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Where Did That Element Come From?

Science >

School starts back in the next couple of weeks for people hither and yon. And some readers of this column may find themselves taking ... A DREADED SCIENCE CLASS!!! In many a science class there hangs the infamous Periodic Table. Here's a question for you: Do you know where all those elements on the Periodic Table came from? Here's an answer: Nearly all were forged in stars.

When the universe was just a newborn the Periodic Table had just two boxes on it: hydrogen and helium. That's it. There was no gold or silver or carbon, not even neodymium! Chemistry class back then lasted only one day.

It wasn't until the first stars were formed that the Periodic Table began to take shape.

Stars are enormous collections of hydrogen and helium gas, they are gaseous works of art. When you get enough hydrogen and helium together, its gravity has enough pull inward to shape it into a ball. But it's at the center of this ball, the core, where the action is.

At the core, hydrogen is pushed together with exceedingly tremendous force. It's a little complicated, but what essentially happens is that the tiny hydrogen nuclei, which usually act like normal brothers and sisters and stay far away from each other, grudgingly join to make a nucleus of helium. This fusion reaction releases an enormous amount of energy, energy which keeps the ball of gas pushed out and which gives the star its "shine."

But when the core starts to run out of energy --- as the hydrogen gets depleted --- gravity starts to win and pulls the star inward. Soon there is enough new pressure to squish the helium nuclei together to make carbon nuclei!

You can see a pattern here. When there is a lot of pressure and energy available you can fuse little nuclei together to make bigger nuclei. And the cosmic Periodic Table gradually picks up extra members.

What's more, when a sun-like star reaches the end of its life it sloughs off its outer layers into space, spewing the newly formed elements all over the place.

Big, big stars, stars ten or twenty times more massive than our sun, can use all their gargantuan pressure to make a lot more elements down near their core, elements like silicon and magnesium and iron.

But the laws of nature say they must stop at iron. Stars big enough to get this far can press all they want and they're not going to make anything bigger --- yet.

The stubborn, newly formed iron just sort of sits there in the core and refuses to fuse. With no energy forming now at the center to push out, gravity gains the upper hand again, but now wins the push-pull game once and for all.

In a rather complicated process, the core actually collapses, causing the whole star to explode violently in a supernova explosion. These bad boys pack enough energy to make the whole rest of the Periodic Table beyond iron.

The final beauty of this is that the explosion itself sends elements all over the galactic neighborhood for billions of miles.

Get enough stars doing this and after awhile you've got a mess all over the place. But it is a magnificent mess. This debris can be used in the building of planets, in the formation of water, in the creation of atmospheres, and as the raw materials for building critters like you and me.

Next time you see a Periodic Table try not to wince. It is a symbol and reminder of a wonderfully designed universe.

Mark Ritter teaches astronomy and chemistry, and actually enjoys both! You can reach him here.

Posted by Administrator at 2001.08.18 08:17 AM | Comments (0)

That Time of Year Again

Comets >

You may have seen one of them already. They started arriving in the late part of July and most will show up with their friends in the wee hours of the morning this coming Sunday. They have arrived for their annual shower. No, it's not Uncle Bob and his family. These are the Perseid meteors.

But what are they and how do they get here. It's thinking cap time!

We'll start with a comet, but not that bright object with a 100-million-mile tail. That classic image of a comet exists for only part of its life. Most of its time is spent out in the dark, cold depths of the outer solar system. There a comet is nothing much more dramatic than what astronomers call a "dirty snowball."

These miles-wide piles of snowy schmutz began their lives as leftovers from the creation of the solar system, orbiting the sun often at distances way beyond Pluto.

Once in a blue moon one is tugged toward the sun by a passing star or by interaction with another heavenly body and it then begins a long (emphasis on long) journey in a new orbit which takes it into the inner solar system. Once they come within Jupiter's orbit, the sun can warm them up enough that things start happening.

The ices start to evaporate off and the once sedate snowball starts firing off geysers of water vapor. When this happens the dirty part of the comet sloughs off, too.

But the dirty stuff doesn't all just zip out into deep space, oh no! A lot of it stays close to home, traveling the same orbit as its parent.

After many, many years of this the comet develops a following, so to speak, of tiny little particles of crud, some leading the comet around the sun, some of it following. This tiny train of debris can stretch out for millions and millions of miles.

Now what if the orbit of our comet and its offspring just happens to cross the orbit of earth? That, my friend, means potential fireworks.

Imagine being one of these tiny grains of comet stuff. You're sailing along, nearing the sun in your orbit around the star, business as usual. Although you can see your parent comet a b-zillion miles away, around you are a lot of your fellow rejects, particles which suffered the same fate of cometary banishment as you have.

Then you realize that that big blue planet, the third one from the sun that was always off in the distance on your other visits through, isn't so far away this time. In fact, as you pick up speed --- as all things do on their close approach around the sun --- you see you also happen to be speeding toward a collision with that blue rock.

Then it happens. Sadly, you both cross orbits at exactly the same moment. You speed directly into the planet's atmosphere traveling at over 20 miles per second. In the twinkling of an eye, your slam into the air, lighting it up in a brilliant flash --- and you vaporize. You were among the oldest and most well preserved "stuff" in the solar system and in an instant you are no more.

If you get a chance to see some the Perseid meteors, do. Particles that have strayed from the main trail will be smacking into us for a couple weeks before and after Sunday. But in the wee hours next Sunday morning we pass through the thickest part of the debris stream and then is the best chance of seeing some fireworks.

Until next time, clear skies!

