Skywatch December 2001

 NOTE: Times given in the scripts are all local Schenectady, New York time.

Saturday, December 1st to Sunday, December 2nd. Written by Susan French

The moon was full this Friday at 3:49 PM Eastern Standard Time. It was the second full moon this month, the first having occurred on November 1. It has become traditional in recent years to call the second full moon in a month a "Blue Moon" and the term has been enthusiastically picked up by the popular press.

Oddly enough, this is not part of some long tradition but stems instead from a mistake in the March 1946 issue of "Sky & Telescope" magazine. It says "Seven times in 19 years there were - and still are - 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, or so I interpret it, was called a Blue Moon."

However, the author's interpretation was incorrect. He cites a 1943 "Sky & Telescope" article and a 1937 issue of the "Maine Farmer's Almanac" as references, but neither claims that the second full moon of the month is called a Blue Moon. Instead, the Farmer's Almanac says there are twelve full moons in most years or three per season. Each full moon has a name appropriate to its season, such as the Harvest Moon, the Lenten Moon, or the Moon after Yule. When there are 13 full moons in a year, one of the seasons has an extra full moon for which there is no seasonal name. The Farmer's Almanac claims that this extra full moon in a season is known as a Blue Moon. The rules the Farmer's Almanac used to determine which of the four moons in a season was the extra one are pretty convoluted, but paging through old almanacs quickly shows that the full moons labeled "Blue" were not the second full moons in a month.

But where did the Farmer's Almanac get its Blue Moon definition? No one seems to know. Researchers have so far been unable to find any written reference giving a calendrical meaning to the term "Blue Moon" predating the 1937 Maine Farmer's Almanac.

You can see the Blue Moon on Friday night very close to the bright planet Saturn. In fact the moon will pass in front of Saturn, with the ringed plate disappearing at 7:47:46 pm EST and reappearing at 8:46:25 pm EST. These times are for Schenectady, but will only differ by seconds across the Capital Region.

On Saturday night, you will see that the moon has pulled quite a distance away from Saturn, and lies almost halfway between Saturn and the even brighter planet Jupiter. By Sunday night, the moon will be near Jupiter.

Monday, December 3rd. Written by Joseph Slomka.

The Sun sets tonight at 4:22 PM, with night falling at 6:03. Dawn breaks at 5:29 tomorrow morning, and ends with sunrise at 7:09 AM.

As the Sun sets, two bright planet attract our attention. Mars shines due South, while Saturn rises in the East. Mars is long past its prime observing season, but it still holds our attention due to its distinctive red color. As the sky darkens, Mars also points to the distant planet Uranus only five degrees to its west. Uranus is normally dim, about sixth magnitude, and requires help in finding it. However, tonight, telescope users can center Mars in their finders, and simply turn left. Uranus appears starlike, but a distinctive blue-green color.

Saturn rises in the East, and is best observed at twilight's end. Saturn has reached opposition, which means that it rises at sunset and sets at sunrise - remaining up all night. Saturn is also at its brightest in the past thirty years; its rings, tipped to about 26 degrees, are also at maximum. Even small telescopes reveal the rings in great detail.

Jupiter rises about 6:31 PM, with the Moon rising a half hour later. Like Saturn, it is best to view Jupiter about two hours after planet rise, to get above the atmosphere's turbulence. Jupiter is grand in any size telescope, but larger instruments yield greater detail. However, lowly binoculars show four moons dancing around the giant planet.

Brilliant Venus rises in the East just before sunrise. It is ending is pre-dawn presentation and will not be seen after a few days. Trees or buildings may hide this planet.

The constellation Canis Major rises tonight to Orion's lower left. The constellation houses the brightest star visible to our skies, Sirius, the "Dog Star". Although the word "Sirius" means "scorching," the ancients have connected the constellation and star with a dog. Sirius is a blue-white double star, larger and hotter than our Sun. It is the closest star visible to northern latitudes, and the fifth closest star to Earth.

Tuesday, December 4th. Written by Jonathan Cassidy.

