To the reader:
The Skywatcher's Diary for August 2004 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 August issue, please send a long,
self-addressed stamped envelope to:
August 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: August 2004
Today corresponds to the ancient holiday of Lammas, one of the "cross-quarter"
days that lie approximately halfway between the solstices and equinoxes. So
today could be considered the middle of the summer season. Lammas derives
from an old Celtic harvest festival. The term literally means "loaf mass" or
blessing of the bread. In modern times it serves to indicate just how fast summer
is speeding by.
Jupiter is the bright "star" visible low in the west just as evening twilight begins.
The planet continues to slide lower as days pass, disappearing into the solar
glare shortly after midmonth. The other evening planet, Mercury, is much more
difficult to locate. It's 12 degrees (a fist width) to the lower right of Jupiter and sets
only 50 minutes after the sun. Don't expect to see Mercury beyond the first week of
August.
The bright "morning star" is Venus, if you hadn't guessed. The planet rises more
than 3 hours ahead of the sun. Saturn is also emerging out of dawn. Look for it 24
degrees (more than 2 fists) to the lower left of Venus. An hour before sunup
Saturn perches 7 degrees above the east-northeastern horizon. Saturn climbs a
little each morning while Venus holds stationary relative to the horizon, so the two
sibling planets meet up at the end of this month.
Along with the two planets Venus and Saturn, early morning sky watchers can bid
welcome to the constellations Orion and Gemini. The famed hunter of winter
evenings now appears to the lower right of Venus. Look for the Twins to the lower
left of that planet. The head stars of Gemini, Pollux and Castor, sit about a fist to
the upper left of Saturn.
Neptune now stands in opposition to the sun. That means, as we look in the
direction of the planet, the sun is at our back. Or taking another viewpoint, when
the sun is setting, Neptune is rising, and vice versa. Opposition is also a cue to
planet observers that they're now in a period when Neptune watching is at its
best. The planet is visible all night long and highest in the middle of the night. The
8th-magnitude planet now resides among the stars of Capricornus, near 4th-
magnitude Theta.
One and a half hours after sunset the galactic center lies due south and about 20
degrees (2 fists) above the horizon for mid northern latitudes (continental U.S.).
Nothing remarkable greets the unaided eye at that location. The serenity is
deceiving, however. Some 30,000 light years in that direction a maelstrom of
energy and matter encircle a gigantic black hole that lies at the heart of our Milky
Way.
The Moon reaches Last Quarter at 6:01 p.m. EDT, although it will be out of sight at
that time from most everywhere in the Western Hemisphere. If you wish to actually
observe Luna, you must now look during the morning half of the day, from
approximately midnight to noon, local time. This morning the Moon appears
slightly less than "half" full and tomorrow morning somewhat more than half full.
Mars just passed its aphelion (greatest distance from the sun). A little less than a
year ago the planet encountered perihelion (closest distance). What made the
headlines about that time, you may recall, was not Mars' nearness to the sun but
rather its extreme proximity to Earth. Then, the Red Planet appeared at its
brightest and nearest in tens of thousands of years. The fact that Mars' record
pass of Earth occurred within two days of its perihelion last year is not mere
coincidence.
Before dawn this morning, the crescent Moon sits between the Pleiades and
Hyades (HY-ah-deez) star clusters. Use binoculars to look 5 degrees (10 moon
diameters) to the upper right of Luna for the Pleiades and 7 degrees below the
Moon for the Hyades. The former cluster is much more compact than the latter.
The bright star among the Hyades is Aldebaran, the eye of Taurus, but that star is
a foreground object and not part of the cluster.
Tomorrow morning the thinning crescent Moon stands 9 degrees (a fist) above
brilliant Venus. Saturn is also in the vicinity. Look for it 18 degrees to the lower left
of Venus. An hour and a half before sunrise Saturn sits about a fist above the
east-northeastern horizon. Don't confuse the star Pollux for Saturn. The star is
fainter, slightly higher, and 7 degrees to the planet's left.
Some research suggests that this year's Perseid meteor shower may be better
than its usual one-a-minute average. Observers in the Eastern Hemisphere
might see a brief burst around 9:00 p.m. Greenwich Time (5 p.m. EDT). For those
of us on the other side of Earth, the best show occurs from late tonight until the
first light of dawn tomorrow morning. The thin crescent Moon will not interfere.
