To the reader:
The Skywatcher's Diary for May 5 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 May issue, please send a long, self-addressed stamped envelope to:
May 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: May 2005
- The Moon passes Last Quarter phase at 2:24 a.m. EDT. Tomorrow morning
before sunrise Luna appears distinctly less than half illuminated. The bright star-
like object 5 degrees (10 moon diameters) to the Moon� upper left is Mars. Can
you detect a slight orange hue to the planet? The following morning, look for the
Moon twice as far from Mars, to the lower left. If at first you don't see the Moon, try
looking lower, in the southeast.
- Saturn perches about half way up in the west as dusk settles in. Telescopic
scrutiny of the ringed beauty is best done as soon as the sky is dark enough. The
later you wait, the lower Saturn slips and the thicker the layer of Earth's
atmosphere the telescope must peer through. Higher magnification only
amplifies the air's blurring effect. To paraphrase an old adage, the early observer
catches the detail.
- The Eta Aquarid meteor shower kicks up over the next few mornings before dawn.
The tiny particles of matter that produce the meteor streaks were sloughed off by
Halley's Comet during one of its passages close to the sun. In some circles, the
shower is considered similar to the famous Perseids, but for northern observers
the radiant point, near the "water jar" of Aquarius, never climbs high enough to
create a topnotch event.
- Early risers may use the waning crescent Moon to locate Mercury, low in the east.
Tomorrow morning, 40 minutes before sunrise, Luna sits 10 degrees to the
upper right of the planet. Mercury, then, rests barely a degree off the horizon. The
following morning the Moon slides 3 degrees to the upper left of Mercury. The
view of the wispy Moon is worthwhile, even if the planet eludes you.
- Have you captured Venus yet? The planet is still a bit of a challenge, as it hugs
the west-northwestern horizon after sunset. Only by month's end will it climb high
enough to become easy for casual skywatchers. If you are up for the game, grab
the binoculars and head to an observing spot with a flat western horizon. Watch
the sun set, carefully noting its location. Twenty-five minutes later Venus sits 2
degrees above that mark.
- The great constellation Orion departs the evening skies. Rigel, the bright star
marking the mighty hunter's foot, sets about 45 minutes after sunset. Rigel, like
all stars, sets 4 minutes earlier each day. Soon, if not already, Rigel will be too
low to pick out of the bright twilight. Astronomers refer to that point as the heliacal
setting date. A number of ancient cultures used the heliacal setting and rising of
various bright stars as calendar markers, since these events occur near the
same date each year.
- Probably the best-known historical example of a helical rising is that of the star
Sirius. The Egyptians associated this brightest of the nighttime stars with the
annual flooding of the Nile. By coincidence the two events occurred at
approximately the same time. The heliacal rising of Sirius was also used to
announce the Egyptian New Year.
- The Moon is New at 4:45 a.m. EDT, so it will be exceptionally young this evening
for most of the U.S. Luna is too close to New phase for observers on the East
Coast to spot it tonight, while those on the West Coast can certainly view it.
Somewhere in between, the conditions will be just right to allow a tenacious
observer to become the first in the world to glimpse that extraordinarily faint wisp
of moonlight. Venus lies 4 degrees to the Moon's upper left.
- The slender crescent Moon is easy to see shortly after sunset tonight. Although
Luna sets 2 hours after the sun, go out early enough to look for Venus, too. Thirty
minutes after sundown, Venus hovers 3 degrees above the west-northwestern
horizon and 9 degrees below the Moon. The star Aldebaran sits 9 degrees to
Luna's lower left and 11 degrees to the planet's upper left.
- While enjoying the sight of our picturesque Moon this evening, soak in the
earthshine, that ashen portion of the Moon that fills in the crescent. Can you
distinguish any detail within the earthshine? Also look for the 2nd-magnitude star
Beta, in Taurus, 2 degrees (4 moon diameters) above the crescent. Beta is the
brighter of the two stars that mark the tips of the bull's horns.
