| Copyright by Paul Derrick. Permission is granted for free electronic distribution as long as this paragraph is included. For permission to publish in any other form, please contact the author at pjderrick@aol.com. |
Dec. 23, 2000: Christmas Day Partial Solar Eclipse
Dec. 09, 2000: Finding Neptune and Uranus
Nov. 25, 2000: Cosmic Distances
Nov. 11, 2000: Days of the Week
Oct. 28, 2000: Fall Sky -- the Rescue Story
Oct. 14, 2000: Colors in the Night Sky
Sep. 30, 2000: The Night Sky the Night You Were Born
Sep. 16, 2000: Astronomy and Everyday Life - Day, Month, Year, Season
Sep. 02, 2000: Starnymph and Songsmith
Aug. 19, 2000: A New "Star" in the Sky - International Space Station
Aug. 05, 2000: Perseid Meteor Shower
Jul. 22, 2000: Summer Sky
Jul. 08, 2000: Things to See without a Telescope
Jun. 24, 2000: Stargazing on the Road
Jun. 10, 2000: Arcturus
May 27, 2000: Omega Centauri
May 13, 2000: Circles in the Cosmos
Apr. 29, 2000: Cosmic Baseball
Apr. 15, 2000: Big Dipper
Apr. 01, 2000: Celestial Soap Opera
Mar. 18, 2000: Earth without Seasons
Mar. 04, 2000: Resources for Amateus Astronomers
Feb. 19, 2000: Winter Stargazing
Feb. 05, 2000: Is Pluto a Planet?
Jan. 22, 2000: The Decade of the 1990s
Jan. 08, 2000: Total Lunar Eclipse
Mother Nature will give much of North America a neat Christmas gift this year -- a Christmas morning partial eclipse of the Sun.
Once each month, at new Moon, the Moon passes between Earth and Sun in its "moonthly" orbit around Earth. Usually it passes slightly above or below the Sun. Occasionally, it passes exactly between the Earth and Sun, producing a total solar eclipse.
When the alignment is less than exact, and the Moon covers only part of the Sun, the result is a partial solar eclipse -- which is what we will see, weather permitting.
In Central Texas, about one-third of the Sun will be covered by the Moon. The eclipse starts about 9:40 a.m., reaches maximum about 11 a.m. and concludes about 12:20 p.m.
If you're traveling for the holidays, you might see more or less of an eclipse depending upon your destination. Those to the north and east (Great Lakes to New England) will see up to 60% of the Sun covered. The southwest's show will be less interesting with a less than 20% eclipse in Southern California. (For data on specific locations, see the December 2000 issue of *Sky & Telescope* magazine, or visit their Website.
Please remember even brief looks at the Sun without proper protection can permanently damage one's eyes -- and no eclipse is worth that. While sunglasses, sooted glass, and telescope eyepiece filters are NOT safe, there are some safe options.
The easiest and safest is a pin-hole projector. Using material like a piece of cardboard, poke a tiny hole in the middle. Then let the eclipsed Sun shine its light through the hole and onto a wall or piece of white paper. It will make a small image of the Sun with a bite taken from it. (Note: DO NOT look through the pin-hole -- look only at the projected image.)
For direct viewing, one may safely use #14 welders' glass or mylar solar glasses made specifically for solar viewing. (The latter are inexpensive and available from the Stargazer.)
While this should be a fun eclipse, don't expect to see the sky darken or the temperature fall. A 30-40% eclipse probably won't even be noticeable if you're not viewing it with one of the above methods. Still, let's hope for clear skies.
Finding Uranus and Neptune are always a challenge. The gas giant twin planets are huge -- much larger than Earth. But they are also quite distant -- the farthest planets except for Pluto. Under very dark skies, Uranus can barely be seen with naked eyes, but further and fainter Neptune always requires optical aids.
The beautiful and brilliant planet Venus, currently the "evening star," can help locate both of these elusive planets as it passes near Neptune, then Uranus, in the next couple of weeks. Monday and Tuesday evenings (Dec. 11 and 12), Venus passes less than 3 degrees (6 moonwidths) to the left of Neptune.
Finding Venus is easy as it's the brightest object in the west. The best time to look for Neptune is around 7 p.m. -- long enough after sunset to be dark, and before the Moon rises in the east. In binoculars, both planets will be in the same field of view. With Venus in the left half of the field, look for Neptune in the right half, looking like a faint blue-green star. Once you find Neptune, you'll see it better if you move your binoculars slightly to the right, eliminating the glare of Venus. At 8th magnitude, Neptune is difficult, even in binoculars. It might be necessary to view from beyond city lights.
If Neptune eludes you, don't despair. There's an even better opportunity for seeing brighter Uranus Dec. 23 when Venus passes just over 1 degree (about 2 moonwidths) to its left. By 7 p.m., the sky will be dark and the pair will be about 20 degrees above the horizon. (The width of your fist held at arm's length is 10 degrees.) After finding Venus in your binoculars, look for Uranus, looking like greenish dot to Venus' right.
Although Uranus and Neptune are the same size, Uranus looks larger and brighter as it is closer to us and to the Sun. Currently at 6th magnitude, it is almost visible to the naked eye under dark skies, and is easy in binoculars.
While the above are the optimum dates for finding Neptune, and then Uranus, Venus approaches, passes and pulls away from each planet gradually. Thus each planet with be in the same binocular field of view with Venus a few days before and after its closest approach.
When looking into the night sky, do you wonder how far away things are? We know the cosmos is enormous, but just how far can we see? Without optical aids, most of what we see is in our own little corner of the universe. The amount of the cosmos we see looking up from our back yard is comparable to the amount of our world we see standing at our front door. So how far away are things, seen and unseen, in the night sky?
Beyond airplanes flying a few miles above Earth, you might think the next nearest objects are visible satellites, most of which orbit at altitudes of 200-300 miles. Far nearer, however, are meteors ("shooting stars") which flash across the sky a mere 50-70 miles above Earth -- nearer to Waco than Dallas or Austin. The next nearest body is the Moon at 240,000 miles above Earth -- the distance a good auto might travel in its lifetime.
