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Comets: From Doomsayers to Delights (Part 3)

Comets >

Two comets are passing through our neighborhood right now. Haven't seen them yet? That's OK --- it is a challenge. The two, scientifically christened NEAT (C/2001 Q4) and LINEAR (C/2002 T7), are visible now, but not to everyone everywhere.

Normally a comet takes the name of its human discoverer. Most of these people are just backyard astronomers scanning the skies and enjoying the great sites. Occasionally one of these amateurs picks up a fuzzy image not found on the star charts. It is an incoming comet, taking us by surprise.

The comet is then named for this person: hence, Comets Hale/Bopp, Hyakutake, West, etc. Nowadays many are found via special telescopes set up to scan the skies for new objects. The newfound comets are then named for these automated sky-survey programs. In the case of the two new comets, they are named for the Near-Earth Asteroid Tracking system (NEAT), and Lincoln Laboratory Near Earth Asteroid Research (LINEAR).

Now finally, after being discovered years ago, these two have finally arrived. But it's turning out that they're ... ahem ... not as spectacular as hoped for. Alas!

Anytime a new comet pops up sky lovers explode in a big bang of wishful thinking. Will we have a tremendous display as we did with Hale-Bopp and Hyakutake just years ago, brighter than the brightest stars, and tails that stretch across the entire sky? Oh boy!

Once we slap ourselves in the face and allow the sober thoughts to take over we must face the reality that most comets are not exactly show-stoppers.

For example, if they are far away when they pass through the inner solar system they may be so dim as to sneak by virtually unseen. If they don't have enough volatiles (stuff that evaporates off the comet body), they won't make a legendary tail.

If the nucleus of the comet --- the original icy rock --- is too small, then it might produce only a small, wimpy tail. Moreover, the comet may have already gone through so many times that all the ice has vaporized away, leaving us with nothing much more than a sojourning rock in space. Ho hum.

Our latest visitors seem to be asking for more than just the naked eye to be seen, unfortunately. For us in Southern California, the easiest to look for is the NEAT comet. Go out tonight about 9 o'clock. NEAT is between Jupiter, the bright planet in the higher southwest sky, and Venus, the bright planet near the western horizon. If you are not in a dark area, scan the sky there with a pair of binoculars until you see the lone fuzzy object. It will continue to rise higher in the sky in the next few weeks.

The other comet, LINEAR, is playing hide and sneak at the moment. It is creeping through the solar system from down under us, from the southside of the planet. Those earthlings literally “down under" have been able to see it for a while.

LINEAR will appear for us --- we hope --- toward the end of May and the beginning of June in the southwest skies. The darker the sky and the flatter your southwest horizon, the easier it will be to see. You can get good sky maps at either skyandtel.com or astronomy.com to follow them both.

What happens to comets once they parade through our part of the realm?

Some never make it through. The daredevils amongst them come too close to the sun and go out in a blaze of glory by crashing into our star.

Others, heavily influenced by Jupiter's or Saturn's intense gravity, get forced from their old, very long orbits into new, shorter ones. As a result they now become local solar system inhabitants and return to our inner system much more often.

Jupiter also has a nasty habit of using its great gravity to eat them whole, or throw these poor creatures right out of the solar system altogether, never ever to return.

Many comets return over and over again, but lose a lot of ice each time. Eventually they might breakup altogether, losing their comet nature and ending up as no more than a dysfunctional family of rocks orbiting the sun.

Finally, and frightfully, some may actually strike here. Earth's orbit is in the very path of some comets as they make their journeys toward the sun. Jupiter, our big brother, protects us from most. But some do hit home.

The prime suspect of the extinction of the dinosaurs was a comet just tens of miles across that hit on the Yucatan Peninsula about 65 million years ago. When a rock only that big hits us, we have a very, very bad day ahead of us. It fills the atmosphere with dust, sets fires worldwide, creates massive tsunamis, poisons the rain, derails the food chain, and so on. Big, complex critters go extinct.

But comet strikes aren't all bad. One theory has it that the ice-laden comets provided the water that covers our planet, a great blessing if there ever was one.

Comets, destructive or life-giving, great spectacles or duds, are an important part of our beautifully designed star system.

Posted by Administrator at 2004.05.15 12:35 PM | Comments (0)

Comets: From Doomsayers to Delights (Part 2)

Comets >

In our previous episode we saw how comets have played a significant cultural role for millennia, usually by scaring people half to death. Only a couple centuries ago was it realized that they were not messengers from the gods, but mere solar system bodies, kin to planets and asteroids. But what exactly were they, where were they from, and why did they have that funny tail? Let's take a look back in the way distant past to find out.

A long time ago a star was born. Around baby Sol was a colossal cloudy disk of scattered building material: rocks, gases, and ices of all kinds stretching out for billions of miles. In some areas in the disk --- eddies in our great swirling whirlpool --- planets were created as gravity swept together some of the dust and gases.

Planets near the hot new sun could only form from rocky material. Far away where it was much colder the newly forming outer planets could use ices and gases as well as the rocky stuff for bulking up their mass.

