ASTRONOMY - Jim Colyer
I have had 3 rounds with astronomy. Round 1 was as a teenager in the early 1960s. I learned the constellations and watched meteor showers. Round 2 was in my 30s. I got into cosmology, learned the features of the moon and wrote my first astronomy paper. Round 3 was in my 50s. I subscribed to Astronomy Magazine, wrote a second paper and went to an Australian Star Party to see the stars of the Southern Hemisphere. Hopefully, I have achieved permanence in the age of the Internet since astronomy is something I enjoy.
History
Each period in history sees the sky in a different way. The way a civilization perceives the sky is related to its travel capabilities. As man's knowledge of geography has increased, so has his understanding of the earth's place in the larger scheme.
Greek astronomer Ptolemy lived in the second century. He wrote a book called The Almagest. He had the earth at the center with the sun and planets going around it. This wrong view stood for 1400 years.
In 1453, Copernicus in Poland got it right. His book expounded a heliocentric doctrine. Modern science was born. Really, Copernicus revived a forgotten idea of the Greek Aristarchus. The Greeks had science. The Scientific Revolution grew out of the Renaissance which was a return to Greek ideas. The Middle Ages were dominated by the Church, and The Bible frowned on science. It put revelation above observation. Galileo clashed with the Church when he taught the earth went around the sun.
The road leading from superstition and false information was a long one. For centuries, man's concepts of reality were shaped by The Bible. Nowhere in The Bible does it state that the earth is flat, but the implications are there: Satan taking Jesus to the mountaintop to show him the world's kingdoms, for example, and references to the "four corners of the earth." Heaven was above. Hell was below. Even Shakespeare retarded the growth of science with legends of ghosts, witches and fairies. No wonder the people who first settled in America knew so little of the real nature of the cosmos.
Things were changing. Europe was expanding, and the printing press was spreading new ideas. By the time Columbus made his voyages, most people knew the earth was round. It became irrefutable when Magellan sailed around it, a gruelling three-year voyage during which Magellan was killed.
Tycho Brahe was an observer. He found a supernova in Cassiopeia in 1572. As a theorist, he was lacking. He knew the planets circled the sun but thought that both planets and sun circled the earth. He built an observatory close to Hamlet's castle in Denmark.
It took Johannes Kepler, Tycho's assistant, to make sense of his work. Kepler's laws of planetary motion showed planetary orbits to be ellipses. They showed the closer a planet is to the sun, the faster it moves.
William Herschel was the father of stellar astronomy. He built big telescopes and made the first model of the Milky Way. Erroneously, he placed our solar system at its center. His sister was an astronomer.
Isaac Newton and Albert Einstein were physicists but laid the groundwork on which modern astronomy is built. Newton gave us the concept of gravity, the tendency of two bodies to attract whether they are the earth and an apple or the earth and the moon. Einstein introduced the theory of relativity. Relativity said time is relative to speed, and the speed of light is the only absolute. While the most distant galaxies are receding at 95% of the speed of light, they will never equal it. Gravity, said Einstein, results from space being curved.
Newton, for all his brilliance, was an alchemist. Einstein did not believe the universe was expanding. Even geniuses can be wrong! There is some question about the speed of light being absolute. Why does it have to be? If we travelled faster than light, would we be in the dark when we reached our destination?
Astronomy is best studied as a series of levels proceeding outward. Space has depth. There are motions within motions. Perspective rules. We explore the solar system. We reach for the stars. The Milky Way is but one of countless galaxies. We question the origin and fate of the universe. We search for extraterrestrial life.
The Solar System
The solar system began as a cloud of dust and gas. The cloud began to spin and contract. It contracted into a disc with the sun at the center. Planets formed from the disk. Gravity caused rocky, terrestrial planets to form near the sun. Gas giants floated further out. Every star in the galaxy may have planets.
I wondered why celestrial bodies are round. They are molded by gravity and the effects of spinning.
The sun is a star. It is average in size. It is 93 million miles from us. Its surface is 11,000 degrees. Sunspots are dark because they are cooler. The sun is a hydrogen bomb, shining by nuclear fusion. Hydrogen turning into helium emits energy in the form of light and heat. Some of this energy is stored in fossil fuels: coal, oil and gas.
The sun is a middle-aged star and will burn another 5 billion years. It will become a red giant. The planets will be consumed. Earth's oceans will boil away. Its atmosphere will go. Its sky will become black.
There are two kinds of objects, those which shine by their own light like the sun and those which reflect light like planets and moons.
The planet Mercury is so close to the sun that many astronomers have never seen it. Mercury's surface is cratered like the moon's. Like the moon, Mercury has no atmosphere.
NASA has launched the Messenger spacecraft to Mercury. Scientists want to know why it is so dense.
Like Mercury, Venus is between Earth and the sun. For that reason, Venus never strays far from the sun in the morning or evening skies. It is seen in the western sky after sunset. Venus goes through phases which can be seen through a small telescope. Venus is brightest in its crescent phase because it is closer to Earth. It gets as bright as -4.5 magnitude.
Venus is about the size of Earth. We might expect similarities. In fact, the surface of Venus is 900 degrees because of the greenhouse effect. Its atmoshere consists of carbon dioxide. It is hell. Still, Venus accompanied by a crescent moon is one of the beautiful sights in nature.
Earth
From space, Earth is a blue planet spotted with cloud tops. Earth is 25,000 miles in circumference and 8,000 miles in diameter. It revolves around the sun every 365 days, the period defined as a year.
Earth's orbit varies over million of years. It stretches and shrinks. This accounts for the 7 ice ages.
Earth tilts on its axis by 23 1/2 degrees. The tilt causes seasons. The northern and southern hemispheres alternately lean into and away from the sun. When it is summer in the United States, it is winter in Australia.
Earth's moderate distance from the sun is a factor in the evolution of life. It is neither too hot nor too cold. Liquid water can exist. Where there is water, there is life. It rained millions of years to create the oceans. Mountains were created by stresses in the earth. Earth's atmosphere came from volcanos. The atmosphere provides pressure and protection from ultraviolet rays. The oxygen in the atmosphere is produced by the photosynthesis of plants. Earth's atmosphere reaches out 300 miles.
