To the reader:
The Skywatcher's Diary for January 2002 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 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
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ftp://www.pa.msu.edu/pub/swd/
Skywatcher's Diary: January 2002
Jupiter is in opposition on this first day of the new year. Earth sits between the planet and sun, so those two bodies are on opposite sides of the sky from our vantage point. Keeping that in mind, where would you expect to see Jupiter tonight just after sunset? How about tomorrow morning before sunrise? The importance of opposition to the casual skywatcher is that the object -- Jupiter, in this case -- is easiest to see around that time. Not only is it visible during all hours of darkness, but it is also brightest.
The Earth is at perihelion -- closest to the sun for the year. The daystar sits in space a mere 91,402,460 miles from us today, providing indisputable proof that the distance of the sun does not produce the seasons and their accompanying temperature variations. If the sun's distance was the cause, we would now expect the hottest temperatures of the year. Seasons occur because somehow, a long time ago, our planet's rotation axis got tilted.
The Quadrantid meteor shower reaches its peak before dawn tomorrow, but moonlight interferes.
An hour after sunset Jupiter perches a fist width above the ENE horizon. It is the brightest object in the sky until the Moon rises near 11 p.m. Saturn sits 31 degrees (3 fists) to Jupiter's upper right and remains second brightest until Sirius rises an hour later. These two planets are by far the best ones to view if you are just learning how to use a telescope. Saturn's rings are tilted wide open now, making them easy to distinguish under low power.
Although the length of daylight has been slowly increasing since December 21, the latest sunrise (at 40 degrees north latitude) didn't occur until this morning. Practically speaking, the length of day, along with sunrise and sunset times, changes so slowly during this part of the year that our victory over darkness is more moral than real. And considering that the coldest time is likely still ahead, about all we can celebrate is that the changes are in the right direction.
The Moon reaches Last Quarter tonight at 10:55 p.m. EST, but don't expect to see it until after midnight, when it comes up. Late rising means late setting, too, so the Moon doesn't go down until after midday tomorrow, offering the opportunity to glimpse Luna during morning daylight hours. The Last Quarter always exhibits this visibility pattern -- rising around the middle of the night and setting near the middle of the day. Each of the four major phases, New, First Quarter, Full, Last Quarter, has its own distinct scheme which, once learned, indicates when you can expect to see that particular phase.
On this 12th day of Christmas (or Christmas, proper, for the Eastern Orthodox church), celestial gifts await the evening observer. With careful timing, four planets can be glimpsed simultaneously. Jupiter and Saturn are the two brightest objects on the eastern side of the sky. Mars, now 1st magnitude, rests almost halfway up in the SSW. Mercury is the one that requires effort to locate because it sets quickly. Look an hour after sunset. Mercury will be about 10 degrees north of due SW, just above the horizon. Fortunately Mercury is brilliant, so you may be able to pick it out even earlier, despite brighter twilight.
Supporting the evening planetary show is a stellar cast of winter constellations. Orion has the leading role. If you've never been certain of finding a constellation before, this is the one to try. Orion is poised low in the east, to the right of Jupiter and below Saturn. The three "belt" stars seem to first catch the eye even though they aren't the brightest members of the pattern. The trio traces a vertical line 2 1/2 degrees from top to bottom. That's about the width of two fingers held at arms length. Then look for four additional bright stars, two to the upper left and two to the lower right. Orion is tilted, making the figure of a hunter harder to imagine. In this orientation the pattern more nearly resembles a bowtie or butterfly shape.
Tomorrow morning the crescent Moon hangs 10 degrees (a fist width) above Antares, the heart of Scorpius. An hour before sunup the star is halfway between the Moon and the horizon. The following morning the Moon is 7 degrees to the left of Antares, and by Friday it drops to 18 degrees to the lower left of the star. That's the last morning the thin crescent will be easy to find. Look for Luna just above the SE horizon, then. The Moon is New two days later.
