To the reader:
The Skywatcher's Diary for April 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 April issue, please send a long, self-addressed stamped envelope to:
April 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: April 2005
- The Moon reaches Last Quarter this evening at 7:50 p.m. EST, although dont
bother looking for it then. At this phase, Luna doesnt rise until somewhere near
the middle of the night. Watch for it to come up in the southeast tonight around 2
a.m. local time. By then the Moon will be distinctly less than "half full." The stars
appearing a few degrees to the Moons upper right form the handle of the
Sagittarius "teapot."
- Sirius, the brightest nighttime star, reaches its highest point, due south, half an
hour before sunset. Try to find it as soon after sunset as possible. It will sit 17
degrees (about 2 fists) to the west of due south and 32 degrees above the
horizon. Remember to "spring forward" tonight. Set your clocks ahead one hour
before retiring.
- This morning before dawn the Moon perches 8 degrees to the right of Mars.
Tomorrow morning look for a thinner Moon 8 degrees to the lower left of the Red
Planet. Mars itself is 1st magnitude and currently passing through one of the
faintest of the zodiac constellations, Capricornus. So the planet is by far the most
conspicuous object in Lunas vicinity.
- Jupiter just passed opposition, so the planets now nearly opposite the sun in the
sky. In other words, Jupiter rises within minutes of sunset, stays up all night, and
sets around sunrise. Opposition also means you can predict where Jupiter will
rise, even though the sky is too bright for you to witness the event. The sun sets a
few degrees to the north of west, so the planet ascends at nearly the same
distance to the south of east.
- The waning crescent Moon sits low in the east-southeast before sunrise. This
morning, 30 minutes before the sun comes up, its 8 degrees (almost a fist)
above the horizon. Tomorrow at the same time, Luna will be only half as high and
13 degrees to the left. This is the last opportunity for northern observers to catch
the Moon before it turns New. Those in southern states can try again on Thursday
morning.
- Look for the "Solitary One" toward the end of dusk. The star, formally known as
Alphard, is the brightest object in a good size parcel of the current southern sky. It
belongs to the constellation Hydra, the Water Snake. Alphard sits due south and
almost halfway up about 2 hours after sunset. To confirm that you have located
the 2nd-magnitude star, notice that it is 40 degrees (4 fists) to the upper left of
Sirius and 23 degrees to the lower right of Regulus.
- First-magnitude Mars passes less than a degree below the 4th-magnitude star
Theta, in Capricornus, over the next two mornings. Tomorrow the planets to the
lower right of the star and Saturday morning to the lower left. Binoculars will help
locate the star, particularly if you have streetlights around. Look both mornings, if
possible, in order to detect the planets motion. Neptune sits only 3 degrees to
the upper left of Mars. The two planets are closest next week.
- The Moon turns New at 4:32 p.m. EDT. With the New phase comes an unusual
solar eclipse -- total for part of its path and annular for the rest. The eclipse path
crosses the Pacific Ocean from New Zealand to Colombia. Skywatchers in the
southern U.S. can glimpse its partial phases. For times and circumstances, visit
http://sunearth.gsfc.nasa.gov/eclipse/OH/LC/LC2005-2.html#2005Apr08H
- Tonight the Moon is about 30 hours old, so you have the special opportunity to
catch an exquisitely thin crescent shortly after sunset. Thirty minutes after
sundown Luna sits 7 degrees (about 3 finger widths) above the horizon and 12
degrees north of due west. Be sure to have your binoculars handy. If you have yet
to see a very young Moon, youll be glad you made the effort.
- Saturn passes "quadrature" today. The term indicates that the planet is 90
degrees, or a quarter circle, from the sun. As a consequence, Saturns shadow,
as seen through a telescope, falls on the rings at nearly a right angle to our line of
sight, producing an attractive three-dimensional effect. Only the outer planets --
those beyond Earths orbit -- reach quadrature. Think about why Mercury and
Venus dont.
