3rd-mag. star Beta in the head of Scorpius, 0.3
degree right of Mercury.
Monday, December 13
At nightfall, look for Mars in SW, 14 degrees lower right of the waxing
crescent Moon. Binoculars show 6th-mag. Uranus 0.7 degree N (upper right)
of Mars and 9 arcminutes (0.15 degree) upper left of 4th-mag. Theta Capricorni.
Tonight and again almost as strongly on Tuesday night, from late evening
until dawn, watch for the Geminid meteors near their annual peak in activity.
For more information, check the website of the International Meteor Organization
at http://www.imo.org
Tuesday, December 14
The relatively slow Geminid meteors, entering Earth's atmosphere at 35
km/sec or 78,000 miles per hour, seem to radiate from a point near Castor,
one of the Gemini twins. Keep watch from late evening until dawn, when
Gemini is well above the horizon.
Wednesday, December 15
If you face the setting Sun this evening, the Moon will be over your left
shoulder, about 90 degrees or one-quarter circle east of the Sun. The Moon
is at First Quarter phase, with its right half illuminated. When we gaze
at the First Quarter Moon in the evening sky, we are looking out the "rear
window" of Spaceship Earth as we orbit around the Sun. At nightfall, note
the lineup of Mars-Jupiter-Saturn and the star Aldebaran, 114 degrees long.
In our faster orbit, we are leaving behind these slower-moving outer planets.
Thursday, December 16
Tonight through December 26, watch the orbiting Moon move east by 14 or
15 degrees per day, passing Jupiter, Saturn, Aldebaran, Castor and Pollux,
and Regulus. The Moon is closer to Earth than usual these nights, and moves
eastward faster than its longterm average of 13 degrees per day against
the stars. The Moon's unusual closeness when Full this time around will
cause it to shine with rare brilliance on nights of December 21 and 22.
Friday, December 17
Final weekend of Season of Light at Abrams Planetarium. Showtimes
are Friday and Saturday at 8:00 p.m., and Sunday at 4:00 p.m. Abrams Planetarium
will be closed Christmas and New Year's holiday weekends.
Friday, December 17 (cont'd) The waxing gibbous Moon is in SE an hour
after sunset, with bright Jupiter 7 degrees to its upper left. Saturn is
16 degrees to Jupiter's lower left.
An hour before sunup on Saturday, Venus gleams in SE. The 3rd- magnitude
star Alpha in Libra or Zubenelgenubi, the "southern claw" of an early version
of the Scorpion, is 2 degrees to Venus' lower right. Using binoculars,
watch for the rising of Mercury 26 degrees lower left of Venus. Viewers
in southern states are favored to spot fainter Antares 5 degrees lower
right of Mercury a few days before northerners can find this star emerging
from the solar glare.
Saturday, December 18
An hour after sunset, the waxing gibbous Moon is in ESE. Bright Jupiter
is about 10 degrees to upper right, and Saturn about 8 degrees to Moon's
left.
Sunday, December 19
Our family show, Bear Tales and Other Grizzly Stories, is presented
at 2:30 p.m.today at Abrams Planetarium. Final showing of Season of Light,
today at 4:00 p.m.
Look in E to SE as sky darkens. Look for Saturn 9 degrees and bright
Jupiter 24 degrees to Moon's upper right, and Aldebaran 21 degrees to Moon's
lower left. Look again on Monday evening.
An hour before sunrise on Monday, locate brilliant Venus in SE. Using
binoculars, scan the horizon in the next 15 minutes, watching for the rising
of Mercury 26 degrees lower left of Venus, and fainter Antares 6 degrees
right of Mercury. Each morning Mercury gets lower, Antares higher, and
soon Antares will replace Mercury.
Monday, December 20
An hour after sunset, the Moon is in the east, with Saturn and bright Jupiter
far to its upper right. First-magnitude Aldebaran, eye of Taurus, is 5
or 6 degrees to Moon's lower left. Using binoculars, look for stars of
the Hyades Cluster between the Moon and Aldebaran. Overnight, the Moon
will pass through the "V" of the Hyades and closely north of Aldebaran.
From mid-Michigan the Moon passes one Moon's width north (upper right)
of the star around 5:30 a.m. EST, not long before they set in WNW.
Tuesday, December 21
For the last time this year, the Moon rises before sunset. About 10 to
25 minutes before sunset, Sun and Moon are just above opposite horizons.
At nightfall, about 1-1/2 hours after sunset, look for Aldebaran 10 degrees
to Moon's upper right, and Betelgeuse, shoulder of Orion, low in east about
15 degrees below the Moon. It's a busy night, astronomically: Winter begins
at 2:44 a.m. Wednesday. Then around 6 a.m. EST, the Moon is 221,614 miles
from Earth, its closest approach of the year. A huge Moon sets in WNW as
morning twilight brightens, not long before sunrise. Since the Moon will
be Full at 12:31 p.m. EST on Wednesday, it will cause a large range in
coastal tides, and will shine with rare brilliance tonight and Wednesday
night. If your landscape is snow-covered, the effect of increased moonlight
will be especially striking.
