To the reader:
The Skywatcher's Diary for February 2000 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 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/
Planet Summary for February Four evening planets! Jupiter is
brightest evening "star," high in SSW to WSW at dusk. Saturn is
bright object 13 degrees to 10 degrees to Jupiter's upper left. Mars
glows in WSW at dusk, 36 degrees to 19 degrees lower right of Jupiter.
During Feb. 6-27, the span of Mars-Jupiter-Saturn shrinks 5 degrees per
week, from 45 degrees to 30 degrees. Keep watching until mid-April, when
the three planets will fit into a field just 5 degrees across! The Abrams
Planetarium Sky Calendar will illustrate them frequently until then.
A fourth planet, Mercury, is very low in WSW to W in first 3 weeks
of February, to lower right of Mars by 28 degrees on Feb. 1, then closing
to 18 degrees when it is highest on Feb. 15 & 16. Mercury fades sharply
after midmonth. Morning Planet: Venus is brilliant low in SE to
ESE at dawn, lower at month's end. The Moon appears near a bright
planet on morning of Feb. 2, and on evenings of Feb. 6, 8, 10, and 11.
The Moon appears near one of the five first-magnitude zodiacal stars on
the evenings of Feb. 13, 16, 18 and 19, and on the mornings of Feb. 19,
23, and 27.
Skywatcher's Diary: February 2000
In Skywatcher's Diary, morning events are described on the previous date.
Tuesday, February 1
From lower Michigan one hour before sunrise on Wednesday, low in SE, brilliant
Venus is within a degree lower left of the sunlit edge of the waning crescent
Moon. Using the Moon as a guide, can you follow Venus past sunrise? From
East Lansing, MI, and other places at lat. 42.7 degrees north, Moon and
Venus reach due south about 2-3/4 hours after sunrise. In East Lansing
at that time, 10:37 a.m. EST, Venus will appear only 0.3 degree lower right
of the Moon's southern cusp (lower point of the crescent), and slightly
closer about 15 minutes earlier. The most spectacular view of this Moon-Venus
pairing in a dark sky will be from the West Coast, where their closest
pairing occurs before sunrise. From New York on the East Coast, Venus-Moon
are 1-1/4 degrees apart an hour before sunrise, and their closest approach
happens about 3-1/2 hours after sunup.
Wednesday, February 2
Four naked-eye planets are arranged in a line 75 degrees long across the
sky at dusk. In order from W to E 40-45 minutes after sunset, they are:
Mercury about to set in WSW, with Mars 27 degrees to its upper left. Bright
Jupiter is high in SSW 35 degrees upper left of Mars. Finally Saturn is
just west of due south and nearly 13 degrees upper left of Jupiter. Mercury
gets higher and easier to see each evening until midmonth.
Telescopically, the two giant planets are showpieces: Jupiter with its
dark cloud belts parallel to its equator, and four bright satellites orbiting
in its equatorial plane, and Saturn with its rings, now tipped 19 degrees
from edgewise.
An hour before sunrise on Thursday, find brilliant Venus low in SE,
with the waning crescent Moon rising within 10 degrees to its lower left.
Thursday, February 3
About 25 minutes before sunrise on Friday, from the Winter Star Party in
the Florida Keys, early risers may spot a very thin crescent Moon, just
risen in ESE 21 degrees lower left of Venus. Just over 25 hours remain
until Saturday's New Moon. For rest of the U.S., it will be harder to see
the Moon. Will anyone spot the old Moon on Friday morning?
Friday, February 4
Our feature show, From Stardust to Life: A Cosmic Journey, is presented
8:00 p.m. Fridays and Saturdays at Abrams Planetarium, and at 4:00 p.m.
on Sundays.
If you're fortunate enough to be in a place with no interference from
man-made lights, then your sky is probably dark enough at nightfall to
detect the zodiacal light. About 1-1/2 hours after sunset, face WSW and
look for a huge, softly luminous cone of light with its base near the horizon
and its axis near the lineup of three planets then visible. The light should
certainly appear to engulf Mars, now 39 degrees from the Sun. Does its
faint outer portion extend as high as Saturn, now 85 degrees from the Sun?
