Spotting meteorites

  • #1
sophiecentaur
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Summary:
We see meteor showers on a regular, annual basis. Can this be a stable situation?
I am planning to catch the Perseid Shower in the next few weeks and I've been thinking about the mechanics of meteorite showers.

So we see clusters of meteorites as we fly through the path of dust, left behind by passing comets. The showers seem to be predictable and some of them have been witnessed for many years on an annual basis, coming from the 'same part' of the celestial sphere (the radiant). I was thinking about what happens to this dust after the comet has left it behind. Why do they all turn up at the same time and in the same place, each year. I realise we are flying through a different part of the tail each year but . . .
Each grain will have an orbit around the Sun, that's determined by it orbital radius and its velocity and it won't be the same as Earth's orbit. Most particles won't have the same orbit period as Earth and they will be travelling (much?) slower than the parent comet but more or less in the same direction. The tail will not be 'frozen' in its position in the Solar System but it will carry on in the general direction of the Sun.
So how come we fly into remnants of any given comet at the same time every year and why does the radiant appear in the same place? Is the story we're told just too simple to be real?
 

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  • #2
DaveE
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Maybe the comet left a dust trail along it's entire orbital path. The particles move, but the path is constant. IDK, just a guess.
 
  • #3
DaveE
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Meteors, BTW. You look down for meteorites. Sorry, I know, it's annoyingly pedantic.
 
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  • #4
DaveC426913
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Meteors, BTW. You look down for meteorites. Sorry, I know, it's annoyingly pedantic.
When I saw the title, I assumed he was looking in rockpiles or icefields...
 
  • #5
DaveC426913
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I think you're conflating a couple of things, while missing the key elements.

1. While the remnants of Kuiper Belt objects certainly produce a large tail and coma when they near the sun, that is a temporary, ephemeral and spectacular phenomenon. The KBO has been around for eons, and will have distributed a halo of particles along its entire orbital path. It just happens to be too faint to see (and so we only them them when they intersect the Earth and burn up).

2. There is a difference between what gas does that comes off a Kuiper object and what particles do. Gas and molecules are easily pushed around by the solar wind. But the particles we see in showers are on the order of grains of sand and larger. These are pushed around a lot less by the solar wind, and thus keep to their orbit.

The takeaway here is that meteor showers are comprised of large particles that aren't shoved out of orbit easily, and are distributed along the orbital path, not just in the tail and not just when near the sun.

* see caveat in sig line
 
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  • #6
sophiecentaur
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Meteors, BTW. You look down for meteorites. Sorry, I know, it's annoyingly pedantic.
That was dumb of me, considering I just bought two!
shoved out of orbit easily, and are distributed along the orbital path, not just in the tail and not just when near the sun.

* see caveat in sig line
That’s what is always said but what orbit is an individual bit of dust in? They would be moving at speed and not sitting where they were left behind. A bit slower than the core perhaps so a trajectory closer to the sun?
Perhaps the explanation is that each year we run into a bunch that’s taken a year longer to get there but laying on the same path, more or less.
so there will be many comets that don’t have a trail that intersects our orbit so no meteors from them although we may see the comet.

The width of the path / orbit must depend on the range of velocities that matter is ejected from the comet.
Cheers: that picture makes sense to me.
 
  • #7
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he width of the path / orbit must depend on the range of velocities that matter is ejected from the comet.
Cheers: that picture makes sense to me.
+1
 
  • #8
DaveC426913
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The trick would be to compare the magnitude of the orbital velocity at some given point to the magnitude of velocities at which particles are jettisoned from the primary body.

I suspect the former outstrips the latter by an order of magnitude or (possibly much) more. And that means - while particles may drift from the orbit somewhat - it won't be very much deviation on a scale that reaches from Pluto to the Sun.
 
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  • #9
Keith_McClary
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  • #10
sophiecentaur
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And that means - while particles may drift from the orbit somewhat - it won't be very much deviation on a scale that reaches from Pluto to the Sun.
The same could apply to asteroids, only worse. If a rogue asteroid is merely broken up by Space Cowboys or others, the stuff will carry on in its original orbit plus-or-minus an shower us on some later pass. But the cross sectional area would be bigger and the scattergun effect could mean we get some of it but not all of it!

The statistics are not too scary though; we haven't been hit for a while but the orbit times for asteroids is in the order of only a few years so significant debris from a broken up asteroid could cross our path much more often than stuff from a comet. But the actual numbers would be very significant and the contents of an asteroid could perhaps (with a big enough nuke) spread out much more than the bits from a comet.
 
  • #11
DaveC426913
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The same could apply to asteroids, only worse. If a rogue asteroid is merely broken up by Space Cowboys or others, the stuff will carry on in its original orbit plus-or-minus an shower us on some later pass. But the cross sectional area would be bigger and the scattergun effect could mean we get some of it but not all of it!
Sure. Although:
- asteroids are less likely to have eccentric Earth-crossing orbits, and
- being rocky, rather than icy, asteroids don't tend to accumulate great trails of particles in their paths.
 