Wednesday, December 22
Tonight's Full Moon before Yule, or Long Night Moon, rises nearly 30 degrees
north of east about 20 minutes after sunset. Thursday's moonrise will occur
near the same point on the horizon about 1 hour 4 minutes later than tonight's.
Moonrises tonight and Thursday are the northernmost of this month. At nightfall
tonight. about 1-1/2 hours after sunset, look for Betelgeuse, shoulder
of Orion, to the Moon's right, and Pollux and Castor, the Gemini Twins,
to the Moon's left. By dawn's first light (about 1-1/2 hours before sunrise)
on Thursday, the Moon is in the west, with the Twins above and Betelgeuse
below.
Thursday, December 23
The Moon rises within 1-1/2 hours after sunset, just before the sky darkens
fully. Three hours after sunset, look very low in east, 15 degrees to Moon's
lower right, for Procyon, brightest star of Canis Minor, the Lesser Dog.
Pollux and Castor, the Twins, are 8 and 12 degrees to Moon's upper left.
By an hour before sunrise on Friday, the Moon is well up in the west, with
Procyon lower left and Twins to its upper right.
Friday, December 24
Three hours after sunset, Moon has just risen in ENE, far below the Gemini
Twins and far left of Procyon in the east. The name Procyon means "before
the Dog"; from the latitude of lower Michigan, Procyon comes up about 30
minutes before Sirius, the "Dog Star," rises in ESE. Follow Orion's belt
downward to find your way to Sirius, brightest nighttime star.
Saturday, December 25
An hour before sunrise on Sunday, the waning gibbous Moon is in WSW, with
Regulus, heart of Leo, 4 degrees to its upper left.
Sunday, December 26
In the SW at nightfall, about 1-1/2 hours after sunset, find first- magnitude
Mars with the 3rd-magnitude star Deneb Algedi, tail of the Sea-goat, 1.5
degrees lower left. The 4th-mag. star Gamma Capricorni is 2.4 degrees below
Mars and 1.8 degrees lower right of Delta. Look for 4th-mag. Theta Cap
10 degrees lower right of Mars. Binoculars show 6th-mag. Uranus 0.7 degree
upper left of Theta.
Monday, December 27
In late December each year, Orion the Hunter rises just before nightfall.
In the opening lines of his poem "The Star-Splitter," Robert Frost wrote
a fine description:
"You know Orion always comes up sideways. Throwing a leg up over our
fence of mountains, ..."
Tuesday, December 28
An hour before sunrise on Wednesday, the "half" Moon is in the southern
sky, with Spica, spike of wheat or ear of corn in hand of Virgo, 18 degrees
lower left. The Moon is at Last Quarter phase, which places it 90 degrees,
or one-quarter circle, west of the rising Sun. When we gaze at the Last
Quarter Moon in the morning sky, we are looking out the "front window"
of Spaceship Earth as we orbit around the Sun. In the SE, faster-orbiting
Venus is pulling away from us. At sunrise, note that the Moon's sunward
or left half is illuminated.
Wednesday, December 29
An hour before sunrise on Thursday, just east of due south, locate the
blue-white first-magnitude star Spica 8 degrees below the fat waning crescent
Moon.
Thursday, December 30
An hour before sunrise on Friday, Venus shines in SE, with reddish Antares,
heart of the Scorpion, 11 or 12 degrees below. They'll move closer to each
other until January 8.
Friday, December 31
Well up in SE an hour after sunset, find bright Jupiter with Saturn 15
degrees lower left. Mars is in SW. By tonight the shrinking lineup of Mars-Jupiter-Saturn
is 73 degrees long. Jupiter and Saturn gradually approach each other until
their closest conjunction within 1.2 degrees apart on May 28, 2000. But
we'll lose sight of the two giant planets in the western evening twilight
glow soon after the middle of April. Before then, while they are still
visible, Mars will overtake Jupiter on April 5, and Saturn on April 15.
On the latter date, all three bright outer planets will fit into a 5-degree
field, their most compact gathering between December 1901 and November
2080. Keep track of Jupiter and Saturn until mid-April 2000, and again
starting in early June, when they begin to emerge into the eastern sky
at dawn.
Conjunctions, or pairings of Jupiter and Saturn occur every 20 years.
After the spring of 2000, the next (a very close one!) will be visible
in the evening sky on December 21, 2020. (Mark your calendar!) For lifetime
naked-eye planet-watchers, Jupiter and Saturn mark the slow hands of the
great celestial clockwork of the solar system.
The daily sky diagrams on the Abrams Planetarium's Sky Calendar
makes following the Moon and planets easy and fun. Subscriptions are $9.00
per year, starting anytime, from Abrams Planetarium, Michigan State University,
East Lansing, MI 48824. Join us in time to catch the simultaneous appearance
of four planets in the evening sky in February 2000.