Joining Orion low in the eastern evening sky is Gemini, the Twins. This constellation is to the left of Orion, centered around the NNE. The bright stars, Pollux and Castor, which mark the heads of the brothers, are farther to the left, closer to NE and sit nearly vertically, Castor on top of Pollux. The bodies stretch back toward Orion and are outlined by several strings of fainter stars. Jupiter is currently positioned near the kneecap of the uppermost twin. Early in the evening the brothers are in a somewhat head-down position, but as the night goes on, they rise and tilt more upright.
Saturn, high in the east as night falls, sits among the stars of Taurus, the Bull. The bull's face is marked by a group of stars that form a "V" shape, tipped over horizontally. The majority of those stars comprise a star cluster known as the Hyades (hy'-a-dees). Binoculars are an ideal aid for exploring the cluster. The 4th-magnitude star Epsilon, 1 degree to the lower right of Saturn, marks one end of the "V", and 1st-magnitude Aldebaran, 4 degrees to the planet's lower right, the other end. The point of the "V" is to the right. Saturn is currently retrograding (moving westward) relative to the stars. When it ends retrograde, on February 8, the planet will be in line with Epsilon and Aldebaran.
Mercury reaches "greatest eastern elongation" today. The astronomical term indicates Mercury is now at its greatest angular distance east of the sun, for this particular appearance. Depending on where Earth and Mercury are in their respective orbits, the greatest elongation can reach as high as 28 degrees. This time around only 19 degrees separate the planet and the sun. Fortunately Mercury is at its brightest, so even though it remains close to the southwestern horizon, you should be able to find it with little difficulty an hour after sunset.
If the winter blahs are attacking, you have the opportunity for a quick shot of summer. Go out some evening an hour to an hour and a half after sunset. Face WNW and look for three bright stars, widely spaced. They are Vega, about 15 degrees (fist and a half) up in the NW, Altair, less than 10 degrees up in the west, and Deneb, almost 40 degrees up in the WNW. You may recall those names from warm-weather stargazing. Collectively they are known as the Summer Triangle, a title that denotes their all-night visibility during the hot season. Look soon. Altair and Vega won't be visible much longer.
The Moon is New at 8:29 a.m. EST. The young crescent will first become visible tomorrow night (14th) at dusk. Look 30 to 45 minutes after sunset. The window of opportunity is narrow, so check your time carefully. Look just above the horizon, about 10 degrees to the right (north) of due SW. If the sky is too bright, use binoculars to locate your quarry. Bright Mercury is only 5 degrees (10 moon diameters) above, and slightly to the right of Luna. The sight of the beautiful hairline crescent will be worth your effort.
Venus has not been mentioned recently in our daily summaries because it is currently passing on the far side of the sun. Today this brightest of the planets is officially in conjunction with Sol, sliding a degree below the sun this morning. The event is not visible; it's only of academic curiosity. Today is also the first day of the new year 2755 of the Roman A.U.C calendar. Retrieve those togas from the dry cleaners and throw a party.
The crescent Moon poses 10 degrees (a fist) to the upper left of Mercury tonight. Look in the SW an hour after sunset. Uranus is also in the vicinity of the Moon, 4 degrees to Luna's upper right. Because Uranus is near the naked-eye brightness limit, you will need a pair of binoculars, a finder chart, and some familiarity with the faint constellation Capricornus in order to successfully spot the planet. Fomalhaut, a 1st-magnitude star in Piscis Austrinus, the Southern Fish, can be found 20 degrees to the Moon's left.
Sirius, the most luminous nighttime star, rises in the ESE near the end of evening twilight. Try to examine the star some night just after it has risen. Pay particular attention to its color. Sirius is considered a white star and appears as such when observed high in the sky. But if you catch it while it's still close to the horizon, you will be treated to a technicolor display. As the star's light passes through the Earth's atmosphere on its way to our eye, the air refracts (bends) the starlight into a series of colors. While you gaze at the star, it will continuously flash different hues: blue, red, yellow, green -- an amazing sight to those who have never before noticed it. Binoculars enhance the effect.