Once we leave Earth's realm, distances increase dramatically. Venus, our nearest neighboring planet, comes within some 30 million miles. The Sun is 93 million miles away. Saturn, the most distant of the easily visible planets, is nearly a billion miles away, and Pluto lies at some 3 billion miles.
Beyond the solar system, where distances are so great that miles are no longer meaningful, astronomers use the light year (ly). That's the distance light travels in one year at its speed of 186,000 miles per second -- nearly 6 trillion miles.
The nearest star beyond our Sun, the Alpha Centauri system, is just over 4 ly away. Most stars we see with our naked eyes lie tens to hundreds of light years away. Most open star clusters are hundreds to thousands of light years away, and globular clusters are tens of thousands of light years distant.
Beyond our Milky Way galaxy (which is some 100,000 ly in diameter) are our companion galaxies, the Large and Small Magellanic Clouds at 200,000 ly. The Andromeda galaxy, one of our nearest galactic neighbors at just over 2 million ly, is the most distance object we can see with the naked eye. Most of the billions of other galaxies which make up the cosmos are many millions, even billions of light years away.
Quasars, the most distant known objects, are only seen telescopically. Incredibly remote, they take us to the fringes of the known universe, believed to extend some 10-15 billion ly. If those distances don't boggle your mind, as they do mine, then consider this: Einstein's theories of relativity suggest that space itself may be curved, altering our very concept of distance. If we could travel far enough into space, we might find ourselves right back where we started.
Nov. 11, 2000
Days of the Week
A few weeks ago in this column, I discussed astronomical influences on our measures of time: the day being one rotation of Earth on its axis, the month being one lunar orbit around Earth, and the year being one revolution of Earth around the Sun. I also stated that the length of the week was arbitrary and not related to any natural phenomenon.
Ernie Casbeer, a teacher in McGregor High School, took me to task by reminding me that the 7-day week also has an astronomical connection, even if not quite like the day, month and year.
Ancient Egyptians used a 10-day week, early Romans an 8-day week, and other cultures had weeks varying from 4 to 8 days, based on market days. The ancient Hebrew 7-day week, as found in the Pentateuch, likely came from Mesopotamia (modern Iraq). Seven days, deriving from archaic astrological beliefs about the influence of planets on human affairs, are based on what were long thought to be the seven celestial bodies orbiting Earth: Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn.
Thus, our current days of the week do indeed have a cosmic connection. Three are straightforward and obvious: Sunday is Sun's day, Monday is Moon's day, and Saturday is Saturn's day.
The other four need some explanation. Mars was identified with the Germanic god Tiw, so Tuesday is Tiw's day. Mercury was equated with the god Woden, so Wednesday is Woden's day. Jupiter was Thor, so Thursday is Thor's day. And Venus was seen as the goddess Frigg, so Friday is Frigg's day.
So, there you have it, thanks to Ernie and the encyclopedia.
It's time once again to take a look at the fall evening sky, and the Greek myth that ties together several of the season's constellations. The story centers around Andromeda, the Princess, and Perseus, the Hero.
Andromeda is the beautiful daughter of Cassiopeia, the Queen, and Cepheus, the King. Cassiopeia, known for her vanity, angered the god Poseidon by her excessive boasting. As punishment, Andromeda was to be sacrificed to Cetus, the Sea Monster.
Enter the hero, Perseus, with some god-friends of his own who told him he could rescue Andromeda using the head of Medusa. Formerly a beautiful woman, Medusa had angered a jealous god who turned her into a hideous creature with snakes rather than hair growing out of her head. She was so frightfully ugly that anyone who looked at her face would turn into stone from terror.
The gods told Perseus to kill Medusa and take her head to Cetus who would be so frightened he would turn into stone. Of course, he had to accomplish the deed without looking at Medusa himself, lest he turn into stone. Using a magic shield given him by another friendly god, Perseus was able to look at Medusa's reflection, rather than directly at her, and decapitate her.
As her headless body fell to the ground, out of it grew a fully-grown winged horse, Pegasus, the Flying Horse. With Medusa's head in a sack, Perseus mounted Pegasus and rode off to find Andromeda chained to a small off-shore island and Cetus licking his chops. Perseus took the ugly head from its sack, held it out for Cetus to see, and sure enough, Cetus immediately turned into stone and sank into the sea. After Perseus rescued Andromeda, they were married and lived happily ever after.
And you thought all the nighttime melodrama was on television?
Although objects in the night sky might appear colorless to the casual observer, the cosmos is actually teeming with color. When you think about it, that should come as no surprise. Our world, made of the same elements found throughout the universe, is full of color, so how could the rest of cosmos not have color. Stars come in reds, oranges, yellows (like our Sun), whites and blues. Nebulae reveal an unbelievably rich variety of colors, as if painted by an abstract artist with imagination.
Closer to home, the planets in our solar system display many colors. Mars, for example, is red because its surface soil is red, like the soil in east Texas. Through a telescope, one sees the varied colors -- browns, yellows, whites, and oranges -- of Jupiter's belts. Uranus looks greenish and Neptune bluish.
The Moon, however, appears drab and colorless because it is. The Apollo astronauts found its surface soil and rocks to be a bland brownish-gray, like rocks and soil found on parts of Earth. Perhaps you've seen the dazzling display of colors in photos, like those from the Hubble Space Telescope, and wondered if that's what astronomers see when they look through their powerful telescopes. Unfortunately, it's not.
That's not to say colors are only seen in photos. Discerning observers can train their eyes to see a wide range of colors, spanning the colors of the rainbow from red to blue. Whether viewing with naked eyes, binoculars and telescopes, colors can clearly be seen albeit they are usually subtle. It takes astrophotography can bring out a richness of colors which the human eye simply can't do, owing to the anatomy of the human eye.