Life began in the sea (or so we have read). Four billion years ago, chemicals began showing characteristics of life. Viruses are on the boundary between the living and nonliving. One-celled organisms developed, microbes. Plants colonized the land. Invertebrates evolved. Vertebrates followed. Fish evolved into amphibians which evolved into reptiles. Dinosaurs lived in the Mesozoic Era between 65 million and 220 million years ago: Tyrannosaurus, Brontosaurus, Triceratops, Stegosaurus, Duckbills and Ankylosaurus. My paper, "The Other Sciences" was dinosaur based. A species is a group of animals whose members interbreed. There are over one million species of animals.
Continents formed one land mass. As continental drift occurred, reptiles evolved into mammals and birds. Some paleontologists believe birds are dinosaurs. There was a golden age of giant mammals in the Cenozoic Era, mammoths and mastadons. Man has existed in some form for 5 million years. He evolved from primates in southeast Africa and spread into Europe and Asia. From Asia, he populated the South Sea islands and walked across the land bridge at the Bering Strait during the last Ice Age into the Americas. That was 50,000 years ago. The races as we know them came into existence at the end of the Ice Age 20,000 years ago. Civilization was born in Egypt and Mesopotamia. Recorded history spans 5,000 years. The colonization of the Americas by Europeans from the Renaissance onward is the most important human migration in history. World population is currently 6 billion. 300 million are in the United States.
We understand natural history in terms of the Geological Time Scale. Paleontologists study the fossil record. Fossils are found in sedimentary rocks, those laid down by water. Radio carbon dating determines the age of rocks. To know the age of a rock is to know the age of the fossil in it.
Environment
I wrote "Save The Planet" because I am a songwriter. I am faced with defending the message of my song. I am not a fanatic. I recall Al Gore's book about the environment. It was so technical, it was unreadable. It was funny when George Bush 41 referred to Gore as "Ozone Man" because of his preoccupation with the ozone layer. I have heard the ozone layer repairs itself. Maybe. The big issue with Gore is global warming. This is the tendency for man-made carbon dioxide to trap heat in Earth's atmosphere. The fear is, the earth will be heated to a point that its polar caps melt, inundating coastal cities. Unchecked, Earth could become a hell like Venus although we would be dead long before. The problem I have is that geologists say we are between Ice Ages. If another Ice Age is inevitable, might not global warming serve as a device for heating the globe? Carbon dioxide in the atmosphere may trap the sun's energy and prevent glaciers from flowing north and south to drive the planet's population toward the equator. This sounds crazy. We are trying to figure out whether we will burn up or freeze to death, if we are going to drown or die of thirst because all the water is locked up in ice. If global warming is taking place (and apparently it is), I am not sure it is an entirely bad thing. It got pretty cold in Nashville last winter. If it is a bad thing, I am not sure that man in his ingenuity will not find a remedy. I stay mainstream. With the population of the earth at 6 billion and climbing, we have to manage natural resources responsibly. The rainforest of South America can not be destroyed without consequences. We should be planting trees in North America, one for each one we cut down. Houses have traditionally been built from lumber. Books have been made from paper. All that may change. New building materials can be developed. Libraries will become electronic. The large mammals of Africa need to be protected, otherwise they will be extinct in a few decades. This is up to the governments of African countries and their National Park systems. At the same time, it is a world problem. Man is one species despite his constant fragmenting into religious sects and nationalities. If man were to act as one species (and I am not promoting a one-race concept) and stop warring, he could put his house in order. The energy and money spent by Muslims, Jews and Christians fighting each other could go a long way toward developing alternative fuels. Fossil fuels will eventually be depleted. It will take time (and no one knows how much), but the amount of coal, oil and gas in the ground is finite. If man does not prepare for the time when they are gone, civilization will collapse. There is a lot of talk about alternative fuels and hybid cars. I am unsure how much research is being done and about the state of practical application. People talk about running cars on vegetable oil. Gasoline is up to $2.75 a gallon. How much is a gallon of vegetable oil?
The Moon
In November, 1981, I used maps to identify the moon's prominent features. The dark maria (seas) are lava plains. Lava flowed from the moon's interior when impacts were hard enough. 5 maria combine to form a foot with 3 toes: the Sea of Serenity, Sea of Tranquillity, Sea of Crises, Sea of Fertility and Sea of Nectar.
The moon is geologically dead. If a meteor hits, its crater is more or less permanent. There are some interesting craters. Copernicus, Kepler and Aristarchus form a Y shape. Tycho in the south stands out. The southern highlands are riddled. Ptolomaeus is a big one. Aristarchus is the brightest spot on the moon. Plato is the darkest. Near Plato, is a formation I call "The hips." Craters have central peaks. They are caused by the ground bouncing back. The most recent craters have rays extending from them. The rays are material which was thrown out. The moon has mountain ranges. The Apennine mountains rise 20,000 feet.
Until recently, it was thought the earth and moon formed at the same time. It now appears that the moon came into existence when a large asteroid crashed into the earth and ripped part of it away. This accounts for the moon having no metal core. Old theories are earth-based. New theories are space-based.
Over time, the earth has slowed the moon's spin until it keeps the same side to us. The moon experiences 2 weeks of daylight followed by 2 weeks of night. There is no such thing as a "dark side" of the moon because the side we do not see gets 2 weeks of light each month.
From the moon, the earth is stationary but goes through phases. The sky on the moon is black because there is no atmosphere. Our blue sky is the result of light being reflected by air.
Earthshine is seen during the moon's crescent phases when the moon is nearly in line with the sun and the earth, evening or morning. Earthshine is sunlight bouncing off the earth, hitting the moon and coming back to our eyes. It is earth lighting the lunar night. It can be noticed the horns of the moon always point away from the sun.
The phases of the moon are new moon, crescent, first quarter, gibbous, full moon, gibbous, last quarter and crescent. The new moon is "no moon" because the side relecting the sun is turned away from us. The moon appears to wax and wane in its monthly orbit.
Light travels between the earth and moon in 1.2 seconds. The line between day and night on the moon is called the terminator.
The moon is about 240,000 miles from Earth, at our doorstep. If we drove around the world 10 times, we could be on the moon.
The moon causes the tides in our oceans. It tugs at our atmosphere as well, but we are so deep in the atmosphere that we are unaware of it. The moon is imperceptively moving away.
In March, 1960, I saw a total lunar eclipse. The moon took on a dark, copper color but remained visible because of sunlight refracted onto it by the earth's atmosphere.
An eclipse of the moon occurs when the moon passes through the earth's shadow. A lunar eclipse occurs during a full moon. Usually, the moon passes above or below the earth's shadow.
