To the reader:
The Skywatcher's Diary for January 2001 has been prepared by
D. 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 January issue, please send a long,
self-addressed stamped envelope to:
January 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
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ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: January 2001
A showy planetary display heralds the third millennium. Venus dominates the SW evening skyÑoutshone only by the Moon. Jupiter and Saturn steal the eastern scene. The two giant planets are about halfway up at the end of twilight. Saturn is to the upper right of its more brilliant partner.
First Quarter Moon occurs at 5:31 p.m. today. Tomorrow morning the first meteor shower of the year reaches its maximum at about 7 a.m. EST. The Quadrantids are characterized by a sharp burst of activity, lasting an hour or two. Sightings as frequent as two meteors per minute have been reported. The shower is named after a now-defunct constellation that occupied the northern part of present day Bootes.
The three evening planets, Venus (SW), Jupiter, and Saturn (ESE), span 90 degrees across the sky. That separation will halve during the next two months. The planets neatly trace the plane of the solar system as it is projected against the starry backdrop of zodiacal constellations.
Although our shortest day occurred on December 21st, today marks the latest sunrise for latitudes near 40 degrees north. The Earth is also closest to the sun todayÑ91,400,000 miles away, or about 1,600,000 less than average. These phenomena are due to the Earth's elliptical, rather than circular, orbit.
The Moon passes Saturn and Jupiter over the next two nights. Luna is 2 1/2 degrees (5 moon diameters) to the lower right of the ringed planet tonight and 7 degrees to the lower left of Jupiter tomorrow night. Notice the bright star Aldebaran, eye of Taurus, 2 1/2 degrees to the Moon's lower left.
Tomorrow night the Moon passes in front of the 3rd-magnitude star (Zeta) that marks the tip of Taurus the Bull's lower horn. During this "lunar occultation," the star will suddenly "blink off" as the Moon's dark (leading) edge covers it sometime before midnight for most places. Use binoculars or telescope. Serious observers can find times for specific locations listed at
http://www.lunar-occultations.com/iota.
Those who have telescopes can watch the shadows of two of Jupiter's large moons cross the face of that planet tonight. Ganymede's shadow starts the show at 9:35 p.m. EST, followed by Io's at 10:13 p.m. Both shadows remain visible until 11:44 p.m. when Ganymede's shadow slides off the disk. Io's shadow disappears at 12:24 a.m., ending the event.
Full Moon occurs tomorrow afternoon. Tonight the Moon can be found in the east at the end of twilight. Look for 2nd-magnitude Gamma in the "feet" of Gemini, the Twins, 5 1/2 degrees (11 moon diameters) to the lower right. Tomorrow night the Moon moves from the feet to just under the heads of the twins. Look then for Pollux, the brighter of the brothers, 6 1/2 degrees to the upper left of the Moon, and Castor, the sibling, another 4 1/2 degrees above Pollux.
The Moon is exactly Full at 3:24 p.m. EST. A lunar eclipse takes place today, centered over the Arabian Peninsula. The eclipse ends at 4:59 p.m. EST. We'll not see it since the Moon does not rise for us until after that time. People in New England and eastern New York State will glimpse the final minutes, just after moonrise.
The Moon was closest to Earth at 4 a.m. this morning. 221,910 miles separated the two bodiesÑsecond fewest of the year. We'll be 173 miles closer on February 7. Since this "perigee" occurs so near the Full Moon, tides will be especially highÑnot something we much worry about near the Great Lakes.
The Moon rises in the ENE about 2 1/2 hours after sunset. Almost an hour later the star Regulus, heart of Leo, the Lion, comes up 6 degrees directly below the Moon. On the opposite horizon, Venus sets within the next hour just to the south of west.
Twilight ends for us 1 1/2 hours after sunset this time of year. Tonight the Moon comes up about 3 1/2 hours after sunset. Between these two events we have two hours of good quality dark skies for observing those fainter showpieces of the winter sky. The Milky Way arches across the sky from SE to NW. The Andromeda Galaxy sits high in the west. The Orion Nebula hangs below the "belt stars" in the SE. Grab those binoculars and head out of town.
The brightest star in the night sky, Sirius, rises in the ESE at the end of twilight. Look carefully at the star's colors when it is close to the horizon. You will see flashes of every hue in the rainbow. Use binoculars to enhance the effect. The star's prismatic display is not intrinsic to the star. It is created as the starlight passes through Earth's turbulent atmosphere on the way to our eyes.
Today is the beginning of year 2754 A.U.C. according to the ancient Roman calendar, from which our present system stems. Celebrate the new year by tallying the number of objects you can find in the sky that have Roman (Latin) names. Hint: start with the planets.
The Last Quarter Moon occurs tomorrow morning at 7:35 a.m., or about half an hour before sunrise. Although you could see the Moon at the instant of Last Quarter, there is no practical reason to do so. Instead, catch the Moon 45 minutes earlier when you'll be able to find Spica, the brightest star in Virgo, 14 degrees (1 1/2 "fist widths") to the lower right.