- Each night at the same level of twilight illumination, the star Sirius is slightly
lower. On what date will you last see Sirius before it surrenders to the bright
sunset glow? The current date of the star's heliacal setting for mid northern
latitudes is around the middle of the month. Look low in the west-southwest each
clear night about 20 minutes after sunset. Use binoculars initially, if needed, and
then sight without optical aid.
- The Moon resides within Gemini tonight. The brightest "star" 8 degrees (a fist
width) to Luna's upper left is Saturn. The heads of the twins are represented by
the stars Pollux, 8 degrees above the Moon and slightly left, and Castor, 7
degrees above and slightly right. Tomorrow night the Moon lands 7 degrees
above Saturn and 5 and 9 degrees to the upper left of Pollux and Castor,
respectively.
- The combination of the unlucky day Friday and ill-fated number 13 combine today
to create what some believe portends misfortune. The origin of
paraskevidekatriaphobia dates back to ancient times, but still has a following
today. Folks who keep track of such things say it's the most widely held
superstition in the U.S. Those who care may take some solace to know that today
is the only occurrence of Friday the 13th this year.
- Mars passes 1 degree below Uranus tomorrow morning. Look for 1st-magnitude
Mars 10 degrees up in the east-southeast at the beginning of morning twilight,
about 1 3/4 hours before sunrise. Sixth-magnitude Uranus is above Mars and
slightly left. Use binoculars. Fourth-magnitude Lambda in Aquarius is a degree to
the left of Uranus. The three objects make an isosceles triangle.
- Over the next two nights the Moon passes by Regulus, the heart of Leo. In
between it turns First Quarter. Tonight look for the star 9 degrees (a fist width) to
the left and slightly below the waxing crescent Moon. Tomorrow night Luna sits 5
degrees to the upper left of Regulus and appears distinctly older than First
Quarter. Officially it is then waxing gibbous phase.
- The Moon reaches First Quarter this morning at 4:57 a.m. EDT. If you haven't
examined the Moon in detail at this phase, aim your binoculars or telescope
tonight and enjoy. Binoculars will work best if mounted on a tripod. The cratering
on the southern (lower) end of the terminator is impressive. Notice the large
circular regions in Luna's upper right section that appear darker than the
surrounding area. They are enormous craters whose floors were long ago filled
with lava.
- Despite its relative brightness, 2nd-magnitude Alphard is a star that is not well
known. The star's lack of fame is probably not helped by its belonging to the faint
and obscure constellation of Hydra, the Water Snake. Alphard is easy to find,
however, because it stands out from its faint surroundings. Look a third of the way
up in the southwest an hour or so after sunset. Confirm your discovery by
checking that it lies halfway between Regulus and the horizon.
- Mars and Saturn reach heliocentric opposition today. In plain English, the two
planets appear on opposite sides of the heavens, as seen from the sun. From
our less hostile environment here on Earth, the planets are only very
approximately opposite one another: Saturn's in the evening sky and Mars shows
up in the morning after Saturn sets. The spread is 230 degrees.
- Try to find Jupiter before sunset. Shortly after moonrise, 3 to 4 hours before
sundown from the East Coast, Jupiter is less than a moon width to the north (left)
of Luna. Use binoculars to bring out the planet against the bright sky. After sunset
Jupiter is easier to pick out but farther away from the Moon. How soon this
evening can you detect Jupiter without optical aid?
- Since last night, the Moon has traveled farther down Virgo, and tonight during
twilight stands 2 degrees (4 moon diameters) to the left of Spica, the alpha star of
that constellation. Observe the Moon at least twice, once during twilight, say 45
minutes to an hour after sunset, and again as late as you can. Compare the
relative separation and orientation of Spica and the Moon at the two times.
- The Summer Triangle, composed of bright stars Vega, Deneb, and Altair, crawls
its way into the evening sky. Vega, the most luminous of the trio, rises 2 hours
before sunset, so it is easily detected low in the northeast as night descends.
Deneb is up next, crossing the horizon 1 1/2 hours before sunset. Altair, the last of
the triad, lingers, as if waiting to make a grand entrance. It rises 2 hours after
sunset.