The retina is a thin layer of material at the rear of the eye where light is sensed, somewhat like film in a camera. It has two types of receptors called rods and cones. Over 100 million rods, concentrated around the periphery of the retina, can see dim light but they are not sensitive to color, whereas 6 million cones, found in the central area of the retina, are sensitive to colors but they work best in brighter light. Thus cosmic objects, which tend to be dim, are seen more with our eyes' black-and-white-seeing rods than the color-detecting cones. This can be demonstrated by looking at the same terrestrial objects by sunlight and by moonlight. Sunlight easily shows Earth's beautiful colors -- the greens of trees and grass, the reds, blues and yellows of flowers. But by moonlight, the colors disappear. Moonlight provides enough light for the rods to show shapes and forms, but not enough for the cones to show colors.
Have you ever wondered about the night sky on the date (and place) of your birth? Your parents were probably too preoccupied with other things --- namely, you -- to notice, but what might they have seen had they looked skyward the night you were born? Was the Moon out? Were there planets in the sky? What constellations were visible?
Determining the constellations is easy. Simply look at the night sky on any birthday and the star patterns will be just as they were the night you were born (assuming you are viewing the sky from a latitude similar to that where you were born).
The Moon and planets, however, almost certainly won't be the same, and until recent years, finding out about them would have taken some research. But now there are computer programs which quickly calculate and display the night sky for any date within a few thousand years (past or future) and any place on Earth.
As I was born just before sunrise, my parents might have glanced at the predawn sky while heading to Parkview Hospital in Houston, Texas, on August 27, 1940. If so, they would have seen a waning crescent Moon high in the east above the brilliant Venus. Overhead they might have marveled at Jupiter and Saturn less than 2 degrees apart. Although it was still summer, given the late hour, they would have seen constellations usually associated with winter -- Orion, Taurus, Gemini -- rising in the east. (Perhaps that's why I love the winter sky.)
If you're curious about the night sky when you were born, and don't have a sky map program available, I'll be happy to print your personal sky map for you free. Send me the date, time and place of your birth with a self-addressed, stamped envelope. (I promise I won't tell anyone your age.)
For most of human history, astronomy had relevance to everyday life. In Europe during the early middle ages, it was one of the "the seven liberal arts" regarded as the essence of a quality liberal education. Indeed, astronomy is considered the first science. But things have changed.
We no longer use the stars to tell us when to plant our crops, when to prepare for cold weather, or to tell time. The Global Positioning System has taken the stars out of navigation. High school and college astronomy courses, when offered, are elective. So are astronomical phenomena now irrelevant to our lives? Absolutely not.
I'm not referring to the pseudoscience of astrology (and horoscopes) which would have us believe the stars and planets affect us in mysterious ways. Most astronomers, professional and amateur, consider this bunk.
Still, astronomy, the scientific study of the cosmos, has relevance in ways we might forget. Perhaps nothing more profoundly affects our daily lives than the very concept of the "day." That 24 hour cycle around which we organize our lives is defined astronomically as one revolution of Earth on its axis.
While having the week consist of 7 days is arbitrary, our month is based on the cycle of the Moon which orbits Earth every 29 1/2 days, creating a "moonth." A year is the length of time it takes Earth to make one orbit around the Sun, and our seasons are defined by the location of the Sun in our sky at different times of the year. (Friday's fall equinox means the sun moves back over the Southern Hemisphere, to which most us are saying, "Thank goodness.")
There are certainly other ways, practical, philosophical and aesthetic, we are touched by astronomy. (Who can view Hubble Space Telescope images of the cosmos without being moved?) But the above are some of the more mundane ways we tend to overlook.
Many eons ago Songsmith made beautiful songs and set them adrift into the heavens. One night, while singing has latest song under the starry sky, a falling star appeared. Now he had seen many falling stars, but this one was blinding. When his sight returned, he saw beside him the beautiful Starnymph.
She softly spoke. "For years I have heard your songs and wanted to come to you, but Starmother said it was too dangerous for Starpeople to come to Earth. Finally, in great loneliness, I told her I must go."
So Starmother said, "Then catch a falling star and ride it to Earth. You may stay with him as long as he makes a new song before each midnight hour. The day he makes no song, you must forever return to the Starpeople. And be forewarned that each day you spend together, your love for each other will deepen, but since Songsmith is human, the day of dread will surely come. The pain of your return might be more than your heart can stand." But I said, "I will chance dying of a broken heart." So she said, "Then be off my lovely child."
So the years passed, and Starnymph and Songsmith were happier than they'd ever been. Each day their love deepened, just as Starmother had said. And day after day, a new song came easily and freely from the heart of Songsmith.
But one evening he said, "I am tired. Before making a song tonight, I must rest."
Starnymph said, "I too am tired."
Soon both fell fast asleep. Before they knew it, the midnight hour was upon them and the new day bell began to ring. On the third chime, Starnymph awoke and tried to awaken Songsmith. But he was so tired he didn't wake up until the twelfth chime. A day had passed that he made no song. Rubbing his eyes, he looked up and saw Starnymph rising into the heavens, her tears falling at his feet. His own tears mixed with hers, forming a reflection pool. Gazing into the pool, he then realized the many wonderful days with the Starnymph had become many years, indeed, decades. He understood why he was tired -- he had become a very old man.
He looked once more into the heavens he knew so well, saw a new star where none had been before, and from his heart came one last song. As he finished, he laid down and died.
As Life slipped from his worn out body, the new star began to twinkle brighter. Starmother had been deeply touched by the great love of Starnymph and Songsmith, and she too had enjoyed his songs. So she decreed, "Songsmith has earned a place among our Starpeople, and he and Starnymph belong together."
And if you look through a telescope at the head star of Cygnus the Swan, now called Albireo, you will see not one star but two -- soft yellow Starnymph and pale blue Songsmith. And if you listen with your heart, you can hear his final song as it still drifts through the heavens.
There's a new "star" in the sky -- one put there by us. The International Space Station (ISS) being assembled 240 miles above Earth is producing some interesting sights in the night sky.
On any given night one can see artificial satellites orbiting Earth. Most look like stars of average brightness slowly moving across the sky. But the ISS, being much larger than any other satellite, is much brighter. According to NASA, it is brighter than any star, being outshone only by the Moon and Venus.