The Moon is on either side of Mars the next two mornings. Look 1 to 1 1/2 hours before sunrise. Wednesday morning the Moon is 6 degrees (12 moon diameters) to the upper right of the Red Planet, and 8 degrees to its left the following morning. Alpha in Libra, a double star you can "split" with binoculars, is less than a degree below Mars.
Venus' angular separation from the sun, as seen from the Earth, is maximum todayÑ47 degrees. Astronomers refer to this event as a "greatest elongation" of Venus. It is one reason the planet is currently perched so high above the horizon after sunset. In a telescope Venus will appear half illuminated, like a quarter-phase moon.
Mercury is edging into the evening sky to join the trio of planets already there. Although Mercury will be easier to spot later in the month, try out your observing skills now. Look not later than 45 minutes after sunset very low in the WSW, slightly closer to SW. Since the planet will be only 4 degrees above the horizon, you'll need a flat, unobstructed view. Use binoculars to aid in initially locating Mercury.
Have you noticed how red Betelgeuse (bet'-tel-jooze) appears? It's the bright star in the upper left corner of the Orion pattern. Find it perched a third of the way up in the ESE at the end of twilight. If you don't see any color, compare Betelgeuse to the even brighter star Rigel (rye'-gel), the hunter's foot, diagonally opposite. Betelgeuse's color indicates it is cooler than our yellow sun.
The waning crescent Moon is a beautiful sight the next couple of mornings. View it an hour before sunup with unaided eye and binoculars, low in the SE. Monday, the 22nd, is the last morning you will be able to find itÑjust to the east of SE. The Moon is New on Wednesday, the 24th.
The International Space Station has been drawing attention now that the large solar panel has been deployed. The ISS may appear nearly as bright as Jupiter, depending on its orientation. You can see it on nights that it passes over you during twilight or dawn. To find out when, you'll need recently calculated information for your specific location. The best way to acquire a timetable is to use the web. Try this site for starters: www.heavens-above.com.
Jupiter now floats high in the SE at nightfall, suspended between the Pleiades and Hyades star clusters. Use binoculars to examine the clustersÑthe Pleiades 5 degrees above Jove and the Hyades (a looser grouping) 7 degrees to the lower left. Try the binoculars on Jupiter. Can you hold them steady enough to see any of the moons?
Sirius, the brightest nighttime star, crosses the meridian (due south) just before midnight this time of year. Do you know the name of the second brightest star? It cannot be seen from here. It only barely breaks the horizon for the lower third of the continental U.S. At the equator it rises as high as 37 degrees. The star is Canopus, in Carina, the Keel.
The Moon is New at 8:07 a.m. EST. Two weeks ago we spoke about the second closest moon of the year. NowÑhalf the Moon's orbit laterÑwe witness the farthest moon. At 2 p.m. EST Luna sits 252,626 miles away from Earth. Guess what will happen in another two weeks.
Time to find Mercury if you haven't bagged it yet. The Moon will point the way. Locate the thin crescent just above the WSW horizon 45 minutes after sunset. The bright "star," 4 1/2 degrees (9 moon diameters) above, is our quarry. This most elusive of the naked-eye planets was named after the fleet-footed messenger of the Roman gods.
Over the next week you have an unusual opportunity to see four planets at once. Tonight the Moon aids in locating the most difficult of the groupÑMercury. An hour after sunset, look almost a "fist width" (8 degrees) to the lower right of the crescent. Venus is 22 degrees above the Moon. Saturn is 60 degrees beyond Venus, and Jupiter is 7 degrees to the ringed planet's left. The foursome span 97 degrees, from the WSW to SE.
As they orbit the sun, planets appear to slowly drift eastward against the backdrop of stars. When Earth overtakes the slower moving outer planets, they give the illusion of moving westward, in "retrograde," as both Jupiter and Saturn have been doing until two days ago. Now they have resumed direct motion. Speedier Jupiter will gradually pull away from Saturn. You currently see the minimum separation of these two planets until 2020 when Jupiter once again "laps" Saturn.
Venus and the Moon team up to coax us outside this evening. They pose 6 1/2 degrees (13 moon diameters) apart in the SW. Mercury stands at "greatest elongation." The planet is "rounding the bend" in its orbit, as seen from Earth, so the apparent angular separation between sun and planet is maximum.
The Moon makes a worthwhile binocular target tonight. Scan the terminator (curve separating moon's light and dark sides). The top half cuts through three large dark ovalsÑmariaÑand the bottom half reveals craters galore. Almost dead center is the site of the Apollo 11 landing. The sun is just rising on the artifacts left by astronauts more than 31 years ago.
The Moon perches between Venus and Saturn this evening. Can you tell that it is nearer Venus? As the night progresses the Moon creeps closer to Saturn. Eventually the Moon is equidistant between the two planets, occurring about the time that Saturn setsÑseveral hours after midnight.
The "Winter Triangle" is a nickname sometimes applied to Betelgeuse, Sirius, and Procyon. Betelgeuse is the reddish shoulder of Orion that hangs halfway up in the SE at the end of twilight. Sirius, the brightest nighttime star, is below Betelgeuse and sits about a fist width above the horizon. Procyon is equally spaced to the upper left of Sirius and lower left of Betelgeuse. The former two stars mark Canis Minor and Canis Major, respectively, Orion's hunting dogs.