[ FirstLight Astronomy Club ] The Skies Above

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Finding the Elderly Universe

The Universe >

You can look up in the sky tonight, dear reader, and with nothing more than a pair of binoculars see some of the oldest creatures in the universe, some over 12 billion years old! Are they ancient planets? Dying stars? The Golden Girls? No, these ancient sky mariners are globular clusters.

Globular clusters, a.k.a. globs, are easily spotted. You may not believe this, but globular clusters are actually clusters of stars moving about together in a globular shape. Go figure.

So, when searching for a glob, look for a circularly symmetrical fuzzy sort of celestial object. I have pictures and easy-to-use maps for finding some easy targets near Sagittarius and Hercules at http://firstlightastro.com.

But don't let the cute fuzzy appearance fool you.
These globs are dense. They are only tens to a couple hundred of light years in diameter --- compared to the 100,000-plus-light-year diameter our galaxy lays claim to --- but contain literally millions of stars in that relatively tiny space.

Living on an imaginary Earth near the middle of a glob would present us with a spectacular night sky. Being a million times denser in stars than our local neighborhood, we would enjoy a star spangled banner above us that would fill the heavens with so many bright points of light you couldn't pick out the Milky Way.

But what are these creatures anyway? They are the firstborn among the stars in our galaxy. Although the details of how our galaxy formed are still fuzzy, the big picture starts billions of years ago with a supermassive cloud of hydrogen and helium gas. Stars begin to form in small bunches as the cloud collapses under its own gravity eventually forming the monstrous Milky Way disk we live in today.

But those little bunches of firstborn stars --- over 150 of them --- survive intact, not getting swept apart in the collapse. They take up touring about the Milky Way, traversing together high above and deep below the disk, and everywhere in between.

About 12 billion years of years have gone by since their birth. They are now just assemblies of old stars living out the ends of their days. But even an old bag of stars can tell us something about ourselves.

Get a map of all their positions and you'll notice that there are a lot of our busy little bees buzzing in the southern summer skies. In 1917, astronomer Harlow Shapley noticed this, worked out all their positions, and figured out the globs were hovering around a place in the Galaxy way over there in Sagittarius, tens of thousands of light years away.

The big deal --- and it was a great big deal back then --- was that it was generally believed the sun was at the center of the Galaxy. Shapley correctly concluded that globular clusters were trying to tell us we were actually off-center --- by a lot.

Some of the more cynical astronomers immediately concluded that our place in the universe was therefore no special place after all, that we were in some random place with no bearing on our existence or importance.

Others today find reasons to rejoice in our so-called inconsequential eccentric real estate. It turns out now that if our little insignificant system were anywhere nearer to the center of the galaxy (high radiation, many supernovae) or farther from it (little to no planet building material), we would be one insignificant lifeless system.

Our present view of the globular clusters is the perfect view, and a constant reminder of the very special place we inhabit in this grand scheme of things.

Questions or comments? Mark Ritter can be reached here.

Posted by Administrator at 2002.08.31 02:34 PM | Comments (0)

Don't Worry: This Catch is Dolphin-Safe

Observing >

Let's go hunting for dolphins. Not the kind of hunting that will get us into international trouble. We'll pursue our prey above, in the oceans of the summer sky, for Delphinus, one of the so-called "minor" constellations.

This will also give us an interesting look into how other cultures have named the skies. But first we have t find our Flipper-like friend.

Go outside in the next few evenings and face east. Look up almost directly above your head. There on the great ceiling above is the Summer Triangle. There are two stars that make up the base of the triangle. The one to the right is Altair; to the left is Deneb.

Follow an imaginary line from Altair a third of the way back toward Deneb. Stop! Now look the same distance downwards. You'll see a collection of stars that looks like a kite. Use your imagination and you may even see ... a dolphin! That's diminutive Delphinus, our star constellation this month.

There are several fish stories related to this minor constellation. One myth is the tale of how a messenger dolphin convinced the sea nymph Amphitrites to marry Poseidon. Its reward for being a successful matchmaker? A place of honor in the sky.