Posted by Administrator at 2001.08. 4 08:18 AM | Comments (0)



Looking for something?	« July 2001 \| Main \| September 2001 » Where Did That Element Come From? Science > School starts back in the next couple of weeks for people hither and yon. And some readers of this column may find themselves taking ... A DREADED SCIENCE CLASS!!! In many a science class there hangs the infamous Periodic Table. Here's a question for you: Do you know where all those elements on the Periodic Table came from? Here's an answer: Nearly all were forged in stars. When the universe was just a newborn the Periodic Table had just two boxes on it: hydrogen and helium. That's it. There was no gold or silver or carbon, not even neodymium! Chemistry class back then lasted only one day. It wasn't until the first stars were formed that the Periodic Table began to take shape. Stars are enormous collections of hydrogen and helium gas, they are gaseous works of art. When you get enough hydrogen and helium together, its gravity has enough pull inward to shape it into a ball. But it's at the center of this ball, the core, where the action is. At the core, hydrogen is pushed together with exceedingly tremendous force. It's a little complicated, but what essentially happens is that the tiny hydrogen nuclei, which usually act like normal brothers and sisters and stay far away from each other, grudgingly join to make a nucleus of helium. This fusion reaction releases an enormous amount of energy, energy which keeps the ball of gas pushed out and which gives the star its "shine." But when the core starts to run out of energy --- as the hydrogen gets depleted --- gravity starts to win and pulls the star inward. Soon there is enough new pressure to squish the helium nuclei together to make carbon nuclei! You can see a pattern here. When there is a lot of pressure and energy available you can fuse little nuclei together to make bigger nuclei. And the cosmic Periodic Table gradually picks up extra members. What's more, when a sun-like star reaches the end of its life it sloughs off its outer layers into space, spewing the newly formed elements all over the place. Big, big stars, stars ten or twenty times more massive than our sun, can use all their gargantuan pressure to make a lot more elements down near their core, elements like silicon and magnesium and iron. But the laws of nature say they must stop at iron. Stars big enough to get this far can press all they want and they're not going to make anything bigger --- yet. The stubborn, newly formed iron just sort of sits there in the core and refuses to fuse. With no energy forming now at the center to push out, gravity gains the upper hand again, but now wins the push-pull game once and for all. In a rather complicated process, the core actually collapses, causing the whole star to explode violently in a supernova explosion. These bad boys pack enough energy to make the whole rest of the Periodic Table beyond iron. The final beauty of this is that the explosion itself sends elements all over the galactic neighborhood for billions of miles. Get enough stars doing this and after awhile you've got a mess all over the place. But it is a magnificent mess. This debris can be used in the building of planets, in the formation of water, in the creation of atmospheres, and as the raw materials for building critters like you and me. Next time you see a Periodic Table try not to wince. It is a symbol and reminder of a wonderfully designed universe. Mark Ritter teaches astronomy and chemistry, and actually enjoys both! You can reach him here. Posted by Administrator at 2001.08.18 08:17 AM \| Comments (0) That Time of Year Again Comets > You may have seen one of them already. They started arriving in the late part of July and most will show up with their friends in the wee hours of the morning this coming Sunday. They have arrived for their annual shower. No, it's not Uncle Bob and his family. These are the Perseid meteors. But what are they and how do they get here. It's thinking cap time! We'll start with a comet, but not that bright object with a 100-million-mile tail. That classic image of a comet exists for only part of its life. Most of its time is spent out in the dark, cold depths of the outer solar system. There a comet is nothing much more dramatic than what astronomers call a "dirty snowball." These miles-wide piles of snowy schmutz began their lives as leftovers from the creation of the solar system, orbiting the sun often at distances way beyond Pluto. Once in a blue moon one is tugged toward the sun by a passing star or by interaction with another heavenly body and it then begins a long (emphasis on long) journey in a new orbit which takes it into the inner solar system. Once they come within Jupiter's orbit, the sun can warm them up enough that things start happening. The ices start to evaporate off and the once sedate snowball starts firing off geysers of water vapor. When this happens the dirty part of the comet sloughs off, too. But the dirty stuff doesn't all just zip out into deep space, oh no! A lot of it stays close to home, traveling the same orbit as its parent. After many, many years of this the comet develops a following, so to speak, of tiny little particles of crud, some leading the comet around the sun, some of it following. This tiny train of debris can stretch out for millions and millions of miles. Now what if the orbit of our comet and its offspring just happens to cross the orbit of earth? That, my friend, means potential fireworks. Imagine being one of these tiny grains of comet stuff. You're sailing along, nearing the sun in your orbit around the star, business as usual. Although you can see your parent comet a b-zillion miles away, around you are a lot of your fellow rejects, particles which suffered the same fate of cometary banishment as you have. Then you realize that that big blue planet, the third one from the sun that was always off in the distance on your other visits through, isn't so far away this time. In fact, as you pick up speed --- as all things do on their close approach around the sun --- you see you also happen to be speeding toward a collision with that blue rock. Then it happens. Sadly, you both cross orbits at exactly the same moment. You speed directly into the planet's atmosphere traveling at over 20 miles per second. In the twinkling of an eye, your slam into the air, lighting it up in a brilliant flash --- and you vaporize. You were among the oldest and most well preserved "stuff" in the solar system and in an instant you are no more. If you get a chance to see some the Perseid meteors, do. Particles that have strayed from the main trail will be smacking into us for a couple weeks before and after Sunday. But in the wee hours next Sunday morning we pass through the thickest part of the debris stream and then is the best chance of seeing some fireworks. Until next time, clear skies! Posted by Administrator at 2001.08. 4 08:18 AM \| Comments (0)
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