[ FirstLight Astronomy Club ] The Skies Above

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Probing the Lord of the Rings

The Solar System >

Saturn, the Beauty Queen of the Solar System, is nearly on the other side of the sun from us now. Only diehard sycophants will try and scope it out as it sets soon after the sun in the western skies, its ring system nearly lost in the twilight and blurring heat waves of the horizon.

Ironically, though, Saturn is about to make headlines. This Wednesday evening a spacecraft that left Earth back in 1997 is finally going to arrive at Saturn and begin a 4-year orbiting mission to help us know the whole place a whole lot better.

Named Cassini-Huygens this multinational effort involving over 250 scientists will complete a 2.2-billion-mile journey and get "inserted" into orbit around the Ringed One.

Cassini-Huygens is named for two 17th century astronomers who made some of the first great discoveries concerning Saturn. It was Galileo, through his tiny telescope, who first saw what he thought were two very big, very close moons around Saturn. But it took the Dutch scientist Christiaan Huygens, with a better scope, to see that these two freakish moons were really both sides of the Saturnian ring system, a sight we have all come to know and be in awe of.

The Italian-French astronomer Jean Dominique Cassini, a contemporary of Huygens, could resolve a narrow gap in the ring system, since then called the Cassini Division. Nowadays, even inexpensive backyard telescopes --- on a clear, steady night --- can see this striking black collar around the ring. Cassini also discovered four of the moons around Saturn, which presently number thirty-one.

Named in their honor, this 3-billion-dollar orbiting laboratory is actually two spacecraft in one. The main lab, Cassini, will spend the next 4 years orbiting the planet more than 70 times, armed with 12 different instruments to pour data back to Earth at a rate of over a gigabyte a day. Huygens, a probe, will be jettisoned from the main craft on Christmas Eve to fall gracefully --- we hope! --- down onto the great moon, Titan, sucking up information the whole way.

Titan is an utter curiosity as moons go. Discovered by Huygens himself, Titan is the only planetary moon with a substantial atmosphere. Below this thick, opaque gaseous covering may be lakes of methane. It is the great hope of planetary scientists that the Huygens probe will actually land safely on the mysterious surface of Titan next January.

But first things first.

Wednesday evening, if all goes well, the Cassini-Huygens combo will be taken prisoner and held in an orbit around Saturn. At the moment it is traveling thousands of miles an hour too fast to get "caught" by Saturn. At this rate it will just fly by Saturn and into the outer solar system. That's why this time is so critical. The spacecraft needs to slow down, and so must fire its main engines "backwards" for a while --- 96 minutes to be precise --- to act as a flaming brake system.

This will decelerate it just enough so that Saturn's gravity will now control it and Cassini-Huygens will become the latest satellite to orbit the Lord of the Rings. Sadly, several missions to Mars in the last few years that were going through similar approaches met with disastrous ends and are a constant reminder of why this time is so filled with angst.

Part of the exciting yet dangerous aspect to this particular slow-down is the fact that Cassini will have to pass through the vast ring system itself. You see, there is a teensy-weensy gap right between the F and G Rings through which Cassini is being sent.

Making it to the gap is not the scary part; that's a no-brainer for the rocket scientists at JPL and NASA. It's what may be in the gap that gets the blood pressure up. If Cassini hits anything at that speed passing through this seemingly empty gap, it's curtains for the spacecraft. Tiny rock plus high-speed spacecraft equals disaster. And more than a decade of research and time and money wasted.

This whole scenario on Wednesday is not unlike flying on a plane. The ride itself is relatively safe. It's the take-off and landing that test one's faith. The take-off of Cassini-Huygens went fine. The last 7 years have been picture perfect. Let us hope that our "landing" this week goes without a hitch. If so, the next four years could be filled with spectacular images and discoveries the likes of which humans have never, ever seen.

For more information than you may ever need about this mission, go to Cassini's website at http://saturn.jpl.nasa.gov.

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

Images courtesy NASA.

Posted by Administrator at 2004.06.27 12:28 PM | Comments (0)

Elliptical Reasoning

The Solar System >

This week is full of celestial phenomena centered on the paths of heavenly bodies circling each other. It's my job to try and put a positive spin on it all.

