Stargazing Spotting Meteorites: Unveiling the Mystery of Annual Showers

[sophiecentaur]

TL;DR 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 realize 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 traveling (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?

 

[DaveE]

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.

 

[DaveE]

Meteors, BTW. You look down for meteorites. Sorry, I know, it's annoyingly pedantic.

 

[DaveC426913]

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...

 

[DaveC426913]

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

 

[sophiecentaur]

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.

 

[Bystander]

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

 

[DaveC426913]

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.

 

[Keith_McClary]

 

[sophiecentaur]

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.

 

[DaveC426913]

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.

 

[sophiecentaur]

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.

 

[DaveC426913]

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.

 

[Vanadium 50]

Meteors, BTW. You look down for meteorites

@davenn looks for them in his mailbox.

 

[sophiecentaur]

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.

 

[sophiecentaur]

@davenn looks for them in his mailbox.

And the result of their impact is on his Bank Balance!

 

[DaveE]

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.

 

[hutchphd]

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...

 

[sophiecentaur]

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.

 

[DaveC426913]

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.

 

[DaveE]

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.

 

[davenn]

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 isn't 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

 

[davenn]

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

 

[davenn]

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 traveling (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

 

[Vanadium 50]

you can't buy a meteor

I'd be happy to sell you one. Delivery not included.

 

[DaveC426913]

There are probably none with the near circular orbit that the Earth or other planets have

Wait. Earth - and the other planets - have their own co-orbiting objects, including - but not limited to -Trojans.

 

[Vanadium 50]

There are probably none with the near circular orbit that the Earth or other planets have

It turns out there is...drum roll please...one. 2010 TK7.

Period: 365.10 days
Semimajor axis: 0.99972 AU
Aphelion: 1.2 AU
Perihelion: 0.8 AU
Eccentricity: 0.19 (less than Mercury)

 

[glappkaeft]

It turns out there is...drum roll please...one. 2010 TK7.

It's not the only one, there is another trojan (2020 XL5 - significantly more eccentric though) discovered recent and if you go to the JPL Small-Body Database Search Engine you can find (say searching for NEOs AND a = [ 0.98, : 1.02 ] (au) AND e < 0.2 ) a bunch of (non-trojan) asteroids in similar orbits to Earth like 469219 Kamo'oalewa.

 

[Vanadium 50]

I don't know which requirement of mine 469219 Kamo'oalewa failed. 2020 XL5 was not included because a) it's eccentricity, and b) the observation arc is only 6 weeks.

 

[glappkaeft]

The co-orbital asteroids are also good candidates, very low eccentricity in some of them like 2002 AA29 and 2003 YN107.

 

[sophiecentaur]

There are probably none with the near circular orbit that the Earth or other planets have

This may be true (or nearly true) but there are a lot of objects with orbits that intersect Earth's orbit +/- little enough to worry us sometimes. (I'm still trying to tie in the trail of a comet with what happens to the resulting bits from a blown-up asteroid) The products of an exploded asteroid will have a range of orbits spread around the CM of the original asteroid. At some point in the future (next or tenth time round - depending) when the orbits of those bits of rock again rendezvous with the Earth, there is a greater chance of a collision with one of them, So they need to be broken up into relatively harmless sized bits, with a consequently greater chance of actually hitting us.
The alternative of guiding an asteroid out of harm's way is more attractive - but only if the rocket power exists. From what I understand of orbital mechanics, shifting an object into a significantly different orbit would involve more than just one impulse. So the rocket would need to sit on the asteroid and give it another nudge at a suitable time.

 

[DaveC426913]

From what I understand of orbital mechanics, shifting an object into a significantly different orbit would involve more than just one impulse.

Not necessarily. A single impulse would change the eccentricity of its orbit, though one of its *apses (either apsis or periapsis) will remain the same.

This surely reduces the overall collision risk by many orders of magnitude - which is probably sufficient.

Consider also that it may be effective to simply change the inclination of a menacing asteroid's orbit. Little energy required for maximum reduction in collision risk.