That "W" is back in the sky. Of the most recognizable constellations The "W" of Cassiopeia ranks as one of the most easily recognized. At star parties with all ages of people there are three constellations that stand out as most easily found and recognized. These are: The Big Dipper; Cassiopeia and Orion.

Cassiopeia is THE constellation of Autumn. I do not understood why the Great Square of Pegasus or the line of the head, back and leg of Andromeda are not as recognizable.

In all cases people, no matter what the age or education, pick out Cassiopeia before Pegasus or Andromeda. The story of Queen Cassiopeia is not flattering to the ancient figure nor is the set of stars as large as other prominent constellations. It might be the near equal brightness and the "W" pattern that make it so easily picked out these nights.

Use Cassiopeia to point your way to other interesting sites in the night sky. See if you can find these naked eye objects: Perseus Double Cluster; M31 Andromeda Galaxy, the Milky Way Galaxy.; Polaris.

Wednesday, December 5th. Written by Ray Bogucki.

Capella, one of the brightest stars after Sirius, and whose name means "the Goat star", is now low in the east at nightfall in the constellation Auriga (or-EYE-gah), the Charioteer. Capella is yellow, much like our Sun, and forms the northeast corner of the well-known pentagonal asterism of stars that helps us to locate Auriga. The constellation, Auriga, is well-known to amateur astronomers as the home of several bright open star clusters, three of which are Messier objects. Auriga also contains a number of eclipsing binary stars. These are variable star systems in which two stars orbit each other in a plane that is edge on to our line of sight. Thus, as each star passes in front of and eclipses the other, the combined light of the system decreases during the eclipse in a regular, predictable manner. The nearby eclipsing binary, Algol, in Perseus, is a famous example, well known to the ancients.

A few degrees southwest of Capella, the Goat star, lies a small, obvious triangle of stars known as "the Kids". Epsilon, the star in the triangle nearest to Capella is a mysterious eclipsing binary very different from Algol. First, whereas Algol is 100 light-years away, Epsilon lies at a staggering distance, estimated at from 4000 to 8000 light-years. To be visible from Earth as a third magnitude star from that distance, Epsilon must be one of the most luminous stars ever discovered. Second, while Algol's orbital period is 2.9 days and the drop in magnitude lasts a few hours, Epsilon's period is 27 years and the drop in magnitude caused by the eclipse of the bright primary by the secondary object lasts for 2 years. In addition, the eclipsing object is invisible. If it is a star, it must be so cool and diffuse that it emits no visible light. Also, in order to require 2 years to pass in front of the primary star, the secondary object must be a billion or more miles in diameter, which would make it the largest star known. Another explanation for Epsilon's unusual behavior suggests that the eclipsing object is an ordinary star hidden inside a huge cloud of obscuring dust and gas, perhaps in the planet-forming stage. Still another group suggests that the secondary object is a black hole. To date, none of the explanations are fully satisfactory and the deep mystery of this innocent-looking star remains.

Thursday, December 6th. Written by Peter Jennes.

Sunset for tonight, Thursday, December 6th will be at 4:21. This Sunday and Monday, the Sun sets at 4:20 in the local area and it should comfort some people that sunset on those two days are the earliest sunsets of the year. After Monday, the Sun will slowly start to set later each night. For other areas of the country, the earliest sunset occurs on different dates. However, for all northern locations, the actual length of daylight continues to get shorter for fifteen more days.

The mechanism governing the date of earliest sunset is the latitude of the observer. The further north an observer is, the later will be the date of the earliest sunset. For instance, an observer in Fairbanks, Alaska at 65 degrees north latitude doesn't see the earliest sunset until around 2:30 PM on December 18th. However, an observer in Miami, Florida, located at 25 degrees north latitude, sees the earliest sunset around December 2nd at 5 PM.

