To the reader:
The Skywatcher's Diary for January 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 January issue, please send a long,
self-addressed stamped envelope to:
January 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: January 2005
The Earth reaches perihelion -- our closest encounter with the sun for the year.
Today we're 91,401,000 miles from our daystar, approximately 2 percent less
than the average span. Because the Earth-sun distance changes little throughout
the year, it has an inconsequential effect on the seasonal temperature variation.
Summer is warm and winter is cold primarily because the tilt of the Earth's axis
shifts relative to the sun.
The Quadrantid meteor shower reaches maximum tomorrow morning before
daybreak. The shower is a good performer -- usually more than a meteor per
minute on average, and sometimes greater. The Last Quarter Moon does provide
interference this year, however. The shower is named after the defunct
constellation of Quadrans Muralis, the Quadrant, which once occupied a spot in
the northern end of Bootes.
The Moon turns Last Quarter at 12:46 p.m. EST. Before dawn this morning the
waning gibbous Moon sits 7 degrees (less than a fist width) to the right (west) of
Jupiter. Tomorrow morning the Moon, now officially waning crescent, appears the
same distance to the other side of the planet. (Notice the star Spica, 2 degrees to
the Moon's lower right.) Between those times, for some places in the Far East,
the Moon covers Jupiter.
The latest sunrise of the year occurs this morning for locations near 40 degrees
north, including most of the continental U.S. Mark the occasion by doing some
dawn sky watching. All five planets are visible, stretching from Venus and Mercury
visible low in the southeast, to Saturn in the west-northwest. Mars perches 17
degrees to the upper right of the Venus-Mercury pair, and Jupiter sits just to the
west of due south.
Venus and Mercury remain close together in the morning skies until they are
engulfed by the brightening dawn in about two weeks. Look for them about 5
degrees (half a fist) up and slightly north of southeast an hour to 45 minutes
before sunup. Tomorrow the two planets are a degree apart. Fainter Mercury is
currently to the upper right but will swing clockwise around Venus in coming days.
Look for the Moon, Mars, and Antares in the southeast before dawn tomorrow
morning. The crescent sits to the right and between the planet and star. Antares
is 4 degrees (8 moon diameters) to the lower left of Luna, and Mars is 5 degrees
to the upper left. Can you detect a slight red-orange tint to Mars and Antares?
Does the star or planet appear brighter to you?
Tomorrow morning is the last chance for mid northern latitudes to see the thin
waning crescent Moon. An hour before sunrise Luna perches 4 degrees (8 moon
diameters) above the southeast point on the horizon. Venus and Mercury are 9
degrees to the left of the crescent and slightly lower. How long can you follow the
Moon as the sky brightens?
Comet Machholz, now in the evening sky, is drawing the attention of amateur
astronomers. It is estimated to be about 4th magnitude, which for comets means
it should be just barely visible to the unaided eye from a dark location. Tonight the
comet sits 3 degrees above the famous Pleiades star cluster, about two-thirds of
the way up in the east-southeast 1 1/2 hours after sunset. Look for yourself before
the Moon moves into the evening sky in a few days. Use binoculars.
The orbits of all the solar system planets are tilted relative to the Earth's orbit.
Consequently, each planet crosses the Earth's orbital plane twice for every time it
loops around the sun, once moving from above to below Earth's orbit and again
going the opposite direction. Today Saturn crosses our orbital plane traveling
from below to above, passing through what astronomers call the ascending
node. Twenty-nine years will elapse before Saturn once again reaches the
ascending node, since that's how long Saturn takes to completely circle the sun.
The Moon reaches New phase this morning at 7:03 a.m. EST. About 2 hours
earlier, the Moon passed closest to Earth for this year. The near coincidence of
these two events produces conditions favorable for unusually large tides. The
situation can be troublesome to coastal areas, particularly when mixed with storm
surges.
Mercury and Venus appear closest over the next two mornings, about one-third
degree apart. Tomorrow morning Mercury stands directly right of brighter Venus.