It was Johannes Kepler way back in the 16th century who first tried to explain the complexities of how the planets go around the sun. Back then, when the philosophy of Aristotle still held a grip around the neck of scientific thinking, it was believed all planets traveled in perfectly circular orbits. And it was Kepler who was destined to discover that heavenly bodies did not circuit the sun in circles --- but in ellipses.

We've all seen ellipses; they are all over the place. The easiest way to see one is to look obliquely at the top of a cup or glass. Look at the lip from directly above; that, of course, would be a circle. But move your point of view from directly above to some other angle and the circle seems to squash. That is an ellipse. Look at the top of the cup from an angle almost level with it and you have one squished circle, or, in astrospeak, one eccentric ellipse.

Kepler, through a lot of intense study and to the absolute surprise of many, discovered that planets journey in ellipses. In fact, all orbiting bodies trace out an ellipse, some nearly circular, some more eccentric.

The Moon travels in an elliptical orbit, too, one that sometimes takes it closer to us, sometimes further. The close approach is called perigee, a word loosely translated from the Greek as "near the earth."

This week, though, on the 17th, the position of the Moon in its monthly swing around the earth will be at apogee, its greatest distance from us. Apogee isn't that much farther away than perigee, but it does make a difference in one special astronomical phenomenon. You see, Thursday the 17th is also the day the Moon is at the point of its orbit when it passes between us and the sun --- New Moon.

If the Moon happened to be passing exactly between the sun and us (it just misses this month), then someone on Earth would be getting a solar eclipse, but not the best one. When the Moon is at apogee it can't quite cover the Sun completely and we get what is called an annular eclipse, a rather disappointing partial covering in which the sun outlines the tinier Moon in a giant, blindingly bright ring.

The orbits of the planets also give us times called conjunctions, a time when three bodies are all lined up. Venus just finished its newsworthy "inferior" conjunction when it traveled directly between us and the Sun. This Friday Mercury will be in the part of its orbit when it is on the farthest side of the Sun in what is called "superior" conjunction.

On Saturday there is an event that you can actually witness, but you will need at least a pair of binoculars to see it. Three of Jupiter's four moons --- Io, Europa, and Callisto --- will be all bunched up together on one side of the great planet.

First discovered by Galileo, a contemporary of Kepler, their existence was a further proof that the old Aristotelian ways were on the way out. Before Galileo spied these four little moons, now called the Galilean satellites, it was believed that everything orbited around the earth. Here, clearly, were tiny heavenly bodies that orbited round something else. You yourself can see their movement over just hours of watching. Or you can come back out Sunday night and see a whole different layout of the four.

Finally, and most important for teenagers, our own orbit is in a special place next Sunday evening at about 6 o'clock. It is then that we are in that part of our path around the sun when we are tilted most toward our sun. At the beginning of next week we experience the longest daytime, the shortest nighttime. Yes, it is the special sacred time in America called the First Day of Summer.

Until next time, clear skies!

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

Posted by Administrator at 2004.06.12 12:30 PM | Comments (0)

Mass Transit

The Solar System >

On June 8, for everyone on this planet who can see the skies, Venus will pass in front of the sun for the first time since 1882. It is one of those phenomena for which nearly everyone on the planet cares ... well ... cares little or nothing quite frankly.

But for a lover of the skies things are different. He or she gets the same warm tingly feeling of excitement as a birdwatcher that finally spots that rare Hawaiian honeycreeper in the rain forest on the windward side of Maui's Haleakala Crater. It almost never happens in a lifetime.

Did I say everyone would be able to see it? That was sort of not altogether entirely true. Of all the places on earth, the only major locations to miss it are the southern tip of South America, and tiny New Zealand. And --- I can barely bring myself to write this --- North America west of the Rockies will miss it, too. Woe is us!!!

As nearly the entire human race gets a chance to experience this cosmic dance, we are literally left in the dark. We will miss all four "contacts" of the tiny planet as it silhouettes across the great face of the sun. There is no chance for us to see the famous "blackdrop affect," the time when the petite planet's disk arrives at the edge of the giant sun, and the shadow of Venus seems to reach out and touch the limb of our star.