Although the date of earliest sunset occurs on different dates for different locations, they all have one thing in common. That commonalty is the fact that all of them occur before the Winter Solstice, the shortest day of the year. Logically, it would seem that the earliest sunset of the year should occur on the shortest day of the year but this is not the case. The reason these two dates are separated is related to how the Earth orbits the Sun. First, because the Earth's axis is tilted with respect to the plane of our orbit, the date of the earliest sunset varies from location to location. Then there are the laws of orbital motion first described by Kepler. These laws state that because the Earth's orbit around the sun is an ellipse, our orbital speed will vary as the Earth proceeds in its orbit. When these variations in orbital speed are combined the Earth's tilted axis, the net result is a lag between the earliest sunset and the shortest day of the year.

Despite the declining nighttime hours, remember to mark your calendar for next Thursday, Friday, and Saturday. Those nights mark the peak of the Geminid meteor shower. With up to 95 meteors per hour visible from a dark site, the Geminid shower is one of the best shows of the year.

Friday, December 7th to Sunday, December 9th. Written by Susan French

This weekend there will be free public observing sessions hosted by the Albany Area Amateur Astronomers. A variety of telescopes will be set up for viewing the wonders of the December sky, including the Andromeda Galaxy, the Seven Sisters, the Great Nebula in Orion, and the planets Saturn and Jupiter.

On Friday, observing will be held at the George Landis Arboretum in Esperance and on Saturday at Sanders Preserve in West Glenville. Both events start at 8 PM, and guests of all ages are welcome. The telescopes are set up outside, so dress warmly. Observing is cancelled if the sky is mostly cloudy, and may be cancelled if heavy snowfall blocks the observing area. For further information call Sue or Alan French at 374-8460.

This weekend also marks the beginning of the Geminid meteor shower. The number of meteors will increase over the week reaching a peak of about 100 per hour on Thursday night. Geminids can be seen any time after about 8 PM with the best views probably around 1:30 AM. After Thursday, the rate will drop with few Geminids being visible after the 17th.

Early evening meteors will favor the eastern half of the sky, but late at night they are likely to be seen almost anywhere. Near maximum, there are many bright fireballs with vivid colors. Geminids travel across the sky more slowly than the Leonid meteors we saw last month.

Most meteor showers are caused by debris left behind by comets. Geminid meteor particles are denser than those from cometary meteor showers. The parent object of the Geminids was unknown until recently. However, the asteroid 3200 Phaethon, discovered by IRAS (the Infrared Astronomical Satellite) in 1983, is now known to be the source of the Geminid meteors. It is the only non-cometary object associated with the evolution of a major annual meteor stream.

Monday, December 10th. Written by Joseph Slomka.

The Sun sets tonight at 4:21, with night falling at 6:03 PM. Dawn breaks at 5:34 tomorrow morning, and ends with sunrise at 7:16.

As the Sun sets, Mars is the brightest object in the southern sky. Mars remains relatively bright, but is so small that amateur telescopes no longer yield useful images.

By twilight's end, Saturn rises in the constellation Taurus. The creamy white planet lies three and a half degrees above the red star Aldebaran.

Jupiter rises about two hours after Saturn, in the middle of Gemini. Jupiter is an interesting object for two reasons. First of all, Jupiter's atmosphere appears as a seething cauldron of various colors. This is evidence of titanic storms, many of which have lasted for decades; the Great Red Spot has been observed continually for about three hundred years. In fact it is possible to hear the storms. If you have access to a shortwave radio and directional antenna, you can hear the static these storms generate. A complex satellite system is Jupiter's other attraction. There are sixteen moons, of which four are visible to small telescopes and binoculars. If you observe Jupiter about 1 AM, you will see Ganymede and Io aligned together

Jupiter's moons could not be more different. For example, Io is a forbidding place where volcanoes spew sulphur and the surface is stained various colors. While Europa is a frozen wasteland; ice, many feet thick, covers most of the planet.