I saw a solar eclipse in Nashville in 1979. During a solar eclipse, the moon passes between the earth and the sun. Solar eclipses are seen less than lunar eclipses because of the relative sizes of the shadows cast by the earth and moon. The earth casts a large shadow, making eclipses of the moon common. The moon casts a small shadow, so eclipses of the sun are fleeting.
A ring of sunlight circles the moon during an annular (ring) eclipse because the moon is at its greatest distance from the earth. It is a coincidence that the sun and moon appear to be the same size in the sky.
American astronauts went to the moon 6 times between 1969 and 1972. 12 men walked on its surface. Neil Armstrong was the first. He made a mistake when he delivered the prepared statement. He said, "One small step for man, one giant leap for mankind." He meant to say, "One small step for a man." Apollo 11 landed in the Sea of Tranquillity. Eugene Cernan was the last man on the moon.
The temperature of the moon's surface varies 500 degrees, from 225 degrees to -275 degrees. There is no sound on the moon because sound is the vibration of air. There is no color except for the blue earth in the sky.
The moon rocks showed the moon's minerals to vary somewhat from those found on Earth. There were no fossils in the moon rocks. Life began in the sea, and at no time has the moon had water.
The Russians took the first pictures of the far side of the moon. There are not as many lava plains on the far side.
A blue moon is the second full moon occurring in any month. Blue moons are not so rare. They occur on an average of every 2.72.
Wierdos claim man did not go to the moon, that it was staged. They offer as proof the American flag blowing in the wind in the picture supposedly taken on the moon. There is no wind on the moon. Fact is, NASA treated the flag to make it stiff so it would stick out and be seen. I do not know if people who think we never went to the moon are crazy or stupid or making a joke. I sat in a parking lot in Nashville and debated Bart Sibrel about this. Bart was convinced man never went to the moon. It came out in the national news that he approached Buzz Aldrin (the second man on the moon) in California and tried to force him to swear on a Bible that the moon landings were real. Aldrin punched him in the nose. Bart tried to sue. The Los Angeles County District Attorney's office refused to file a battery charge. Rest assured, man set foot on the moon and is on his way to Mars.
The Outer Planets
The outer planets exhibit retrograde motion. They appear to travel backwards against the stars as the faster earth overtakes and passes them. Mars is a dramatic example.
Percival Lowell studied Mars. From his observatory in Flagstaff, Arizona, he saw what he mistook as canals built by Martians.
Mars gets its red color from dust storms whipping around it. Its surface contains iron oxide (rust). Its polar caps are made of frozen carbon dioxide (dry ice). Mars has a huge volcano known as Olympus Mons and a canyon called Valles Marineris.
Mars' atmosphere is too thin for liquid water. There is evidence that water flowed in the past. If it did, life may have evolved. The way to know is to go there and bring back rocks to see if they contain fossils. A journey to Mars will take a year, 6 months to get there and 6 months to return.
The Viking spacecraft landed on Mars in 1976. It found chemicals said to mimic life. 3 essentials for life are water, nutrients and energy. Scientists study the Atacama Desert in Chile, the driest place on earth to learn about Mars.
The Mars Science Laboratory will be launched in 2009 and land in 2010. Its purpose will be to determine whether microbes evolved on Mars. There may have been a zone of life extending from Venus to the asteroids in the early solar system.
The two Martian moons are Phobos and Deimos. In Homer's Iliad, they were Fear and Panic. They attended the god of war.
The asteroid belt lies between Mars and Jupiter. Jupiter's influence kept this collection of rocks from coalescing into a planet. Ceres and Vesta are asteroids.
Difference in size means a difference in gravity. Large worlds like Earth and Venus hold atmospheres. Small worlds like the moon and Mercury do not. Mars, which is medium-sized, holds a thin atmosphere. Worlds with atmospheres do not have many craters because atmospheres vaporize meteors and erode craters. Earth has few craters. Venus and Mars have some. The moon and Mercury are heavily cratered.
Gas Giants
Voyager 1 flew by Jupiter and Saturn and was deflected. Voyager 2 went on to Uranus and Neptune. Voyager 2 spent 12 years (1977-89) on its Grand Tour. All the gas giants have rings.
Jupiter is a failed star. If it had been larger, nuclear reactions would have begun and it would shine by its own light. It is made of hydrogen and helium, the most common elements.
Jupiter has bands because it rotates so fast that its clouds get stretched into patterns. The Great Red Spot is a huge storm. The Galileo probe reached Jupiter in 1995.
Jupiter has 60 moons. Io, Europa, Ganymede and Callisto are the largest, named for Jupiter's lovers. They were first seen by Galileo who invented the telescope in 1610. Io is interesting. It has the only volcanos in in the solar system beyond Earth.
Saturn is a butterscotch ball of gas. It is light enough to float in water. Saturn's rings are its glory. There are 7 main rings. They are made of rock and ice. As Saturn orbits the sun every 29 years, we see the rings open at the top, edge-on, open at the bottom and edge-on again.
Saturn has 31 moons. Titan is larger than Mercury. It is the only moon in the solar system with an atmosphere. Its atmosphere is orange and dense.
Cassini discovered the major gap in Saturn's rings. Huygens discovered Titan.
The Cassini-Huygens spacecraft is the first to orbit Saturn. The probe descended into Titan's atmosphere sending data. The reason for studying Titan's atmosphere is that it is believed similar to that of the early earth. Scientists want to know how life developed. $3.3 billion was spent on Cassini. They should have given me a million and cut some corners. It is strange, the money spent and the hype surrounding these projects and how so little is achieved.
Uranus was knocked on its side. Modern astronomy is explained in terms of collisions. Consider that dinosaurs were killed by an asteroid. If the ancients thought the heavens benign, today's universe is a place of violence. Uranus is a featureless, green pool ball. It was discovered by William Herschel in 1781.
Voyager 2 photographed Neptune's Great Dark Spot surrounded by blue methane.
Small, rocky Pluto at the edge of the solar system breaks the rules. Its orbit is erratic, bringing it inside Neptune. Pluto may have been a moon dislodged from somewhere else or part of the Kuiper Belt. It has a companion, Charon. Clyde Tombaugh discovered Pluto in 1930. NASA launched the New Horizons spacecraft in January, 2006. It will take nearly 10 years to reach Pluto at a distance of 3 billion miles. Pictures will arrive in the summer of 2015. I will be almost 70 and plan on being here.