Way off in the distance, beyond Neptune's orbit, the debris was spread so thin it couldn't get it together to form planets. The original building blocks of the solar system remain there untouched even today in what is called the Kuiper Belt.

Some of the paraphernalia that was being collected into planets were actually evicted. Planets, because of their great gravity, can actually fling poor passing icy rocks right out of the solar system. Much thrown off debris resides in an unimaginably vast and very distant sphere around the sun called the Oort Cloud. This giant nebula of tenuous dirty ice extends nearly a third of the way to the nearest star.

Our comets come from these two reservoirs. Short-period comets, those that come and go quickly and can return in just dozens of years probably come from the Kuiper Belt. The long-period comets, some of which pass through our neighborhood never to return, are from the Oort Cloud.

So how do they get here? Why rouses them to leave their sleepy, dark, distant abode?

Occasionally a few of these ice rocks collide with each other and get knocked towards the sun. Or, possibly, out in the Oort Cloud, a star may pass close by disrupting the orbits of some of these critters and in they fall.
What happens next is what most of us know as the traditional comet, tail and all.

As this "dirty snowball" makes its way into the solar system proper, it begins to warm. By the time it reaches about the orbit of Mars, some of the so-called volatiles --- substances that can easily evaporate --- start to turn from solid to gas.

This doesn't bode well for the comet's constitution. As the volatiles, including water ice, boil off they carry away some of the dirt as well. The escaping gases and dirt expand out for millions of miles. This would be nothing much more than a vast smoggy sort of atmosphere if it weren't for that sun!

The sun spews off photons of light, of course, but also atomic particles in a phenomenon called the solar wind. Both the light and the wind work together to blow the comet's atmosphere away. This, my friends, produces the tail of the comet.

Consequently the tail, which gives the illusion that the comet is racing through the night sky, is always pointing away from the sun. Even as the comet steers round the sun and back towards the outer worlds, the tail points away. As a result, the tail can actually be out in front of the comet on its trip outward.

Unfortunately, all comets do not perform as advertised. Some have little ice left after coming by so often, so they have little tail material and are rather unspectacular. Some, being loosely held together, actually split up into pieces as they head around the sun.

What will our two visitor comets be like by the end of the month, our best chance to see them? Will they be Hale-Bopps or Big Flops. We'll wait, hope, and see.

Next time: Who these two visitors are, and the fate that awaits comets ...

Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com.

Posted by Administrator at 2004.05. 2 12:36 PM | Comments (0)



