Skywatch April 2001

April 2 - 8  |   April 9 - 15   |    April 16 - 22   |    April 23 - 29  |    April 30

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

Monday, April 2nd. Written by Joseph Slomka.

The Sun sets tonight at 7:22 Daylight Savings Time; twilight ends at now at 9 PM. Dawn breaks at 4:55 AM and ends with Sunrise at 6:33.

The Sun has been causing dramatic news recently. The largest sunspot in over ten years exploded and sent a cloud of particles in Earth's direction. According to news accounts, brilliant aurorae, or Northern Lights, have been seen as far south as Phoenix. Aurorae are caused when the Sun's particles slam into our magnetic atmosphere. Powerful electric currents are generated. Satellites, space probes, and orbiting astronauts are all in danger. In fact, power stations in Quebec were shorted out by these atmospheric currents, during the last sunspot cycle over a decade ago. Photographs documented giant transformers simply melted down. As the solar particles make their way through our atmosphere, they hit particles of oxygen and nitrogen. These encounters make these atoms become excited and glow green and red. These are the most frequent colors seen during an aurora. No two episodes are alike. Sometimes there are faint glows in the northern sky. Other times, bright curtains of green and red flutter in the general direction of the north. These displays occur relatively close to the Earth, between 100 and 1000 kilometers high

This weekend's displays come approximately a year after solar scientists proclaimed the maximum to this solar cycle, which lasts about 11 years. However, weather has conspired against the Capital District. Clouds have blocked these glows. If the weather breaks tonight, try to see the Northern Lights. No optical aid is needed. Just look north and hope that the Sun eruption continues and that weather is clear. If clouds remain or the eruption has petered out, don't be discouraged. Even if the sunspot cycle is in the downswing, patience will favor the persistent observer. The Internet has several sites that monitor the Sun, and newspapers frequently mention strong sunspots. Radio amateur magazines are also good sources of information, since aurorae also disrupt shortwave radio communications.

Tuesday, April 3rd. Written by Bob Mulford.

During the month of April, the wintertime stars can be seen in the west. Taking their place in the east are the constellations of springtime. Dominating these stars of spring is the ancient constellation Leo the Lion. Leo contains a distinctive star pattern called the Sickle. A star pattern which is part of a larger constellation is called an asterism, and the Sickle of Leo looks like a backwards question mark with the bright star Regulus at the bottom. Tonight, if the sky clears, it will be easy to find the Sickle of Leo; look for it just to the left of the waxing gibbous Moon.

The constellation Leo traces its origins to the early mideastern people, who named it after the king of the beasts. The graceful sickle shaped curve in the front of the star picture does suggest the mane of a Lion, but Leo's location in the sky also gives it regal status. During the time of the early mesopotamian cultures, the constellation was near the summer solstice. In other words, Leo marked the position in the sky where the Sun appears at the beginning of Summer. The early mideastern people associated the fierce summer heat with the constellation of Leo. They believed that the Sun gathered extra strength when among the Lion's stars. The egyptians also associated summer with the lion because these creatures tended to travel to the Nile valley in the summer to seek relief from the heat. Summer was also the time when the Nile river overflowed its banks and provided water to irrigate egyptian fields. The egyptians carved heads of lions on the gates of their irrigation canals, a practice which lead to the lion-head water fountains still seen today.

Wednesday, April 4th. Written by Susan French.

One of the most awe-inspiring astronomical sights is a display of the Aurora Borealis or Northern Lights. Some people feel that they favor the time of year near the equinoxes. In general, but not always, aurorae are strongest around local midnight (1 AM Daylight Savings Time). The only way to make sure that you see one of these magnificent displays is to gaze north whenever you're under a clear, dark sky.

Our sun has been extremely active recently with huge storms that send solar particles far into space. Some end up trapped in the Earth's magnetic

field, and when the field is overloaded, these charged particles can rain down onto the Earth's atmosphere in an oval around the Earth's magnetic poles. The electrically charged particles from the Sun make the air glow in much the same way that the gas inside a neon light glows. And like neon lights, aurorae come in many colors.

We live too far south to see some of the vividly colorful aurorae that are sometimes visible in Alaska or northern Canada, but bright colors are occasionally visible here too - mostly various shades of red. No picture can convey the beauty of the Northern Lights. They are a highly dynamic phenomenon.

A typical display starts as an amorphous glow low along the northern horizon. As the aurora grows it may develop shafts reaching high into the sky. The horizon glow may begin to fold in on itself creating a diaphanous curtain of light in the sky. During a really good display, the aurora can climb high overhead in a display known as a zenith aurora or corona. The corona can take on astonishing shapes, and once it develops you may even see Northern Lights extending into the southern sky.