 

[davenn]

Wait. Earth - and the other planets - have their own co-orbiting objects, including - but not limited to -Trojans.

Those are NOT comet trails which is what is being spoken of ... ... dust trails left my comets and the resulting meteor showers

 

[davenn]

This may be true (or nearly true) but there are a lot of objects with orbits that intersect Earth's orbit +/- little enough to worry us sometimes.

Yes, there's lots of meteoroids and asteroids with orbits that cross Earths orbit, but as I just replied to DaveC ... you are asking about comet dust trails and their paths are all highly elliptical

 

[davenn]

The co-orbital asteroids are also good candidates, very low eccentricity in some of them like 2002 AA29 and 2003 YN107.

Again ... those are asteroids you speak of, not cometary dust trails that the thread is about

 

[davenn]

It's not the only one, there is another trojan (2020 XL5 - significantly more eccentric though) discovered recent and if you go to the JPL Small-Body Database Search Engine you can find (say searching for NEOs AND a = [ 0.98, : 1.02 ] (au) AND e < 0.2 ) a bunch of (non-trojan) asteroids in similar orbits to Earth like 469219 Kamo'oalewa.

You are naming asteroids not comets

 

[sophiecentaur]

you are asking about comet dust trails and their paths are all highly elliptical

I realize that I have shifted the thread a bit but, as OP, I feel I have some editorial rights and there are clear parallels between all objects which go near Earth at some stage. It must be a matter of the difference between extremes. The eccentricity of an orbit will affect details but which details are relevant?
I now understand about how particles ejected from a comet with equal speeds in all directions will be spread out along the path (at 1AU) much more than across it and that was useful for me. For an asteroid with a less elliptical orbit, this difference will be less so there will be much less of a 'trail' if it explodes and the result will be more of a 'cloud' than a trail. So that could imply that we would need to coincide in time as well as in position with asteroid pieces, whereas bits of the comet trail are always present when we get to that particular position in our orbit.
I think that has been a useful clearing up lesson - for me if for no one else. I like it when things tie together.

 

[DaveC426913]

Those are NOT comet trails which is what is being spoken of ... ... dust trails left my comets and the resulting meteor showers

Yes. But you/we keep expanding the scope of the thread.

I mean, I know we're touching on a number of related subjects, but I think the parameters of the original thesis may have gotten clouded.

 

[snorkack]

I realize that I have shifted the thread a bit but, as OP, I feel I have some editorial rights and there are clear parallels between all objects which go near Earth at some stage. It must be a matter of the difference between extremes. The eccentricity of an orbit will affect details but which details are relevant?
I now understand about how particles ejected from a comet with equal speeds in all directions will be spread out along the path (at 1AU) much more than across it and that was useful for me. For an asteroid with a less elliptical orbit, this difference will be less so there will be much less of a 'trail' if it explodes and the result will be more of a 'cloud' than a trail. So that could imply that we would need to coincide in time as well as in position with asteroid pieces, whereas bits of the comet trail are always present when we get to that particular position in our orbit.

No.
It starts as a cloud - but quickly turns into trail along orbit.
Why?
Imagine that a number of particles are ejected from, for example, Earth, in all directions with equal speed.
Say that ejection happens when Earth is at perihelion, 147 million km from Sun, and a particle ejected backwards goes to an elliptical orbit for which 147 million km is aphelion, with perihelion at 142 million km.
In half a year, the Earth is at its aphelion at 152 million km, and the ejected particle is at its new perihelion at 142 million km... 10 million km from Earth orbit.
This is the furthest it ever gets from Earth orbit, and Earth´s meteor trail. For it follows its new closed orbit, and over the next half year returns to its original point of impact, as it always must.
It returns to its original point of impact... but does not need to fall back to Earth. Because while its new orbit intersects Earth orbit, it has a different (though close) period. With long half-axis of ellipse 5 million km shorter than Earth it has orbital period 18 days shorter. So it passes the exact point of collision on Earth orbit... but Earth is then not there, but 50 million km behind.
Over a number of orbital periods, the displacement along orbit accumulates freely. Displacement across orbit faces a returning force and is maximized in the first half orbital period.