Unlike high flying airplanes, satellites have no lights. We see them only when their shiny surfaces reflect sunlight -- like we see the Moon and planets. Orbiting much higher than airplanes fly, they remain in sunlight after the ground below has grown dark, but just for a while. They are only seen for a few hours after sunset and before sunrise; deep into the night they are in Earth's shadow.
The ISS is huge -- more like a large orbiting building than a cramped spaceship. Upon completion, the million pound station will be 290 feet long, 143 feet tall and have a wingspan of 356 feet (longer than a football field). With 46,000 cubic feet of pressurized space -- the amount of space in three or four average-size American homes -- there will be six research labs and living quarters for up to 7 astronauts and scientists.
A join project of the U.S., Russia and 14 other nations, the ISS is scheduled for completion in about 2003. The first of over 100 components was launched in November 1998. The initial crew, (two Russian cosmonauts and one American astronaut) will arrive in November for a five-month stay after which they will be replaced by another crew.
As large as it is, the ISS still appears only as a bright star-like point of light to naked eyes. Actually seeing it would be like trying to see Waco's 22-story Alico Building from Corpus Christi (ignoring the Earth's curvature). However, with optical aids some structural features would be visible.
Viewed through 10X binoculars, the ISS would appear to be only 24 miles away, and seeing the Alico building at 24 miles would be possible. Through a 6- to 8-inch telescope at 240X, the ISS would seem a mere 1 mile away -- close enough to see structural definition and almost close enough to see spacewalking astronauts. Unfortunately, finding and tracking a fast moving object in a telescope is quite difficult -- but not impossible.
The ISS orbits Earth every 92 minutes. To find out when it will be visible from your location, check NASA's website: http://spaceflight.nasa.gov/realdata/sightings/. Unfortunately Waco is not one of the listed cities, so we have to use the schedules for Austin and Dallas, looking for passes north of Austin and/or south of Dallas.
Wouldn't you know it? There's good news and bad news about the annual Perseid meteor shower expected to peak late Friday night and early Saturday morning.
The good news: We will have front row seats as our part of the world will be on Earth's leading edge when we pass through the largest concentration of Perseid meteors.
The bad news: There will be a glaring gibbous Moon in the sky most of the night, washing out all but the brightest meteors. But it could still be a show worth catching. The Moon will set an hour or so before dawn, giving a short moonless viewing window. For central Texans, this will be from about 4:15 to 5:30 a.m. Saturday.
Perseus, the constellation from which Perseid meteors appear to come, rises in the northeast just after midnight. By early morning it will be high in the northeast. While meteors may be seen in all parts of the sky, you're likely to see more higher in the sky.
Looking like stars shooting across and falling from the sky, one can understand why meteors are popularly called shooting stars and falling stars. Of course, they are not really stars but rather tiny pieces of space debris burning up as they enter Earth's atmosphere at many thousands of miles per hour. Composed of rock or metals, some meteors weight upwards of a few pounds on entry. Most, however, are much smaller--the sizes of marbles, B-Bs, grains of sand, and even microscopic particles.
The Perseid meteor shower occurs each year as Earth passes through the stream of cometary debris left by Comet Swift-Tuttle. Perseid meteors are usually fast and bright with many leaving visible trails..
Watching meteors does not require telescopes, binoculars or other special equipment. Simply lay back on a blanket or reclining chair in a dark area away from trees and look up. A final note: While the Perseids are expected to peak late Friday night, that's not the only time they might be seen. Meteor activity gradually builds for a couple of weeks before the peak, then tapers off for another couple of weeks afterward. So don't be surprised to see some early or late Perseid meteors.
For many stargazers, the evening sky of summer is their favorite of all the seasons, and for good reason. It features many bright stars, distinctive star patterns, and the brightest parts of the Milky Way.
Of the 16 first magnitude (brightest) stars ever visible from our area during the year, six are easily visible now, even from light polluted urban areas.
In the northwest, the Big Dipper is getting lower each night while Cassiopeia is beginning to peer above the horizon in the northeast. Draco, the long winding dragon, is at its highest in the summer, winding around and above the North Star.
Two first magnitude stars are in the west. The Big Dipper's curved handle points first to Bootes' Arcturus, the brightest star high in the west, the to Virgo's Spica below Arcturus.
In the south about a third of the way up is Scorpius' Antares, the reddest first magnitude star in the sky. Scorpius actually looks somewhat like what it's supposed to be--a scorpion. With Antares as its head, its pinchers are to the upper right and its fishhooked-shaped body curves to the lower left.
Left of Scorpius is the constellation Sagittarius, the Archer. He has no first magnitude stars and doesn't much resemble an archer, but he does look remarkably like a teapot, complete with steam coming from its spout and a teaspoon nearby.
High in the east are three first magnitude stars forming the Milky Way Triangle, also known as the Summer Triangle. The brightest and highest is Lyra's Vega, with Cygnus' Deneb to Vega's lower left. The triangle is completed by Aquila's Altair to the lower right of Vega.
While the brighter stars and some constellations are visible from urban areas, dark skies are required to see the beautiful Milky Way. It stretches from Scorpius and Sagittarius in the south, through the Milky Way Triangle high in the east, and down to Cassiopeia in the northeast.
A couple of viewing tips: since it's summer, the skies won't darken until rather late, and don't forget insect repellent.
Folks sometimes ask, "What can I see in the night sky without a telescope?" To which stargazers reply, "Plenty."
For starters, many solar system objects (things which revolve around our Sun) can be seen without a telescope. In addition to our Moon, the five nearest planets--Mercury, Venus, Mars, Jupiter and Saturn--can be seen. With binoculars, one can even see some moons of Jupiter and Saturn (but not Saturn's rings). Some comets reach naked-eye visibility, and many come within reach of binoculars. And meteors, of course, are seen with the naked eye.
Things beyond our solar system are called deep sky objects. In addition to individual stars, many other deep sky objects are within reach without a telescope.
Individual stars, even through telescopes, look like points of light which isn't too interesting. But the naked eye can easily note that stars come in different colors and brightnesses. With some stars (called variable stars) even their brightness changes. Upon close inspection one can detect that some stars have companions. Called double stars, these can be of interest, especially when they are of different color or brightness. A few are visible to the naked eye and binoculars show many more. Various kinds of groupings of stars don't require scopes.