The aurora is always changing. The curtains wave, the shafts grow and shrink, and subtle colors play across the sky. The motion may be slow or rapid. Sometimes the Northern Lights seems to flame like the rapidly rising tongues of a fire gone wild.

Auroral predictions can be found on the web at spaceweather.com Alerts can be e-mailed to you if you subscribe to this free service. For anyone with a shortwave radio, WWV (found at 5, 10, 15, and 20 MHz) gives reports at 18 minutes after each hour. If the K-index is 5 or higher, look for aurora. If WWV won't come in on any of those frequencies, look for aurora.

No words can prepare you for the sight of a bright aurora. You must be lucky enough to see it for yourself to appreciate its awe-inspiring beauty.

Thursday, April 5th. Written by Peter Jennes.

Tonight, the waxing gibbous Moon fills the sky with light. With the naked eye, all of the dark lunar seas are visible. These seas are actually vast lava plains like the Ocean of Storms and the Sea of Rains which occupy the Moon's northwest quadrant. At the otherwise unmarked boundary between these two seas, the crater Aristarchus appears as a brilliant splotch. Because this brilliant crater sits on a dark, flat plain, it is easily visible even to the naked eye. To find Aristarchus, simply look for the brightest feature near the upper left corner of the Moon.

Aside from being one of the most recognizable features on the Moon, Aristarchus and the region surrounding it hold some of the Moon's most interesting landmarks. Although Aristarchus is only 25 miles in diameter, its bright ejecta blanket makes it appear much larger. The brilliance of the ejecta indicates that the crater is relatively young because the ejected material has not had time to darken under the onslaught of the solar wind in the 400 or so million years since the crater formed.

A telescope shows that the region around Aristarchus is a jumble of broken terrain. To the southwest of Aristarchus lies the crater Herodotus. Herodotus is just slightly smaller than Aristarchus but its interior is flooded with lava. To the north of Aristarchus, the ground can take on the appearance of a tilted triangle of hills and small craters. Although this area does contain some low hills, the illusion of tilt is caused by the many valleys that crisscross the region. The largest of these valleys is named after the German astronomer, Johannes Schroter. Schroter's Valley resembles a meandering snake. It starts at a small crater to the north of Herodotus then widens creating a formation known as the Cobra Head. From there, the valley stretches almost 100 miles.

If you draw a line from Herodotus through Aristarchus, it points northeast in the general direction of an ancient flooded crater called Prinz. Just north of Prinz, you should be able to observe a few isolated low hills protruding from the lava plain. These are the Harbinger Mountains and their isolated appearance together with the flooded remains of Prinz, only hint at the great depth of lava filling the Ocean of Storms and the Sea of Rains.

Friday, April 6th to Sunday, April 8th. Written by David Lynch

A glance at the area of the sky a few degrees above the eastern horizon at about 9:00 p.m. will provide you with a look at the constellation Bootes. Bootes is known as the herdsman and is a very ancient constellation. The name of this constellation was mentioned in Homer's Odyssey, written in the 8th century B.C. The most prominent feature of Bootes is the star Arcturus, the 4th brightest star in the sky (about magnitude -0.06). The name Arcturus means "guardian of the bear", a reference to it's proximity to the constellation Ursa Major, the great bear.

Arcturus is one of the stars that is closest to the sun, being only about 37 light years away. It is much larger than the sun, 20 million miles in diameter (about 25 times the diameter of the sun), and is approximately 115 times brighter than the sun. Arcturus is moving towards us at roughly 3 miles per second. A few thousand years from now it will pass us and begin to recede in the distance. In another 500,000 years or so it will disappear into the distance.

Scientists have measured the amount of heat reaching the earth from Arcturus and estimate it to be about the same as that felt from a candle at a distance of 5 miles. Clearly it doesn't add much to the warmer weather we have been experiencing. Some older observers may recall that Arcturus is the star whose light opened the "Century of Progress" exhibition held in Chicago in 1933. Light from the star was focused through a telescope on a photoelectric plate, which generated a current that operated a switch that turned on the lights at the exhibition. This was done because it was thought that Arcturus was 40 light years away and that the light reaching earth in 1933 had started its journey in 1893, the date of a similar exhibition in Chicago. The distance was subsequently revised to 37 light years. To find it locate the handle of the Big Dipper and "follow its arc to Arcturus". It's so bright you won't have any problem locating it. Enjoy your observing!