 

[sophiecentaur]

It starts as a cloud - but quickly turns into trail along orbit.
Why?

I am not in favour of using the Earth as a model because any particles ejected from Earth will not have escape velocity. I would think the better to stick with the comet explanation in terms of a comet.
A comet trail won't start as a cloud. It will be formed over a long part of the comet's path as it approaches the Sun and bits boil off.
Then apply simple orbital mechanics (and ignore the attraction to the comet itself) the behaviour of an object in orbit (just one of the particles that are ejected by the comet as it heats up). A single impulse will cause its orbit to change but it will always revisit the point at which it was ejected. This will mean that the trail will be constrained to its original path (plus or minus a bit) and every bit will arrive back on the comet's orbit but at a different time. The speed of the comet is far greater than the speed of the ejecta and the escape velocity from such a lightweight as a comet can easily be exceeded by some of the ejecta so we need only be concerned with the orbits of the particles around the Sun.

 

[neilparker62]

@davenn looks for them in his mailbox.

So who's mail order was this ?

 

[Oldman too]

If you like https://earthobservatory.nasa.gov/images/149554/finding-meteorite-hotspots-in-antarctica

You will love https://www.science.org/doi/10.1126/sciadv.abj8138

 

[Keith_McClary]

A comet trail won't start as a cloud. It will be formed over a long part of the comet's path as it approaches the Sun and bits boil off.

 

[sophiecentaur]

I wonder about that video. I have always understood that the tail points away from the Sun all the way round. I expect an Artist may have intervened at some stage(?).

 

[DaveC426913]

I wonder about that video. I have always understood that the tail points away from the Sun all the way round. I expect an Artist may have intervened at some stage(?).

Many comets have two tails. Only one points away from Sun.

 

[Keith_McClary]

I wonder about that video. I have always understood that the tail points away from the Sun all the way round. I expect an Artist may have intervened at some stage(?).

These are the particles so large that they are more influenced by gravity than light.

Cometary dust trails are the collections of large (greater than 0.1 mm) particles that closely follow a comet's orbit, similar to how a contrail follows a jet. Dust trails are the youngest meteoroid streams, and when they intersect the orbit of a planet they can create meteor showers.

 

[sophiecentaur]

Many comets have two tails. Only one points away from Sun.
View attachment 298315

I know about dust trails but are they ever on the Sun-side of the orbit? What mechanism woul cause their trajectory to take the particles towards the Sun?
Particles that have not totally escaped the core will return and cross the main track eventually (at some time). Would that intersection take significant numbers back in enough numbers to be visible?

 

[sophiecentaur]

These are the particles so large that they are more influenced by gravity than light.

Dust trails: is there some orbital thing which causes the ejected particles to re-appear on the comet's orbital path only to one side. I already made the point that slow particles will hang around the comet's path but the form of the dust trail seems to suggest strongly that the Sun(?) is having an effect. Also, there is a distinction between the two tails where I would (naively?) have thought it would cause a widened single tail.
Edit; the distinction seems to be due to ionisation in one case and the solar wind in the other - both causes being of solar origin so you'd expect displacement away from the Suns general direction (modified by magnetic fields).

 

[davenn]

Many comets have two tails. Only one points away from Sun.

both those are pointing away from the sun

but there is one style that does point in the opposite direction tail
An anti-tail

Wiki
""Most comets do not develop sufficiently for an antitail to become visible, but notable comets that did display antitails include Comet Arend–Roland in 1957, Comet Hale–Bopp in 1997, and Comet PANSTARRS in 2013. The coma and tail at the main Comet article.""

Arend-Roland comet - C/1956 R1

 

[Keith_McClary]

re-appear on the comet's orbital path only to one side.

I think their motion is due to the ejection speed from the comet. Most of the ejection is from the hot (sunny) side.