Rather it, along with Venus, 9 degrees (a fist) to Luna's right, enhances the
scene.
The next two mornings offer pleasant views of the retreating crescent Moon.
Tomorrow morning Luna nestles between Saturn, 5 degrees (10 moon
diameters) to its lower right, and Pollux, 3 degrees to the Moon's left. The
following morning (Saturday) Luna sits alone, 7 degrees above the east-
northeastern horizon an hour before sunup. The Moon reaches New on Sunday.
This is the last weekend of moonless evenings in August. The final bit of sunlight
leaves the sky about an hour and 45 minutes after sunset for observers in the
continental U.S., and then the heavens are dark. The shimmering glow of Milky
Way flows from just west of south to east of north, passing near overhead. Can
you imagine a better time to leisurely explore the dark summertime sky? Enjoy.
Explore the immediate region surrounding the bright star Vega -- near overhead
during evening hours. Use unaided eye at first, looking for close pairs of stars,
then follow up with binoculars. Four degrees (almost half a fist) to the southeast
of Vega is a relatively wide pair known collectively as Delta in Lyra. These should
be easy to perceive as two stars without optical aid. About 2 degrees to the
northeast of Vega is the famous "double-double" star, Epsilon. With better than
average eyesight and excellent sky conditions Epsilon is barely detectible as
double, but it becomes obvious in binoculars. To determine that each of those
stars has an even closer partner requires a moderate telescope.
The Moon turns New at 9:24 p.m. EDT, so it won't be visible tonight. The Great
Square of Pegasus is now well placed in the eastern evening sky. The Square
consists of four stars approximately equally spaced and similar in brightness,
between 2nd and 3rd magnitude. The figure appears rotated a quarter turn, so
look for a diamond shape. Not far from the northern most (left) corner of the
Square sits the famous Andromeda Galaxy.
There's a chance tonight to see a one-day-old Moon. You will need a flat skyline
and haze-free atmosphere. Half and hour after sunset look about 15 degrees (fist
and a half) to the north (right) of due west and 2 degrees above the horizon. To get
a closer approximation, note the sun's position 20 minutes before sunset (for
eastern states, 25 minutes for western states). Thirty minutes after sunset the
Moon will appear 1 to 1 1/2 moon diameters below the sun's former position.
Binoculars may be helpful.
The crescent Moon sits 4 degrees (8 moon diameters) to the right of Jupiter early
this evening. It may be your last opportunity to glimpse the giant planet before
Jupiter's overwhelmed by the twilight glow. Forty-five minutes after sunset the pair
perches 3 degrees above the horizon, a few degrees to the north (right) of due
west. Bring your binoculars.
Pretty Moon alert. The picturesque crescent appears low in the west to west-
southwest evening sky for the next several nights. Look 45 minutes to an hour
after sunset. In the morning sky, Venus just achieved greatest elongation, which
means its angular distance from the sun has reached maximum (46 degrees) for
the current morning appearance. Through a telescope the planet appears close
to half full.
Cygnus, the Swan, is a good summertime constellation to know. It's part of the
quasi-constellation that we call the Summer Triangle. Find Deneb, the brightest
star in Cygnus, by looking 24 degrees (2 1/2 fists) to the northeast of (below)
Vega, the brilliant star near overhead as darkness falls. The Northern Cross is a
common nickname for Cygnus and suggests a shape that people more readily
identify than the swan. The main staff of the cross runs for about 20 degrees
south to southwest from Deneb. The cross staff is 6 degrees below Deneb.
How soon after sundown can you find the 1st-magnitude star Spica? Take a
companion along to compare notes or enjoy a friendly wager. Begin half an hour
after sunset. The Moon provides guidance: tonight Spica sits 4 degrees (8 moon
diameters) to the lower right of Luna. An hour after sundown, look for Spica 9
degrees above west-southwest.
If you haven't caught Venus and Saturn in the dazzling dawn show, take a peek
soon. The planets are clearly closer than they were at the beginning of the month.
The gap continues to narrow until the last day of August when they stand 2
degrees apart. Follow the rapid change over the next ten days. Saturn rises about
3 hours before the sun, so a good time to look is 1 to 2 hours before sunup.