  • #12
sophiecentaur
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Sure. Although:
- asteroids are less likely to have eccentric Earth-crossing orbits, and
- being rocky, rather than icy, asteroids don't tend to accumulate great trails of particles in their paths.
I was assuming it has been blasted into pieces by the Space Cowboy and the pieces spread over its otherwise unperturbed orbit. But isn’t the frequency of near misses of no negligible concern? (Compared with being whacked by comets.)
Good point of the difference in content and th
the trails are fairly harmless.
 
  • #13
DaveC426913
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I was assuming it has been blasted into pieces by the Space Cowboy and the pieces spread over its otherwise unperturbed orbit.
Yes, I bypassed that parameter of the scenario as I am not sure where you're going with it as it applies to the OP.
 
  • #14
Vanadium 50
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Meteors, BTW. You look down for meteorites
@davenn looks for them in his mailbox.
 
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  • #15
sophiecentaur
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Yes, I bypassed that parameter of the scenario as I am not sure where you're going with it as it applies to the OP.
Having partly sorted out and found a mechanism for the apparently endless visits of Perseid etc., I fell to thinking about other random visitors to Earth's vicinity. That was how the segue arose.
 
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sophiecentaur
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  • #17
DaveE
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Meteors, BTW. You look down for meteorites. Sorry, I know, it's annoyingly pedantic.
Plus, why do we need two names anyway? We don't rename hail or rain drops when they hit the ground. Birds are still birds whether they are flying or not. I'm OK with asteroids vs. meteors, after all they are doing different things. But falling towards Earth and burning up in the atmosphere is a lot like falling towards Earth, burning in the atmosphere, and hitting the ground. It's not just pedantic, it's pointlessly pedantic.
 
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  • #18
hutchphd
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Nobody mentioned explicity that the perturbations to the orbit of the comet detritus occurs very near the perihelion of a relatively eccentric orbit. This doubtless affects the paths of these particles at aphelion but when back near the sun not much will change except their arrival time. I hadn't thought this through previously..... thanks to all.
Birds are still birds whether they are flying or not.
We do usually call them dead birds....
 
  • #19
sophiecentaur
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We don't rename hail or rain drops when they hit the ground.
We call them a puddle when they have landed. And, anyway, you can't buy a meteor but you can buy a meteorite. There's a difference for you.
Many of these astronomical terms were introduced long before anyone actually knew what the things were but inappropriate names for things are still alive and well in the world of elementary particles. You could always demand an explanation for why Charm is Charm but I don't think you'd get very far with it.
 
  • #20
DaveC426913
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Plus, why do we need two names anyway?
Because one is an astronomical object and one is a geological mineral - thus the obligatory suffix -ite.
 
  • #21
DaveE
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We call them a puddle when they have landed.
Like rocks and landslides, or cars and traffic, I guess.

Many of these astronomical terms were introduced long before anyone actually knew what the things were
And what an amazing coincidence that they choose to name one meteor and the other meteorite! Anyway, it's a losing position, I know. I'll just be happy that I don't hear meteoroid used too.
 
  • #22
davenn
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I'm OK with asteroids vs. meteors, after all they are doing different things. But falling towards Earth and burning up in the atmosphere is a lot like falling towards Earth, burning in the atmosphere, and hitting the ground. It's not just pedantic, it's pointlessly pedantic.


No it isnt pedantic ... it's two totally separate phenomena
and asteroids ARE meteors when blazing through the atmosphere
Asteroids vs meteoroids is the thing that you need to clarify.
1) Asteroid is any rock over 1 metre in diameter, meteoroid for anything smaller. When in space
2) Meteor describes the incandescent object in the atmosphere, bolide or fireball for larger
bursts of light
3) Meteorite describes any remaining rock/iron that makes it to the ground,
regardless of if it was a meteoroid or an asteroid
 
  • #23
davenn
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I'll just be happy that I don't hear meteoroid used too.

It does get used, it has a very specific definition .... see my previous post
In the "space rocks" field of study (etc) meteoroid is used all the time
 
  • #24
davenn
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Summary:: We see meteor showers on a regular, annual basis. Can this be a stable situation?

Most particles won't have the same orbit period as Earth
Of course not, many/most are on highly elliptical orbits through the solar system and around the sun.
There are probably none with the near circular orbit that the Earth or other planets have

Summary:: We see meteor showers on a regular, annual basis. Can this be a stable situation?

and they will be travelling (much?) slower than the parent comet but more or less in the same direction.

yes, they will follow the comets orbit around the sun

Summary:: We see meteor showers on a regular, annual basis. Can this be a stable situation?

The tail will not be 'frozen' in its position in the Solar System but it will carry on in the general direction of the Sun.

Not the tail but the trail (dunno if you typo'ed?) it position in the solar system relative to the sun and planets will remain relatively unchanged.

Summary:: We see meteor showers on a regular, annual basis. Can this be a stable situation?

So how come we fly into remnants of any given comet at the same time every year and why does the radiant appear in the same place?


because of my previous response, the Sun and all the planets, asteroids and every other thing in the solar system is moving through space collectively as a group
 
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  • #25
Vanadium 50
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you can't buy a meteor
I'd be happy to sell you one. Delivery not included.
 
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