Monday, April 9th. Written by Joseph Slomka.

The Sun sets tonight at 7:30 and twilight ends at 9:11 PM. Dawn breaks at 4:41 AM tomorrow, and ends with sunrise at 6:21.

As the Sun sets, two planets appear in the southwest sky. They are Jupiter and Saturn. Both are still good observation targets, since they set at least an hour after twilight's end. Saturn's rings are nicely tipped for our observations, while Jupiter is still a giant ball with several small moons orbiting about it. Jupiter can be spotted with binoculars, but Saturn requires a telescope to see its rings and satellites.

Mars rises at 12:43 AM in the constellation of Scorpius and remains up the rest of the night. The nearly Full Moon lies just to the right of Scorpius, in Libra. Mars is now a small spot, but it is growing larger every day. By the Summer, astronomers will be enjoying the closest and largest planet Mars since 1988. If sky conditions on both Earth and Mars permit, details of the Martian surface can be spotted with good telescopes. Monthly magazines are now featuring Mars, and providing guides on how to observe it.

If you follow the constellation Leo's tail to the southeast, you come across a hazy patch of stars, the Constellation Coma Berenices. Unlike most, this constellation celebrates a real person and a true love story. Berenices was a princess in ancient Cyrene, modern Libya, in the Third Century B.C. She married Ptolemy III, who ruled Egypt. After the wedding, Ptolemy had to lead armies to assist his nephew, another ruler. Like all wives, Berenice worried about her husband in battle. To insure his safe return, Berenice vowed to donate her beautiful hair to the goddess Aphrodite if Ptolemy returned safe and sound. Upon his return, Berenice fulfilled her vow. The royal couple later asked the court astrologer what happened to the hair. The priest pointed to the hazy patch of stars. Berenice is the great grandmother of another famous female - Cleopatra. Her name lives on even today. The Libyan town of Benghazi is named in her honor.

April 10th. Written by Bob Mulford.

On the next clear evening, look toward the west at around 9 PM. The brilliant starlike object you see is the planet Jupiter. Now turn toward the southwest. The brightest true star in our sky can be seen low in this part of the sky. This is Sirius, in the constellation Canis Major, the large dog. Sirius is bright enough that it is easy to recognize.

Sirius is not only one of the brightest stars in the sky, it is one of the nearest. Only four other star systems are nearer to the Sun than Sirius. Of these, only the Alpha Centuari system is bright enough to be seen without a telescope, and Alpha Centuari can only be seen from southern latitudes. So, Sirius is the nearest star you can see from New York. Sirius is about eight light years away. Although this is nearby for a star, it is still a tremendous distance. If we call a million miles a mega-mile, a light year is six million mega-miles. To get an idea of this scale, imagine a model with the Sun represented by a ping pong ball. The Earth would be a pin point 13 feet away. Sirius would be a tennis ball nearly 1400 miles away!

Because Sirius is so bright, it was important in the legends of many early civilizations. To the Egyptians, Sirius was known as the Nile star. This was because it rose just before dawn at the beginning of summer, when the Nile river flooded. Egyptian agriculture depended on the annual flood of the Nile, and so they attached special significance to the star Sirius which had just returned to the morning sky.

Wednesday, April 11th. Written by Ray Bogucki.

Just forty years ago tonight, a Soviet Cosmonaut became the first human to orbit the Earth in an artificial satellite, opening the era of space exploration. It took almost a year for the U.S. to send the first American astronaut into orbit. But, in an incredible burst of activity, after dozens of attempts, mostly launch failures, the U.S. succeeded in sending the spacecraft Apollo 11 to deposit two astronauts on the surface of the Moon on July 20, 1969. It is remarkable to remember that the computers that controlled the landing and the successful return to Earth were very primitive, with much less power than today's personal lap-top computers.

In the intervening years, the inner planets, Mercury and Venus, have been studied by several fly-bys and landings. The outer gas giants and their moons have been photographed and measured by several Pioneer, Voyager and Galileo probes which transmitted thousands of exquisite photographs. Still, the planet that grips the human imagination most strongly is our nearest outer neighbor, the red planet, Mars. During the favorable opposition of Mars in 1877, Italian astronomers claimed to have detected channels on the surface of Mars. In the U.S., the astronomer Percival Lowell was motivated to establish the Lowell Observatory in Flagstaff, Arizona so he could observe Mars during the next favorable opposition in 1894. He claimed to have observed extensive networks of canals, presumably built by ancient civilizations to bring water from the polar ice caps to Martian cities at lower latitudes. Also, at this time, H.G. Wells wrote his novel "War of the Worlds", in which Martians invade Earth. In 1938, Orson Welles threw much of the northeast into a panic with his realistic radio dramatization of Wells' book.