Constellations, those large imaginary sky patterns made up of stars, are best seen with the naked eye.
Star clusters come in two types: open and globular. Naked eyes can see many open clusters and a few globulars, while binoculars reveal many dozens of both.
Nebulae are cosmic clouds composed of gas and dust. Some are areas where stars are forming (called star nurseries). Others are remnants of stars which died in explosive bangs. A few nebulae are seen with naked eyes, and many more with binoculars.
Finally, there are galaxies, those gigantic "island universes" composed of billions of stars. From our part of the world, only our own Milky Way and neighboring Andromeda galaxies are visible to the naked eye, however, binoculars reveal dozens more.
So, indeed, there is plenty to see in the night sky without a telescope. A final note, however, helps put the vastness of the cosmos in perspective: except for the Andromeda galaxy, all we ever see with the naked eye is within our Milky Way galaxy, and mostly within our little outer corner of the galaxy.
This column is being written on the road while the Stargazer is camping in Maine. Traveling to other parts of the country provides interesting perspectives on stargazing.
A disheartening factor relates to the pervasiveness of light pollution. When camping one expects dark skies, but even many campgrounds have interfering security and other lights. And while camping in forests is great for my wife's fascination for birding, those lovely trees play havoc with seeing stars.
But when one escapes the lights and trees, the rewards are worth the effort--much better viewing than from urban areas. And other campers seem to be appreciating the dark skies. Some parks offer stargazing sessions in their interpretive programs, and it's not unusual to find astronomy items in park bookstores.
Traveling north makes one appreciate stargazing in the south. Longitude (traveling east or west) generally doesn't affect what one sees, but latitude (traveling north or south) does. As one travels north, there are fewer different stars to see.
Polaris, the North Star, is always situated the same number of degrees above the horizon as the latitude of one's viewing location. From Waco's latitude of 31 degrees north, Polaris is 31 degrees above the horizon. In Bar Harbor, Maine, however, at latitude 44 degrees, Polaris is 44 degrees above the horizon.
All other stars appear to circle Polaris every 24 hours due to Earth's daily rotation. Stars closer to Polaris than Polaris is to the horizon (called circumpolar stars) never rise or set.
Their positions change like the hands on a clock but those same stars are always up. The further north one goes, the percentage of stars which are circumpolar increases and that can get boring. The great panorama of different stars takes place toward the south, giving southerners an advantage. From southern locations, fewer stars are circumpolar and more stars in the celestial southern hemisphere become visible. Thus southern observers enjoy a wider variety of stars throughout the night (and the year).
Another north-south difference relates to day length. In the north the summer sun rises earlier and sets later, yielding fewer hours of darkness for stargazing. The situation is reversed in the winter with longer northern nights, but those longer nights are also colder nights.
We're enjoying our travels, and Maine is quite beautiful, but it's made me appreciate southern stargazing all the more.
Most stargazers know that the brightest star in our night sky is Sirius in Canis Major, the Big Dog, which is located in the southern celestial hemisphere. But most probably can't name the northern celestial hemisphere's brightest star. That honor goes to Arcturus in Bootes, the Herdsman. It is the night sky's fourth brightest star, appearing nearly as bright as Sirius.
Sirius, being in the southern hemisphere, is never seen high overhead from our part of the world. It is best seen during the winter months. Arcturus, however, residing in the northern hemisphere, it gets higher in our sky and is prominent more of the year, being well seen in the spring and summer.
Because of Arcturus' proximity to Ursa Major, the Big Bear, the ancient Greeks regarded it as "the bear-watcher" and "the guardian of the bear." The Arabs knew it as "the keeper of heaven." There is even reference to it in the Book of Job.
Arcturus is a red giant 25 times the diameter of our Sun and over 100 times brighter. It is even brighter than Sirius, which only appears brighter because it is nearer. At a distance of 37 light years, Arcturus is 4 times further away. (That translates to 215 trillion miles--215 followed by 12 zeros--so you can see why astronomers use light years and parsecs rather than miles to measure cosmic distances.)
Although we don't notice it, heat as well as light from Arcturus reaches Earth, even from such a vast distance. While we regularly feel heat from our Sun, it is easy to forget that all stars, being nuclear infernos, give off heat. (By the way, measuring heat, called infrared radiation, given off by stars and other cosmic objects will be a major function of SOFIA, the airborne infrared observatory being "built" into a Boeing 747SP at Raytheon here in Waco.)
As for Arcturus, according to *Burnham's Celestial Handbook*, the heat we feel from the distant star is equal to that of a candle at a distance of 5 miles.
Being a red giant, Arcturus is an aging star nearing the end of its stellar life. With its hydrogen nearly burned up, it will soon (perhaps in a few million years) run out of fuel, enter its death throes, and die--long before our "middle-aged" Sun.
This is the best time of year to see an elusive jewel of the southern sky -- Omega Centauri. Located in the constellation Centaurus the Centaur, Omega is the largest and arguably most beautiful of the globular clusters.
Those of us in the southern latitudes of the U.S. are fortunate as this giant is too far south to be seen from much of North America. Hovering near the horizon, it is visible to the naked eye under dark skies. Its richness, however, becomes especially apparent with binoculars and telescopes.
Globular clusters are something of a mystery, quite different from ordinary open star clusters such as the well-known Pleiades, Hyades and Beehive clusters. Open clusters contain young stars recently formed from star-birthing nebulae like the Orion nebula. In a few million years, the Orion nebula will become a star cluster when all its dust and gas has formed into stars. Our Milky Way galaxy has many thousands of open clusters, each of which typically contains a few hundred to a few thousand stars.
Globular clusters, however, are much rarer, numbering in the hundreds. They are much older, vastly larger, and each contains hundreds of thousands of stars. While open clusters are found within galaxies, globulars are outside of them, swarming just beyond their central bulges. How they formed is still unknown.
Look for Omega Centauri around 10:30 p.m. from a site away from urban lights and with an unobstructed view to the south. To the naked eye, it will look like a subtle moon-sized fuzzball. There is a convenient path to help you "star-hop" down to Omega using your fist, given that the width of your fist held at arm's length is very nearly 10 degrees.