The Voyagers have left the solar system and are on their way to the stars. They contain records of earth sounds, language and music.
Comets and Meteors
The solar system and everything in it is 4.6 billion years old. This includes the sun, the planets and their moons, comets and meteors.
Comets are scraps left over from the formation of the solar system. In that early period, there was a lot of debris. Craterization took place on a massive scale. Comets circle the sun. They develop tails as the sun melts ammonia and methane. The tails extend for millions of miles and point away from the sun, forced out by the solar wind. Halley's comet goes out past Neptune, returning every 75 years. Halley was not the first to see the comet but the first to predict its return.
I saw comet Ikeya-Seki on Halloween morning, 1965. It was dim and fuzzy but worthwhile. Kohoutek and Halley's bombed. I saw Hyakutake in 1996 and Hale-Bopp in 1997.
It took 30 years to see my second comet, which I spotted the morning of March 24, 1996. Hyakutake was bright as the Big Dipper stars and extended its handle. It was fuzzy but with no discernible tail. Two mornings later, it had moved by the Little Dipper. The morning of March 27, it was under the North Star. Hyakutake upstaged Hale-Bopp which had gotten advanced publicity. Japanese are comet hunters.
Shoemaker-Levy 9's impact with Jupiter gave astronomers their first glimpse of a collision in space. Jupiter is like a vacuum cleaner, sucking in stuff and protecting Earth.
In the early 1960s, I began watching the Perseids. The Perseids is the best meteor shower and occurs annually in August. The night of August 11 and morning of August 12, 1964, I counted 351 meteors. Toward morning, they were dropping in the east like snowflakes. Many were bolides, leaving bright trails. The best one appeared after daybreak. Cousin Larry was yelling, and I looked up to see a meteor as large as a full moon. It was exploding and changing colors.
Meteor showers are associated with comets. As comets orbit the sun, they leave behind debris. Meteoroids get strung out along their paths. Most of the stuff that enters our atmosphere is no larger than sand. Meteors are vaporized by friction about a hundred miles up. In any shower, meteors emanate from a point in the sky called the radiant. Showers are named after the constellations behind their radiants. We see more meteors toward morning because we are driving into them. The Perseids are associated with comet Swift-Tuttle.
Meteors are called meteorites when they survive and fall to earth. Meteorites are composed of iron and nickel. Meteor Crater near Winslow, Arizona is evidence of a large meteorite which hit 50,000 years ago. It is privately owned.
200 impact craters have been found around the world. One is near Odessa, Texas. Wolf Creek Crater is in Australia. Thousands of meteorites have been found on ice in Antarctica. O. Richard Norton says meteorites are pieces of asteroids. The largest meteorite found in the United States came from Willamette, Oregon. I saw it in the American Museum of Natural History in New York City.
There is one instance of a person being hit by a meteorite. In 1954, a woman in Alabama was sleeping on her couch when a meteorite came crashing through the roof. It ricocheted and hit her in the side, inflicting a bruise.
Craters have been mapped from the Space Shuttles. Comets and asteroids create craters. The idea that dinosaurs were killed by a large asteroid became popular in 1980. Scientists point to Chicxulub (Cheek-shoe-lube) crater in Mexico's Yucatan peninsula as being the impact that killed not only the dinosaurs but 2/3 of all species. That is really pinning it down. The evolution of life may be driven by impacts.
Something hit Siberia in Russia in 1908. It is called the Tunguska Event. Trees were flattened but no crater was found. It was a comet or asteroid which vaporized before impact.
The earth's atmosphere acts like sandpaper, constantly smoothing things out. Water erodes craters. Otherwise, the earth would look like the moon. Plate tectonics also reshape the earth.
Stars
The stars are always there, even in the daytime when they are blotted out by the sun. That is something we may not understand as children. As the earth revolves in its yearly orbit, different parts of the stellar panorama are exposed in the night sky. Constellations are identified with seasons.
Constellations are two dimensional. They are illusions. They existed in the minds of the ancients who imagined them. Stars are three dimensional. They are at various distances. Some appear bright because they are close. Others appear dim because they are far away.
The most easily identifiable constellations are the Big Dipper (Ursa Major), Orion, Scorpius and the Southern Cross.
The pointers in the bowl of the Big Dipper point to Polaris, the North Star. Polaris is overhead at the north pole and retains its fixed position as the earth spins. It is a tiny bit off. This causes precession of the equinoxes and a shift away from Polaris as the North Star. Given enough time, 26,000 years, the earth wobbles like a top.
The Zodiac consists of Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius and Pisces. The sun, moon and planets remain against the background of the Zodiac because of the flatness of the solar system. It is all in the same plane. Its flatness is caused by spinning.
The most elaborate story in the sky is that of Perseus and Andromeda, told by a group of autumn constellations. There are Andromeda's parents, Cepheus and Cassiopeia, and the monster, Cetus. Pegasus is there, the winged horse ridden by Perseus. In Perseus' hand, is the head of evil Medusa as represented by Algol.
The constellations are a product of Greek and Roman mythology. But even the Greeks borrowed from the Babylonians. Despite their relative distances, stars forming the constellations are in the vicinity of the sun when we picture the entire Milky Way.
The Greeks saw the Milky Way in poetic fashion. Legend had it that Hercules was born of an affair between Zeus and a mortal. When Zeus tried to get his wife, Hera, to suckle the baby, she pushed it away and her milk flowed across the sky.
Visible stars range from 1st to 6th magnitude. The brightest stars are Sirius, Canopus, Alpha Centauri, Arcturus, Vega and Capella. The Arabs named them. Stars twinkle because of our atmosphere. We see 4000 at any one time. Stars are so far away that they appear only as points of light in our largest telescopes.
The stars are trillions of miles away. Their distances are measured in light-years. A light-year is the distance light travels in a year, 6 1/2 trillion miles. Light is the fastest thing in the universe (does it have to be?) at 186,000 miles per second. The closest star is Proxima Centauri, a companion of Alpha Centauri, 4 light-years or 25 trillion miles out.
Double stars are the rule. Algol is a double star. So is Mizar, the second star in the handle of the Big Dipper. Another double is Albireo at the end of Cygnus the Swan. The contrast between the blue star and its yellow companion is striking. Castor in Gemini is a system of 6 stars.
Stars are like people. They are born. They age. They die. Stars are born when gaseous nebulae shrink under their own gravity. Mass determines whether a celestial body will be a star. If the mass is great enough, the pressure and temperature at the core will be great enough for nuclear reactions to begin.
