To the reader:
The Skywatcher's Diary for March 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 March issue, please send a long,
self-addressed stamped envelope to:
March 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: March 2005
Star light, star bright, first star you see tonight is . . . Sirius. How soon after sunset
can you detect this brightest nighttime star? Thirty minutes after sundown the star
sits 25 degrees (2 1/2fists) above the south-southeast horizon. Theres no penalty
for using binoculars to help guide the unaided eye. Notice the scintillation --
astronomers term for twinkling, a characteristic they dislike. Steady light makes
for better research data.
Before sunrise tomorrow morning, the Moon occults (passes in front of) the bright
star Antares, heart of Scorpius. The event is visible from the continental U.S. The
star disappears behind the bright edge of the Moon and reappears on Lunas
shadowed side. For the eastern approximately third of the U.S., Antares emerges
after sunrise. Precise timings for major cities are available from the International
Occultation Timing Association (www.lunar-occultations.com/iota).
[Times EST for Antares disappearance, reappearance:
Detroit: 5:52 a.m., 7:11 a.m.
Kalamazoo: 5:47 a.m., 7:06 a.m.
Lansing: 5:49 a.m., 7:08 a.m.]
The Moon reaches Last Quarter at 12:36 p.m. EST. If you watch the occultation of
Antares this morning, you should be able to tell that the Moon is slightly more than
half lit (gibbous). Tomorrow morning Luna will appear distinctly crescent shaped.
Antares then sits 14 degrees (1 1/2 fists) to the upper right, with the "teapot" of
Sagittarius to the lower left, and Mars beyond Sagittarius.
Saturn is currently retrograding, that is, traveling westward against the distant
starfield. The motion is an illusion created as Earth carries us by Saturn, similar
to a slower car appearing to back up as you pass it. Saturn seems to be
approaching the 4th-magnitude Delta star in Gemini, about 2 degrees to its upper
right. The retrograde effect for Saturn ends later this month.
Tomorrow morning the waning crescent Moon appears 6 degrees (12 moon
diameters) below Mars. An hour before sunup the pair sits low in the southeast
sky. The following morning at the same time the Moon lurks just above the
horizon and 13 degrees farther to the left. Thats the last likely opportunity to catch
Luna before New, at least without optical aid.
The southern face of Saturns rings is tilted 24 degrees toward us. Since thats
only 3 degrees less than maximum, the current view through even a modest
telescope is spectacular. Tonight Saturns giant moon Titan sits about 3 ring
diameters to the planets west. You may recall that Titan is the atmosphere-laden
orb that the Huygens space probe successfully landed upon in January.
If you enjoy the hunt for thin crescent moons, be outdoors with binoculars at 20
minutes before sunrise tomorrow morning. Look very low in the east-southeast.
The wispy crescent lies a scant 1 degree (2 moon diameters) above the horizon.
The Moon is 46 hours before New, which means it is relatively broad, as old
moons go, and therefore should compete favorably with the bright twilight.
Mercury is now on display in the evening sky. An hour after sunset the bashful
planet sits 5 degrees (half a fist) above due west. The planet is bright enough
(magnitude -0.8) to stand up to even brighter twilight, so you might wish to look
closer to sundown. Mercury is slowly fading while climbing higher, so it will
remain easily visible for another week.
What constellation lies between the two prominent winter dogs Canis Major and
Canis Minor? You can be pardoned for not knowing Monoceros, the Unicorn.
Although Monoceros covers an area of the sky greater than either Canis Major or
Minor, its brightest star is only 4th magnitude. Monoceros is a "modern"
constellation, dating to a star map of 1624, although possibly earlier.
New Moon occurs at 4:10 a.m. EST. Observers in the southwest U.S. and points
farther west may glimpse a very young crescent tonight shortly after sunset. Look
just above the west horizon 20 minutes after sunset. Use binoculars. From
southern California the Moon is about 17 hours old at the appropriate observing
time. Any Moon less than 24 hours after New is considered a special sight.