The star-hop begins at Virgo's brightest star, Spica, which can be found using the Big Dipper. Following the curve of the dipper's handle, "arc to Arcturus," the bright orange star high overhead. Then continue the arc the same distance to Spica, the bright white star mid way up in the south.
From Spica, hop straight down about 12 degrees to the 3rd magnitude star Gamma Hydrae. Then hop down another 13 degrees to the 3rd magnitude star Iota Centauri. One more 11 degree hop will bring you to Omega Centauri which itself will be about one fist above the horizon in Central Texas.
When folk singer Harry Chapin sang "All my life's a circle," he could have been singing for the cosmos as most cosmic objects spend their lives traveling in circles which we call orbits. (For the purists, these imperfect circles are technically called ellipses.) Thus, virtually all cosmic objects exist, not in isolation, but in relationship to other objects.
Our Moon circles Earth which circles our Sun. Indeed, nine planets circle our sun, all but two of which have moons circling them. And the Sun is also circled by billions of meteoroids, asteroids and comets. The solar system is metaphorically referred to as the Sun and its family.
Recent discoveries suggest that most stars probably have planetary families. And stars themselves also travel in circles as members of even larger families called galaxies, such as our Milky Way galaxy. The center of most galaxies is believed to be occupied by a supermassive black hole.
But that's not the end of the cosmic relationships. Galaxies exist as members of yet larger families called galaxy clusters, groups of galaxies which move through space together (although apparently not in circles). Beyond that, as we approach the limit of our current knowledge, it appears that clusters of galaxies might bunch into even larger bubble-like associations.
So, indeed, it seems virtually every object in the cosmos exists in relationship to other cosmic objects. The force binding objects to one another and creating this huge cosmic family is, of course, gravity.
Back on Earth, the English poet John Donne wrote long ago: "No man is an island." In his famous poem he asserts that humans too are bound to one another, that our lives circle around the lives of others, and that none of us exists in isolation.
If so, what then is the "gravity" which binds us? What force creates the human family? Can this force be understood and formulated into laws like the laws of gravity?
Some suggest such questions are challenges for scientists, perhaps geneticists, anthropologists or psychologists. Others say they transcend the realm of science and are questions for philosophers and theologians. Yet others think they might point to areas where science and philosophy intersect.
At the very least, they're certainly something to think about while out enjoying the beauty of the night sky.
Batter up! It's time for cosmic baseball. As if to recognize baseball season which gets underway each spring, the night sky displays a cosmic baseball field which remains in the evening sky throughout baseball season, until early fall.
It's time to grab a bat and step up to home plate which is Arcturus, the brightest star high in the east. It's easy to find using the Big Dipper high in the north. Follow the arc of the dipper's handle and "arc to Arcturus" 30 degrees to the right. (The width of your fist held at arm's length is 10 degrees.) Continuing the dipper's arc another 30 degrees brings us to the brightest star in the southeast, Spica, which is first base. Spica is not quite as bright as Arcturus.
Second base is Denebola in Leo the Lion. It is 30 degrees above, and not as bright as, Spica.
Third base, Cor Caroli, is less bright than Denebola. Back to Denebola's left 25 degrees, Cor Caroli is the brightest star beneath the handle of the Big Dipper.
Short stop will be difficult to see from light-polluted urban areas. Located between second and third (Denebola and Cor Caroli) is Coma Berenices which is a faint but large, beautiful open star cluster.
The four stars serving as our bases are also the well-known Diamond of Virgo. They don't form a perfect square but they're close enough for cosmic baseball.
Leo the Lion, now straight overhead, is center field. Leo is most easily recognized by its head which is shaped like a sickle or backward question mark. His little brother, Leo Minor, is left field. Leo Minor, located in the space above Leo's head, is faint and virtually imperceptible.
It takes three constellations to make up right field: Corvus the Crow, Crater the Cup and Sextans the Sextant. All are rather faint and difficult to make out. Well, there you have it -- cosmic baseball. If you're feeling too lazy to play, then just kick back in a lawn chair and enjoy the star-studded field.
This is the time of year when the Big Dipper is high in the north during the evening. Since its bowl now upside down, it is, according to legend, pouring out water and producing our April showers.
Although probably the best known of all the star patterns, the Big Dipper is not an official constellation. Rather, it is an informal pattern called an asterism. It is part of a larger constellation called Ursa Major, the Big Bear. (In Europe, by the way, the Big Dipper is known as the Plough.)
This famous pattern has several interesting features.
During a shameful period in our country's history when our white ancestors enslaved our black ancestors, the Dipper played an important role. Countless desperate slaves sought freedom by fleeing to Canada in the north. Traveling at night without maps and compasses, these courageous men and women found guidance from the night sky, as told in the song "Follow the Drinkin' Gourd."
The outer two stars of the dipper's bowl are known as the "pointer stars" because they point to Polaris, the North Star. Thus the innocent sounding folk song held subversive instructions for escaping slaves: follow the drinking gourd (the Big Dipper) and it will show the way to freedom.
The "Horse and Rider" are another interesting feature. The dipper's handle is made up of three stars. Looking closely at the middle star (named Mizar), one might see that this "horse" has a faint companion "rider" star (named Alcor). Seeing Alcor with naked eyes requires good vision as it is near the limit of what we can see without assistance.
With binoculars, however, one can easily distinguish the individual stars. While Mizar and Alcor appear close together, they really aren't--Alcor is considerably more distant. Such stars are called optical double stars.
But Mizar does have a true companion star which can be seen with a telescope. This smaller and fainter companion orbits Mizar, much like Jupiter orbits our Sun. Dual star systems such as this are called binary stars.
Finally, the Big Dipper area is home to several galaxies which are visible in amateur telescopes, some even in binoculars. These galaxies are vastly farther away than the dipper's stars. While the stars, all within our Milky Way galaxy, are tens to hundreds of light years away, the other galaxies, each composed of billions of stars, are millions of light years distant.