Stars form in clusters. The Pleiades are stars condensing from surrounding gas. The Trifid Nebula is a stellar nursery. The Orion Nebula is. Nebulae glow because they reflect starlight. The Horsehead Nebula is a dark nebula outlined by starlight behind it.
Stars come in colors. Blue-white stars are the youngest and hottest. They are in the spiral arms of the Milky Way. Red giants are the oldest and coolest. Yellow stars like our sun are in the mid-temperature range. The oldest stars are in globular clusters surrounding the hub of the Milky Way. Walter Baade studied star populations.
Stars die in two ways. Average stars like our sun become red giants. They die peacefully by exhausting their fuel. Antares and Betelgeuse are red giants.
When a star uses its hydrogen it starts burning helium to make carbon. Elements are created in the cores of stars. Our bodies are made from remnants of ancient stars.
A dying star becomes a planetary nebula when it gives off a shell of gas. The Ring Nebula in Lyra is a planetary nebula. "Planetary nebula" is a bad name as it has nothing to do with planets.
A dying star shrinks to become a white dwarf. A white dwarf is the core of a red giant. White dwarfs can be red or brown but are still known as white dwarfs.
Massive stars die by becoming a supernovae and blowing themselves up. A supernova was seen in the Large Magellanic Cloud in 1987. Supernovae become pulsars. A pulsar can become a black hole. A black hole is a collapsed star whose gravity is so great that light can not escape it. Black holes are at the centers of some galaxies. Cygnus X-1 is a black hole. A quasar is a galaxy falling into a black hole.
The Milky Way
The Milky Way is our own galaxy, and we are locked inside it. This is not apparent right away as we tend to think of it as a glimmering arch in the night sky. The ancients thought of spilt milk. But the Milky Way consists of 400 billion suns 100,000 light years across and 2,000 light-years thick. If we could stand outside the Milky Way we would see a disk with a bulge in its middle. It is shaped like a flying saucer. Our solar system revolves 2/3 of the way from the center toward the rim. It takes 200 million years for the solar system to revolve around the galaxy. This is a cosmic year. The last time the sun and planets were in this same position, dinosaurs roamed the earth. In the desert in 1979, there was an instant when I felt myself revolving around the galactic center.
Since we are inside the galaxy, trying to divine its shape is like a person inside a house trying to determine the shape of the house. The structure of the Milky Way and our sun's position in it was ascertained by Harlow Shapley in 1917. We can see it if we know what we are looking at. The Milky Way circles the sky. The bulging center of its disk lies in the direction of Sagittarius where the star clouds are thick. The thinnist part of the circle, visible in winter, is in the direction of the outer rim. When we look at right angles to the Milky Way we are looking out the top or bottom of the disk where the stars are sparse. As we might expect, more galaxies can be seen out the top or bottom.
Patches of dust like the Coalsack and Cygnus Rift obscure parts of the Milky Way. People once thought they were holes. Because of dust, radio telescopes are used to study the center of the galaxy. The Milky Way is 10 billion years old.
Cosmology
The universe is 15 billion years old. 15 billion years ago, all the stuff in the universe was concentrated in a singularity, a mathematical concept for the primeval atom, a speck of infinite density. It exploded. This is what astronomers call the Big Bang, the point at which time began. The term was coined by George Gamow.
Primordial energy and matter began flying in all directions. It cooled. Gas clouds condensed into galaxies. Galaxies are aggregates of stars, the building blocks of the universe. Estimates put the number of galaxies in the universe at 100 billion. Some are distinctive. The Whirlpool and Sombrero look like works of art. Some collide. Galaxies are categorized according to their structures: spiral, barred spiral, elliptical. The Milky Way is a spiral. The Magellanic Clouds of the Southern Hemisphere are irregular. They are satellites of the Milky Way.
The Milky Way belongs to a Local Group of 31 galaxies. The Andromeda Galaxy, M31, is part of the Local Group. It is a spiral similar to the Milky Way but larger. It is 2.3 million light-years from us and the only galaxy visible to the naked eye from the Northern Hemisphere. It is a faint, hazy patch. It is the fartherest visible object.
Numbers were assigned to fuzzy patches in the sky by Charles Messier, an 18th century comet hunter. He cataloged 103 objects so as not to mistake them for comets. Nebulae, globular clusters and galaxies were lumped together. The more thorough New General Catalog (NGC) dates from the 19th century.
Galaxies are found in clusters, and these in turn comprise superclusters. The Virgo supercluster and the Coma Berenices supercluster are enormous. Our Local Group is part of the Virgo supercluster. In spite of this, the universe is mostly empty.
Proof of the Big Bang came from the work of Edwin Powell Hubble. By applying the Doppler Effect to light, Hubble found that light from galaxies showed a redshift. This suggests galaxies are receding or travelling away from each other. This is what we mean by Expanding Universe. If you run it backwards, there is a point at which all galaxies converge. The primeval atom! Furthermore, the farther apart the galaxies get, the faster they travel. This is as Hubble's Law. The question becomes whether the expansion will continue forever or whether there is enough gravity in the universe to pull it back together. This would be the Big Crunch and suggests an oscillating universe, one that is alternately expanding and collapsing. Black holes may provide the gravity to cause a Big Crunch. The universe is not expanding in space. Space is being created as the universe expands. The balloon analogy is used, blowing up a balloon with dots on it to represent galaxies.
We ask what there was before the Big Bang. The answer is nothing. There was no space, no time and no events. It was the beginning in the truest sense. Penzias and Wilson provided further proof of the Big Bang when they detected its background radiation.
E.P. Hubble was the greatest astronomy of the 20th century. Shapley was great but believed external galaxies were inside our own.
Cosmology was the step I was trying to take since I was a teenager. Carl Sagan's Cosmos series in 1980 was a breakthrough. To paraphrase Sagan, "The Cosmos is everything that has been, everything that is and everything that will be." Sagan saw man as poised on the shore of the cosmic ocean, intelligent life as a means for the cosmos to know itself. The terms "cosmos" and "universe" are interchangible.