By 7:00 PM, the constellation Gemini, The Twins, rises in the east. Simply follow the distinctive "V" of Taurus and locate two stars that seem equally bright. The constellation indeed resembles stick drawings of men. Castor is the northern and slightly dimmer star; Pollux is his brother. Castor was an expert horseman, while Pollux was a boxer. Their names reflect these occupations. They were sons of the Greek god Zeus, and Helen of Troy's brothers. Greek sailors revered them as protectors. The phrase "by jimminy" is a variation of "by Gemini," an ancient oath.

Tuesday, December 11th. Written by Jonathan Cassidy.

Tonight the slim crescent moon is just one day from new and does not add any light to the night sky. The new moon is in conjunction with the sun and does not appear at night.

So tonight is a dark night. A good night to see things not normally visible when the moon is up. So what is up there to see? How about star clusters? Directly overhead tonight is the "W" of the constellation Cassiopeia. To the east is Alpha Persei. Half way between is a dim smudge of stars. This is the Perseus Double Cluster. It can be found naked eye on dark sky nights like tonight.

Further to the north east after 8 PM you will see the bright star Capella in the constellation Auriga. This constellation looks like a lop-sided pentagon.

Notice that the Milky Way Galaxy goes through Cassiopeia, Perseus and Auriga. Star clusters found in these constellations reside in our home galaxy.

With binoculars, on a dark night, you will find several star clusters in the area of Auriga. Just cruise around the area with any power or size binoculars and you will be rewarded.

Wednesday, December 12th. Written by Ray Bogucki.

This Friday, Dec. 14, will see a special New Moon when the center of the Moon passes directly in front of the center of the Sun, producing a solar eclipse. Because the Earth is near perihelion, its closest approach to the Sun, the solar disk is larger than usual, and because the Moon is receding from the Earth at this point, its disk is diminishing. The result is that, at the moment of eclipse, the Moon's disk will be almost 2 arc-minutes smaller in diameter than the Sun's, and thus unable to cover it completely. This type of eclipse is called annular, and at mid-eclipse a razor-thin ring of sunlight will remain around the black disk of the Moon. While this apparition may not be as dramatic as a total solar eclipse, the sight of the Sun with 97% of its center punched out by what appears as a large, black hole is startling in its own right. The Moon's shadow will trace a path across the open Pacific Ocean with the only landfall occurring just before the end of the eclipse in Costa Rica and Nicaragua in Central America. At Albany, viewers will see the first intrusion of the Moon's disk into the limb of the Sun at 4:13 Friday afternoon, unfortunately just a few minutes before sunset.

Tomorrow night the Earth will pass through the orbiting debris that generates the Geminid meteor shower. It is unusual that this stream of debris has no known comet as a parent, but rather, it follows, almost exactly, the orbit of the asteroid, Phaeton. This 4 -mile wide, silicate rock orbits the Sun with a period of 1.43 years, its highly elliptical, cigar-shaped orbit bringing it within 13 million miles of the Sun and then far out beyond the orbit of Mars. Phaeton has no known history of cometary activity and it is not clear by what mechanism it could have generated a stream of orbital debris.

The Geminids are relatively slow-moving, about half the speed of the recent Leonids, and often feature bright fireballs. Because tomorrow night's forecast is for clouds and rain, it would be worthwhile to spend some time tonight watching for early arrivals of this unusual meteor shower.

Thursday, December 13th. Written by Peter Jennes.

Tonight and tomorrow night marks the peak of the Geminid meteor shower. Since the Moon is less than one day from new, it will not interfere with meteor observations. Unlike the recent Leonids, the Geminids are more predictable but also more mysterious. The Geminids were unknown until 1862 when observers began to notice a minor meteor shower with a radiant in the constellation Gemini. Since then, the Geminids have intensified to the point of becoming one of the best annual meteor showers, comparing with the summer's Perseid meteor shower.

The biggest difference between the Geminid and Perseid meteors comes from parent body of the two showers. The Perseids are born from Comet Swift-Tuttle while the Geminids are remnants of a mysterious object called 3200 Phaethon. It took 120 years of searching and a modern astronomical satellite to find this object. In 1982, NASA's Infrared Astronomical Satellite discovered a curious object moving in the same orbit as the Geminid meteoroid stream. The orbital match was so good that it had to be the source of the debris, but to the surprise of many, it wasn't a comet. Instead, Phaethon looks like an asteroid and has an asteroid's spectrum. However, Phaethon has the orbit of a comet.