The brightening crescent Moon will begin to interfere on Monday evening,
but beginning on Feb. 21, the sky at nightfall will again be moonless.
Zodiacal light is from sunlight scattered by cometary and asteroidal dust
particles in the inner solar system, concentrated near the plane of the
ecliptic.
Saturday, February 5
New Moon occurs today at 8:03 a.m. EST. There is a partial solar eclipse
in Antarctica and the southern Indian Ocean. This New Moon marks the Chinese
New Year.
Sunday, February 6
Our family show, The Little Star That Could, is presented at 2:30
p.m. Sundays at Abrams Planetarium, and our feature, From Stardust to
Life: A Cosmic Journey, is shown at 4:00 p.m.
Watch the Moon climb past four bright planets this week! Tonight about
45 minutes after sunset, locate the thin crescent Moon about 4 degrees
up in WSW, with Mercury about 2 degrees to the Moon's north (right). Binoculars
give a fine view of this pairing low in twilight. To Mercury's upper left
(or above it from extreme southern U.S.) lie Mars 23 degrees from Mercury,
bright Jupiter 33 degrees beyond Mars, and finally Saturn 12 degrees beyond
Jupiter. The lineup of four planets is 68 degrees long tonight, shrinking
to 60 degrees by Feb. 12, 55 degrees by Feb. 18-22.
Monday, February 7
About 45 minutes after sunset, locate the crescent Moon with earthshine
in WSW, with Mercury about 12 degrees lower right, and Mars nearly as far
above Moon. High in SSW to SW lies the pair of giant planets, bright Jupiter
with Saturn 12 degrees to its upper left.
Tuesday, February 8
About 45 minutes after sunset, look in WSW for the waxing crescent Moon
with Mars 4 or 5 degrees to its right, and Mercury near the horizon 22
degrees lower right of Mars. Bright Jupiter is 31 degrees upper left of
Mars, while Saturn is just 12 degrees upper left of Jupiter.
Wednesday, February 9
During evening twilight, the 4-1/2-day-old crescent Moon is well up in
SW, with Mars some 15 degrees lower right, and Mercury low in the twilight
glow 21 degrees lower right of Mars. Bright Jupiter is some 17 or 18 degrees
upper left of Mars, and Saturn still 12 degrees upper left of Jupiter.
Thursday, February 10
Some 45 minutes to an hour after sunset, locate the crescent Moon high
in SW with Jupiter 5 or 6 degrees above or upper right. Saturn is 12 degrees
to Jupiter's upper left. This evening and Friday, Mars is 30 degrees lower
right of Jupiter, and Mercury 20 degrees lower right of Mars.
Friday, February 11
Some 45 minutes to an hour after sunset, locate the fat crescent Moon high
in SSW to SW, with Saturn some 3 or 4 degrees to its upper right. Note
the star Aldebaran, eye of Taurus, about 30 degrees to Moon's upper left,
and the lineup of three additional planets to the Moon's lower right. Tonight
six bodies span 90 degrees along the zodiac. In order of increasing angular
distance from the Sun, they are: Mercury and Mars in WSW; bright Jupiter
high in SW; Moon and Saturn to Jupiter's upper left; and Aldebaran in SSE.
Watch nightly as the Moon continues eastward through the zodiac.
Saturday, February 12
This evening's First Quarter Moon is 90 degrees or one-quarter circle east
(left) of the Sun. Look high in SSE at sunset or in S as sky darkens. As
we face the Moon tonight, we are loking out the "back door" or "rear window"
of Spaceship Earth in our journey around the Sun. At dusk the four visible
planets, Mercury-Mars-Jupiter-Saturn, span 60 degrees of sky. We are leaving
behind the slower moving outer planets Mars, Jupiter, and Saturn, so in
coming months they will disappear on the far side of the Sun. Swift Mercury
is catching up with us; in a couple of days, it will appear farthest from
the Sun, and then by March 1st will pass nearly between our planet and
the Sun.