Looking for something?	« April 2004 \| Main \| June 2004 » Comets: From Doomsayers to Delights (Part 3) Comets > Two comets are passing through our neighborhood right now. Haven't seen them yet? That's OK --- it is a challenge. The two, scientifically christened NEAT (C/2001 Q4) and LINEAR (C/2002 T7), are visible now, but not to everyone everywhere. Normally a comet takes the name of its human discoverer. Most of these people are just backyard astronomers scanning the skies and enjoying the great sites. Occasionally one of these amateurs picks up a fuzzy image not found on the star charts. It is an incoming comet, taking us by surprise. The comet is then named for this person: hence, Comets Hale/Bopp, Hyakutake, West, etc. Nowadays many are found via special telescopes set up to scan the skies for new objects. The newfound comets are then named for these automated sky-survey programs. In the case of the two new comets, they are named for the Near-Earth Asteroid Tracking system (NEAT), and Lincoln Laboratory Near Earth Asteroid Research (LINEAR). Now finally, after being discovered years ago, these two have finally arrived. But it's turning out that they're ... ahem ... not as spectacular as hoped for. Alas! Anytime a new comet pops up sky lovers explode in a big bang of wishful thinking. Will we have a tremendous display as we did with Hale-Bopp and Hyakutake just years ago, brighter than the brightest stars, and tails that stretch across the entire sky? Oh boy! Once we slap ourselves in the face and allow the sober thoughts to take over we must face the reality that most comets are not exactly show-stoppers. For example, if they are far away when they pass through the inner solar system they may be so dim as to sneak by virtually unseen. If they don't have enough volatiles (stuff that evaporates off the comet body), they won't make a legendary tail. If the nucleus of the comet --- the original icy rock --- is too small, then it might produce only a small, wimpy tail. Moreover, the comet may have already gone through so many times that all the ice has vaporized away, leaving us with nothing much more than a sojourning rock in space. Ho hum. Our latest visitors seem to be asking for more than just the naked eye to be seen, unfortunately. For us in Southern California, the easiest to look for is the NEAT comet. Go out tonight about 9 o'clock. NEAT is between Jupiter, the bright planet in the higher southwest sky, and Venus, the bright planet near the western horizon. If you are not in a dark area, scan the sky there with a pair of binoculars until you see the lone fuzzy object. It will continue to rise higher in the sky in the next few weeks. The other comet, LINEAR, is playing hide and sneak at the moment. It is creeping through the solar system from down under us, from the southside of the planet. Those earthlings literally “down under" have been able to see it for a while. LINEAR will appear for us --- we hope --- toward the end of May and the beginning of June in the southwest skies. The darker the sky and the flatter your southwest horizon, the easier it will be to see. You can get good sky maps at either skyandtel.com or astronomy.com to follow them both. What happens to comets once they parade through our part of the realm? Some never make it through. The daredevils amongst them come too close to the sun and go out in a blaze of glory by crashing into our star. Others, heavily influenced by Jupiter's or Saturn's intense gravity, get forced from their old, very long orbits into new, shorter ones. As a result they now become local solar system inhabitants and return to our inner system much more often. Jupiter also has a nasty habit of using its great gravity to eat them whole, or throw these poor creatures right out of the solar system altogether, never ever to return. Many comets return over and over again, but lose a lot of ice each time. Eventually they might breakup altogether, losing their comet nature and ending up as no more than a dysfunctional family of rocks orbiting the sun. Finally, and frightfully, some may actually strike here. Earth's orbit is in the very path of some comets as they make their journeys toward the sun. Jupiter, our big brother, protects us from most. But some do hit home. The prime suspect of the extinction of the dinosaurs was a comet just tens of miles across that hit on the Yucatan Peninsula about 65 million years ago. When a rock only that big hits us, we have a very, very bad day ahead of us. It fills the atmosphere with dust, sets fires worldwide, creates massive tsunamis, poisons the rain, derails the food chain, and so on. Big, complex critters go extinct. But comet strikes aren't all bad. One theory has it that the ice-laden comets provided the water that covers our planet, a great blessing if there ever was one. Comets, destructive or life-giving, great spectacles or duds, are an important part of our beautifully designed star system. Posted by Administrator at 2004.05.15 12:35 PM \| Comments (0) Comets: From Doomsayers to Delights (Part 2) Comets > In our previous episode we saw how comets have played a significant cultural role for millennia, usually by scaring people half to death. Only a couple centuries ago was it realized that they were not messengers from the gods, but mere solar system bodies, kin to planets and asteroids. But what exactly were they, where were they from, and why did they have that funny tail? Let's take a look back in the way distant past to find out. A long time ago a star was born. Around baby Sol was a colossal cloudy disk of scattered building material: rocks, gases, and ices of all kinds stretching out for billions of miles. In some areas in the disk --- eddies in our great swirling whirlpool --- planets were created as gravity swept together some of the dust and gases. Planets near the hot new sun could only form from rocky material. Far away where it was much colder the newly forming outer planets could use ices and gases as well as the rocky stuff for bulking up their mass. Way off in the distance, beyond Neptune's orbit, the debris was spread so thin it couldn't get it together to form planets. The original building blocks of the solar system remain there untouched even today in what is called the Kuiper Belt. Some of the paraphernalia that was being collected into planets were actually evicted. Planets, because of their great gravity, can actually fling poor passing icy rocks right out of the solar system. Much thrown off debris resides in an unimaginably vast and very distant sphere around the sun called the Oort Cloud. This giant nebula of tenuous dirty ice extends nearly a third of the way to the nearest star. Our comets come from these two reservoirs. Short-period comets, those that come and go quickly and can return in just dozens of years probably come from the Kuiper Belt. The long-period comets, some of which pass through our neighborhood never to return, are from the Oort Cloud. So how do they get here? Why rouses them to leave their sleepy, dark, distant abode? Occasionally a few of these ice rocks collide with each other and get knocked towards the sun. Or, possibly, out in the Oort Cloud, a star may pass close by disrupting the orbits of some of these critters and in they fall. What happens next is what most of us know as the traditional comet, tail and all. As this "dirty snowball" makes its way into the solar system proper, it begins to warm. By the time it reaches about the orbit of Mars, some of the so-called volatiles --- substances that can easily evaporate --- start to turn from solid to gas. This doesn't bode well for the comet's constitution. As the volatiles, including water ice, boil off they carry away some of the dirt as well. The escaping gases and dirt expand out for millions of miles. This would be nothing much more than a vast smoggy sort of atmosphere if it weren't for that sun! The sun spews off photons of light, of course, but also atomic particles in a phenomenon called the solar wind. Both the light and the wind work together to blow the comet's atmosphere away. This, my friends, produces the tail of the comet. Consequently the tail, which gives the illusion that the comet is racing through the night sky, is always pointing away from the sun. Even as the comet steers round the sun and back towards the outer worlds, the tail points away. As a result, the tail can actually be out in front of the comet on its trip outward. Unfortunately, all comets do not perform as advertised. Some have little ice left after coming by so often, so they have little tail material and are rather unspectacular. Some, being loosely held together, actually split up into pieces as they head around the sun. What will our two visitor comets be like by the end of the month, our best chance to see them? Will they be Hale-Bopps or Big Flops. We'll wait, hope, and see. Next time: Who these two visitors are, and the fate that awaits comets ... Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com. Posted by Administrator at 2004.05. 2 12:36 PM \| Comments (0)
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