To the reader:
The Skywatcher's Diary for October 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 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
Skywatcher's Diary: October 2005
- The planet Mars begins retrograde motion today. For the next 2 1/2 months the Red
Planet appears to travel slowly westward against the background stars. That is, if
you keep track of the planet's position relative to the constellations, rather than
the horizon, the planet moves westward as the weeks pass. The effect is an
illusion that occurs roughly every two years as faster moving Earth overtakes and
passes Mars.
- This morning is the last chance to see the hairline thin crescent Moon before it
turns New and disappears. Look due east 30 minutes before sunrise. At that time
the Moon perches just under 4 degrees (8 moon diameters) above the horizon,
so you will need an unobstructed view. Bring binoculars along in case the
atmosphere is not crystal clear. As sunrise approaches, the Moon climbs higher
but the sky brightens.
- The Moon reaches New phase this morning at 6:28 a.m. EDT. The Moon passes
directly in front of the sun for observers in certain parts of Spain and Africa,
creating an annular solar eclipse. Back in the U.S., Luna may be visible tomorrow
night to observers in the Deep South and southwestern states. The rest of the
U.S. must wait until Wednesday evening.
- Ramadan, the Islamic month of fasting, begins today for some Muslims. Islam
uses a calendar based on lunar phases. Many groups hold to the idea that the
month begins at the first sighting of the crescent Moon after New. That event
occurs tonight for the Middle East and southern locations in the western
hemisphere. Other Muslims begin the month at the first sunset that occurs after
the time of New Moon, regardless of whether the Moon is actually visible. For
those, Ramadan commenced at sunset last night.
- Look for the exquisitely thin Moon tonight after sunset. Even though Luna is about
2 1/2 days past New, the crescent could still be difficult to spot for observers at mid
northern latitudes. Thirty minutes after sunset the Moon sits just 3 degrees (6
moon diameters) above the west-southwest horizon. You may notice Venus first,
15 degrees (fist and a half) to the upper left of Luna.
- Celestial Scenery Alert. The Moon perches near Venus tonight, 4 degrees (8
moon diameters) to the lower right of that dazzling planet. Tomorrow Luna slips 9
degrees to the left, and slightly above Venus. Then, the star Antares appears a
little more than 2 moon diameters to the upper left of the Moon. Antares is the
brightest star in the constellation of Scorpius.
- We are one month away from opposition with Mars. Currently Earth gains on the
Red Planet by more than 200,000 miles each day. Already conspicuously bright,
the planet's luminosity continues to increase, as we get nearer. Mars currently
rises in the east-northeast about 1 1/2 hours after sundown. The planet comes up
4 to 5 minutes earlier per night. Early next month it will rise as the sun sets.
- Mars is now highest and due south about 4 hours before sunrise, or around 3
a.m. local time. As dawn begins, look for it more than halfway up in the
southwest. The planet currently sits near the Taurus-Aries border. Because Aries
is a rather faint group, brilliant Mars is easy to identify. Just look for the brightest
object to the west of Taurus. In fact Mars is the brightest object in the entire
morning sky. The planet's orange tint also helps.
- Tonight the less than "half full" Moon rests within the constellation of Sagittarius,
among the familiar "teapot" pattern of stars. If you haven't looked at the magnified
Moon in a while, drag out those binoculars, lean against something solid, and
scan Luna's sunlit side. Notice the darker areas on the top half. These are the
lunar "seas." The dark gray oval just above center is Mare Tranquilitatis, the Sea
of Tranquility, and landing site of Apollo 11.
- The Moon reaches First Quarter phase at 3:01 p.m. EDT, about the time Luna
rises in that time zone. After nightfall try to detect that the moon phase is slightly
beyond First Quarter. Venus pauses near a bright 2nd-magnitude star tonight.
Look for Dschubba or Delta in Scorpius about a degree (2 moon diameters) to
the upper right of Venus. Binoculars may be helpful in locating the star.