Mercury begins a dramatic drop in brightness, fading nearly a magnitude in 4 days. If the weatherman provides a string of clear evenings, watch every night to witness the sudden plunge, both in brightness and in altitude. Mercury soon disappears from the evening sky, until late April, when it then joins the four other bright planets in a dazzling display of all five naked-eye planets in the western sky. Spring is shaping up to be a planet-watcher's dream.
The Moon cruises by Mars tonight. This evening Mars is 5 degrees (10 moon diameters) to the Moon's upper right. By tomorrow night, Luna has traveled 11 degrees (a fist width) in its orbit to the east, appearing to the planet's upper left. Mars is also moving to the east in its own orbit, but at a much slower apparent rate than the Moon. If you want to keep track of Mars' motion, note its position relative to the Great Square of Pegasus, a box of 2nd-magnitude stars 20 to 30 degrees to the planet's upper right and 10 to 15 degrees on a side. Mars aligns with the east side of the Square on January 24th.
Even though the eastern evening sky is littered with brilliant winter stars, the planet Jupiter absolutely dominates the scene. Your eye can't help but be drawn to this -2.7-magnitude beauty. Compare the planet to Sirius, the brightest nighttime star. The star is 40 degrees (4 fists) to the lower right of Jupiter. The planet is more than 3 times brighter than Sirius. Notice the twinkling of Sirius and the steady radiance of Jupiter -- confirming the old adage: "Stars twinkle and planets don't." Although not 100 percent reliable, it's a handy rule to keep in mind.
The Winter Triangle is an unofficial pattern of stars some skywatchers find helpful to identify. Like its summer counterpart, the three bright stars forming the shape are borrowed from three separate constellations. Sparkling Sirius, part of Canis Major, the Big Dog, sits low in the SE 2 hours after sunset. Twenty-seven degrees (3 fists) above Sirius look for Betelgeuse, the reddish shoulder of Orion. Procyon, in Canis Minor, the Small Dog, to the lower left of Betelgeuse and upper left of Sirius, completes the equal-sided triangle.
The First Quarter Moon occurs at 12:46 p.m. EST. It will make a wonderful telescopic target this evening. In fact, the three best objects for telescope novices are visible at the same time over the next several nights. Each is bright, easy to find, and offers enough to satisfy even the pros. In the order they should be observed: the Moon, Saturn, (two-thirds of the way up in the SE -- its rings are magnificent), and Jupiter (its 4 major moons are easy to pick out, the cloud bands are subtle and depend on sky clarity and experience of the observer).
Jupiter sits in the middle of a long, nearly vertical line. The bottom endpoint is Procyon, bright star in Canis Minor, the Small Dog. It's 24 degrees (2-3 fists) below the giant planet. About the same distance above is Capella, a zeroth-magnitude star in Auriga, the Charioteer (fellow who drives a chariot -- Sparty, for example). Capella and Jupiter also form an equilateral triangle with Saturn, found to the right of those two objects. Ten degrees above Saturn is the beautiful Pleiades star cluster. Binoculars bring out the cluster's elegance.
For a star map to help you locate these and other interesting objects, send a self-addressed, stamped envelope to Sky Calendar, Abrams Planetarium, Michigan State University, East Lansing, MI 48824.
The waxing gibbous Moon is 9 degrees (a fist) to the upper right of Saturn and 7 degrees to the lower right of the Pleiades. Tomorrow morning, when Saturn and the Moon are below our horizon, Luna passes within a degree below the planet. For central Africa (during daylight) and southern Asia, the Moon crosses right in front of Saturn, temporarily blocking out the planet from those locations. If you are curious about the details of this event, known as an occultation, visit the website http://www.lunar-occultations.com/iota/planets2002/planets2002.htm.