Several theories have been proposed as to how an asteroid could create a meteor shower. At this time, the most widely accepted theory is that 3200 Phaethon has accumulated a crust making it appear like an asteroid. However, underneath this crust lies a comets burned out nucleus. Astronomers propose that when Phaethon passes the sun, pieces of the nucleus break off to form the Geminid meteoroids. Studies of Geminid fireballs support this theory. By observing these fireballs, scientists have estimated that Geminid meteoroids are less dense than a typical asteroid but denser than a comet.

The Geminid Meteor Shower radiant places meteors in the sky all night. Early in the evening, the Geminid shower tends to produce earth-grazing meteors that make long trails arcing up from the eastern horizon. Later in the evening, the trails get shorter but from a dark site, the hourly count jumps up to an average rate of 100 meteors per hour. From urban areas however, this number drops off to about 4 meteors per hour.

Friday, December 14th to Sunday, December 16th. Written by Greg Nowell

As you look into the eastern sky at about 9 p.m. tonight you will see two constellations, Taurus and Auriga. Taurus is a compact V-shaped constellation that points south. Just above it is a small cluster of stars known as the seven sisters, or the Pleiades. Taurus represents a mythological bull. A fairly bright reddish star, called Aldebaran, was thought to be the eye of the bull. Taurus' horns actually extend further north than the highly defined V-shape that follows the Pleiades through the winter sky.

The tip of one of Taurus' horns is of particular interest. This star is called Al-Nath. It is on the exact boundary between the constellations of Taurus and Auriga, and is in fact counted as the second brightest star in Auriga as well as the second brightest star in Taurus. Al-Nath lies below Capella, which with the exception of the planet Jupiter is one of the brightest objects to be seen in the sky at this time. Al-Nath, sometimes also transcribed from Arabic as El-Nath (with an "E"), is itself the 25th brightest star visible to the unaided eye. Since the human eye can pick out thousands of stars on a clear night, ranking 25th in brightness is no small achievement. But Al-Nath has another claim to fame. It is the closest of the naked eye stars to a part of the sky astronomers call the "anti-center."

Standing under the starry sky, it is hard to imagine that the stars we see have any relation to the dazzling photographs of galaxies and deep space that we see occasionally in magazines. But this little planet of ours is in a galaxy, and as it spins around we see different parts of that galaxy. When you look at Al-Nath, you are looking almost exactly in the direction of the edge of the galaxy that is closest to Earth. If you could draw a line from Al-Nath through your eyes, out the back of your head, through the Earth itself, and out deep into space again, that line would take you straight to the heart of our own galaxy, the galactic center. The anti-center is the extreme edge of our galaxy, and lies at the very end of a straight line that starts in the galactic center, passes through Earth, and ends at the galactic rim.

The famous eighteenth French astronomer Charles Messier did not know that Al-Nath was near the galactic center, because in his day galaxies were not understood as vast collections of stars. That knowledge came over a century after his death. But it is a curious coincidence that Messier began his famous list of deep sky objects with the gaseous remnants of an exploded star that we call the Crab Nebula. The Crab Nebula cannot be seen with the naked eye, but it is easily viewed in small telescopes. The Crab Nebula is designated M1, number one on Messier's list. M1 lies even closer to the galactic anti-center than Al-Nath. It seems remarkable that the most famous of earthly lists of sky objects should begin with the very one that lies nearly on top of the galactic anti-center.

Monday, December 17th. Written by Joseph Slomka.

The Sun sets tonight at 4:22, with night falling at 6:05. Dawn breaks at 5:51 AM, with sunrise taking place at 7:22.

As you hear this Skywatch Line, it is most likely snowing hard. For centuries, people thought that weather only existed on Earth. Now we know that there is all kinds of weather in most of the Solar System.