Hope you didn't miss last night's surprise meteor storm with the beautiful aurora borealis flashing in the background
as the space shuttle passed in front of Halley's Comet. April Fool! (Sorry, I couldn't resist.)
Now, if I haven't blown your trust, do you recall the royal planetary scandal a few years back. It's still the talk of the cosmic kingdom.
Early in 1997 King Jupiter and Queen Venus quarreled in the morning sky. In a huff, the queen abruptly moved into the evening where she soon found the opportunistic playboy, Mars. This rogue twosome had not one but two brazen liaisons as they twice passed within a breath of each other late in the year.
As the year was drawing to close, Venus noticed the angry Jupiter had moved into the evening sky and was getting uncomfortably close. So she decided it was time to retreat back into the morning sky, leaving poor Mars to face the mighty king. Since planetary gods are immortal, all Jupiter could do was give Mars a frightful warning. The king then joined his queen in the morning where they kissed and made up in the spring of 1998.
We're now faced with yet another episode in this planetary soap opera. For the past few months, Mars, Jupiter and Saturn have been in the evening sky while Venus has graced the morning. But soon Jupiter and Saturn will head for the morning sky after which Venus returns to the evening to join the lingering Mars.
Taking no chances, Jupiter decides to have a heart-to-heart talk with Mars before leaving. Thursday evening, he'll get right in Mars' face and issue some strong advice. And as if that were not enough, Jupiter's father, Saturn will then do the same April 15. Will Mars heed these intimidating warnings and stay clear of Venus? Or will he succumb to yet another tryst with the royal beauty? Stay tuned and we'll find out over the next few months.
Monday is the first day of the season we call spring. It is one of the two times of year when day and night are of equal length, the other being the beginning of fall. It is also the time of year when temperatures are more-or-less average for the year--not real hot, not real cold.
Earth's seasons are due to the fact that our planet is tilted on its axis some 23 degrees from perpendicular. During our winter, the north pole is tilted away from the Sun. This produces colder weather in two ways. First, days are shorter, giving us fewer hours of warming sunshine.
The second way is less obvious. During the winter, sunlight strikes Earth at a greater angle, thus the Sun's warming rays have more filtering atmosphere to pass through before reaching Earth's surface. Perhaps you've noticed that the Sun is higher in the sky at noon in the summer than in the winter.
The summer is opposite--longer days with more hours of warming sunlight, and sunlight beating more nearly straight down.
The seasons of the southern hemisphere are reversed from ours. During our winter when the north pole is tilted away from the Sun, the south pole is tilted toward the Sun, creating their summer. And vice versa during our summer and their winter.
But imagine no tilt and no seasons. Every day of the year would be about like Monday--wherever you live. The nearer the poles, the colder the weather every day of the year; the nearer the equator, the hotter the weather every day.
Here in Texas, visualize no sweltering summers or cool winters, or in the northern states, no bitter, snowy winters and mild summers. Would you enjoy that or find it boring?
Also days and nights would be of equal length throughout the year with sunrise and sunset at exactly the same time every day. Would you like that or find that boring, too?
It's tempting to speculate about what effects a seasonless Earth might have on life--especially plant life with its growing seasons, flowering and the like. But such speculation is futile. If Earth had no seasons, plant and animal life would simply have evolved in ways necessary to adapt to that condition. Predicting the direction of evolution on Earth would be as impossible as envisioning what forms life might take on other planets.
Today's column might be a keeper for those with more than a passing interest in stargazing as we'll survey some amateur astronomy resources.
Two popular monthly magazines are Sky & Telescope (800-253- 0245 or www.skypub.com) and Astronomy (800-533-6644 or www.astronomy.com). At $40 a year, each contains timely articles, beautiful photos and calendars of astronomical happenings. Every serious stargazer should subscribe to at least one.
If you plan to buy a telescope or other equipment beyond the limited offerings of local department stores, you'll need to shop by mail or Internet or travel some distance to a specialty store. One reputable catalog dealer is Orion Telescopes & Binoculars (800-676-1343 or www.telescope.com). Their free catalog, in addition to displaying a wide range of products, contains many informative sidebars.
The nearest store I'm aware of is Skywatch Products in Ft. Worth (817-249-3767 or member.aol.com/skywatchpr/home.html). It has part-time hours so call before visiting. There are a growing number of Web sites, most of which provide links to others. In addition to ones already mentioned, here are some others: www.spaceflight.nasa.gov (NASA's Human Space Flight), www.stsci.edu (Hubble Space Telescope Science Institute), www.heritage.stsci.edu (HST photo archives), www.origins.jpl.nasa.gov (NASA's Origins program), www.sofia.arc.nasa.gov (SOFIA and airborne astronomy), and www.badastronomy.com (dedicated to dispelling misinformation about astronomy).
Perhaps the best resource of all is meeting others who share an interest in stargazing. They can be found in local astronomy clubs, which in this area is the Central Texas Astronomical Society. You can find more about CTAS at ctasociety.tripod.com or by calling Johnny Barton at 254-881-2125. For another local resource, consider the following.
Thank goodness for the stars. With the mild weather we've been having here in the southwest, it would be easy to forget it's still winter if not for the presence of the constellations we associate with cold weather.
The signature constellation of winter, Orion, is easily recognized with his three-in-a-row equally-bright, equally-spaced belt stars. The great hunter is high in the south at 9 p.m. To his upper right is Taurus, the raging bull, snorting in Orion's face. Taurus is home to the Hyades and Pleiades star clusters, both easily seen with the naked eye.
Another sure sign of winter is the Great Winter Arc, a large semi-circle of bright stars cradling Orion and Taurus. The arc begins with Sirius, the night sky's brightest star, found half way up in the south, and to Orion's lower left. Some 25 degrees to Sirius' upper left is the bright star Procyon. (The width of your fist held at arm's length is about 10 degrees.) The arc continues another 20 degrees to the upper left with the two equally bright Gemini Twins, Pollux and Castor. It then ends at Capella, the brightest star overhead.
The Great Winter Arc region is one of the richest areas of the sky, containing 7 of the 16 brightest stars ever visible from the continental U.S., and one reason the winter sky is my favorite.