Telescopes
In "Swim With Dolphins," I wrote, "I wanna see the stars, Mauna Kea's calling me." September 13, 2003, I stood atop this extinct volcano, 13,750 feet above sea level. "This is beautiful!" I thought. The mountain was stark and brownish, barren of vegetation. There was a Mars-like surrealism. I watched the sun set above the clouds. I saw the stars. They blazed. The Milky Way, the plane of our galaxy, arched brilliantly overhead. I was in the middle of the Pacific Ocean on the Big Island of Hawaii. It gets no better than this. Hawaii is at 20 degrees northern latitude, so the north star appears lower in the sky and Scorpius higher than from Kentucky/Tennessee although nowhere near as high as from Australia where it gets straight up. I sensed the curvature of the earth. Mars was at its closest. I wondered why it was less red than when it is farther out. "Increased sunlight on its surface neutralizes its redness," I was told. The moon rose. I like astronomy and got to see a bit of everything. 13 telescopes spread across the summit of Mauna Kea. There are the Keck domes and the Japanese telescope called Subaru. Sabaru is Japanese for the Pleiades. The University of Hawaii and Caltech run Mauna Kea. It is the only large observatory I have seen. I was above 40% of our atmosphere's oxygen but felt no different. It misted on the drive up. Rainbows were everywhere. I felt invigorated. Beauty heals.
There are two kinds of telescopes. Galileo invented the refractor. Isaac Newton invented the reflector. The purpose of each is to collect light. The refractor does it with an object lens. The reflector does it with a mirror. The biggest telescopes are reflectors like those at Kitt Peak in Arizona and Mount Palomar in California.
The invention of photography revolutionized astronomy. Photographic plates record more detail than the human eye. The pictures we see in books are long-exposure photographs. The CCD (charge-coupled device) is a camera replacing photographic plates.
The Hubble Space Telescope was put into orbit by the Space Shuttle. Because it was above the atmosphere, its pictures are superior to those of earthbound telescopes. I was disappointed with the Space Telescope. It produced books full of chaotic pictures with no comprehensive breakthrough in knowledge or theory. The far side of the moon is the ideal spot for an observatory.
Planetariums are places where sky shows and lectures are given. Star patterns are projected inside a dome. I have visited planetariums in Louisville, Nashville, Salt Lake City and New York City.
Space Travel
The Soviet Union kicked off the Space Age with Sputnik in 1957. The following year, the United States established NASA (National Aeronautics & Space Agency) I remember standing in the yard waiting for Echo I to fly over.
Th original 7 Mercury astronauts were John Glenn, Gus Grissom, Alan Shepard, Wally Schirra, Deke Slayton, Gordon Cooper and Scott Carpenter.
John Glenn got a hero's welcome in after orbiting the earth 3 times. Gus Grissom died with Roger Chaffee and Ed White in a fire.
Saturn 5 rockets sent men to the moon. Apollo 11 was the first landing. Neil Armstrong's footprints will last millions of years. Buzz Aldrin was the second man on the moon. Apollo 13 was brought back when an oxygen tank exploded. That was 1970. I was on my way to Germany. The 12 Apollo astronauts who walked on the moon are:
Apollo 11 - Neil Armstrong, Buzz Aldrin
Apollo 12 - Charles Conrad, Alan Bean
Apollo 14 - Alan Shepard, Ed Mitchell
Apollo 15 - Dave Scott, James Irwin
Apollo 16 - John Young, Charles Duke
Apollo 17 - Harrison Schmitt, Eugene Cernan
The Apollo program has been followed by a golden age of planetary exploration. NASA worked with the Jet Propulsion Laboratory of the California Institute of Technology. JPL launched the Voyagers.
Competition between the United States and Soviet Union drove the Apollo program. The spirit of cooperation which is supposed to put men on Mars is proving less of a motivator. The Space Shuttles orbit 200 miles up and circle the globe in 90 minutes. Challenger and Columbia blew up. The most famous people to fly in the Shuttles are women, Sally Ride and the ill-fated Christa McAuliffe.
The International Space Station is up, and Michael and I got a feeling for it at the Kennedy Space Center at Cape Canaveral. Shuttle missions have flown to the ISS. 21 nations are involved.
The Shuttles will be retired in 2010. The Crew Exploration Vehicle (CEV) will carry crews and supplies to the ISS. NASA has plans to return to the moon by 2018 and to go to Mars by 2030. The CEV will take 4 men to the moon and 6 men to Mars.
Futurists let their imaginations run wild. They foresee mining the moon, terraforming Mars and colonizing the galaxy.
Congress is skeptical of SETI (Search for Extraterrestrial Intelligence) although interest remains. Estimates of the number of alien civilizations range from zero to a certainty that the universe is teeming with life.
Astronomers began finding extrasolar planets in 1995. The first planet spotted in another solar system orbits 51 Pegasi. 180 extrasolar planets have been found. A system with 3 planets was found around a star in Andromeda.
Extrasolar planets found thus far are gas giants like Jupiter, unlikely candidates for harboring life. A microlensing technique is used to search for Earth-like planets.
The idea that life began in the sea has come into question in the Space Age. It may be that Earth was seeded from another solar system within the Galaxy. The seeds of life may have travelled through interstellar space to take root in the favorable conditions of planet Earth. This is the theory of Panspermia.
Spores are the hardiest form of life. They may travel between planets via comets and meteors. Spores are less likely to travel through interstellar space, but we can not rule out the possibility. Our perception is evolving as we reach into space.
One thing is sure, the UFO sightings that began after World War II, the close encounters and abduction stories are false. Such phenomena are explainable as aircraft or balloons, Jupiter or Venus, science fiction, psychiatric cases, hoaxes and lies. Roswell is a hoax. Suspicion that the government is concealing information about UFOs is absurd.
Physics
Energy is the ability to do work. There are 4 forces in nature: the strong and weak nuclear fields, the electromagnetic field and the gravitational field. The strong nuclear field holds protons and neutrons together. Atomic and hydrogen bombs use this energy. The weak nuclear field is associated with radioactive decay. Electromagnetism involves electric and magnetic fields. Gravity is the weakest but is very long-range.
Wierd
The more exotic ideas seem like something from a Star Wars movie. Dark Matter is supposed to account for 90% of the mass in the universe. We can not see it nor can it be detected by instruments. Is it there?
Wormholes are far out. They are tunnels in black holes which lead to parallel universes. An infinite number of universes make up the multiverse. Each universe has its own Big Bang. Are these ideas true or fantasy?
Science versus Religion
According to The Bible, the Virgin Mary got pregnant without Joseph's sperm or genetic material. An egg fertilized by Spirit? An angel informed Mary's husband of her pregnancy. Should we believe angels exist as Billy Graham does or regard them as relics of Hebrew mythology, fabrications of man's fertile brain?
