To the reader:
The Skywatcher's Diary for March 2003 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
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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
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Current and back-issues of the Skywatcher's Diary are available in our
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Skywatcher's Diary: March 2003
If you've not glanced at the Big Dipper recently, take a look this evening after dark. The Great Bear has left his winter den and climbed halfway up the sky in the northeast. Notice how the middle of the Dipper is even with the North Star, which sits a dipper length to the left. Travel another dipper length farther left and you find yourself in the middle of Cassiopeia. The telltale "W" shape of this constellation is standing on end, opening to the right. It resembles the Greek capital letter sigma.
The Moon is New at 9:35 p.m. EST this evening, so the next several nights offer the last opportunity to view in a moonless sky for a while. Of course, moonlight makes little difference if you must observe from a well-lit city environment. Assuming you can find a dark location, carefully examine the Orion Nebula with unaided eye, binoculars, and telescope. Look for subtle twists and knots of light and dark within the immense dust cloud out of which stars are forming. If you are unfamiliar with this object, first find Orion's Belt, the three equally spaced stars halfway up in the south in early evening. Look directly under the belt, about one "belt length" below, for a "fuzzy star." Zero in with binoculars
This evening you have a rare chance to catch a very young Moon, less than 24 hours old (past New). The hairline crescent sits 1 1/2 degrees (3 moon diameters) above the horizon between west and west-southwest 25 minutes after sunset. Start looking 10 minutes earlier. Use binoculars to slowly scan the area. Tomorrow night the Moon is much easier because the crescent is wider and the Moon sets in a darker sky. Look 45 minutes to an hour after sunset then.
As you gaze at the thin crescent tonight, imagine Muslims in the Middle East intently scanning the western horizon looking for that same Moon eight hours earlier. Their purpose was to establish the beginning of the New Year under the Islamic Hijrah calendar. That calendar is strictly lunar based, marking months by the first sighting of the crescent Moon after sunset. The Moon goes through its cycle of phases 12 times in only 354 days, about 11 days shorter than the familiar 365-1/4-day Gregorian calendar. The Muslim New Year, therefore, drifts earlier each year by 11 days.
Today the planet Mars passes between two of the more famous nebulas, or giant gas clouds. The brighter of the two is familiar to amateur astronomers as the Lagoon Nebula, named for its distinctive dark dust lane. It appears less than a degree to the lower right of Mars tomorrow morning. The Trifid Nebula sits to Mars' upper right less than a degree away. This nebula is often remembered because of the vivid blue and pink colors that appear in observatory photographs. Those hues are generally not visible when peering through the telescope. To verify Mars' position, go out when the sky is still dark, at least 1 1/2 hours before sunrise. Although binoculars will reveal the Lagoon, the Trifid requires a modest telescope.
Mars now rises almost 4 hours ahead of the sun. About 2 hours later, Venus, its brighter sibling, joins the Red Planet. Another hour passes and Venus is hard to miss, blazing away 7 degrees (almost a fist width) above the horizon just to the north of due east. Mars is 33 degrees (3 fists) farther right, in the south-southeast, and more than twice as high as Venus. Don't mistake the star Antares for Mars. It is at the same height and brightness but appears more nearly due south.
Algol, or Beta in Perseus, is a famous variable star that marks the eye of Medusa, the gorgon. The star, normally magnitude 2.1, drops to 3.4 and returns to 2.1 in about a 10-hour period every 2.9 days. Algol is an eclipsing binary, that is, what appears to us as one star is really two stars that orbit each other so that from our viewpoint they periodically pass in front of one another. The "eclipse" causes the combined light to dim for a while. Algol reaches one of the dips tonight at 9:07 p.m. EST.
Some evening compare the two brightest star-like objects, Jupiter, high up in the southeast, and Sirius, a third of the way up in the south. Although Sirius is the brightest star, Jupiter outshines it by a magnitude. The planet's light has a slight yellow-white cast, while Sirius appears whiter - some say blue-white. The star's color derives from its temperature. Sirius is one of the hotter stars, similar to summertime's Vega. Jupiter's color results from the combination of hues in the planet's methane and ammonia clouds.
The fat crescent Moon sits between two star clusters tonight. Aldebaran, the eye of Taurus, the Bull, perches 8 degrees (not quite a fist width) to Luna's left. The faint stars loosely gathered to the right and below Aldebaran comprise the Hyades star cluster. To the Moon's right, about 7 degrees, the more tightly grouped stars of the Pleiades appear. Examine both clusters with binoculars. The Hyades barely fit into the field of view of typical binoculars, while the Pleiades show beautifully.
The Moon reaches First Quarter over night at 2:15 a.m. EST. In early evening see if you can tell that the Moon is slightly less than half illuminated. Luna approaches Saturn all night. The two bodies begin the evening 6 degrees (12 moon diameters) apart with the planet to the upper left. By the time the pair sets, tomorrow morning about 2 a.m., 4 degrees separate them. Tomorrow night look for Luna on the other side of Saturn, sitting 8 degrees to the upper left of the planet in early evening.