- The Big Dipper reaches its maximum height above the northern horizon during
dusk this time of year. The well-known pattern sits so high that casual star
watchers might overlook it, expecting to find the group more at eye level. Most
people, if asked, would say the Dipper is overhead when, in fact, it sits 15 to 20
degrees below the zenith. Judge for yourself.
- The Moon turns Full at 4:18 p.m. EDT. Overnight, Luna occults, or covers, the star
Antares, brightest in Scorpius, for observers in most of North and Central
America. The show begins about midnight on the West Coast and 4 a.m. on the
East Coast. Maximum duration is on the order of an hour, since that's how long it
takes the Moon to travel its own diameter. For specific times, go to the
International Occultation Timing Association's website:
http://www.lunar-occultations.com/iota.
[Disappearance and reappearance times for select Michigan cities:
Detroit, 4:09 am, 5:06 am EDT
Kalamazoo, 4:06 am, 5:02 am EDT
Lansing, 4:07 am, 5:03 am EDT]
- Leo, the Lion, can be found high up in the southwest near the end of dusk. Most
observers readily identify the "head" region, Regulus and the group that's shaped
like a backward question mark known as "The Sickle". The tail of the lion also
contains a prominent star, 2nd-magnitude Denebola. This luminary is white,
alerting us that it's hotter than our sun. Denebola is similar to Altair, the Summer
Triangle member, but farther from us, so it appears fainter than that star.
- Denebola's name derives from Arabic meaning "lion's tail." The term "deneb"
appears in several star names and in all cases refers to the tail of some animal.
Denebola, along with Spica (lower left of Jupiter), and Arcturus (35 degrees left of
Denebola), forms a large equilateral triangle, sometimes dubbed the "Spring
Triangle."
- Denebola belongs to a select class of stars that appear to be wrapped in dusty
shells. Vega is another such star that's known for its dust cloud. Because
astronomers believe that planets form out of dust surrounding stars, Denebola
may be spawning planets in some early stage of formation, although no direct
evidence exists for these planets.
- Those observing from a dark location may notice that the Milky Way is missing
from the evening sky. Not missing, exactly, but lying along the horizon and
therefore impossible to observe. With some imagination you can picture the flat
disk of our galaxy stretching out along the horizon in all directions. Turning toward
the northeast puts you facing the path we're following as we orbit the Milky Way's
center. Turn 90 degrees right (southeast) to look toward the direction of that
center.
- Venus continues its slow ascent out of the sunset glow. Forty-five minutes after
sundown look for the brilliant planet 4 degrees above the west-northwestern
horizon. Venus sets about 30 minutes later. Saturn lies in Gemini, 31 degrees (3
fists) to the upper left of Venus. Saturn, Gemini, and the other western
constellations are drifting lower each night. In about a month, Saturn reaches the
vicinity of Venus, which by then is joined by Mercury, producing an intriguing
gathering of the three planets. Stay tuned.
- Tomorrow morning the Moon turns Last Quarter (7:47 a.m. EDT). A few hours
earlier you can catch Luna in a dark sky among the stars of Aquarius and near the
planet Uranus. The Moon's illumination makes locating Uranus difficult, so if
that's your intent, mentally mark the spot for later reference. Sixth-magnitude
Uranus sits 4 degrees (8 moon diameters) to the upper left of Luna.
- Tomorrow morning the waning crescent Moon sidles near Mars. It hangs 1
degree below the planet during early dawn. Mars is now officially zeroth
magnitude and makes a pretty sight in the morning darkness. The planet is still
too far from us to be a fruitful telescope target, so don't bother. Instead, you might
like to stand for a moment looking at Mars, then wave to those incredibly prolific
Mars rovers that are still active on its surface.
- How soon after sunset can you spot Antares rising in the southeast? Antares is
the 1st-magnitude star that marks the heart of Scorpius, although don't expect to
see much of the constellation for several hours. Antares'sluminosity is deceiving
because of its great distance from Earth 600 light years. The star is actually
12,000 times brighter than our sun. Antares is an enormous red giant.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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