- View the crescent Moon tonight with binoculars and youll get a surprise. The 3-
day-old Moon is a pretty sight in its own right, but the real treat lies to the right of
Luna. That sprinkling of stars is the Pleiades cluster, a condensation of stars that
lies about 400 light years away. Several hundred stars belong to the cluster, with
a dozen or so brighter ones. From ancient Greek times the group has also been
known as the Seven Sisters.
- Tomorrow morning Mars sits a half-degree (1 moon diameter) to the upper right
of the 4th-magnitude star Iota, in Capricornus. The following morning, look for
Mars a quarter-degree to the left of Iota. Eighth-magnitude Neptune also lies in
the vicinity, 1.3 degrees above Iota. Binoculars are adequate for Iota and Mars, but
you will need a telescope to capture Neptune.
- Jupiter now rises a little more than an hour ahead of sunset, so watch for the
brilliant planet to appear during early dusk. At sunset Jove sits 13 degrees
(somewhat more than a fist width) above the east-southeast horizon. An hour
later, the Giant Planet has climbed another 11 degrees higher and drifted the
same distance south (right). By the end of evening twilight (about 1 1/2 hours after
sunset), Jupiter is high enough for telescopic viewing.
- Look for the bright star Arcturus in the east after sundown. You are not likely to
mistake the star for Jupiter if both objects are visible, but it could happen if the
planet is momentarily hidden behind a building or tree. Both objects are the same
height above the horizon. Arcturus is close to due east, while Jupiter lies closer to
southeast, about 30 degrees (3 fists) to the right of the star.
- The Moon rests 5 degrees to the upper right of Saturn tonight. Recall from a note
in last weeks column that Saturn is currently about 90 degrees away from the
sun (quadrature). One definition of the Moons Quarter phase is that it occurs
when Luna and the sun are 90 degrees apart. Realizing this, it should come as
no surprise to find the almost-First Quarter Moon near Saturn.
- The Moon reaches First Quarter at 10:37 a.m. EDT. Today marks the 33rd
anniversary of National Astronomy Day. Each year amateur astronomy clubs,
planetariums, observatories, and science centers around the country offer public
events to promote interest in astronomy. Check with your local astronomy group
to see what activities are available and then participate.
- Orion is now low in the west during dusk. Soon it will drift into the brilliant twilight
and be lost for several months before reappearing in the morning sky ahead of
sunrise. Enjoy what time this favorite constellation remains in the evening. Notice
how now Orions Belt sits nearly horizontal, pointing to Aldebaran and its
constellation Taurus on the right, and Sirius and its constellation Canis Major to
the left.
- Tonight the waxing Gibbous Moon perches above Regulus, the heart of Leo, the
Lion. Five degrees (10 moon diameters) separate star and Moon. A fainter star
Eta, in Leos neck, lies not quite 2 degrees to Lunas left. Tomorrow night the
Moon hangs beneath the midsection of the lion, and the following night
(Wednesday) its 10 degrees to the lower right of Denebola, the cats tail.
- If you have been following Mars travels past various stars in Capricornus, youll
want to watch the planet carefully over the next several mornings. This morning
and tomorrow the planet is closest to 4th-magnitude Gamma. Mars appears 1
degree above the star during early dawn today and slightly more than a degree to
the upper left tomorrow. The next morning Mars moves a degree to the upper right
of 3rd-magnitude Delta. By Friday its to Deltas upper left. Binoculars are the best
way to watch the scene play out.
- Early risers get a preview of the August evening stars. The three widely spaced
bright stars sitting high in the southeastern sky before dawn comprise the
Summer Triangle. Scorpius and Sagittarius, two other summer stalwarts, ride low
across the southern horizon. The bright star less than half way up in the west is
Arcturus, belonging to the constellation Bootes.
- The Lyrid Meteor Shower peaks before dawn tomorrow, but dont expect much of
a show. First, the shower is one of the less active major displays, producing an
average of one meteor every 4 or 5 minutes. Secondly, the bright Moon remains
visible from dusk until dawn, allowing only the most luminous meteor streaks to
appear. Unless you are a meteor fanatic, stay in bed.