Thus, the notion of life on Mars became firmly rooted in the human imagination. Recently some astronomers studying a meteorite from Mars reinforced this notion by reporting micro-structures that look suspiciouslylike fossilized primitive life forms. Other astronomers dispute this interpretation. While recent satellite photographs of Mars show no sign of organized canals, you can look for yourself during the next 3 months. Mars now rises in the southeast about midnight, and as we draw closer, it will rapidly grow in size and brightness until opposition in June. A small telescope should begin to reveal surface markings at this time and observations will continue to improve for the next two months.

Thursday, April 12th. Written by Peter Jennes.

Forty years ago today, our destiny changed as humanity stepped into space. For 108 brief minutes, the Russian cosmonaut Yuri Gargarin slipped the bonds of gravity and saw our planet as it never was before. While Gargarin's journey was brief, tonight you can easily see a galactic wanderer whose journey spans the entire breadth of human history. Our wanderer's story begins 5,000 years ago when the Ice Age's fading chill turned the Sahara desert green. In this lush paradise, nomadic herders watched the night sky and made patterns in the stars. From the patterns, they made celestial stories and recorded them as carvings in the rocks. Many of these stories involved people herding animals across the sky.

Today, one of these celestial herdsmen still follows his charge across the night sky. That herdsman is the constellation Bootes which is best known by Arcturus, the brightest star in the northern sky. The name, Arcturus, means "guardian of the bear" and his charge is none other than Ursa Major. Aside from having the honor of guarding one of the most prominent constellations, Arcturus is special for other reasons.

First, Arcturus is both nearby and large which makes it so brilliant. The large size comes about because Arcturus has used up most of its nuclear fuel and evolved into a red giant. Red giants like Arcturus are special because they give scientists a peek into our Sun's future. Billions of years from now, as the Sun uses up its fuel, it will also become a red giant like Arcturus.

Arcturus is also special because its orbit is highly inclined to the plane of our galaxy. This orbit has now brought Arcturus within 36 light years of our Solar System and also makes Arcturus' prominence in our night sky temporary. In reality, our sun and the Guardian of the Bear are passing like ships in the night and in 500,000 years, Arcturus will fade into the galactic distance leaving the Bear to stand alone. To find this galactic wanderer, simply look for the Big Dipper. Then extend the Handle of the Dipper away from the Bowl of the Dipper. The first bright star you come to is Arcturus. By following the arc to Arcturus, you will complete a part of the Sky Bear legend for yourself.

Friday, April 13th to Sunday, April 15th. Written by David Lynch

If going out on Friday the 13th makes you nervous (this is one of two this year), stay home this weekend and do a little star gazing. Sunday is Easter, which is supposed to be the Sunday after the first full moon on or after the vernal equinox, which was March 20. However, time zones and other considerations come into play, so it doesn't always work out that way. This weekend Jupiter and Saturn are still in the night sky. Jupiter shines at about magnitude -2.1. It's low in the southwestern sky after dark. Saturn appears to the lower right of Jupiter. It shines at a less brilliant, but still very noticeable magnitude -0.2. Both are in the constellation Taurus.

Near Jupiter is the star Aldebaran. Both planets are lower in the sky every night, and Saturn will be lost in the sun next month. The Moon will be nearest Saturn on Friday, so that part of the sky will be well lit indeed. Venus doesn't rise until a little more than an hour before sunrise. Although it doesn't offer the kind of surface detail that Saturn and Jupiter offer through a telescope, it still makes an interesting target for backyard astronomers. Meanwhile, in Taurus where Jupiter and Saturn reside this weekend, two star clusters are easily spotted by the naked eye. Above and to the right of Jupiter is the Pleiades star cluster. This "stellar nursery" includes some very young stars and observing from a dark site with a telescope or binoculars can even reveal some wisps of the nebulous gases that are leftover from the star formation process. You'll need to be at a dark site to see that, however.

The Hyades star cluster, found in the horns of Taurus the Bull, is another open star cluster that makes a nice observing target. Don't forget Orion the Hunter, who will be disappearing from view shortly, as the constellations of srpring rise higher in the sky. The brightest of all the constellations, Orion includes the Orion Nebula, or M42, which is very easy to locate and is beautiful to look at. Look for the hazy spot in Orion's sword, hanging from the left side of his belt. Even through a small telescope you can appreciate this huge, gaseous structure, which is in reality a stellar nursery. Enjoy your observing!