Dont miss the young Moon tonight. The delicate crescent poses 4 degrees (half
a fist width) to the upper left of Mercury, so you gather two prizes for your effort.
Look due west about an hour after sunset. The pair sits less than 10 degrees
above the horizon. Be careful not to dawdle. Mercury sets 1 1/2 hours after the
sun.
Mercury reaches greatest elongation today. Its 18 degrees (2 fists) east of the
sun, a little less than the average separation. For example, its next greatest
elongation, in April, is 27 degrees. Yet this appearance is very good for mid
northern latitudes because the planets orbit sits more perpendicular to the
horizon at sunset during this time of year. So Mercurys 18 degrees of elongation
contribute primarily to raising the planet above the horizon, making it easier to
find.
Mercury begins a noticeable decline this week, both in brightness and height
above the horizon at dusk. The double whammy means the curtains falling fast
on the planets current evening show. Do look for Mercury at your next opportunity,
since it may be your last for a while. An hour after sunset tonight, the planet
appears 6 degrees (half a fist) above west.
The constellation Monoceros, the Unicorn, although faint, receives some notoriety
due to a number of celestial wonders that reside within its boundaries. You may
have seen photos of its component star clusters and nebulae (gas clouds). The
Rosette Nebula and Cone Nebula are probably the most famous. The colorful
clouds and dark gas mixed with star clusters make these objects particularly
photogenic. A quick search of the Web will turn up numerous images of these two
beauties.
The Moon sits comfortably between two star clusters tonight. The Pleiades, the
well-known group also dubbed the Seven Sisters, hangs 5 degrees (10 moon
diameters) to Lunas lower right. The Hyades, a looser collection of stars, is
about 8 degrees to the Moons left. The brighter stars of the Hyades form a "V"
shape. Aldebaran, the brilliant star at one end of the "V", does not belong to the
group.
Tonight the Moon, a robust crescent, perches near the ends of the horns of
Taurus, the Bull. Six degrees (12 moon diameters) to the upper left of Luna sits
Beta, the brighter of the horn tips. Eight degrees to the lower left of Beta and 10
degrees left of the Moon resides the other tip, Zeta, more than a magnitude fainter
than Beta. If you imagine the Hyades as the head of Taurus, then the horns
extend some 15 degrees in length, presenting a formidable challenge to the
mighty hunter Orion.
The Moon reaches First Quarter at 2:19 p.m. EST. It sits among the radiant stars
of the "winter ellipse," an oval formed by these stars (listed with distance and
direction from the Moon): Capella, 20 degrees above and right; Pollux, 24 degrees
left; Procyon, 33 degrees lower left; Sirius, 46 degrees below and left; Rigel, 37
degrees below and right; Aldebaran, 22 degrees right and below.
Pluto and Mars reach heliocentric conjunction today. As seen from the suns
position in space, the two planets would appear in the same direction, between
the constellations Sagittarius and Scorpius. As observed from Earth, Pluto
doesnt seem to change its position much. The planet is far enough away that
moving from Sun to Earth creates little parallax. Mars, however, shifts 35 degrees
east, ending up between Sagittarius and Capricornus.
Tonight the gibbous Moon visits Saturn. Look for the planet 6 degrees (12 moon
diameters) to Lunas lower right. Now examine the area above the Moon. Pollux,
the slightly more luminous Gemini Twin, perches there, 2 degrees (4 moon
diameters) away, and Castor, another 4 1/2 degrees above Pollux. As the night
passes, watch the Moon creep farther left (east) of the two stars.
The Vernal Equinox occurs at 7:33 a.m. EST. At that instant the sun stands directly
over the Earths equator. Try a mental exercise. Where on Earth would you have to
stand at that moment to see the sun directly overhead? Yes, on the equator, but
where on the equator? Hint: the time is noon at the mystery location. The spot
must be about 4 1/2 hours east of the Eastern Time Zone meridian or half an hour
west of Greenwich. Answer: South Atlantic Ocean south of the Ivory Coast of
Africa.