Sunday, February 13
The slightly gibbous Moon, appearing within the "V"-shaped head of Taurus
formed by Aldebaran and the Hyades star cluster, will pass narrowly north
of Aldebaran this evening. Closest approach of the Moon to Aldebaran, eye
of the Bull, occurs shortly after 11:00 p.m. EST from lower Michigan, and
earlier from western U.S. Use binoculars to follow the Moon's eastward
motion against the stars during evening hours.
Monday, February 14
This evening, Mercury appears at greatest elongation, at its farthest apparent
distance from the Sun this time around, 18 degrees. Within an hour after
sunset, look for Mercury low in WSW to W, 19 degrees lower right of Mars
and 46 degrees lower right of bright Jupiter. Note also Saturn 11 degrees
upper left of Jupiter. Another good chance to see these same four planets
simultaneously will come in November's morning sky, but not until April-May
2002 will it be possible to see a greater number of naked-eye planets (all
five) at once!
The daily sky diagrams on the Abrams Planetarium 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. Sky Calendar is also one of the benefits
of membership in the Friends of Abrams Planetarium (a one-year Individual
Membership, tax-deductible, is $25 per year; other categories are available).
The current issue of the calendar illustrates the simultaneous appearance
of four planets at dusk, and the April issue will show a rare compact gathering
of Mars, Jupiter, and Saturn.
Tuesday, February 15
Tonight and Tuesday evenings, within an hour after sunset, Mercury appears
18 degrees west (lower right) of Mars, the minimum angular separation of
these two planets during the current trip of Mercury around the Sun. Later
this year, Mercury-Mars will appear very close to each other on May 18
at dusk and on August 10 at dawn, but those pairings will be harder to
see, low in bright twilight.
Wednesday, February 16
Face E to ESE an hour after sunset. Pollux and Castor, the two bright stars
marking the heads of the Gemini twins, are 4-1/2 degrees apart, 8 and 12
degrees to Moon's upper left. Procyon, brightest star in Canis Minor the
Lesser Dog, is 15 degrees to Moon's lower right. Sirius, brightest nighttime
star, is in SE 26 degrees lower right of Procyon. Note Orion's belt points
to Sirius, and that Jupiter outshines Sirius by a wide margin.
Thursday, February 17
Just before nightfall, note the lineup of four planets in the western sky.
>From upper right to lower left, they are Saturn, bright Jupiter, Mars,
and Mercury. This lineup of four can be seen only a few more evenings,
as Mercury will fade rapidly, to mag. +1.5 by Feb. 22. Tonight as the sky
darkens, the east side of the Great Square of Pegasus points to Mars, while
its west side points to Mercury.
Friday, February 18
From lower Michigan today, the nearly Full Moon rises about an hour before
sunset. Half an hour before sunset, it should be easy to see Sun and Moon
simultaneously, the last evening this month it's possible to do so. As
evening sky darkens, look for the star Regulus, heart of Leo the Lion,
low in E about 8 degrees to Moon's lower left. As seen from Michigan an
hour before sunrise on Saturday, the Moon pulls within 3 degrees west (lower
right) of Regulus, which will then be low in W. The Moon will set only
10 minutes after sunrise on Saturday. Full Moon occurs later that morning,
at 11:27 a.m. EST.
Saturday, February 19
From lower Michigan, the Moon, just past Full, rises 10-15 minutes after
sunset, about 17 degrees north of due east. The Moon has overtaken Regulus;
look for that star about 6 or 7 degrees to Moon's upper right an hour after
sunset. By an hour before sunup on Sunday, Regulus will be found 11 or
12 degrees to Moon's lower right.
Sunday, February 20
The four planets visible at dusk, Mercury-Mars-Jupiter-Saturn, reach their
shortest span across the sky this evening, 55 degrees. Most prominent is
Jupiter, high in WSW 45 minutes to an hour after sunset. Next, find Saturn
11 degrees to Jupiter's upper left, and Mars 24 degrees lower right. Most
difficult is fading Mercury, now of mag. +0.8 low in the twilight glow
20 degrees lower right of Mars. The Moon rises 10 degrees north of east,1
hour 20 minutes after sunset from lower Michigan.