Monday, April 16th. Written by Joseph Slomka.

The Sun sets tonight at 7:29 with the sky becoming totally dark at 9:22. Dawn breaks at 4:30 AM tomorrow , and ends with sunrise 6:11.

As the sky grows darker. the giant planets Jupiter and Saturn appear in the southwest. Jupiter, being brighter, appears first; Saturn becomes visible below Jupiter several minutes later. Both planets are nearing their spring apparition; now is the time for last looks before they are too low for useful observation.

Mars rises before Midnight between the constellations Sagittarius and Scorpius. Mars grows larger and brighter daily and is becoming a worthwhile object. But Mars also points to two deep sky objects, the Lagoon and Triffid Nebulas. Both objects are about one binocular field to Mars' left. These objects are best seen in telescopes, but even binoculars show them to be glowing clouds of gas, which are obscured by dark patches of cold dust. These are only a few examples of dark matter which blot out stars and nebulas. Later on this summer, when the Milky Way stretches overhead, a wide band of dark matter splits the starry band into halves.

As night falls, Leo occupies center stage. To the East of the Lion's Tail, a hazy patch of stars marks the constellation Coma Berenices. Coma Berenices is interesting to observe. The star cluster is no illusion. It is a true group of about 37 stars approximately 250 light years distant. It is an interesting mix of single and multiple stars, stars as much as fifty times brighter than our Sun, and stars as dim as a third. The group appears older than the Pleiades and younger the Hyades. Besides this group of nearby stars, Coma Berenices features many stars clusters and galaxies extensions of the Virgo cluster of galaxies. The most prominent of these are the pair of star clusters M 53 and NGC 5053. This pair is located one degree south of the primary star, Alpha. In binoculars they appear as a pair of hazy patches; in telescopes, they are wonderful balls of >starlight.

Tuesday, April 17th. Written by Bob Mulford.

Wednesday, April 18th. Written by Ray Bogucki.

Tomorrow morning, Venus and the waning crescent Moon will rise together about 5 a.m. as morning twilight begins to brighten the eastern sky. Venus' orbital motion is carrying it rapidly away from Earth but its brilliance is increasing, because even though its disk is shrinking in size, the percentage of the disk illuminated is increasing. Well up in the south at this hour, the planet Mars is also increasing in brightness each day as our orbital motion brings us closer. In the western evening sky, Jupiter and Saturn are presenting the last opportunities for telescopic viewing before they become obscured by the lengthening evening twilight next month. In the late evening, the constellations Leo, Virgo and Coma Berenices stand high in the southern sky.

When we look toward these star patterns, we are looking away from the spiral arms of our Milky Way galaxy toward the north galactic pole. In the absence of the great clouds of obscuring dust that lie along the disk of our own galaxy, hundreds of other galaxies become visible in the great Virgo and Coma clusters. Dozens of these galaxies are visible in a modest-sized telescope, and finding and identifying them remains one of the most rewarding challenges to the amateur astronomer.

Closer to home, and requiring no optical aids, observers can watch for Lyrid meteors this Saturday night. This is a modest meteor shower that may present 10 meteors per hour. The Lyrids occur each year on this date when the Earth passes through the debris left by comet Thatcher, which orbits far beyond the orbit of Pluto and swings in to visit the Sun only once each 415 years. Meteors are best viewed in a dark sky, and while the night will be Moon-less, there is always a chance that aurora borealis may be present to brighten the sky and present an alternative viewing opportunity.

Thursday, April 19th. Written by Peter Jennes.

The moon is now a slender crescent in the predawn sky. With the moon out of the way, tonight could be a good time to practice star hopping. Amateur astronomers use star hopping as a way to find dim stars by moving from bright, easily recognized stars to the dimmer target stars. The dim stars of Virgo are good targets for beginning star hoppers. At first magnitude, Spica is the brightest star in Virgo and will act as our starting point. Star hop to Spica by starting with the Big Dipper's bowl and follow the curved handle away from the dipper to the first bright star you see.

This is Arcturus, the brightest star in the Bootes and the third brightest star in the sky. By finding this star, you have followed a star hopper's mnemonic, "arc to Arcturus." From Arcturus, use another mnemonic to find Spica. This one is stated, speed south to Spica. That is, a line drawn south from Arcturus leads to Spica. By following the saying, arc to Arcturus, speed south to Spica, you have found the sky's sixteenth brightest star by using the sky's third brightest star.