The Sun is a raging ball of hydrogen gas, which is fusing into helium and other elements. However, the Sun's output is not steady. The Sun goes through an eleven year period in which the number of sunspots vary. The exact mechanism is still not thoroughly understood, but as the number of spots increase, so do the number and degree of solar storms. These storms spew vast quantities of particles in all directions. If Earth gets in the way of such a storm, its atmosphere reacts to these particles, creating beautiful auroras, or Northern Lights. If the storm is really energetic, radio communications may be disrupted, satellites damaged, and even power grids disrupted. One giant eruption blacked out Canada's Quebec providence in 1989.

Mercury and the Moon have no weather, because they have no atmosphere. Pluto's weather is unknown, since no spacecraft has visited the last planet of the Solar System. Most likely, Pluto's atmosphere is so cold that no significant weather would be found.

Venus is perpetually cloudy, an example of a greenhouse effect gone wild; in addition, its clouds rain sulfuric acid. Mars is a planet that is well known for having weather. Clouds and dust storms are visible in backyard telescopes, as are polar ice caps. Jupiter' s storms are easily seen in backyard instruments. One storm, the Great Red Spot, had been documented for three hundred years, and lesser storms are frequently seen on the planets cloud belts. Saturn also displays rare variations in its cloud cover, revealing possible weather - features also available to larger backyard telescopes. Spacecraft have found Uranus and Neptune with similar variations in their cloud systems, again indications of atmospheric variations.

Tuesday, December 18th. Written by Jonathan Cassidy.

Earth's Sun is not the only star to show an eclipse. The star Algol, beta Persei, in the constellation Perseus is an eclipsing binary set of stars. That is two stars orbiting the same center of gravity locked together in space.

The plane of orbit of these two stars is in line with our planet. Thus we can see the two stars eclipse each other. We can not see that there are two stars there but we can see that the combined light from the stars varies over a short period. The variation in light is enough that naked eye observers can see it happen in just a few days.

Algol has a maximum magnitude of 2.1 and a minimum of 3.3, but nearly as dramatic as the long period variables. The cycle, from brightest to dimmest, is only 2.9 days. This makes the cycle easier to see and plot than other types of variable stars.

This means that the two stars are going around each other in less than three days. That is quite fast. In comparison we take 365 & 1/4 days for Earth to go around our Sun. Algol's light curve shows this quick speed the dip in magnitude is short relative to the length of the cycle. On some nights it is possible to watch the entire dip and return brightening in one session.

Wednesday, December 19th. Written by Ray Bogucki.

The Sun is rapidly approaching two points in its orbit that mark extremes in its orbital behavior. On Friday, Dec. 21, the Sun's northern axis will reach its maximum tilt away from the Sun, producing the winter solstice. This is the day with the minimum number of sunlit hours, only 9 hours and 18 minutes at this latitude. It is also the day when the Sun rises and sets at its most southerly points, and stands at its lowest elevation above the horizon when it crosses the southern meridian at noon. One might reasonably assume that this day would mark the latest sunrise and earliest sunset, but, in fact, the earliest sunset occurred 10 days ago. Sunrise, however, will continue to occur later each day until about January 2, when the daylight hours begin lengthening at both ends of the day. The asymmetry in times of sunrise and sunset is caused by the tilt of the Earth's axis and the variations in orbital velocity at different times of the year. It might seem logical to describe the day when the Sun is at its lowest as the middle of winter, but the seasonal delay in weather gives us the coldest two months in January and February. Thus, the solstice is usually designated as the beginning of winter.

January 2 also marks the point in the Earth's elliptical orbit when it reaches perihelion, its closest approach to the Sun for the year. On this day we will be 3 million miles closer to the Sun than when we are at our farthest point on the sixth of July. Perihelion also marks that point in our orbit when the Earth achieves its highest orbital velocity, almost as though the Earth was trying to help out by speeding the residents of the northern hemisphere a little faster through their coldest months, and the people in the southern hemisphere a little faster through their hottest months.

Thursday, December 20th. Written by Peter Jennes.