Another myth related to Delphinus has a dolphin saving the life of the ancient Greek poet Arion after he was chucked into the ocean by a scurvy gang of mutineers. The Arab culture embraced that dapper Greek dolphin and called it Dulfim, a sort of savior to submerging sailors.

Biblical peoples saw Delphinus as the Leviathan of the beautiful Creation Psalm, Psalm 104. And the Hindu people perceived there a portly porpoise, Zizumara.

It's hard to find a non-nautical theme anywhere.

The stars themselves that make up Delphinus are not the most interesting critters in the sky. They are typical stars, 100-300 light years away. What's more interesting, though, are their names.

For example the tail of the kite (or dolphin) --- the brighter star to the right --- is known to astronomers as Epsilon Delphini. The Chinese called this little stray Pae Chaou, which means --- ahem --- The Rotten Melon. Personally, I think that name stinks.

To some early Christian sects the entire constellation of Delphinus was known as the Cross of Jesus, and Epsilon Delphini itself was known in Arabia by a related name, Al Amud al Salib, The Pillar of the Cross.

But the most mysterious names belong to the two brightest stars in the constellation, Alpha and Beta Delphini. They would be the most northwesterly ones. Alpha is known commonly as Sualocin, Beta is called Rotanev. Both were first christened thusly in the Palermo Star Catalogue of 1814. But where did those names come from?

The Reverend Thomas W. Webb, an English astronomer in the 19th century, discovered the answer to the mystery:

In the early 1800's, the Palermo Observatory was headed by astronomer Giuseppe Piazzi. He's best known for discovering and naming the first asteroid, Ceres. He had an assistant named Niccolo Cacciatore. Cacciatore's Latin name was Nicolaus Venator.

Apparently Piazzi, in naming the two stars, reversed the spelling of Nicolaus to Sualocin, and Venator to Rotanev, in this way honoring his assistant and dauphin (successor).

Here's an interesting activity I use in class and you can use if you teach. Give the students a blank star chart. Let them draw in their own constellations and create their own stories to go with them. You'd be amazed at the stories they can come up with.

Questions or comments? Mark Ritter can be reached here.

Posted by Administrator at 2002.08.17 02:36 PM | Comments (0)

The Persieids are Back in Town

Comets >

Had a shower recently? Think about going outside tonight and taking one in. The peak to the annual Perseid Meteor Shower has arrived and under pretty good conditions. What are these shooting star visitors anyway, you may ask?

Our solar system has much more to it than meets the eye. Beside one bright star and all those planets, there are asteroids and comets and a menagerie of other tiny things left over from the creation of the solar system.
One of these comets --- Swift-Tuttle by name --- buzzes around the sun in a 130-year orbit that takes it close to Earth's orbit. Unknown to many, it is the source of the Perseid Fireworks Show.

Comets shed material like a bad case of dandruff. As these comets made of rock and ice come close to the sun, they get warm. Millions of tons of water and other compounds get boiled off. This evaporation carries with it sandgrain-sized samples of schmutz that travel with the comet in its orbit, getting spread out over the eons into a long train of dirty debris.

It is that dross which gives us the spectacular shower.

As Earth orbits along nonchalantly it ploughs right through Swift-Tuttle's polluted orbit. Then kaboom zaloom! --- we get hit. When we run into the grit train our combined collision speed is about 40 miles per second! Which is precisely why they light up. Imagine driving down the highway at 40 miles per second when your dog next to you in the passenger seat decides to hang its head out the window. We have a fireball of flaming, charbroiled hot dog.

This is the demise that meets the tiny, unsuspecting grains of comet waste as they dive headlong into our atmosphere. Instant meteor.

Monday afternoon is when we pass through the thickest part of the river of rubble. Unfortunately our sun makes it rather difficult to see the meteors then. But not to worry!

The good side to this is that both Sunday night and Monday night should offer us good showers. The Moon will set early both evenings leaving a dark sky. But the best time to see the shower is --- ahem --- after midnight. Why?