The Moon is to the lower left of Saturn tonight. In early evening it forms a small nearly equal-sided triangle with the planet and the bright star Aldebaran, 5 degrees (10 moon diameters) to the Moon's lower right. By the time the trio sets (around 4 a.m.) the Moon slides 8 degrees away from planet and star. Tomorrow night Luna is two-thirds of the way from Saturn toward the other giant evening planet, Jupiter. The Moon drifts along in its orbit, covering its own diameter in an hour.
Three planets are currently above the horizon at the end of evening twilight. The forgotten member of the group is Mars. Literally outshone by its two brighter cousins, Jupiter and Saturn, Mars is "only" 1st magnitude. And because the Red Planet's current telescopic image is poor, it gets little notice. The planet can be interesting to watch, however, because its apparent orbital motion is swift enough to be easily noticeable. It's also easy to find, sitting all alone, a third of the way up in the SW at dusk. Notice this evening that Mars is in line with the left side of the Great Square of Pegasus, two stars to the upper right of the planet, 14 and 28 degrees away, respectively. Watch the planet move out of alignment with those stars over the next week.
The waxing gibbous Moon, two days away from Full, perches close to Jupiter tonight -- 4 degrees (8 moon diameters) to the planet's lower left in early evening. Earlier this afternoon, before either object rose, the Moon passed less than a degree below (south) of the planet. A lunar occultation of Jupiter occurred for places far north -- Iceland, Greenland, Siberia, among others. Take peeks at the Moon as often as you can tonight to see it pull away from Jupiter. Tomorrow night it lines up with the Gemini Twins, 5 degrees below Pollux.
Mercury is at inferior conjunction today, an astronomer's way of noting that the planet is passing between Earth and Sun. Because Mercury's orbit is tilted relative to Earth's, rarely does Mercury directly cross the face of the sun. Today the planet slides several degrees above (north of) Sol. Inferior conjunction also means Mercury will next appear to the right (west) of the sun and emerge as a morning "star." The swift planet makes a brief morning appearance in mid February.
Full Moon occurs at 9:50 p.m. EST. This moon was referred to as the "Winter Moon" or "Moon after Yule" in the American colonies. The Native American Algonquin Tribe knew it as the "Wolf Moon."
Uranus is in conjunction with the sun today. The distant gas giant passes on the far side of the sun. It next appears in the morning sky, around late February.
The Moon rises in the ENE about an hour after sunset tonight. Forty-five minutes later Regulus, the 1st-magnitude star in Leo, rises in nearly the same place. Regulus and the Moon are then separated by a little more than 5 degrees (11 moon diameters). As the night progresses and Earth rotates, the pair travel toward the west. The Moon also gradually slips to the east, relative to Jupiter. The orientation of the pair also rotates, relative to the horizon. Before sunrise the two are visible in the west, with the Moon still apparently above Regulus, despite all of the motion. The separation of the two bodies has decreased by a degree.
The three planets, Mars, Saturn, and Jupiter, now span 87 degrees across the evening sky, from SW to E. As Mars moves east relative to the other two planets over the next several months, watch the spread diminish. The trio of planets will be joined by Venus in late March and Mercury in late April to produce a rare display of all 5 naked-eye planets through early May. Watch the spectacle develop by occasionally taking stock of the separation among all of the bright planets.
At dawn's first light the Summer Triangle sits in the ENE. The Scorpion, with its gleaming heart Antares, is low in the SSE. The spring stars Arcturus and Spica are two-thirds and one-third of the way up in the south, respectively. The Big Dipper is high in the NW, with Leo near the horizon in the west. These constellations can be seen in the same positions in the evening sky of late May. By observing in early morning you get a preview of the evening skies about 4 months hence.
Please send any comments, suggestions, or questions to
Thomas G. Ferguson:
fergus52@msu.edu
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