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Thread: Orionid meteor shower

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    Orionid meteor shower

    According to this article the Orionids may be spectacular this year. It also says the meteors are caused by debris left over from Haley's comet.

    The Q:

    How is this an annual event?

    As far as I know, nothing is static in the solar system. Thus, it can't just be a bunch of rocks sitting in one place waiting for the earth to pass through that area.

    If Haley's comet dumped a bunch of junk behind it, why hasn't it followed Haley's back to the outer reaches of the solar system?

    Can someone explain how this works?

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    This will help:

    http://en.wikipedia.org/wiki/Meteor_shower

    A meteor shower is the result of an interaction between a planet (Earth in our case) and a comet. Comets are like "dirty snowballs" made up of ice and rock, orbiting the Sun. Each time a comet swings by the Sun in its orbit, some of its ice melts and it sheds a large amount of debris. As the debris streams from the comet, it forms the comet's visible tail. The solid pieces of debris are a form of meteoroid. The meteoroids spread out along the entire orbit of the comet to form a meteoroid "stream". As the Earth orbits the Sun, its orbit sometimes takes us through a meteoroid stream and a meteor shower ensues. The meteoroids encounter Earth's atmosphere at high speed. As the meteoroids streak through the atmosphere, friction causes the particles to burn and incandesce, forming meteors. When the meteoroid stream is particularly dense, we occasionally see a spectacular "meteor storm." The comets that spawn most known meteor showers have been identified.

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    So, the debris trail we're about to pass through is 20 years behind it's parent - but in the same orbit?

    This suggests an object like Haley's probably has a "trail of crumbs" dotting its entire orbital path. Kind of like a ring, but in a very oblong orbit.

    Is that correct?

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    Quote Originally Posted by DyerWolf View Post
    So, the debris trail we're about to pass through is 20 years behind it's parent - but in the same orbit?

    This suggests an object like Haley's probably has a "trail of crumbs" dotting its entire orbital path. Kind of like a ring, but in a very oblong orbit.

    Is that correct?
    Exactly. In an elliptical path, just like the Earth but with a much greater eccentricity. In some places along the orbit the debris may be a little denser - this is when the shower exceeds expectations.

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    And, from what I understand, the particles may be in slightly different orbits at slightly different speeds, thus giving them different periods. This is why they are distributed.
    And because they are highly elliptical, and the disturbance that creates the particles is at perihelion, then the path nearer perihelion will be denser than at aphelion, since each particle's aphelion may be greatly different.

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    Anyone know of a good meteor shower animation on the Web?

    I've seen some animations that show what the meteors look like as they radiate from the radiant point but haven't found a good one that shows the Sun, the Earth's orbit, and the comet's orbit (with debris).

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    Quote Originally Posted by DyerWolf View Post
    If Haley's comet dumped a bunch of junk behind it, why hasn't it followed Haley's back to the outer reaches of the solar system?
    The explanations are good-- but it's Bill Haley and the comets. If you are talking about the real comet, it's Halley. (Wiki says he would have pronounced his own name "Holly", so you really can't win no matter how you say it.)

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    Quote Originally Posted by Ken G View Post
    (Wiki says he would have pronounced his own name "Holly", so you really can't win no matter how you say it.)

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    Quote Originally Posted by Ken G View Post
    The explanations are good-- but it's Bill Haley and the comets.
    If that were true, shouldn't it be "Ice Around the Clock"?

    If you are talking about the real comet, it's Halley. (Wiki says he would have pronounced his own name "Holly", so you really can't win no matter how you say it.)
    I've heard it pronounced with the "a" like it is in "HAL." (I'm sorry, Dave, but I can't produce a meteor shower this year.)

    Enough with the bad jokes, I promise.

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    Quote Originally Posted by dunham View Post
    DyerWolf, the Wiki article may be a little erroneous, since they are still not 100% certain they are ""dirty snowballs" made up of ice and rock". So the rest is also open for interpretation!

    .
    Who are "they"?

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    Quote Originally Posted by dunham View Post
    DyerWolf, the Wiki article may be a little erroneous, since they are still not 100% certain they are ""dirty snowballs" made up of ice and rock". So the rest is also open for interpretation!