Friday, December 21st to Sunday, December 23rd. Written by Susan French

This Friday is the December Solstice and marks the beginning of winter in the Northern Hemisphere.

The Earth's North Pole points toward a spot in the constellation Ursa Minor, the Little Bear. This spot is called the North Celestial Pole, and it lies very close to the star we call Polaris or the North Star. In the same way, the South Celestial Pole indicates the spot toward which our South Pole points, but it is not marked by any bright star. On the Earth we draw an imaginary line halfway between the North and South Poles called the Equator, and in the sky we draw a line halfway between the North and South Celestial Poles called the Celestial Equator.

The Sun blots different constellations in the sky as the Earth we live on travels around it. The Sun's apparent path through these constellations is known as the Ecliptic, and it runs through the familiar constellations of the Zodiac. Some of these constellations lie above the sky's equator, and some lie below it. Right now, the Sun is in the constellation Sagittarius, the Archer. Sagittarius is farther below the Celestial Equator than any of the other zodiacal (zoh DYE ah cahl) constellations, so we see the Sun taking its lowest path across the sky for the year.

The moon is at First Quarter on Saturday at 3:56 PM EST. The term First Quarter Moon may seem confusing since it is obvious that more than one quarter of the moon's face is lit. Instead, First Quarter refers to the fact that the moon is one-fourth of the way around the Earth as seen from the sun. When the moon is at First Quarter phase, it appears about half lit.

The Ursid meteor shower peaks this weekend. These meteors favor the northern half of the sky, but the best place to focus your attention may be straight up where the sky is clearest. The Ursid shower produces many faint meteors and some fireballs. The rate usually peaks at about 10 or meteors per hour, but there are occasional outbursts of up to 50 per hour. Best viewing is after moonset at about midnight. The debris that causes Ursid meteors comes from Comet Tuttle.

Monday, December 24th. Written by Joseph Slomka.

Tuesday, December 25th. Written by Jonathan Cassidy.

The Sun is up latter now. Even though the Sun is still rising later, and will continue to do so till some time in January, it is now setting slightly later each day, thus the days are lengthening.

In relation to its north south travel, due to Earth's tilt on it's axis, the Sun stands nearly still twice each year. This is the time that the tilt of the Earth related to the Sun is at the maximum or minimum, that is winter of summer solstice.

During the second week in December, this year the Sun stood at nearly the same place each day at noon. Now it is moving higher in the sky each day. You can check this by noting the position of a tall structure's shadow at the same time each day, usually noon.

If you mark the position at the same time of the day and same day of the month you will construct a figure on the ground. If done correctly the figure will look like the numeral "8". The figure is called an Analema. This week is a good time to start one and is a good activity during the dark cold months of winter.

Wednesday, December 26th. Written by Ray Bogucki.

Continuing in a series of occultations, the Moon will pass in front of the planet Saturn early Friday morning. A few minutes after 4 a.m. the dark northern limb of the Moon will begin to cover the planet. Saturn will reappear from behind the sunlit part of the Moon's limb about a half hour later. The next occultation in this series will occur on February 20 at the more convenient time of 7 p.m.

Even when it is not being occulted, Saturn presents an intriguing target for observation. Earth just passed between the Sun and Saturn earlier this month, so it is still near its closest approach for this cycle. Although Saturn is a little smaller than Jupiter and almost twice as far away, it nevertheless presents a sizable 20 arc-second disk. Its extensive ring system extends its apparent diameter to about 46 arc-seconds, the size of Jupiter. The rings are tilted about 26 degrees to our line of sight, just about the maximum possible. The extra sunlight reflected by the rings greatly add to the brightness of Saturn which currently shines brighter than a zero magnitude star. The spectacular ring system is 170,000 miles in diameter but less than one mile in thickness. It is made of chunks of rock and ice ranging in size from that of a sand grain to large, house-sized boulders. When the rings are edge-on to our line of sight, they disappear in small, or medium sized telescopes and appear as a razor-thin straight line in large telescopes. In its current configuration, even a small telescope will show the dark, Cassini division between the outer A and B rings and Saturn's largest moon, Titan. Saturn is located a few degrees north of Aldebaran, the red eye of Taurus, the Bull in the eastern sky at nightfall. It rises before sunset and is well-placed for observation throughout the night.