Imagine driving your car through the rain. You are traveling forward, the rain drops are falling down from above. But the overall affect is that most of the drops are smacking into the front windshield, not the rear windshield.

It's like that with meteors. Before midnight our part of the Earth is like the rear window. Around midnight is when we spin around towards the incoming meteoroids. It is after midnight that, if predictions are correct, we should get about 60 per hour under dark sky conditions.

And the Perseids can be beautiful. The big ones burn themselves into your memory forever. Michael Seeds, professor of astronomy at Franklin and Marshall College, has watched them religiously for decades. "I have seen spectacular Perseids," he says, "rushing fireballs flashing colors and breaking into pieces." The Perseids really are a breed apart.

Get thee outside to the darkest place you can find with the fullest view of the sky. Lay back and look up. Weather permitting, they will light up all around.

Think about making this an annual event for you and your family. The warm summer evenings make it ideal. Says Dr. Seeds, "The most spectacular thing about the Perseids is their dependability. They have returned year after year since I was a little boy and I suppose they will continue for a long time after I am gone."

Questions or comments? Mark Ritter can be reached here.

Posted by Administrator at 2002.08.10 02:39 PM | Comments (0)

Our Annual Summer Celestial Fireworks Show

Comets >

It's the time of the summer that meteor lovers love. Our annual summer celestial fireworks show, the Perseid Meteor Shower, has arrived. But rather than just looking up for meteors this year, use this time to get to know the summer skies, too.

First, though, a brief background on meteor showers.

When comets whiz around the sun, they dump a lot of dust. This debris travels along in pretty much the same orbit as the parent comet.

Some of these comet orbits intersect our own orbit. When Earth plunges through a comet's debris train, the dust slams into our atmosphere like bugs on a windshield. The friction with the atmosphere vaporizes the debris in flashes of light that we call meteors.

On the days of August 11 and 12, Earth passes through the big chunk of a debris train resulting in a meteor shower. The best time to "shower" will be after midnight early Monday morning when our side of the planet turns into the stream, resulting in the most meteors. A good Perseid peak might give us about 30 meteors an hour, but less where it is light polluted.

Unfortunately, you may be unwilling to stay up that late and will be meteor hunting before the midnight hour. Because Perseid sightings will be few and far between for you, this may be a good time to get to know some of the summer sky while you wait. Let's take a quick tour.

On the evening of the 11th, a four-day-old crescent Moon will be setting alongside a magnificently bright Venus. This Moon-Venus pose is one of those aesthetic pleasures that happens several times a year, but never ceases to command awe.

Try and actually see the "dark" side of the Moon, the non-crescent part. You'll notice it is just slightly lit, allowing you to see the whole disk of the Moon. This is due to "earthshine" which happens when the sun's light reflects off Earth's surface, dimly lighting the surface of the Moon.

Venus is about at its brightest now as it swings around the Sun in its orbit, passing us on an inside lane. The brightness of the Evening Star is due to its complete cloud cover. But she isn't covered in clouds made of water like our planet is --- those clouds are made of corrosive sulfuric acid.

Find the Big Dipper in the northern skies. Using the stars in the handle as pointers follow an imaginary curve, about one Dipper away, to the bright star Arcturus, a red giant seventy times bigger than the sun.

Keep following the curve over into the skies near the setting Moon to a big bright blue star called Spica. Spica spews out more energy in a minute than the sun does all day. Better look early, though; Spica sets about 9 o'clock.

Directly overhead later in the evening is the Summer Triangle, starring Deneb, Altair and bright blue Vega, the three of which make up the edges of the triangle. Each has an invisible binary companion star orbiting with it.

It's later in the evening that the Milky Way shows up in full glory, stretching from the south to the north. Those with binoculars can search the skies of the southern Milky Way and easily pick out abundant nebulae and star clusters.

The Perseid Shower is a great opportunity to see some really stunning meteors, to be sure. But use the night to get familiar with the rest of the spectacular summer sky, as well!

Questions or comments? Mark Ritter can be reached here.