Yesterday Mars reached its lowest declination for this circuit around the sky. Astronomers use declination to refer to how high or low an object is relative to the stars without regard to the observer's location. The low declination implies that our ability to view the planet (in the northern hemisphere) will improve as the planet moves farther north. You may have noticed Mars currently never rises very high in the sky. Fortunately, Mars' maximum viewing altitude will increase nearly 10 degrees by late August when the planet reaches opposition and puts on quite a show.
Early today the sun crosses the boundary between the astronomical constellations of Aquarius and Pisces. It remains among the stars of Pisces for a little more than a month before moving into Aries on April 19. Reckoning by the astrological signs rather than the astronomical constellations, the sun has already been in the sign of Pisces, since February 19. It shifts into the sign of Aries at the time of the Vernal Equinox, in about a week.
The Moon lines up nicely with the Gemini Twins tonight. In evening twilight, from the eastern time zone, a line drawn through the two bright stars Pollux and Castor passes just to the left (east) of the Moon. The stars and Moon align exactly about 3 hours after sunset. On the west coast the Moon will already appear east of the Twins by the time those stars appear in twilight. Tomorrow night the Moon jumps to Jupiter, sitting 3 degrees (6 moon diameters) to the upper left of that planet.
The shadow of Saturn cast upon its rings creates a beautiful sight for those observers who have access to a telescope. The shadow appears especially pronounced now due to the relative positions of Sun, Earth, and Saturn. And with the rings currently tilted their maximum extent toward us, planet watchers get a particularly pleasing view of this famous world. Even in modest telescopes Saturn takes on a strong 3-D appearance. Try to sneak a peek in the next several weeks.
An hour after sunset the Moon sits over top Regulus, the bright star that marks the heart of Leo, the Lion. Eight degrees (less than a fist) separate the pair. The semicircle of fainter stars, immediately to the Moon's left, outlines the animal's head. Tomorrow night the Moon slides 9 degrees to Regulus' lower left and lies in the belly of the beast. The following night (Monday), Luna hangs 8 degrees to the lower right of Denebola, a 2nd-magnitude star punctuating the tip of the lion's tail.
Mars is parading through a part of the sky rich with deep-sky objects, those faint wonders amateur astronomers love to seek out. Earlier in the month Mars traveled between two nebulas. Over the next two mornings the Red Planet passes within half a degree of a nice globular cluster, known by the designation M22. This spherical concentration of tens of thousands of stars lies 10,000 light years from us in the general direction of the center of the Milky Way Galaxy. In a moderate telescope M22 gives the appearance of a faint cotton ball.
Orion is a magnificent sight on winter evenings. The seven major stars create a pattern that easily attracts the eye and sticks in the memory. Because of the prominence of this group, all of its major stars have been assigned proper names by various cultures, past and present. Betelgeuse (bettle-jooze), the reddish star at the upper left, is the name you are most likely to know. It represents a shoulder of the giant, often pictured with up stretched arm and club. The name comes from Arabic and is frequently translated as "armpit of the giant."
The Moon turns Full at 5:34 a.m. EST, not long before it sets. Unlike the quarter phases, the date of Full Moon is difficult to pinpoint by casual examination. Most people, when glancing at the Moon two days either side of the official date, would pronounce the Moon Full. In colonial times the Full Moon of March was known as the Sap moon or Crow moon. This is the closest Full Moon to the spring equinox, and as such, rises considerably later each evening, about 1 hour 20 minutes for mid northern latitudes
This morning before sunrise the Moon sits 13 degrees (slightly more than a fist) to the right of Spica, a 1st-magnitude star in Virgo, the Maiden. Look for the pair low in the southwest. Tomorrow morning the Moon slips past Spica. The star hardly appears to have moved from the previous morning at the same time, while Luna now perches 5 degrees to the upper left of it. If you observe close to the same time over the next several mornings, the Moon seems to skip horizontally toward the south and then east.
The Vernal Equinox occurs at 8:00 p.m. EST. Calendars using Greenwich time will show the date as the 21st. At the moment of the equinox, the sun appears directly overhead on the equator at longitude 167 degrees E. That spot is in the Pacific Ocean northeast of Australia, very near Nauru, the world's smallest independent republic. In case you'd like to visit this Pacific island to check the sun's position for yourself, you should know that this nation measures 8 square miles and has a total population estimated at 12,329, according to the CIA World Factbook 2002.
Mercury is in superior conjunction with the sun today, which means it is on the backside of its orbit. From our viewpoint, the planet is nearly, but not exactly, in line with the sun. Mercury swings about a degree below Sol. Mercury has its next conjunction with the sun on May 7. Then the swift planet cuts between the sun and us - inferior conjunction. That time Earth, Mercury, and sun will be aligned well enough that observers some places on Earth will be able to witness the tiny silhouette of the planet transiting the sun's disk.