Thursday, December 27th. Written by Peter Jennes.

At 4 AM tomorrow morning, Saturn disappears behind the Moon's dark limb. This event occurs 10 degrees above the horizon so if you are hoping to see this occultation, you will need a clear western view. As the Moon covers Saturn, it will be two days away from full. December's Full Long Nights Moon occurs early Sunday and at that time, it is more or less opposite the Sun. Usually, the Moon is slightly out of line from the Sun, while at other times, the Moon is directly opposite the Sun and a total lunar eclipse occurs. This month the Moon is almost on a direct line with the Sun and passes through the outer fringes of the Earth's shadow. This type of eclipse is called a penumbral eclipse and unless you have specialized equipment, the effects of these eclipses are barely visible.

One simple observation that is easy to overlook during the full Moon is that the full Moon, because it is roughly opposite the Sun, actually rides higher in the sky during the winter when the Sun is low to the horizon. In contrast, during the summer the Sun rides high in the sky while the full Moon hugs the horizon. In fact, if you measure the angle between the horizon and the almost full Moon around midnight on Saturday, you would find that it is about 70 degrees above the horizon. In contrast, at noon on Sunday, the Sun will be a mere 24 degrees above the horizon. Six months from now, during June's Full Strawberry Moon, the angle between the Moon and the horizon decreases to 20 degrees above the horizon, while the Sun will be high overhead at 70 degrees above the horizon.

To further illustrate how the Sun and Moon change places in the sky, on Sunday the moon will be drifting through the stars of Gemini and the Sun will be in Capricorn. During June, you will find that the Moon and Sun have changed places. Instead of the Sun, you will find the full Moon sitting in Capricorn while the Sun will be in Gemini. Simple observations like this seasonal place changing between the Sun and Moon led to some of humankind's greatest astronomical discoveries.

Friday, December 38th to Sunday, December 30th. Written by Susan French

Monday, December 31st. Written by Joseph Slomka.

The Sun sets tonight at 4:31, with night falling at 6:13 PM. Dawn breaks at 5:56 AM, with sunrise taking place at 7:26.

As the Sun sets, two bright planets occupy our attention, while two others require skill and luck. Saturn blazes moderately high in the eastern sky in the constellation Taurus. Mars is still the brightest object in western skies. Uranus and Neptune lie to Mar's right, but require skill and luck to find them in the darkening sky.

By nightfall, Jupiter occupies the constellation Gemini. One of Jupiter's most famous features - the Great Red Spot is now in the news. It has apparently shrunk over the past century. No one knows why, but observers hope to clear up the mystery.

Since the nearly full Moon dominates the sky, and blots out most galaxies and star clusters, let us concentrate on Earth's satellite. Our Moon is very unusual. It is about one sixth the Earth's diameter, one sixth the gravity, and one eightieth the mass. These facts amount to a double planet system; only Pluto's satellite, Charon, is larger in relation to the main planet. Its low gravity means that it has no atmosphere. Despite the fact that the Moon was visited several times by astronauts and is only two light seconds away, we know remarkably little about its history and composition. The only certainty is that the Moon underwent a severe history of bombardment, leaving behind craters that binoculars can see. There are three competing theories. One is that the Moon formed the same time as the Earth, with the two bodies orbiting about a common axis. A second hypothesis is that the Moon is a body that accidentally wandered into Earth's gravity field and was captured. The most recent speculation is that Earth, very early in its history, was hit by a very large body, and the Moon formed from the debris of that collision. If this third option is correct, it explains many oddities about the Earth-Moon relationship.

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Dudley Observatory
107 Nott Terrace, Suite 201
Schenectady, NY 12308
(518) 382-7583
info@dudleyobservatory.org