So let's make the most of it from where we are, OK?

The reason Venus travels in front of the sun at all is, of course, because the planet is in an orbit between the sun and us. But the laws of physics are set up so that she takes a mere 224 of our days to travel around the sun once --- a venerian year --- so this passing in front, this "transit," should happen much more often, correct?

Earth's and Venus' orbits are slightly tipped relative to each other so Venus doesn't always pass directly in front of the sun as she passes us on her inside lane. Most of the time the cloudy planet moves by just over or just under the sun. You may recall that the Moon's orbit doesn't always take it directly in front of the Sun, either, causing the famous solar eclipse. Venus' transit really is a rare event; no one alive has seen one.

It's time to use the imagination to see the Big Picture and put it all in perspective. Venus is about to pass in front of the Sun, in just days. You may have noticed Venus already; she's the extremely bright planet in the west after the sun goes down. The more observant among us may have noticed Venus getting lower and lower in the skies over the last month or so.

Go outside just after sunset and look to the west. Make sure no one is watching you, then tilt your head far to the right to get a better idea of Venus' orbital path as she passes by us. Imagine that Venus is moving in its orbit toward the just set sun. Watch in the next days as the Evening Star gets closer and closer to the sun, finally disappearing into its brightness in the day or two before the transit.

Though we won't be able to see the crossing, we can see it live over the internet. Check out The Exploratorium's excellent site.

After Venus passes by to the "other side" of the sun, we will soon be able to see her again! But now she will rise before the sun rises in the morning, and now she will be called the Morning Star. Watch in the coming weeks as Venus rises earlier and earlier, higher and higher.

Yes, we are completely left out of this transit, but mark your calendars for June 5, 2012. Through another coordination of the orbits of our planets, we in Southern California get our chance to see a transit that afternoon. But you'd better see it then because it will have to last a lifetime --- the next one isn't until 2117!

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

Posted by Administrator at 2004.06. 6 12:32 PM | Comments (0)