Tomorrow morning before daybreak, the Moon sits 3 degrees (6 moon diameters) to the upper left of Antares, heart of the scorpion. An hour before sunup the star and Moon are a few degrees to the west (right) of due south. At that time the primary stars that give Scorpius its distinctive shape are all above the horizon from most of the Continental U.S. If your southern horizon is unobstructed, and the sky is quite clear, try to trace the scorpion's body all the way to the tip of its stinger. Proceed to the lower left of Antares and follow a loose curve of stars almost to the horizon, then curl back up just to the east of due south in a "J" shape.
The brightest star in Orion is Rigel (RYE-jell), the lower right corner of the familiar pattern. This blue-white beauty is similar to the star Sirius in both temperature and color, but the comparison stops there. Rigel is a supergiant, 70 times the size of our sun, where Sirius is only twice as large. Sirius appears brighter because it is much closer to us, only 9 light years, compared to 800 light years for Rigel. If Rigel were placed at the same distance as Sirius, it would shine almost 2,000 times brighter!
The Moon reaches Last Quarter phase at 8:51 p.m. EST. The event is out of sight for the U.S. since Luna doesn't rise until after midnight. Look for the Moon tomorrow morning an hour before sunrise. It sits 5 degrees (10 moon diameters or half a fist) to the lower left of Mars. A 3rd-magnitude star, Phi in Sagittarius, is only 1 degree to the Moon's left for those in the eastern U.S. The Moon occults that star (passes in front of it) in a couple of hours, after it has set in the eastern states but still visible from the West.
Betelgeuse marks one of Orion's shoulders, and Bellatrix (bell-LAY-triks) the other. Bellatrix's name comes from Latin for 'female warrior," so sometimes it goes by the nickname "Amazon Star." Like Rigel below it, Bellatrix is blue-white and hot, more than 36,000 degrees F on its surface. It shines at 2nd magnitude, just missing 1st by a tenth of a magnitude. The star is about 6 times the size of the sun and resides 240 light years from the solar system.
Asteroid Vesta reaches opposition today, so we're now in the best period to observe this minor planet. Vesta is just over 300 miles wide, forth largest of the asteroids. However, it is almost always the brightest of the group because of its higher reflectivity and smaller orbit. The asteroid is now technically naked eye at magnitude 5.9. With a good finder chart it's an easy binocular target. Vesta is in Virgo, 5 degrees west of 3rd-magnitude Epsilon and 1 degree south of 5th-magnitude Rho.
If you would like a star map that can help you identify Vesta and other interesting objects in the current sky, send a stamped, self-addressed envelope to Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, MI 48824.
Tomorrow morning Venus and Uranus provide the closest gathering of any two planets this year, in fact the closest observable conjunction in more than a decade. They will pass within 3 minutes of arc (1/20th degree) of each other after sunrise in the eastern states and shortly after the pair rises on the west coast. Although the moment of minimum separation will be difficult to observe, skywatchers with moderate size telescopes and excellent observing conditions may enjoy the challenge.
The old crescent Moon provides an attractive and potentially challenging target the next two mornings. Tomorrow morning, 40 minutes before sunrise, Luna can be found 5 degrees (half a fist) to the lower right of Venus, just above the east-southeast horizon. The crescent is thinner and lower the following morning (Sunday). Look 15 minutes before sunup, 12 degrees to Venus' lower left. Timing, a flat horizon, and a transparent sky are critical factors for success.
Jupiter sits in a relative void between the bright stars of Leo, to the east, and Gemini, to the west. Look for it high in the south-southeast in early evening. The giant planet is among the stars of faint Cancer. Although luminosity challenged, Cancer does hold a jewel. Look at Jupiter with binoculars some particularly clear night. You should see a swarm of faint stars to the planet's upper right. The object is the Beehive star cluster, a collection of a few hundred stars that are held together by their mutual gravity. The group is currently about 600 light years from Earth.
The faintest of the four stars that mark the outer corners of Orion is Saiph (pronounced "safe"), a 2nd-magnitude star located at the lower left, below Betelgeuse. The name comes from Arabic for "sword," although the star is not part of the hunter's weapon, as we now think of it. That designation today goes to the three fainter stars that fall in a line below Orion's belt. The middle of that trio marks the location of the Great Nebula in Orion.
If you wish to be the first on your block to spot Mercury as it begins its best evening apparition of the year, tonight is a good time to start looking. The illusive planet sets about 50 minutes after sunset, so timing is important. Half an hour after sunset may be the optimum time to find it, but start observing at least 10 minutes earlier. Thirty minutes before sunset Mercury perches 3 degrees above the horizon, 8 degrees to the north of due east. Keep trying each clear night until you are successful. Binoculars are helpful. By mid April the planet will be much easier to see.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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