Just remember; don't be fooled by Mars. Mars is currently near Spica but Mars is much brighter than the star. Having found Spica, you are now ready to begin tracing the dimmer parts of Virgo. The brightest sections of Virgo occupy a fifteen degree patch of sky stretching west from Spica. Use Spica as the lower left corner of an imperfect rectangle that is tipped upwards on its west end. Three, third magnitude stars make up the other corners of this rectangle. This starry rectangle is longer east to west than it is north to south.

Now, use the two most western stars of the rectangle as pointer stars. Draw a line north from these two stars. Extend this line about one and one half times the distance between the two stars. In that region of space, you will find another third magnitude star. This star is Epsilon Virgo, otherwise known as Vindamiatrix. Having found these stars, you have outlined most of a somewhat dim constellation. With a star atlas and a little more star hopping, you should be able to find the remainder of this famous springtime constellation.

Skywatch Line for Friday, April 20th to Sunday, April 22nd. Written by David Lynch

Ursa Major is perhaps the easiest to find and the most recognizable constellation in the sky in the northern hemisphere. That is because Ursa Major contains the Big Dipper. The Big Dipper is a pattern of stars within the larger constellation. A pattern such as the Big Dipper that is not itself a constellation is called an "asterism". The seven-starred figure of the dipper is instantly recognizable to people with only a passing acquaintance with the night sky. Ursa Major is a circumpolar constellation. It lies relatively close in the sky to Polaris, the "north star" or the "pole star". As the Earth's rotation appears to cause the stars to arc across the sky, Polaris appears to remain virtually stationary, as it occupies a spot in the sky almost directly above the Earth's northern geographic pole. Therefore, any object that is close to Polaris will be visible all night at northern latitudes.

One of the most interesting targets for observing near Ursa Major is one of the Messier objects, M51. M51 is one of the objects that were catalogued by the 18th century French astronomer Charles Messier. While he was looking for comets he found lots of other interesting things. M51 is a galaxy located just below the handle of the Big Dipper. It's a spiral galaxy much like our own Milky Way, known as the Whirlpool. The Whirpool can be observed through binoculars from a reasonably dark site, so you can see it even if you don't have a telescope. To find the Whirlpool through binoculars first locate the star known as Alkaid, which is the last star in the handle of the Big Dipper's handle. About 2 degrees west, or one third of the width of the field seen through 7 power binoculars, there is a 5th magnitude star called Canum Venaticorum (KANE-um ven-ati-KOR-um). Go another 2 degrees to the southwest and you'll find an 8th magnitude glow which is M51. Naturally a telescope, with its higher power, can give you a more detailed view, but binoculars are easier to use and still provide an interesting view. So whether you look for M51 through binoculars or a telescope, take advantage of the opportunity to look at another galactic island in the universe. Who knows, maybe somebody is looking back! Enjoy your observing!

Monday, April 23rd. Written by Joseph Slomka.

The Sun sets tonight at 7:47 and twilight lasts until 9:34 PM. The Moon turned "New" this morning, and is not seen tonight. Dawn breaks at 4:13 AM tomorrow, and ends with sunrise at 6 AM.

As the Sun sets, Jupiter and Saturn sparkle low in the West. Saturn sets at twilight's end, but Jupiter lingers until 11 PM. Both planets are too low for details, but it is still possible to see their moons and Saturn's rings.

Mars rises after midnight and gains brightness and size daily, in anticipation of its June opposition. Mars is now definitely brighter than its "rival", the star Antares in nearby Scorpius. Mars points to several deep sky objects, the Lagoon and Triffid Nebulas. Both clouds of glowing gas and dust are just to the left of Mars, between the planet and the constellation Sagittarius. All three objects can be seen in binoculars; telescopes enhance with detailed views. This whole area of sky is ideal for binocular sweeps of star, gas and dust clouds along the rim of our galaxy, the Milky Way.

If an observer looks north tonight, he sees a long chain of stars between the Big and Little Dippers. This chain ends with a small rectangle pointing at Hercules. This is the constellation Draco, the Dragon. Draco is important for several historical reasons. One of its stars, Thuban, was the pole star about 2830 BC. There is speculation that ancient Egyptians used Thuban as a reference point in building the great pyramids. There is no specific mention of Draco in any Greek legend, and the origin of this constellation seems lost. However, this large constellation makes a fitting guardian of the North Pole. Draco was originally pictured as a true dragon, with wings sprouting from its midsection. Draco's wings were clipped around 600 BC, and reshaped into a new constellation, Ursa Minor, the Little Dipper. Its brightest star, Gamma Draconis, is slowly approaching our Solar System. In a million and a half years, Gamma will be as bright as Sirius is today.