The following morning Mercury drops to Venus' lower right. Forty-five minutes
before sunrise, look 4 degrees (half a fist) above the horizon, 9 degrees to the left
(north) of southeast. Continue to follow the planetary pair's escapades each
morning for a long as you can.
The mighty hunter, Orion, now rises about sunset, so the constellation pattern is
high enough to be seen in its entirety by nightfall. The rightmost of the three
middle stars goes by the Arabic-derived name Mintaka, which means "belt."
Mintaka lies very close to astronomers' celestial equator, telling us, among other
things, that the star rises almost exactly east, and sets as precisely west.
Saturn reaches opposition today, which is astronomical shorthand indicating that
Saturn and the sun are on opposite sides of the sky. One consequence of this
arrangement is that the planet rises at sunset, sets at sunrise and so is visible all
night long. Opposition also means that since the sun currently sets some
distance to the south of west, Saturn must rise a similar angle to the north of east.
Happy New Year to those who follow the Julian calendar, the method of keeping
track of the year made popular by none other than Julius Caesar. The Julian
calendar is the direct predecessor to our Gregorian calendar that we currently
use. Today begins the year 2758 AUC. The initials are a Latin abbreviation
meaning "from the founding of the city," referring to Rome. The traditional date for
that event is accepted to be 753 BC.
For the next two nights, the 4th-magnitude Comet Machholz sits near the star
Algol in the constellation of Perseus. That constellation is high in the east after
nightfall, above Auriga and Capella. The comet is 2 degrees to the lower right of
Algol tonight and somewhat closer to the lower left tomorrow. Use binoculars.
Algol is a variable star. It will be near minimum brightness (mag. 3.4) tonight and
about a magnitude brighter Sunday.
Mercury is now below Venus and gradually pulling away. The two planets are
separated by 0.7 degree this morning and about 0.9 degree tomorrow. Look for
the pair 10 degrees (a fist) to the left of due southeast 45 minutes before sunrise.
They sit only 2 degrees above the horizon, so you'll need an unobstructed view in
that direction. You'll be able to spot this planet pair for only a few more days.
The Moon turned First Quarter in the wee hours of the morning, at 1:57 a.m. EST.
During its recent waxing crescent period, the Moon journeyed through a stretch of
faint zodiac constellations, and consequently never appeared near anything
notable. That trend continues the next two nights as Luna travels through Aries,
the Ram. The drought will end by Wednesday, thought, when the Moon begins its
trip through the bright winter constellations.
The Summer Triangle, composed of the bright stars Vega, in the constellation of
Lyra, Deneb in Cygnus, and Altair in Aquila, is disappearing into evening twilight.
See if you can still detect all three stars. Vega and Deneb should not be difficult
but Altair could be a challenge. An hour after sunset Vega and Deneb sit in the
northwest 14 and 36 degrees up, respectively. Altair is in the west, only 6 degrees
up.
Look for the Pleiades star cluster 2 degrees (4 moon diameters) above the Moon.
Luna's glare may force you to grab binoculars in order to pick out the faint group.
Another cluster, the Hyades, is 10 degrees below and slight left of Luna. The
Hyades cluster is much more diffuse than the Pleiades and therefore harder to
recognize as a grouping, particularly with the bright star Aldebaran in the same
part of the sky.
The sun just crossed over the boundary into Capricornus. It will remain among
the stars of this constellation for almost a month, moving about a degree per day
eastward. Within a few hours of that event, the sun entered into the astrological
sign of Aquarius, which doesn't correspond to the star pattern of the same name.
These two frameworks for marking the sun's position were more nearly aligned
in the first century B.C.
Tonight Comet Machholz sits 3 degrees above Mirfak, the brightest and Alpha star
in the constellation Perseus, the Hero. The brilliant Moon will make naked-eye
detection of the comet difficult, but try it with binoculars. Can you distinguish a faint
tail? The tail should be pointing downward. The comet will be nearest to the sun
in a few days. It passed closest to Earth earlier this month.