Capella, the brightest star in Auriga, the Charioteer, lies about 40 degrees (4
fists) above Orions head. Capella sits farthest north of all the 1st-magnitude, or
brighter, stars. The name derives from Latin meaning "She-goat" or Mother Goat.
The small triangle of fainter stars, about 4 degrees to Capellas lower right, is
nicknamed "The Kids," or baby goats.
The waxing gibbous Moon hovers about 3 degrees (6 moon diameters) to the
upper left of Regulus, heart of Leo. Although faintest of the 1st-magnitude stars,
Regulus has held a place of honor for thousands of years. The name comes from
Latin denoting "little king" because the star was believed to rule the heavens. It
was also considered leader of the Four Royal Stars of ancient Persia.
Regulus sits closest to the ecliptic of any of the bright stars, only half a degree
from that imaginary line. The ecliptic traces the suns movement through the
zodiac over the course of a year. This apparent motion is created as the Earth
orbits our star, causing Sol to seem to drift eastward against the starry
background. Each year on August 22 the sun, following the ecliptic, passes
beneath Regulus, missing the star by only a quarter degree.
The brightest nighttime star, Sirius, belongs to the constellation Canis Major. The
brightest 2nd-magnitude star also resides in that group. Its name is Adhara and
its magnitude is 1.50. Look for the star 12 degrees (a fist) below Sirius. It is part of
a triangle of bright stars that marks the hindquarters of the Great Dog. Although
Sirius has Adhara beat in apparent magnitude, Adhara wins in absolute
luminosity. Adhara only appears fainter because it is much farther from us than
Sirius.
The Moon passes Full at 3:58 p.m. EST. The March Full Moon has been known as
the Sap, Crow, or Lenten Moon. Luna rises at sunset, followed about 40 minutes
later by Jupiter, seven degrees (14 moon diameters) below the Moon. Throughout
the night the Moon slides toward Jupiter. By dawn tomorrow the pair appears only
3 degrees apart and Luna is below Jupiter.
Tonight the Moon rises after Jupiter, about an hour after sunset. Two hours or
more after sundown look for the star Spica 3 degrees (6 moon diameters) below
and slightly right of Luna. Spica and the Moon stay close all night. Tomorrow
morning the two are 2 degrees apart, low in the west-southwest.
Take a lead from the Brits. Begin summertime a week early, or rather Summer
Time -- with capital letters. Its what we yanks call Daylight Saving Time. The
British set their clocks ahead an hour today. About 70 countries worldwide
observe the quaint custom of fiddling with their clocks during the summer
months. Two notable exceptions: China and Japan remain on standard time year
round.
Now that the Moon rises well after sunset, we are in a two-week window of
opportunity for observing the zodiacal light. Sunlight scatters off dust particles in
the plane of the solar system. Once all traces of dusk are gone from the sky, a
faint glow is noticeable this time of year after sunset. The optimum time to
observe the phenomenon is right at the end of evening twilight, which now is
about 1 1/2 hours after sunset. Look for a faint triangle-shaped glimmer rising
from the western horizon.
Today Mercury passes between the sun and us -- what astronomers call inferior
conjunction. The alignment isnt perfect, so the planet does not cross the suns
face. Instead, from our vantage point, it slides 3 degrees above the sun.
Coincidentally, 35 hours later Venus also aligns with the sun, slipping about a
degree below Sol. While Mercury is on the near side of its orbit, Venus is on the
far side, and so the latter event is known as a superior conjunction.
You might recall that this month began with an occultation of the star Antares.
Luna has made a complete orbit in the intervening time and today covers Antares
again. North American is not favored this time around, however. Instead,
observers in part of China, Japan, Korea, the northern Pacific Ocean, and the
Hawaiian Islands will witness the event.
Mars continues to slowly pull away from the dawn glow, now rising 1 1/2 hours
before sunrise in the east-southeast. Look for it an hour before sunup in the
southeast 12 degrees (a fist) above the horizon. It sits within the constellation of
Capricornus, 9 degrees west of Neptune. Mars moves significantly swifter than
Neptune and will pass that planet in mid April.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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