Looking for something?	« May 2004 \| Main \| July 2004 » Probing the Lord of the Rings The Solar System > Saturn, the Beauty Queen of the Solar System, is nearly on the other side of the sun from us now. Only diehard sycophants will try and scope it out as it sets soon after the sun in the western skies, its ring system nearly lost in the twilight and blurring heat waves of the horizon. Ironically, though, Saturn is about to make headlines. This Wednesday evening a spacecraft that left Earth back in 1997 is finally going to arrive at Saturn and begin a 4-year orbiting mission to help us know the whole place a whole lot better. Named Cassini-Huygens this multinational effort involving over 250 scientists will complete a 2.2-billion-mile journey and get "inserted" into orbit around the Ringed One. Cassini-Huygens is named for two 17th century astronomers who made some of the first great discoveries concerning Saturn. It was Galileo, through his tiny telescope, who first saw what he thought were two very big, very close moons around Saturn. But it took the Dutch scientist Christiaan Huygens, with a better scope, to see that these two freakish moons were really both sides of the Saturnian ring system, a sight we have all come to know and be in awe of. The Italian-French astronomer Jean Dominique Cassini, a contemporary of Huygens, could resolve a narrow gap in the ring system, since then called the Cassini Division. Nowadays, even inexpensive backyard telescopes --- on a clear, steady night --- can see this striking black collar around the ring. Cassini also discovered four of the moons around Saturn, which presently number thirty-one. Named in their honor, this 3-billion-dollar orbiting laboratory is actually two spacecraft in one. The main lab, Cassini, will spend the next 4 years orbiting the planet more than 70 times, armed with 12 different instruments to pour data back to Earth at a rate of over a gigabyte a day. Huygens, a probe, will be jettisoned from the main craft on Christmas Eve to fall gracefully --- we hope! --- down onto the great moon, Titan, sucking up information the whole way. Titan is an utter curiosity as moons go. Discovered by Huygens himself, Titan is the only planetary moon with a substantial atmosphere. Below this thick, opaque gaseous covering may be lakes of methane. It is the great hope of planetary scientists that the Huygens probe will actually land safely on the mysterious surface of Titan next January. But first things first. Wednesday evening, if all goes well, the Cassini-Huygens combo will be taken prisoner and held in an orbit around Saturn. At the moment it is traveling thousands of miles an hour too fast to get "caught" by Saturn. At this rate it will just fly by Saturn and into the outer solar system. That's why this time is so critical. The spacecraft needs to slow down, and so must fire its main engines "backwards" for a while --- 96 minutes to be precise --- to act as a flaming brake system. This will decelerate it just enough so that Saturn's gravity will now control it and Cassini-Huygens will become the latest satellite to orbit the Lord of the Rings. Sadly, several missions to Mars in the last few years that were going through similar approaches met with disastrous ends and are a constant reminder of why this time is so filled with angst. Part of the exciting yet dangerous aspect to this particular slow-down is the fact that Cassini will have to pass through the vast ring system itself. You see, there is a teensy-weensy gap right between the F and G Rings through which Cassini is being sent. Making it to the gap is not the scary part; that's a no-brainer for the rocket scientists at JPL and NASA. It's what may be in the gap that gets the blood pressure up. If Cassini hits anything at that speed passing through this seemingly empty gap, it's curtains for the spacecraft. Tiny rock plus high-speed spacecraft equals disaster. And more than a decade of research and time and money wasted. This whole scenario on Wednesday is not unlike flying on a plane. The ride itself is relatively safe. It's the take-off and landing that test one's faith. The take-off of Cassini-Huygens went fine. The last 7 years have been picture perfect. Let us hope that our "landing" this week goes without a hitch. If so, the next four years could be filled with spectacular images and discoveries the likes of which humans have never, ever seen. For more information than you may ever need about this mission, go to Cassini's website at http://saturn.jpl.nasa.gov. Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com. Images courtesy NASA. Posted by Administrator at 2004.06.27 12:28 PM \| Comments (0) Elliptical Reasoning The Solar System > This week is full of celestial phenomena centered on the paths of heavenly bodies circling each other. It's my job to try and put a positive spin on it all. It was Johannes Kepler way back in the 16th century who first tried to explain the complexities of how the planets go around the sun. Back then, when the philosophy of Aristotle still held a grip around the neck of scientific thinking, it was believed all planets traveled in perfectly circular orbits. And it was Kepler who was destined to discover that heavenly bodies did not circuit the sun in circles --- but in ellipses. We've all seen ellipses; they are all over the place. The easiest way to see one is to look obliquely at the top of a cup or glass. Look at the lip from directly above; that, of course, would be a circle. But move your point of view from directly above to some other angle and the circle seems to squash. That is an ellipse. Look at the top of the cup from an angle almost level with it and you have one squished circle, or, in astrospeak, one eccentric ellipse. Kepler, through a lot of intense study and to the absolute surprise of many, discovered that planets journey in ellipses. In fact, all orbiting bodies trace out an ellipse, some nearly circular, some more eccentric. The Moon travels in an elliptical orbit, too, one that sometimes takes it closer to us, sometimes further. The close approach is called perigee, a word loosely translated from the Greek as "near the earth." This week, though, on the 17th, the position of