Posted by Administrator at 2002.08. 3 02:40 PM | Comments (0)



Looking for something?	« July 2002 \| Main \| September 2002 » Finding the Elderly Universe The Universe > You can look up in the sky tonight, dear reader, and with nothing more than a pair of binoculars see some of the oldest creatures in the universe, some over 12 billion years old! Are they ancient planets? Dying stars? The Golden Girls? No, these ancient sky mariners are globular clusters. Globular clusters, a.k.a. globs, are easily spotted. You may not believe this, but globular clusters are actually clusters of stars moving about together in a globular shape. Go figure. So, when searching for a glob, look for a circularly symmetrical fuzzy sort of celestial object. I have pictures and easy-to-use maps for finding some easy targets near Sagittarius and Hercules at http://firstlightastro.com. But don't let the cute fuzzy appearance fool you. These globs are dense. They are only tens to a couple hundred of light years in diameter --- compared to the 100,000-plus-light-year diameter our galaxy lays claim to --- but contain literally millions of stars in that relatively tiny space. Living on an imaginary Earth near the middle of a glob would present us with a spectacular night sky. Being a million times denser in stars than our local neighborhood, we would enjoy a star spangled banner above us that would fill the heavens with so many bright points of light you couldn't pick out the Milky Way. But what are these creatures anyway? They are the firstborn among the stars in our galaxy. Although the details of how our galaxy formed are still fuzzy, the big picture starts billions of years ago with a supermassive cloud of hydrogen and helium gas. Stars begin to form in small bunches as the cloud collapses under its own gravity eventually forming the monstrous Milky Way disk we live in today. But those little bunches of firstborn stars --- over 150 of them --- survive intact, not getting swept apart in the collapse. They take up touring about the Milky Way, traversing together high above and deep below the disk, and everywhere in between. About 12 billion years of years have gone by since their birth. They are now just assemblies of old stars living out the ends of their days. But even an old bag of stars can tell us something about ourselves. Get a map of all their positions and you'll notice that there are a lot of our busy little bees buzzing in the southern summer skies. In 1917, astronomer Harlow Shapley noticed this, worked out all their positions, and figured out the globs were hovering around a place in the Galaxy way over there in Sagittarius, tens of thousands of light years away. The big deal --- and it was a great big deal back then --- was that it was generally believed the sun was at the center of the Galaxy. Shapley correctly concluded that globular clusters were trying to tell us we were actually off-center --- by a lot. Some of the more cynical astronomers immediately concluded that our place in the universe was therefore no special place after all, that we were in some random place with no bearing on our existence or importance. Others today find reasons to rejoice in our so-called inconsequential eccentric real estate. It turns out now that if our little insignificant system were anywhere nearer to the center of the galaxy (high radiation, many supernovae) or farther from it (little to no planet building material), we would be one insignificant lifeless system. Our present view of the globular clusters is the perfect view, and a constant reminder of the very special place we inhabit in this grand scheme of things. Questions or comments? Mark Ritter can be reached here. Posted by Administrator at 2002.08.31 02:34 PM \| Comments (0) Don't Worry: This Catch is Dolphin-Safe Observing > Let's go hunting for dolphins. Not the kind of hunting that will get us into international trouble. We'll pursue our prey above, in the oceans of the summer sky, for Delphinus, one of the so-called "minor" constellations. This will also give us an interesting look into how other cultures have named the skies. But first we have t find our Flipper-like friend. Go outside in the next few evenings and face east. Look up almost directly above your head. There on the great ceiling above is the Summer Triangle. There are two stars that make up the base of the triangle. The one to the right is Altair; to the left is Deneb. Follow an imaginary line from Altair a third of the way back toward Deneb. Stop! Now look the same distance downwards. You'll see a collection of stars that looks like a kite. Use your imagination and you may even see ... a dolphin! That's diminutive Delphinus, our star constellation this month. There are several fish stories related to