    .
    I don't think DyerWolf was looking for all the very latest scientific papers - he just wanted to know how a meteor shower works.

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    ...he would have pronounced his own name "Holly"
    As in Buddy Holly and the Comets?

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    Exactly-- they got the wrong lead man!

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    ... and Bill Haley and the Crickets!

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    There is a big difference between boiling at ~1 atm and sublimation at zero pressure!

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    Quote Originally Posted by Tucson_Tim View Post
    I don't think DyerWolf was looking for all the very latest scientific papers - he just wanted to know how a meteor shower works.
    Pretty much. I understand the basics of how meteor showers occur. I was just startled to learn that these meteors were related to a comet that last crossed the inner planets in 1986.

    I guess I presumed that most of the material associated with the comet would have been near the comet itself. Knowing that there is a debris field spread out over the entire eliptical orbit is quite interesting.

    Here's another question: If the comet can pass at perihelion on so many different months:
    1P/−239 K1 (25 May 240 BC)
    1P/−163 U1 (12 November 164 BC)
    1P/−86 Q1 (6 August 87 BC)
    1P/−11 Q1 (10 October 12 BC)
    1P/66 B1 (25 January 66 AD)
    1P/141 F1 (22 March 141)
    1P/218 H1 (17 May 218)
    1P/295 J1 (20 April 295)
    1P/374 E1 (16 February 374)
    1P/451 L1 (28 June 451)
    1P/530 Q1 (27 September 530)
    1P/607 H1 (15 March 607)
    1P/684 R1 (2 October 684)
    1P/760 K1 (20 May 760)
    1P/837 F1 (28 February 837)
    1P/912 J1 (18 July 912)
    1P/989 N1 (5 September 989)
    1P/1066 G1 (20 March 1066)
    1P/1145 G1 (18 April 1145)
    1P/1222 R1 (28 September 1222)
    1P/1301 R1 (25 October 1301)
    1P/1378 S1 (10 November 1378)
    1P/1456 K1 (9 June 1456)
    1P/1531 P1 (26 August 1531)
    1P/1607 S1 (27 October 1607)
    1P/1682 Q1 (15 September 1682)
    1P/1758 Y1, 1758 I (25 December 1758) [2]
    1P/1835 P1, 1835 III (16 November 1835)
    1P/1909 R1, 1910 II, 1909c (20 April 1910)
    1P/1982 U1, 1986 III, 1982i (9 February 1986)
    Next perihelion predicted 28 July 2061
    (Source)
    ...why do the Orionids appear to come out of the constellation of Orion always in October?

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    Quote Originally Posted by DyerWolf View Post
    Here's another question: If the comet can pass at perihelion on so many different months:

    ...why do the Orionids appear to come out of the constellation of Orion always in October?
    That's when the Earth's orbit and Halley's Comet's orbit intersect. The orbit of Halley's Comet is stable (for the most part) and Earth's Orbit is stable (also for the most part). But both orbits have differents periods around the Sun. The Earth's is 1 year (close) and Halley's Comet is approx every 76 years.

    By the way, did you see Halley's Comet when it was here in 1986 or were you too young? I saw it. It wasn't a great event but not bad.

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    FYI: dunham was banned shortly after making that post.

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    I was out last night from about 2:30 AM to about 5:00 AM and saw about 20 really good ones plus a few strays, even though the peak was the previous night. The Orionids is a longer duration shower, which means that either the Earth hits the comet's orbit directly or the debris field is pretty wide (or a combo of both). A lot of showers have a very narrow peak and you won't see many a day or two on either side of the peak.

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    Keep an eye on the Astrophotography section of this forum - maybe some of the members caught a few.

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    Quote Originally Posted by Tucson_Tim View Post
    FYI: dunham was banned shortly after making that post.
    Must have been something egregious - because the entire post has been removed.

    Hope it wasn't merely for citing to wiki (*checks backside)...