Tuesday, April 24th. Written by Bob Mulford.

This month you can see the bright constellation Leo high in the eveningsky. You can locate Leo as follows: find the Big Dipper. The stars at the end of the Dipper's bowl are called the pointer stars. A line drawn through the pointer stars to the north leads to the North Star.

Extending this line to the south, however, points to the constellation Leo. Leo can be recognized by its brightest star, Regulus, which marks the bottom of a graceful arc of stars shaped like a backwards question mark. This star pattern is called the Sickle and marks the head of Leo the Lion. To the left of the Sickle is a triangle of stars forming the rear of the Lion.

Just 20 arc minutes north of the star Regulus is the position of a dwarf eliptical galaxy called "Leo One". This galaxy is among the smallest and faintest of all galaxies known. A galaxy is an association of stars like our own Milky Way. Between the galaxies is the space is empty of stars. This is why Galaxies are sometimes called by the descriptive name "Island Universes". Our home galaxy, the Milky Way, is relatively large, and contains a lot of hydrogen gas and dust as well as stars. The Milky way is only one of a group of nearby galaxies called the "Local Group". Leo-One also belongs to this group. Leo-1 is so faint that it cannot be seen visually in any telescope. It was discovered by photographs taken in 1950 with the 48 inch Schmidt camera at Mt. Palomar in California. In photographs Leo-1 is about a half degree across. This is almost exactly the same size as the Full Moon. Leo-One is 750,000 light years away, about three times as far as the great Spiral Galaxy in Andromeda.

Wednesday, April 25th. Written by Ray Bogucki.

This evening, the two-day-old Moon sits as a thin crescent halfway between Jupiter and Saturn in the western sky. Because the Sun is setting about 10 minutes later each week, the two giant planets will seem to disappear very quickly into the Sun's glare in the next few weeks. The red planet, Mars, rises about midnight and stands at its highest in the southern sky as Venus, the morning star, rises in the east about an hour and a half before sunrise.

The southern evening sky is dominated by the bright constellation, Leo, the Lion. The familiar sickle and triangle shapes of Leo are surrounded by several less conspicuous constellations. One of these, Canes Venatici (KAY-neez veh-NAT-i-sigh), the Hunting Dogs, is nearly at the zenith, north of Leo, tucked beneath the curve in the handle of the Big Dipper. The only noticeable star in this constellation is Cor Caroli, a fine double star, easily split with a small telescope. Two other objects worth searching for with a telescope are M3 and M51.

M3 is a globular cluster located about halfway between Cor Caroli and the nearby bright star, Arcturus. Discovered by Messier in 1764, M3 lies about 48,000 light-years away, well outside the disk of our galaxy in the spherical "halo" surrounding the center of the galaxy. It contains hundreds of thousands of stars and is one of the brightest and most elegantly symmetrical clusters visible in the northern hemisphere.

M51, the "Whirlpool Galaxy", is a beautiful, face-on spiral galaxy lying about three and a half degrees southwest of the end star in the Handle of the Big Dipper. First observed as a faint smudge of light by Messier in 1773, it was studied in 1845 by the Irish astronomer, Lord Rosse, with his new 6-foot mirror, who recognized for the first time that it had a spiral structure. At first, these spiral objects were thought to be nearby clouds of gas and dust whose bright centers were new stars in the process of formation, while the spiral arms were coalescing into planets to form new solar systems within our galaxy. Only in the 1920s did astronomers begin to realize that these spirals were actually massive systems of billions of stars lying at vast istances whose spiral patterns provided a model for the structure of our own Milky Way galaxy.

Thursday, April 26th. Written by Peter Jennes.

Sunset for tonight, Thursday, April 26th will be at 7:51. The moon is now about half way between new and first quarter and is easily visible as a slender crescent in the southwest at sunset. Below the moon, Jupiter and Saturn form a straight line along the ecliptic. Over the next few days, Mercury will join this string of planets. By May 5th, Mercury will be 4 degrees to the right of Saturn and both may be visible in binoculars shortly after sunset on that day.

In binoculars or a telescope, the most prominent feature on tonight's moon will be Mare Crisium or the Sea of Crises. This lunar feature is one of the easiest lunar features to recognize because of its nearly circular shape and dark coloration. The north-south diameter of this lunar sea is almost 280 miles while the east-west diameter is almost 350 miles. This makes the Sea of Crises about equal in area to the state of Washington. One unique feature of the Sea of Crises is that, unlike the other major lunar maria, the Crisium basin is completely isolated from all other maria.