The constellation Cygnus, the Swan, now appearing high in the eastern evening
sky, is full of intriguing objects. To begin with, its brightest star, Deneb, is an
enormous blue-white supergiant that is 200 hundred times the size of our sun
and produces a surface temperature that's 5,000 degrees F hotter. The star
consumes fuel at a prodigious rate and likely will explode in a few million years.
The Moon passes First Quarter this morning at 6:12 a.m. EDT. Tonight, therefore,
it should appear slightly more than half full. Watch Luna move over the top of
Antares, the brightest star in Scorpius. From the eastern states, the Moon is
clearly to the west of the star an hour after sunset. Two hours after sundown it's
closest to Antares -- about a moon diameter away. Luna's plainly beyond the star
after another hour passes. Follow the event from first sight of Antares until
moonset.
Albireo is the famous colored double star in Cygnus. It sits at the head of the
swan or foot of the cross, depending on which pattern you prefer. The star is
known for the vividly contrasting colors that the components display when viewed
through a modest telescope. The brighter of the pair is yellow-gold and the fainter
an obvious blue. Whether the stars form a true binary, that is, orbit about each
other, or are merely cosmic neighbors is uncertain. They lie almost 400 light
years from us.
Another of Cygnus' many wonders is the North America Nebula, an enormous
dust and gas cloud. The name is merely descriptive -- the nebula's shape
roughly resembles the continent. The cloud is too faint for the unaided eye to
detect and difficult in most amateur telescopes. But the rose-colored light of the
hydrogen gas shows up prominently in photographs, even when taken with
modest equipment and time exposures as short as a minute. The nebula is
located about 3 degrees to the east (below) Deneb.
Venus and Saturn appear 4 1/2 degrees (half a fist) apart tomorrow morning.
Coincidentally, the Gemini Twins, Pollux and Castor, are separated by the same
distance. And since the planet pair now sits 8 degrees to the right of the Twins
twosome, making the comparison for yourself is straightforward. Try it tomorrow 1
to 2 hours before sunrise. Venus and Saturn are moving quickly enough that by
the following morning the relationship will no longer hold true.
The planet Uranus reaches opposition today, so we're now in the period of best
visibility for this outer gas giant. It shines at magnitude 5.7, which makes it a
"naked eye object" for average eyesight. Of course, you'll need a dark sky and
good transparency. The planet sits among the stars of Aquarius less than a
degree to the west of Sigma, a 4.8-magnitude star near the center of the
constellation. To tackle the planet, wait until the Moon is out of the way then arm
yourself with a detailed star map of the Aquarius region, a red flashlight, and
binoculars.
An interesting pair of 4th-magnitude stars resides 5 degrees (half a fist) to the
west of Deneb, the brightest star in Cygnus, the Swan. The stars are widely
spaced, about a degree apart, and similar in luminosity and color (yellow-
orange). They are known by the designations Omicron 1 and Omicron 2. Pay
particular note to the southernmost of the two (Omicron 1). Binoculars reveal its
two fainter blue-white companions. The stars are roughly on opposite sides of
Omicron 1, and the brighter one is 3 times farther from Omicron 1 than the fainter.
The Moon turns Full at 10:22 p.m. EDT. If you haven't carefully examined the Full
Moon in a while, take a moment to notice the shapes of the light and dark areas.
Most of the dark portions are enormous craters that have been filled with lava.
Use binoculars to look for particularly dark and light sections. Can you see the
bright streaks across the Moon's southern region? Look at the Moon during
different phases and note how various features are enhanced or possibly
disappear.
Venus and Saturn are closest before sunrise tomorrow. Two degrees separate
the planets, with brighter Venus on the right. They are best seen 1 to 2 hours
before sunup but you should be able to spot the pair up until 30 minutes before
sunrise. Don't forget to look for the Gemini Twins, Pollux and Castor, about 8
degrees (less than a fist) to the upper left of the planets, and Procyon, the
brightest star in Canis Minor, 15 degrees to the lower right.
A 5th-magnitude star in northern Cygnus is worth seeking out. It goes by the
numerical designation "61." The star sits 8 degrees to the southeast of Deneb
and near a wide pair of 4th-magnitude stars. You may need a star chart to track it
down, but do so. The star is a nice double in a telescope, consisting of two
orange 6th-magnitude stars. But it's also historically significant. 61 Cyg was the
first star whose distance was measured. The value determined in 1838 was 10.3
light years, quite close to our modern figure of 11.4
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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