The name Mirfak comes from Arabic and refers to an elbow -- but not the Hero
Perseus'. Instead the name's meaning is associated with the Pleiades, probably
meant to indicate Mirfak is beside the star cluster. Curiously, Mirfak is part of a
cluster itself, usually termed the Alpha Persei Cluster. Aim binoculars at Mirfak
and notice the abundance of 4 and 5 magnitude stars in the field of view.
The waxing gibbous Moon rises two hours ahead of sunset. Once the sky
darkens notice Saturn 6 degrees (half a fist or 12 moon diameters) below and
somewhat right of Luna. The Moon sits squarely in the constellation of Gemini.
The Twins, Pollux and Castor, rest 5 degrees to Luna's left, Pollux to the lower left
and Castor to the upper left. Use binoculars if you have trouble detecting them.
Mars officially reaches 1st magnitude after having spent the last nine months
wallowing below that threshold. The rising luminosity is a pronouncement of
things to come. The Red Planet continues to brighten, reaching 2.3 -- a 30-fold
increase in luminosity -- at opposition in early November of this year. Check out
Mars' brilliance for yourself. Look low in the southeast an hour before sunrise.
The Moon reaches Full this morning at 5:32 a.m. EST. In earlier times, the Moon
of January was known as the Cold Moon or Winter Moon. Luna rises within
minutes of sunset tonight, significantly north of due east. You may recall that the
New Moon of two weeks ago occurred when the Moon was nearest Earth. The
Moon is now on the other side of its orbit, giving us the most distant Full Moon of
the year.
Tonight the lion nibbles the Moon. Wait for the Moon and Leo to climb above the
horizon, 2 1/2 to 3 hours after sunset. The bright star 5 degrees (half a fist) to the
lower right of Luna is Regulus, the lion's heart. Notice a large semicircle of fainter
stars, a little more than a fist width across, to the upper left of the Moon. That's the
animal's head. With some imagination, Leo's mouth could be right where the
Moon sits.
Although Mercury has disappeared from the morning sky, Venus is bright enough
to be detected against the bright dawn twilight, with a little work. If you wish to
accept the Venus challenge, look tomorrow morning between southeast and
east-southeast 45 minutes before sunup. At that time Venus perches 1 1/2
degrees above the horizon. Keep watching until you spot the planet. Use
binoculars if necessary.
With the bright Moon out of the evening sky, the Milky Way flourishes. Our great
galaxy passes diagonally across the heavens this time of year, flowing from
northwest to southeast. From a dark location the glittering stream is magnificent.
We are now viewing the Perseus and Orion spiral arms edge on. There's no
visual cue to help determine where one arm stops and the other begins. They
seem to merge into a continuous ribbon of light.
The constellation Lynx is another of the faint, relatively modern patterns concocted
by Polish astronomer Johannes Hevelius in the late 1600's. In explaining the
name, Hevelius is reported to have said that an observer needs to have the eyes
of a Lynx in order to find the constellation. Lynx resides in the sparse area
between Gemini and the Big Dipper. Tonight look toward the northeast at the end
of evening twilight.
If you are out late enough to watch moonrise, about 6 hours after sunset, keep an
eye peeled for Jupiter, rising 2 degrees (4 moon diameters) to the Moon's lower
left. As the night progresses, Luna slides beneath the planet. For some locations
in the south Pacific and Antarctica, the Moon occults (passes in front of) Jupiter.
By the start of dawn tomorrow morning the objects have switched places. The
Moon then sits 2 degrees to the lower left of Jupiter.
Sirius, the brightest nighttime star, rises in the east-southeast about sunset. As
the sky darkens, watch for it to appear toward the southeast. How soon after
sundown can you spot the star? If the sky is quite transparent, you should see
Sirius twinkling. Look for flashes of blue, red, and green coming from the star.
The colors are created as the light from Sirius passes through the Earth's
atmosphere on its way to our eyes. Binoculars will enhance the colors.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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