South of Mare Crisium, a portion of another lunar sea, the Sea of Fertility is visible. With a telescope, several major craters are visible around thewestern edge of the Fertility basin. Beginning in the north, this chain of craters includes Langrenus, Vendelinus, and Petavius. Langrenus is nearly 90 miles in diameter and it is located on the right edge and almost directly on the centerline of the Sea of Fertility. If conditions are just right, you may be able to spot this large crater's unusually small central peak. Vendelinus is 10 miles larger in diameter than Langrenus, yet it is more difficult to spot because it is flooded by lava flows and its northeast corner has been destroyed by a newer crater, Lame.

The final crater, Petavius is the largest of the three. This crater is slightly over 100 miles in diameter and nearly 14,000 feet deep. The floor of this ancient but well preserved crater displays not one central peak but an entire group of mountains with the tallest peaks rising over 8,000 feet above the crater's floor.

Friday, April 27th to Sunday, April 29th. Written by David Lynch

The constellation that is most visible to people around the world, at least those living in the northern hemisphere, is Ursa Major, the Great Bear, high overhead in the northern sky. Ursa Major contains the most recognizable pattern of stars in our northern sky, the "Big Dipper."

The Big Dipper is a pattern of stars that looks like a dipper or ladle, and is located within the constellation of Ursa Major. Star patterns like this are called "asterisms". Ursa Major is a circumpolar constellation. As the earth rotates the stars nearest the north celestial pole go around and around, but stay visible all year long. Ursa major is relatively close in the sky to Polaris, the "north star" or the "pole star". As the Earth's rotation appears to cause the stars to move across the sky, Polaris seems to remain virtually stationary, as it occupies a spot in the sky almost directly above the Earth's northern geographic pole. It does have a slight amount of movement, because it's not exactly at the pole, but you won't notice it. Two of the stars in the dipper, Dubhe and Merak, are called the "pointer stars", because they point toward Polaris. They are the two brightest stars in Ursa Major. A straight line drawn between the two stars leads the eye directly to the pole star. At this time of year the dipper appears to be upside down, so the imaginary line pointing towars the pole star goes downward.

Duhbe is an Arabic word derived from a phrase meaning "back of the great bear". Merak translates as "loin of the bear", also in Arabic. Five of the seven dipper stars are actually a star cluster. They are associated with one another in space and move together in the same direction, Dubhe is, however, not a proper member of the group. The cluster in the dipper is made up of five of the most visible stars plus a number of fainter stars visible only through a telescope (about 17 stars in all). At a distance of about 75 light years from Earth, the dipper is the closest star cluster to us. Enjoy your observing!

Monday, April 30th. Written by Joseph Slomka.

The Sun sets tonight at 7:55 PM, with night falling at 9:45. Dawn begins at 4 AM, and ends with sunrise at 5:50.

As the Sun sets, the Moon and several planets pop into view. The First Quarter Moon is found high in the southwestern constellation of Cancer. The Moon marks this otherwise faint constellation, but drowns it out. Return to the area of the sky in about two weeks to appreciate its beautiful star clusters.

Above the western horizon, brilliant Jupiter glows. Jupiter is now too low to have steady views of its cloud belts, but it is still possible to watch the four moons in their eternal dance. Saturn is the dimmer object to Jupiter's lower right. In binoculars, Saturn appears as an oval; it takes a telescope to see that the ring system is responsible for this illusion. Finally, Mercury is to Saturn's lower right. At magnitude, -1.4, it should be fairly bright right after sunset, but trees, hills, or other obstructions easily hide this elusive planet.

Mars rises about midnight and is best viewed before sunrise. By 4 AM, Mars is due south. Its brilliant red color easily identifies it. Mars is now quite large in your binoculars or telescope. There is an added treat tonight, Mars is found next to two Messier objects, the Lagoon and the Triffid Nebulas. In binoculars, both glowing gas clouds should occupy the same view as Mars. Low power telescope eyepieces should also show Mars close to these objects. Additional power displays their true beauty, as well as surface markings on Mars.

Venus is best seen just before sunrise. The planet is fairly high in the east and is easily the brightest object in the sky. On May 4, Venus reaches its greatest brilliancy. Binocular views should show that the planet is not a perfect sphere, but is now about a quarter illuminated. Telescopes will verify this impression and permit the observer to follow Venus' progress across the sky, as it daily changes phase and size.

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Dudley Observatory
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