this minor constellation. One myth is the tale of how a messenger dolphin convinced the sea nymph Amphitrites to marry Poseidon. Its reward for being a successful matchmaker? A place of honor in the sky. Another myth related to Delphinus has a dolphin saving the life of the ancient Greek poet Arion after he was chucked into the ocean by a scurvy gang of mutineers. The Arab culture embraced that dapper Greek dolphin and called it Dulfim, a sort of savior to submerging sailors. Biblical peoples saw Delphinus as the Leviathan of the beautiful Creation Psalm, Psalm 104. And the Hindu people perceived there a portly porpoise, Zizumara. It's hard to find a non-nautical theme anywhere. The stars themselves that make up Delphinus are not the most interesting critters in the sky. They are typical stars, 100-300 light years away. What's more interesting, though, are their names. For example the tail of the kite (or dolphin) --- the brighter star to the right --- is known to astronomers as Epsilon Delphini. The Chinese called this little stray Pae Chaou, which means --- ahem --- The Rotten Melon. Personally, I think that name stinks. To some early Christian sects the entire constellation of Delphinus was known as the Cross of Jesus, and Epsilon Delphini itself was known in Arabia by a related name, Al Amud al Salib, The Pillar of the Cross. But the most mysterious names belong to the two brightest stars in the constellation, Alpha and Beta Delphini. They would be the most northwesterly ones. Alpha is known commonly as Sualocin, Beta is called Rotanev. Both were first christened thusly in the Palermo Star Catalogue of 1814. But where did those names come from? The Reverend Thomas W. Webb, an English astronomer in the 19th century, discovered the answer to the mystery: In the early 1800's, the Palermo Observatory was headed by astronomer Giuseppe Piazzi. He's best known for discovering and naming the first asteroid, Ceres. He had an assistant named Niccolo Cacciatore. Cacciatore's Latin name was Nicolaus Venator. Apparently Piazzi, in naming the two stars, reversed the spelling of Nicolaus to Sualocin, and Venator to Rotanev, in this way honoring his assistant and dauphin (successor). Here's an interesting activity I use in class and you can use if you teach. Give the students a blank star chart. Let them draw in their own constellations and create their own stories to go with them. You'd be amazed at the stories they can come up with. Questions or comments? Mark Ritter can be reached here. Posted by Administrator at 2002.08.17 02:36 PM \| Comments (0) The Persieids are Back in Town Comets > Had a shower recently? Think about going outside tonight and taking one in. The peak to the annual Perseid Meteor Shower has arrived and under pretty good conditions. What are these shooting star visitors anyway, you may ask? Our solar system has much more to it than meets the eye. Beside one bright star and all those planets, there are asteroids and comets and a menagerie of other tiny things left over from the creation of the solar system. One of these comets --- Swift-Tuttle by name --- buzzes around the sun in a 130-year orbit that takes it close to Earth's orbit. Unknown to many, it is the source of the Perseid Fireworks Show. Comets shed material like a bad case of dandruff. As these comets made of rock and ice come close to the sun, they get warm. Millions of tons of water and other compounds get boiled off. This evaporation carries with it sandgrain-sized samples of schmutz that travel with the comet in its orbit, getting spread out over the eons into a long train of dirty debris. It is that dross which gives us the spectacular shower. As Earth orbits along nonchalantly it ploughs right through Swift-Tuttle's polluted orbit. Then kaboom zaloom! --- we get hit. When we run into the grit train our combined collision speed is about 40 miles per second! Which is precisely why they light up. Imagine driving down the highway at 40 miles per second when your dog next to you in the passenger seat decides to hang its head out the window. We have a fireball of flaming, charbroiled hot dog. This is the demise that meets the tiny, unsuspecting grains of comet waste as they dive headlong into our atmosphere. Instant meteor. Monday afternoon is when we pass through the thickest part of the river of rubble. Unfortunately our sun makes it rather difficult to see the meteors then. But not to worry! The good side to this is that both Sunday night and Monday night should offer us good showers. The Moon will set early both evenings leaving a dark sky. But the best time to see the shower is --- ahem --- after midnight. Why? Imagine driving your car through the rain. You are traveling forward, the rain drops are falling down from above. But the