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    Quote Originally Posted by Tucson_Tim View Post
    I was out last night from about 2:30 AM to about 5:00 AM and saw about 20 really good ones plus a few strays, even though the peak was the previous night. The Orionids is a longer duration shower, which means that either the Earth hits the comet's orbit directly or the debris field is pretty wide (or a combo of both). A lot of showers have a very narrow peak and you won't see many a day or two on either side of the peak.
    I forgot - there are at least two another factors contributing to the length of a shower: (1) The angle that the Earth intersects the comet orbit and, to a much lesser degree, (2) the speed of the Earth in its orbit. When Earth is farthest from the Sun it is travelling the slowest in its elliptical orbit (relative to the Sun).
    Last edited by Tucson_Tim; 2007-Oct-21 at 11:32 PM.

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    Quote Originally Posted by DyerWolf View Post
    Must have been something egregious - because the entire post has been removed.

    Hope it wasn't merely for citing to wiki (*checks backside)...
    Sock puppet. But his comment about wiki is true - it should never be used as a last (or only) source of info.

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    Quote Originally Posted by Tucson_Tim View Post
    That's when the Earth's orbit and Halley's Comet's orbit intersect. The orbit of Halley's Comet is stable (for the most part) and Earth's Orbit is stable (also for the most part). But both orbits have differents periods around the Sun. The Earth's is 1 year (close) and Halley's Comet is approx every 76 years.

    By the way, did you see Halley's Comet when it was here in 1986 or were you too young? I saw it. It wasn't a great event but not bad.
    I saw it - and agree that it wasn't the type of event to spawn a new religion. (I did think it was cool to see the comma shape amongst the stars).

    Here's what I'm trying to get at: does Halley's orbit always cross Earth's orbit in October and May - or does it shift (Picturing the eliptical orbit swinging around the sun like the hand of a very slow clock) at all? If the sun is moving, I would presume that eliptical orbits might precess (if that's the right word) in a noticeable way.

    I'm guessing from your answer that it does not.

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    Quote Originally Posted by DyerWolf View Post
    I saw it - and agree that it wasn't the type of event to spawn a new religion. (I did think it was cool to see the comma shape amongst the stars).

    Here's what I'm trying to get at: does Halley's orbit always cross Earth's orbit in October and May - or does it shift (Picturing the eliptical orbit swinging around the sun like the hand of a very slow clock) at all? If the sun is moving, I would presume that eliptical orbits might precess (if that's the right word) in a noticeable way.

    I'm guessing from your answer that it does not.
    Yes, the orbits precess but not enough to matter in a lifetime. That's why I used the words "for the most part". The closer to the Sun, the more the orbits change. Mercury's orbit change is measureable and (I believe) Einstein's General Theory of Relativity was the first to explain this motion satisfactorily, but we're getting pretty far from my knowledge base. Others will have to chime in here.

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    (Wiki says he would have pronounced his own name "Holly", so you really can't win no matter how you say it.)
    I thought it rhymed with "valley".

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    Quote Originally Posted by Ken G View Post
    If you are talking about the real comet, it's Halley. (Wiki says he would have pronounced his own name "Holly", so you really can't win no matter how you say it.)
    The wiki I found says (in phonetics) to say it (as I have rewritten it for you) "Hawley". Which is fortunate, because that is how informed commentators in Britain generally say it these days. But I can imagine in some parts of the USA there would be little difference in pronunciation between "Holly" and "Hawley".

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    A couple of other factors that affect a meteor shower are (1) how close the comet is to the sun at closest approach and (2) the period of the comet - how often it completes an orbit.

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    Here's a pretty good article about the Orionids from the NASA website. It's from 2000 but the info about the shower is still good:

    http://science.nasa.gov/headlines/y2000/ast18oct_1.htm

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    Quote Originally Posted by Ivan Viehoff View Post
    The wiki I found says (in phonetics) to say it (as I have rewritten it for you) "Hawley". Which is fortunate, because that is how informed commentators in Britain generally say it these days. But I can imagine in some parts of the USA there would be little difference in pronunciation between "Holly" and "Hawley".
    Point taken. In the U.S., it is so common to hear "Haley" that you almost can't be understood if you say it any differently!

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