The star of Bethleham! Chances are it was a literary star with no counterpart in nature. Someone is always trying to prove it was a comet or planets lined up.
So much in The Bible is perceived as the fulfillment of prophecy. Should we take this stuff literally or view it as a body of legends which took shape in the collective mind of ancient Middle East tribes. With prophecy, we work backwards. We invent it after the fact.
Is there such a thing as sin? Sin does not exist in nature. A cat kills a mouse. No sin.
Billy Graham believes in demons. I am 60 years old and have never seen a demon or evidence of a demon. Nor have I seen a miracle. The Bible is a string of impossibilities. Some people say these things do not happen today but happened back then. The notion is ludicrous. Why do we bend over backwards to try to force reality into a theological frame?
If Jesus is God, why not make things right now? We are waiting. If the universe is 15 billion years old, will it take Him another 15 billion?
Can we believe Jesus ascended into heaven? He floated into space? Have astronauts in the Shuttle orbited past Him? In film biographies of Jesus, he has the piercing blue eyes. The Anglo-Saxon Jesus! He reels off vague parables which are riddles to the modern world. The surest way to confuse is to use a parable, analogy, metaphor or simile. What is the Kingdom of God? What is God? Where is He and where did He come from? Is theology man's invention? Books, art and movies take things out of context. They distort reality into episodes with a hope of commercial success. Does The Bible do this? If not, why do we have to buy a Bible in a book store to read the word of God? Why do preachers preach until they are blue in the face and then ask for money? Is the bottom line money?
Apart from imagination and art, how could Jesus have raised Lazarus from the dead? The supernatural does not exist in a natural universe. Faith can not make the impossible happen. Yet, Jesus said, "I am the Resurrection, and the Bible says all things are possible with God. Those who speak of an empty tomb as evidence of the Resurrection, are they not failing to distinguish between an actual tomb and a tomb of the mind?
Preachers wear suits and ties and give the appearance of being sane, rational people. When they speak of a rapture and physically rising through the atmosphere to leave behind the unredeemed, we realize something is amiss.
Evangelist Jimmy Swaggert extolled virtue while patronizing prostitutes. Morality seems most plausible when it has a scientific foundation. It was not science that used nuclear energy for bombs. It was a clash between tax-funded military establishments which have traditionally embraced religion. If one gets paid to perpetuate ignorance, he will generally do it.
Mormons are on the cutting edge of Christianity. They claim Jesus came to western America to save Indians. If intelligent life is discovered in another part of the galaxy, a sect will arise claiming Jesus appeared to redeem lost aliens.
The age of theology lay between 3,000 B.C. and 600 A.D. The age of science began only 400 years ago. Carl Sagan, in his book, "The Demon-Haunted World," called science the candle in the dark.
Science is the way, evolution over creationism, observation over revelation, objectivity over subjectivity. Our eyes and ears tell us the way things are. It is as we suspected when we were kids, before organized religion sapped our energy. Religion is flawed thinking. We are physical, not spiritual. We are alive when we are alive. We are dead when we are dead. We are not dead when we are alive. We are not alive when we are dead.
We live in a natural universe. The supernatural does not exist apart from man's imagination and his tendency toward myth. Carl Sagan left us with these words, "Extraordinary claims require extraordinary evidence." Science is the candle, not religion, not mythology, not astrology. The Carl Sagan Center for the Study of Life in the Cosmos is being built in Washington, D.C.
This being said, I still subscribe to the ultimate message of the Gospels. If the Universe is 15 billion years old and middle age, Jesus Christ will return in another 15 billion years. His return will be in the nick of time to save believes at the brink of the universe's demise. He will save the souls of all believers in the cosmos. At that point, science and religion become one and the same. The 1% of truth in The Bible merges with the 1% of truth in science. Eternity is liquid consciousness, part of it blissful moderation, part of it flaming hot, heaven and hell.
Southern Constellations
We never see the constellations of the southern hemisphere from our latitudes because the tilt of the earth in its orbit is not great enough. To see the southern stars, we must journey to the equator.
There are 88 constellations. 32 can only be seen from the southern hemisphere. Many of the southern constellations were named by the Frenchman, Nicolas Lacaille.
Animals dominate. There are 2 mammals, 6 birds, 2 reptiles, 1 fish and 2 insects.
..1 Centaurus - centaur
..2 Lupus - wolf
..3 Pavo - peacock
..4 Tucana - toucan
..5 Grus - crane
..6 Apus - bird of paradise
..7 Phoenix - phoenix
..8 Columbia - dove
..9 Hydrus - water serpant
10 Chamaeleon - chamaeleon
11 Dorado - swordfish
12 Volans - flying fish
13 Music - fly
Scientific tools belong to Lacaille. He was the last man to create constellations.
14 Horologium - pendulum clock
15 Pictor - painter's easel
16 Octans - octant
17 Circinus - compass
18 Antlia - air pump
19 Telescopium - telescope
20 Norma - carpenter's level
21 Ara - altar
22 Reticulum - the net (in an eyepiece)
23 Fornax - furnace
24 Sculptor - sculptor
25 Caelum - chisel of the sculptor
4 groupings are part of the constellation, Argo Navis, the ship on which Jason and the Argonauts sailed after the Golden Fleece.
26 Carina - keel of Argo
27 Vela - sail of Argo
28 Puppis - stern of Argo
29 Pyxis - ship's compass
This leaves (30) Indus, the Indian, (31) Triangulum Australe, the southern triangle and the symbol of the Southern Hemisphere, (32) Crux, the Southern Cross. The Cross points to the south celestial pole. Its 3 bright stars are called the 3 Marys.
According to the Gospel of John, the 3 Marys at the cross when Jesus was crucified were Mary Magdalene, the Virgin Mary and her sister. I understand Magdalene being there. People question whether she was Jesus' lover. What I do not get is why sisters would have the same name.
The bright stars of the south are:
1 Canopus - Carina
2 Alpha Centauri - Centaurus
3 Achernar - Eridanus
The missing piece of the Milky Way circle is seen in the south. The Magellanic Clouds look like pieces of the Milky Way.
On Michael's 18th birthday, March 11, 2002, I took American Airlines to Los Angeles and flew Qantas down to Sydney, Australia. We crossed the equator and international dateline at about the same place. I got a motel and took a train to Sydney Harbor. I saw the Opera House, the Harbor Bridge and the Rocks (Old Town).