the Moon in its monthly swing around the earth will be at apogee, its greatest distance from us. Apogee isn't that much farther away than perigee, but it does make a difference in one special astronomical phenomenon. You see, Thursday the 17th is also the day the Moon is at the point of its orbit when it passes between us and the sun --- New Moon. If the Moon happened to be passing exactly between the sun and us (it just misses this month), then someone on Earth would be getting a solar eclipse, but not the best one. When the Moon is at apogee it can't quite cover the Sun completely and we get what is called an annular eclipse, a rather disappointing partial covering in which the sun outlines the tinier Moon in a giant, blindingly bright ring. The orbits of the planets also give us times called conjunctions, a time when three bodies are all lined up. Venus just finished its newsworthy "inferior" conjunction when it traveled directly between us and the Sun. This Friday Mercury will be in the part of its orbit when it is on the farthest side of the Sun in what is called "superior" conjunction. On Saturday there is an event that you can actually witness, but you will need at least a pair of binoculars to see it. Three of Jupiter's four moons --- Io, Europa, and Callisto --- will be all bunched up together on one side of the great planet. First discovered by Galileo, a contemporary of Kepler, their existence was a further proof that the old Aristotelian ways were on the way out. Before Galileo spied these four little moons, now called the Galilean satellites, it was believed that everything orbited around the earth. Here, clearly, were tiny heavenly bodies that orbited round something else. You yourself can see their movement over just hours of watching. Or you can come back out Sunday night and see a whole different layout of the four. Finally, and most important for teenagers, our own orbit is in a special place next Sunday evening at about 6 o'clock. It is then that we are in that part of our path around the sun when we are tilted most toward our sun. At the beginning of next week we experience the longest daytime, the shortest nighttime. Yes, it is the special sacred time in America called the First Day of Summer. Until next time, clear skies! Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com. Posted by Administrator at 2004.06.12 12:30 PM \| Comments (0) Mass Transit The Solar System > On June 8, for everyone on this planet who can see the skies, Venus will pass in front of the sun for the first time since 1882. It is one of those phenomena for which nearly everyone on the planet cares ... well ... cares little or nothing quite frankly. But for a lover of the skies things are different. He or she gets the same warm tingly feeling of excitement as a birdwatcher that finally spots that rare Hawaiian honeycreeper in the rain forest on the windward side of Maui's Haleakala Crater. It almost never happens in a lifetime. Did I say everyone would be able to see it? That was sort of not altogether entirely true. Of all the places on earth, the only major locations to miss it are the southern tip of South America, and tiny New Zealand. And --- I can barely bring myself to write this --- North America west of the Rockies will miss it, too. Woe is us!!! As nearly the entire human race gets a chance to experience this cosmic dance, we are literally left in the dark. We will miss all four "contacts" of the tiny planet as it silhouettes across the great face of the sun. There is no chance for us to see the famous "blackdrop affect," the time when the petite planet's disk arrives at the edge of the giant sun, and the shadow of Venus seems to reach out and touch the limb of our star. So let's make the most of it from where we are, OK? The reason Venus travels in front of the sun at all is, of course, because the planet is in an orbit between the sun and us. But the laws of physics are set up so that she takes a mere 224 of our days to travel around the sun once --- a venerian year --- so this passing in front, this "transit," should happen much more often, correct? Earth's and Venus' orbits are slightly tipped relative to each other so Venus doesn't always pass directly in front of the sun as she passes us on her inside lane. Most of the time the cloudy planet moves by just over or just under the sun. You may recall that the Moon's orbit doesn't always take it directly in front of the Sun, either, causing the famous solar eclipse. Venus' transit really is a rare event; no one alive has seen one. It's time to use the imagination to see the Big Picture and put it all in perspective. Venus is about to pass in front of the Sun, in just days. You may have noticed Venus already; she's the extremely bright planet in the west after the sun goes down. The more observant among us may have noticed Venus getting lower and lower in the skies over the last month or so. Go outside just after sunset and look to the west. Make sure no one is watching you, then tilt your head far to the right to get a better idea of Venus' orbital path as she passes by us. Imagine that Venus is moving in its orbit toward the just set sun. Watch in the next days as the Evening Star gets closer and closer to the sun, finally disappearing into its brightness in the day or two before the transit. Though we won't be able to see the crossing, we can see it live over the internet. Check out The Exploratorium's excellent site. After Venus passes by to the "other side" of the sun, we will soon be able to see her again! But now she will rise before the sun rises in the morning, and now she will be called the Morning Star. Watch in the coming weeks as Venus rises earlier and earlier, higher and higher. Yes, we are completely left out of this transit, but mark your calendars for June 5, 2012. Through another coordination of the orbits of our planets, we in Southern California get our chance to see a transit that afternoon. But you'd better see it then because it will have to last a lifetime --- the next one isn't until 2117! Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com. Posted by Administrator at 2004.06. 6 12:32 PM \| Comments (0)
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