- The Moon is now passing through the faintest stretch of zodiac. This patch of sky
is sometimes referred to as the watery sector because the constellations all
share some reference to water. It includes Capricornus, the Sea Goat, in which
the Moon now sits, Aquarius, the Water Carrier, to the left of Capricornus, and
Pisces, the Fish, still farther left. There's no star brighter than 3rd magnitude
within the entire group.
- Saturn currently resides in the morning sky, not rising until after 1 a.m. local time.
In early dawn the planet sits more than halfway up in the east-southeast. It is the
brightest of several bright objects in that part of the sky. Saturn is flanked by the
star Regulus 20 degrees (2 fists) to the lower left and the Gemini Twins, Pollux
and Castor, about 20 degrees above it.
- When observing Saturn in the morning sky, be sure to bring along a pair of
binoculars to look for the Beehive star cluster 3 degrees (less than a binocular
field width) above and slightly right of the planet. The cluster is a physical object,
that is, the stars are held together by the mutual attraction of their gravity. If the sky
is particularly clear, the Beehive can be seen with unaided eye as a faint, soft spot
of light.
- At the end of evening twilight, the constellation Cygnus sits overhead. Its brightest
star Deneb will pass northward of the zenith for observers south of about 45
degrees north latitude. For most U.S. skywatchers in the contiguous states,
however, the star is high enough that it seems to be at the very top of the sky.
Deneb is one of the most distant naked-eye stars, residing at least 1600 light
years away.
- Watch Venus pass Antares over the next several nights. This evening the 1st-
magnitude star appears 2 degrees (about a thumb width at arm's length) to the
lower left of the brilliant planet. Tomorrow night the two bodies are slightly closer,
about 1 1/2 degrees separation. On October 17th Venus and Antares are again 2
degrees apart, but now the star is to the lower right.
- The Moon turns Full tomorrow morning at 8:14 a.m. EDT. Traditionally this Moon
is known as the Hunter's Moon. For several nights around Full, the Moon rises
only slightly later than the previous night, providing illumination for evening
hunting activities. The effect is similar to last month's Harvest Moon. A partial
lunar eclipse takes place tomorrow before sun up. See Monday's description.
- The Moon just nicks the Earth's shadow this morning, producing a partial lunar
eclipse. The eclipse is completely visible from the western U.S. before moonset.
The farther east an observer is located, the less eclipse will be seen, with none of
it visible from the East Coast. At best only 7 percent of the Moon's diameter is
"blackened" by the Earth's shadow, so this is a minor eclipse. For specific times,
see http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2005.html
- The Moon rises in the east-northeast less than an hour after sunset tonight.
Shortly after Luna's appearance Mars pops up slightly to the right of where the
Moon debuts. Three hours after sunset the planet-Moon pair sits 6 degrees (12
moon diameters) apart and about 20 degrees up in the east. During dawn
tomorrow look for Mars and Moon in the west, 4 degrees apart.
- Take a careful look around the Moon tonight. Let it rise a bit until, say, 10 p.m.,
then inspect the region above Luna. You should see a swarm of stars 1 to 2
moon diameters away. It is the famous Pleiades star cluster. If the glare from the
nearly full Moon is too much, binoculars will help bring out the stars. In fact, many
observers consider binoculars the preferred instrument for enjoying the Pleiades.
- If you see a meteor or two before twilight tomorrow morning, they likely are
members of the Orionid meteor shower. As showers go, the Orionids are not a
major event. Typically the shower produces one meteor every 4 or 5 minutes. This
year bright moonlight will drown out the faint ones, making the count even less.
The Orionids are relatively swift, so they do produce some nice bright streaks that
will penetrate the moonlight.
- Fomalhaut (FOE-mal-ought) is a 1st-magnitude star that doesn't get much
recognition, at least not from mid northern latitudes. That's because it never rises
very high above the horizon. At best, when it is due south, the star is only about 20
degrees (2 fist widths) up. Furthermore, Fomalhaut is in an indistinctive
constellation, Piscis Austrinus, the Southern Fish. Isn't it time you paid the star a
little respect. Take a look some night soon, due south, around 10 pm.