Monday, February 21
The waning gibbous Moon rises 4 degrees north of east nearly 2-1/2 hours
after sunset from the latitude of lower Michigan, allowing a brief window
of very dark evening skies before moonlight brightens the scene for the
rest of the night. An hour before sunrise on Tuesday, look for the blue-white
first-magnitude star Spica in SW, 16 degrees left of the Moon and a bit
lower.
Tuesday, February 22
Tonight the Moon rises 3 degrees south of east, just over 3-1/2 hours after
sunset from the latitude of lower Michigan. Another hour later, watch for
Spica in Virgo rising 8 degrees to Moon's lower right. An hour before sunrise
on Wednesday, they're in SW, with Spica 6 or 7 degrees to Moon's lower
left.
Wednesday, February 23
An hour before sunup on Thursday, the waning gibbous Moon, three- quarters
full, is in SSW, with Spica 13 degrees to its lower right. Reddish first-magnitude
Antares, heart of Scorpius, is approaching the south.
Thursday, February 24
Orion the Hunter stands high in the south at nightfall. Below his prominent
belt of three stars is his sword, containing the famous Great Nebula of
Orion, which appears as a hazy patch in binoculars. Extend the belt 22
degrees upper right to ruddy Aldebaran, eye of Taurus. Another 14 degrees
beyond Aldebaran is the compact Pleiades or Seven Sisters star cluster,
another beautiful target for binoculars. Take advantage of dark, moonless
skies to enjoy these deep-sky objects as well as the winter Milky Way and
the zodiacal light.
Friday, February 25
An hour before sunrise Saturday, Moon is in S with reddish Antares 13 degrees
lower left.
Saturday, February 26
By an hour before sunrise on Sunday, the Moon is several hours past Last
Quarter and so appears slightly less than half full. Face the southern
sky to find Antares, heart of Scorpius, 8 degrees to Moon's lower right.
As we face the Last Quarter Moon 90 degrees west of the Sun, we are looking
out the "front window" of Spaceship Earth. By end of May our orbital motion
will carry us between Antares and the Sun, and that star will be up almost
all night. Venus, just rising in ESE an hour before sunup, is pulling away
from us, and will pass on the far side of the Sun in June.
Sunday, February 27
Face WSW an hour after sunset to find bright Jupiter, with Saturn 10 degrees
to its upper left, and Mars 20 degrees to Jupiter's lower right. These
three planets now span 30 degrees. Keep watching as their arrangement shrinks
to just 5 degrees long in mid-April!
Monday, February 28
An hour after sunset, locate the lineup of three planets in the west, and
extend their line eastward across the sky to these bright zodiacal stars:
Aldebaran, eye of Taurus the Bull; Pollux, the brighter and more southerly
of the Gemini twins (but still several degrees north of the pathway of
the Moon and planets); and finally to Regulus, heart of Leo the Lion.
Tuesday, February 29
The length of the year of four seasons is not 365 days, nor 365-1/4 days,
but is instead very nearly equal to 365-97/400 days. A calendar with 365
days in every year would be too short to prevent the starting dates of
the seasons (the solstices and equinoxes) from drifting about a week later
every 29 years. A calendar with a year of 365-1/4 years (the Julian Calendar,
with a extra or "leap" day every four years, initiated by Julius Caesar)
is more accurate, but just a little too long, so that the dates of the
seasons would drift earlier by about 3 days in 400 years. The currently
used Gregorian Calendar fixes this problem by requiring that century years
be divisible by 400 in order to be a leap year. Thus in the Gregorian Calendar,
1700, 1800, and 1900 were not leap years, but 2000, being divisible by
400, is a leap year. By eliminating three of the Julian Calendar's quadrennial
leap years every 400 years, the Gregorian Calendar gives us 97 leap years
every 400 years, keeping the seasonal dates from drifting forward or backward
over time. After today, the next leap year day which occurs in a century
year will be February 29, 2400, which will also be on a Tuesday! You can
confirm this by showing that the number of days in 400 years (on the Gregorian
Calendar) is divisible by 7.