overall affect is that most of the drops are smacking into the front windshield, not the rear windshield. It's like that with meteors. Before midnight our part of the Earth is like the rear window. Around midnight is when we spin around towards the incoming meteoroids. It is after midnight that, if predictions are correct, we should get about 60 per hour under dark sky conditions. And the Perseids can be beautiful. The big ones burn themselves into your memory forever. Michael Seeds, professor of astronomy at Franklin and Marshall College, has watched them religiously for decades. "I have seen spectacular Perseids," he says, "rushing fireballs flashing colors and breaking into pieces." The Perseids really are a breed apart. Get thee outside to the darkest place you can find with the fullest view of the sky. Lay back and look up. Weather permitting, they will light up all around. Think about making this an annual event for you and your family. The warm summer evenings make it ideal. Says Dr. Seeds, "The most spectacular thing about the Perseids is their dependability. They have returned year after year since I was a little boy and I suppose they will continue for a long time after I am gone." Questions or comments? Mark Ritter can be reached here. Posted by Administrator at 2002.08.10 02:39 PM \| Comments (0) Our Annual Summer Celestial Fireworks Show Comets > It's the time of the summer that meteor lovers love. Our annual summer celestial fireworks show, the Perseid Meteor Shower, has arrived. But rather than just looking up for meteors this year, use this time to get to know the summer skies, too. First, though, a brief background on meteor showers. When comets whiz around the sun, they dump a lot of dust. This debris travels along in pretty much the same orbit as the parent comet. Some of these comet orbits intersect our own orbit. When Earth plunges through a comet's debris train, the dust slams into our atmosphere like bugs on a windshield. The friction with the atmosphere vaporizes the debris in flashes of light that we call meteors. On the days of August 11 and 12, Earth passes through the big chunk of a debris train resulting in a meteor shower. The best time to "shower" will be after midnight early Monday morning when our side of the planet turns into the stream, resulting in the most meteors. A good Perseid peak might give us about 30 meteors an hour, but less where it is light polluted. Unfortunately, you may be unwilling to stay up that late and will be meteor hunting before the midnight hour. Because Perseid sightings will be few and far between for you, this may be a good time to get to know some of the summer sky while you wait. Let's take a quick tour. On the evening of the 11th, a four-day-old crescent Moon will be setting alongside a magnificently bright Venus. This Moon-Venus pose is one of those aesthetic pleasures that happens several times a year, but never ceases to command awe. Try and actually see the "dark" side of the Moon, the non-crescent part. You'll notice it is just slightly lit, allowing you to see the whole disk of the Moon. This is due to "earthshine" which happens when the sun's light reflects off Earth's surface, dimly lighting the surface of the Moon. Venus is about at its brightest now as it swings around the Sun in its orbit, passing us on an inside lane. The brightness of the Evening Star is due to its complete cloud cover. But she isn't covered in clouds made of water like our planet is --- those clouds are made of corrosive sulfuric acid. Find the Big Dipper in the northern skies. Using the stars in the handle as pointers follow an imaginary curve, about one Dipper away, to the bright star Arcturus, a red giant seventy times bigger than the sun. Keep following the curve over into the skies near the setting Moon to a big bright blue star called Spica. Spica spews out more energy in a minute than the sun does all day. Better look early, though; Spica sets about 9 o'clock. Directly overhead later in the evening is the Summer Triangle, starring Deneb, Altair and bright blue Vega, the three of which make up the edges of the triangle. Each has an invisible binary companion star orbiting with it. It's later in the evening that the Milky Way shows up in full glory, stretching from the south to the north. Those with binoculars can search the skies of the southern Milky Way and easily pick out abundant nebulae and star clusters. The Perseid Shower is a great opportunity to see some really stunning meteors, to be sure. But use the night to get familiar with the rest of the spectacular summer sky, as well! Questions or comments? Mark Ritter can be reached here. Posted by Administrator at 2002.08. 3 02:40 PM \| Comments (0)
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