My purpose in going to Australia was to see the southern stars and constellations. Monte Wilson of the Astronomical Society of New South Wales (ASNSW) picked me up at my motel. We drove through the Blue Mountains to Wiruna, their Dark Sky Site, 3 hours northwest of Sydney, for the South Pacific Star Party (SPSP)
I was lucky. The weather was great all 3 nights. I got to stay in the house, referred to as the "White House" because they let Americans stay there. There was a couple named Tom and Lucy from Texas who proved invaluable. Lucy had grown up in Louisville around the Bardstown Road area.
"I saw The Southern Stars burning in their glory!" I saw the Southern Cross and Coalsack next to it. I saw the Magellanic Clouds. They were fainter than I thought. I saw the bright stars, Canopus, Alpha Centauri and Achernar.
Tom kept finding galaxies and nebulae in Tony Buckley's 20 inch. We looked at Jupiter and Saturn. Orion was upside down. Scorpius was straight up in the sky. The hub of the Milky Way in Sagittarius was high and prominent. I looked into our galaxy's thickest part, something I only saw along the horizon as a teenager.
The southern constellations are abstract. To trace out even Argo and Centaurus takes more time. Seeing Scorpius overhead stayed with me, that and seeing Scorpius and Orion in the sky at the same time.
The southern sky is more glorious than the northern because we also get the bright winter stars we see here.
I was impressed at how close Canopus is to Sirius and how the Southern Cross is not all that far below Scorpius.
I will never forget when I walked out of the house that first night and looked up at the southern sky for the first time. It was a revelation! The sky was ablaze with stars!
Treasurer Max Gardner drove me back to Sydney. He took me to his home and showed me the city. We crossed the Harbor bridge. We drove on the left side. Sydney is beautiful.
Max explained how Australia is part of the British Commonwealth, that the Queen is head of state. Australia is a constitutional monarchy.
I saw a book about Alaska in Max's bookcase. Crossing the Pacific again, I noticed how close we came to Hawaii. I wondered how long it would be before I saw Hawaii.
I arrived back in Nashville, March 18, 2002. One week. Sydney is halfway between the equator and the south pole.
Karen and I went to the Tennessee Spring Star Party, April 1-2, 2006, at Fall Creek Falls State Park. We sat with other star gazers and worked out the spring constellations. Frogs croaked and made hideous noises. A guy had his telescope set up and was showing galaxies in the constellation, Coma Berenices, on a screen. His technology was futuristic. He showed the Whirlpool Galaxy live. It was like an image from a magazine, large and detailed. We talked about the chances of life elsewhere in the universe.
The Whirlpool Galaxy M51 is 23 million light years away in the constellation, Canes Venaciti. The small galaxy to the left is behind the Whirlpool. We know this by the dust from the Whirlpool's spiral arm in front of it.
We looked at Bode's Galaxy M81, a spiral 11 million light years out in Ursa Major.
I am thinking Alaska. I will contact astronomy people in Anchorage and Fairbanks. The northern lights can be seen 240 nights a year in Fairbanks. I will fly to Anchorage, journey by train to Danali National Park to see Mount McKinley and on to Fairbanks close to the Arctic Circle. The northern lights, or Aurora Borealis, is caused by solar wind hitting gases in our upper atmosphere. The waves and curtains of red, blue and green light can be spectacular. These lights occur at the poles because the earth acts as a magnet, pulling particles of the solar wind north and south. A similar phenomenon occurs near the south pole. We do not hear as much about it because the big population centers are in the north. Other planets have northern and southern lights.
Another astronomy trip can be to the Grand Canyon. The Tucson Astronomical Society meets at the Grand Canyon each June for a Star Party. This will be an ideal experience. I want Michael to see the Grand Canyon. There is a Las Vegas Astronomical Society. It will be nice to see the Perseids from the Valley of Fire. Larry is interested.
Bibliography
..1 Apfel, Necia. Voyager to the Planets. New York, Clarion Books, 1991
..2 Baker, Robert H. Introducing the Constellations. New York, Viking Press, 1957
..3 ________. When the Stars Come Out.
..4 Bernhardt, Bennet & Rice. Handbook of the Heavens
..5 Branley, Franklin M. The Milky Way: Galaxy Number One.
..6 Couper, Heather and Nigel Henbest. Space Scientist Series. New York, Franklin Watts, 1980s
..7 Fanning, A. E. Stars, Planets and Galaxies.
..8 Ferris, Timothy. Coming of Age in the Milky Way. New York, William Morrow, 1988
..9 ________. The Red Limit: the Search for the Edge of the Universe. New York, William Morrow, 1977
10 Hathaway, Nancy. The Friendly Guide to the Universe. New York, Viking, 1994
11 Knight, David C. Galaxies: Islands in Space. New York, William Morrow, 1979
12 Moore, Partick. The Moon.
13 Muirden, James. The Amateur Astronomer's Handbook. Third Edition. New York, Harper & Row, 1983
14 Norton, O. Richard. Rocks from Space: Meteorites znd Meteorite Hunters. Missoula, Montana, Mountain Press, 1994
15 Ride, Sally and Tam O'Shaughnessy. Exploring Our Solar System. New York, Crown, 2003
16 ________. The Mystery of Mars. New York, Crown, 1999
17 ________. The Third Planet: Exploring the Earth from Space. New York, Crown, 1994
18 Sagan, Carl. Billions & Billions: Thoughts on Life and Death at the Brink of the Millennium. New York, Random House, 1997
19 ________. Cosmos. New York, Random House, 1980
20 ________. Pale Blue Dot: A Vision of the Human Future in Space. New York, Random House, 1994
21 ________. The Demon-Haunted World. New York, Random House, 1995
22 ________. Spangenburg, Ray and Kit Moser. A Look at Saturn. New York, Franklin Watts, 2001
23 Steel, Duncan. Target Earth: The Search for Rogue Asteroids and Doomsday Comets. Pleasantville, Reader's Digest, 2000
24 Wilford, John Noble. Mars Beckons: the Mysteries, the Challenges, the Expectations of Our Next Great Adventure in Space. New York, Alfred A. Knopf, 1990
25 Zim, Herbert S and Robert H. Baker. Stars: A Guide to the Constellations, Sun, Moon, Planets and Other Features of the Heavens. New York, Golden Press, 1975
Jim Colyer
Originally written 1995-1996
Revised 2002-2006
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