- Last night the Moon perched 8 degrees (less than a fist) above Jupiter, and
tonight its 5 degrees below the Giant Planet. In between Luna slid close enough
to cover (occult) Jupiter for skywatchers located in extreme southern locations,
namely southern Africa, the Indian Ocean and parts of Antarctica. The star you see
2 degrees above Jupiter tonight is 3rd-magnitude Gamma in Virgo. Watch Jupiter
creep closer to Gamma over the next month or so.
- The Moon remains in Virgo tonight, 7 degrees (14 moon diameters) from the
constellations Alpha star, Spica. Spica is sometimes thought of as the
quintessential 1st-magnitude star because its almost exactly magnitude 1.0.
Actually, the star is slightly variable, changing in light output by 0.03 magnitudes.
Furthermore, the star is not single. It has one bright and three fainter companions
a five-star system.
- Full Moon occurs at 6:06 a.m. EDT. In colonial times the April Moon was known as
the Planters Moon or Egg Moon. For observers in western North America, the
Moon passes through the extremely faint outer edge of the Earths shadow early
this morning. This penumbral eclipse results in a subtle darkening of the Moons
upper edge, at best. Maximum shading occurs around 3:00 a.m. PDT.
- Can you tell that the Moon is a day past Full tonight? Once it rises, 2 to 3 hours
after sunset, look for a slight out-of-roundness on Lunas western (upper right)
limb. Binoculars will help. The Moon sits near the stars marking the head region
of Scorpius. Bright Delta, or Dschubba, lies 4 degrees to the Moons left.
Tomorrow night Luna rises a little more than an hour later. Then, it hangs 3
degrees below Antares, the luminous heart of the scorpion.
- Mercury reaches greatest elongation (farthest angle from sun) today. Normally we
encourage observing the speedy planet around the time of greatest elongation,
but not now, at least not for northern observers. While Mercury sits 27 degrees
from the sun, this time of year the planets orbit lies relatively flat to the morning
horizon. So Mercury remains mired in bright dawn twilight. For southern observers
the horizon angle is much more favorable. For them, Mercury is making its best
morning appearance of the year.
- Tomorrow morning before daylight look for the 3rd-magnitude star less than a
degree to the lower left of the Moon. The star, Gamma in Sagittarius, or Alnasl,
marks the point of the "teapots spout." The name Alnasl comes from Arabic and
means "the point" -- but not of the spout. The ancient nomenclature refers to the
tip of an arrow belonging to The Archer, which is the classical form of Sagittarius.
- Whats the faintest 1st-magnitude star? Its near the meridian (due south) an hour
after sunset and 60 degrees above the horizon. Its the brightest member of Leo.
Thats right, Regulus, shining at magnitude 1.35. In an absolute sense, the star is
much more luminous than our Sun. Regulus is significantly hotter, 140 times
brighter, and 3.5 times larger than Sol. Whats more, it belongs to one of the most
pleasing star patterns in the sky.
- Venus is beginning its emergence into the evening sky. Although not yet easy to
spot, its not that difficult for the eager observer. Armed with binoculars, position
yourself where theres a clear view of the western horizon. Be on site by sunset.
Mentally mark the suns setting position. Within 15 minutes Venus should appear
in that same direction, 3 degrees (2 finger widths) off the horizon.
- Now that the Moons out of the evening sky, look for the Praesepe, or Beehive, a
faint star cluster in the constellation of Cancer. Astronomers know the Praesepe
as an open cluster, similar in nature, if not in appearance, to its more famous
cousin, The Pleiades. To capture the Beehive, observe from a dark site at the end
of evening twilight (about 1 hour 45 minutes after sunset). Point your binoculars
along a line between Pollux and Regulus. Aim slightly closer to Gemini and less
than a binocular field of view below the line. By scanning around the area you
should eventually run across a collection of faint stars, the swarm of bees.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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