Seventy years ago this month, 24-year old Clyde Tombaugh discovered Pluto, our solar system's ninth planet -- or did he? On Feb. 18, 1930, the young astronomer, working at the Lowell Observatory in Flagstaff, AZ, discovered a new object on photographic plates he had taken the previous month.
This object was determined to be the long-sought "Planet X." The seventh planet, Uranus, was discovered in 1781 and the eighth, Neptune, in 1846. It was believed by many that a ninth planet existed beyond Neptune although it had eluded previous searches. So Tombaugh's find was a welcomed discovery.
For 50 years, few questioned the distant Pluto's status as a planet. It was even believed to be larger than Mercury, however now it is known to be smaller than our Moon.
In 1980, astronomer Brian Marsden created a furor when he proposed that Pluto be demoted to the status of an asteroid or "minor planet." He had some compelling arguments.
Pluto is smaller than any other planet. It orbits near the realm of the Kuiper Belt, a ring of asteroids well beyond Neptune, similar to the asteroid belt between Mars and Jupiter. Its solid composition is more like that of an asteroid than of the outer planets which are gas giants. Like many asteroids, its orbit is far more elliptical, and the plane of its orbit more inclined, than that of any other planet.
Others, however, vigorously came to Pluto's defense. While Pluto is smaller than any other planet, it is twice the size of any known asteroid. Unlike asteroids which come in a variety of odd shapes, Pluto has sufficient mass (and thus gravity) to have formed into a spherical shape like the other planets. It even has a moon, discovered in 1978 (although some asteroids have recently been found to have tiny "moons" as well). Not the least of the arguments is the long tradition of calling Pluto a planet.
The controversy simmered for years. Finally in 1999, the International Astronomical Union, the body with final say in such matters, declared they had no intention of changing Pluto's status as a planet. Case closed -- at least for now.
Regrettably, this decision came too late to reassure Clyde Tombaugh that he would remain in the history books as discoverer of a planet. He died in New Mexico in 1997 at the age of 90.
All logical arguments aside, there are many (including me) who, out of respect and admiration for Tombaugh, hope Pluto will always be considered a planet. Having had the pleasure of visiting with the man in his home three years before his death, I found him to be delightful, modest, charming, witty, full of life and still sharp as a tack at 87. That's my kind of a hero.
Ten years ago, on January 20, 1990, this column was born, thanks to invaluable assistance from Waco Tribune-Herald Managing Editor Barbara Elmore and City Editor Becky Gregory.
In reflecting on the decade of the 1990s, it is amazing to consider the discoveries, explorations and dramatic astronomical events which have occurred in just 10 years. Here's a sampling.
For a long time astronomers have hypothesized the existence of planets around other stars, but not until 1995 was one of these new worlds was found--orbiting a star with the unassuming name of 51 Pegasi. Since then several others have been found and a crude photo of one has even been made. This alone would put the 1990s into astronomy history books. But there's more.
The Galileo space probe, which reached Jupiter in 1995, found strong evidence for the existence of liquid water oceans on one or more of the giant planet's moons. This invites fascinating speculation about possibilities for finding primitive forms of extraterrestrial life in our own cosmic neighborhood.
Another discovery raises the possibility of past life in the solar system. In 1996 a meteorite of Martian origin was found in the Antarctic which might contain fossils of microbes.
The Hubble Space Telescope, launched in 1990 with an optical flaw and fixed in 1993, has taken images which have stunned even veteran astronomers--unbelievable images of the birth of stars and planetary systems, and awesome explosions of dying stars. HST has enabled us to peer deeper into the cosmos than ever, producing images of more galaxies, and at greater distances, than most of us can even imagine.
In 1998, Voyager 1, launched in 1977, left the realm of the planets and began its endless journey into interstellar space. It is sobering to realize our little robotic emissary could well be traveling among the stars long after our species is extinct.
As for astronomical events of the decade, none was more spectacular than the crash of Comet Shoemaker-Levy 9 into Jupiter in 1994. And speaking of comets, Hyakutake in 1996 and Hale-Bopp in 1997 put on the best cometary displays in years.
The 1990's also took from us American astronomer Carl Sagan in 1996, and Pluto discoverer Clyde Tombaugh and astro-geologist and Comet Shoemaker-Levy 9 co-discoverer Gene Shoemaker in 1997.
Locally, the McLennan County Astronomy Club was formed in 1993 and renamed the Central Texas Astronomical Society in 1998.
It's been quite a decade, and the Stargazer appreciates your readership, calls and correspondence. Clear skies for the 2000s.
This year starts off with an astronomical bang as there will be a total eclipse of the Moon the evening of Jan. 20. For more than an hour, the full Moon will darken noticeable as it passes through the shadow of Earth.
The eclipse begins about 8 p.m. however significant darkening won't become apparent until around 9 p.m. Totality will be from about 10:00 to 11:20 p.m. Then for the next hour or so, the Moon will leave Earth's shadow, gradually returning to its usual full Moon brilliance.
Making no light of its own, the Moon is visible only by reflecting sunlight. Thus, one might think the Moon would disappear entirely while hiding in Earth's shadow during a total eclipse. And indeed it would if not for the fact that light rays can bend.
As sunlight travels past Earth, our atmosphere bends rays of sunlight so that some of them curve around into the shadowed area behind our planet. Light from the red end of the spectrum (i.e., red light) bends more readily than light from the blue end (blue light). So rather than temporarily disappearing, the Moon during an eclipse often has a beautiful but eerie looking reddish glow.
In addition to viewing the eclipsed Moon, which itself should be a lovely sight, look for the nearby Beehive star cluster. Normally washed out by the glare of a full Moon, the Beehive might become visible during totality. Look about 10 degrees (the width of your fist held at arm's length) to the Moon's lower left. Without binoculars the Beehive looks like a faint fuzzy patch about the size of the full Moon. When viewed through binoculars, however, a swarm of individual stars come into view. (The Beehive, also known as Praesepe, is the manger referred to in our last column.)
For North Americans, this total lunar eclipse is the best since 1996, and the next good one won't come around until October 2004. So cross your fingers for clear skies.