- Today Jupiter is in conjunction with the sun. That is, the giant planet is now on the
far side of its orbit almost directly behind the sun. Jupiter is in the middle of its
period of invisibility when the planet is up only during daylight hours. Early next
month Jupiter drifts far enough away from the sun's direction to emerge in the
eastern dawn just ahead of sunrise.
- The Moon comes up about 5 hours after sunset. Rising with Luna, 2 degrees (4
moon diameters) to its left, is Pollux, brightest of the Gemini Twin stars. The
sibling Castor is 4 1/2 degrees above and slightly left of Pollux. The group climbs
high in the south by dawn. Then Pollux and the Moon are about the same
distance apart, but all three bodies are aligned.
- The Moon reaches Last Quarter phase tonight at 9:17 p.m. EDT. Tomorrow
morning before sunup, look for Saturn 5 degrees (half a fist) below Luna. Both
objects are among the stars of the faint zodiac constellation Cancer. By
Wednesday morning the Moon slides past Saturn, ending up 10 degrees to the
lower left of the planet.
- Tomorrow Neptune ends its retrograde, or westward, motion. The planet
resumes traveling slowly eastward against the starfield background. It sits in the
faint zodiac constellation of Capricornus. If you wish to see the 8th-magnitude
planet, the ideal time to look is at the end of twilight, 1 1/2 hours after sunset. Then
Neptune is at its highest, about 30 degrees up, and due south. Look on the web
for a finder chart. Optical aid is required.
- Tomorrow morning before sunrise the waning crescent Moon perches beside
Regulus, 3 degrees (6 moon diameters) to Luna's right. Regulus is the Alpha
star of Leo, the Lion. While out among the morning stars, be sure to take in Mars,
low in the west. It's almost at its peak brilliance and a real beauty with its red-
orange hue. The striking object low in the south is Sirius, the brightest nighttime
star.
- Mercury has been hanging around the western horizon near sunset all month.
This is its poorest evening appearance of the year. But with a little perseverance
it's possible to capture the elusive planet. Begin looking about 30 minutes after
sunset. Use Venus as a rough guide. Mercury is 24 degrees to the lower right of
Venus and 3 degrees off the horizon. Don't mistake it for the star Antares, 15
degrees to Venus' lower right and higher but fainter than Mercury. Binoculars are
required.
- By the end of evening twilight the famous Andromeda Galaxy, alias M31, is well
placed for observing. With no interfering moonlight, a fine opportunity is awaiting
skywatchers in dark locations. Use the Great Square of Pegasus as a starting
point. This "sky mark," now rotated into a diamond shape, sits more than halfway
up in the east. Sight across the diamond from the right corner to the left. Continue
in that same direction an equal distance beyond the left corner, and then slowly
scan the area with a good pair of binoculars. You are looking for a faint oval glow
that easily fits in the binocular field of view.
- Mars and Earth come closest late today. We are 43 million miles away from our
outward neighbor. We pass by Mars once every two plus years. Last time, in
August of 2003, we came nearer that now. The distance at each successive
passage will continue to increase for a number of years. So today we are closer
to Mars than we will be again until 2018.
- Mars is still a week away from opposition. That's when Earth is exactly between
the sun and Mars, so from our vantage point Mars is opposite the sun. Opposition
is casually considered the time when the two planets are closest. That would be
true if both planet orbits were circles. But the actual paths are ellipses or ovals.
So closest passage is determined by how the orbits angle one to the other rather
than the moment of opposition.
- With Mars this close, the occasion calls for a telescope. If you don't have one of
your own, look for public observing sessions at observatories or planetariums.
The features on Mars are never as obvious as those of Jupiter and Saturn. But
with some patience -- waiting until Mars is near its highest point (due south), and
the luck of a clear night when the air is also very steady -- tantalizing views of
dark and light markings on the surface of Mars are possible. Help, including
maps showing Mar's features at various times, is widely available on the web.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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