Very, very, very SLOW meteoroids.

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King Author
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Very, very, very SLOW meteoroids.

Postby King Author » Mon Apr 11, 2011 2:18 am UTC

I'm a self-described "ruddy stargazer." I've seen a lot of shooting stars in my comparably short years on this earth, and I've noticed a phenomenon that seems odd to me.

Sometimes (it's pretty rare, maybe once or twice a year), I'll notice what appears to be an incredibly slow-moving meteoroid. Most shooting stars, of course, just flash through the sky in a second (usually less than a second in my experiences), but these move improbably slow. A pinprick of light will flare into existence, sometimes that itself will be quite slow (ten to fifteen seconds), like a new star being born or something, and then it'll creep across the night sky no faster than a potato bug. Sometimes it'll just go a few "inches" (by my estimation -- I don't know how distance across the sky is measured. arcsecs?) but sometimes almost two feet, before flaring back out of existence, which again can be a very slow, gradual process (again, ten to fifteen seconds), like a star slowly dying.

I'm highly confident that this phenomenon is indeed astronomical, not simply a plane or some such; while I can't be 100% absolutely sure, I've been stargazing long enough to know the difference, so I'm very confident.

The reason I'm perplexed is, well, how could a meteroid travel so slowly? If you dropped a very large, light-emitting rock from an airplane it would move much faster than these bug-crawl meteroids I've seen. Now, granted, anything from space is gonna be slowed significantly by entering the atmosphere from the void, but it seems improbable to me that a shooting star could move that slow.

Can they?
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Re: Very, very, very SLOW meteoroids.

Postby ajd007 » Mon Apr 11, 2011 2:32 am UTC

I'm certainly no expert on this, but perhaps the meteor was moving towards you (ie vertical), so that from your perspective it only appears to be moving very slowly horizontally, when in fact it is moving very fast although mostly vertical. This would also explain the long duration, as the meteor enters the Earth's atmosphere and completely burns up as opposed to just grazing the top of the atmosphere and exiting back into space. I'm just speculating, but it seems plausible to me.

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Re: Very, very, very SLOW meteoroids.

Postby The EGE » Mon Apr 11, 2011 2:51 am UTC

Satellites. You're seeing satellites, and it's the neatest thing.

The flaring into existence is the satellite coming out of the Earth's shadow; it's also the reason why they disappear. (Shadow, plus rotation, is why they are only visible for short periods of time, and may vary in brightness).

Heavens-Above has real neat charts for tracking them; I've spotted the ISS and Hubble, as well as a number of old Russian Cosmos-series satellites. On a clear evening, it's actually possible to see one every few minutes from a rural area.

Can you offer a brightness estimate? (I.E, full moon / planet / brightest stars / average naked-eye star / faintest you can see without binoculars)?

Also: sky measurements: whole sky is 360 degrees; a fist at arm's length is 8-10 degrees wide. Each degree of arc can be subdivided into 60 arcminutes, each of which can be divided into 60 arcseconds. Most satellites move at 0.1 to 3 degrees per second depending on their orbit.
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Re: Very, very, very SLOW meteoroids.

Postby Mighty Flaming Frying Pan » Mon Apr 11, 2011 5:25 am UTC

The Edge essentially has it right. Likely satellites, likely not meteors. Why is this? Meteors are traveling at very high speeds (thousands of km/s) when they hit the Earth's atmosphere, so they are only in the atmosphere, and thus visible, for less than a second. There isn't really a way you would see a meteor stay in the sky for several seconds, unless (and this happens VERY rarely) it skipped off the Earth's atmosphere and back into orbit.
So, you're either seeing satellites of UFOs. ;)

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Re: Very, very, very SLOW meteoroids.

Postby Korrente » Mon Apr 11, 2011 6:00 am UTC

I agree, likely satellites. I think the Iridium line had parabolic dishes or something to that nature that caught the sun's light and if you were at the Perfect spot on Earth, you'd get a somewhat slow (3-5 seconds) buildup to a very bright glow, then a slow diminish. They're pretty awesome to watch, especially the brightest flares.

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Re: Very, very, very SLOW meteoroids.

Postby Technical Ben » Mon Apr 11, 2011 8:17 am UTC

I reckon I got to see Mir this way, plus some other satellite. I say Mir, as it was the expected day and time for the sighting. The other satellite was moving at 90 degrees to it, so that was cool.
Then there was a shooting star. Best night star gazing ever!
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Re: Very, very, very SLOW meteoroids.

Postby King Author » Tue Apr 12, 2011 4:07 am UTC

Satallites! Why didn't I think of that? That's probably it. Good diagnosis.

A brightness estimate? They look like stars. When they first come into view, during those ten to fifteen seconds when they go from nothing to appearing, they look like weak, dim stars but gradually brighten during that time to as bright as a bright average star. And by "bright average" I mean, like, not as bright as the North Star, but as bright as most stars typically get.

EGE, your speed estimation also sounds like exactly what I'm seeing. And that's so bitchin' that the reason they take awhile to come to full brightness is because I'm seeing them come out of Earth's shadow. I'm visually seeing, in real time, an effect of the Earth's rotation!

Hey, as long as I've already made this topic, a second question -- how often do visible meteroids appear in your average suburban area? I presume that meteroids are probably essentially constantly raining down on the earth, but local light sources make most of them, which are probably quite tiny, invisible.

I ask because I live just thirty miles from a big city, in a relatively active suburban area (thus there's a lot of light pollution where I live) yet I can still pretty much see a handful of meteroids a night any cloudless night I stare skyward. It seems like a lot more than I should be seeing.
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Re: Very, very, very SLOW meteoroids.

Postby Carnildo » Tue Apr 12, 2011 11:26 am UTC

King Author wrote:Hey, as long as I've already made this topic, a second question -- how often do visible meteroids appear in your average suburban area? I presume that meteroids are probably essentially constantly raining down on the earth, but local light sources make most of them, which are probably quite tiny, invisible.

Under good seeing conditions, and assuming there's not a meteor shower going on, you can get five to ten meteors an hour. A suburban sky is hardly "good seeing" -- I wouldn't expect to see more than one or two a night.

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Re: Very, very, very SLOW meteoroids.

Postby The EGE » Tue Apr 12, 2011 9:06 pm UTC

I live in southeastern Connecticut, about five miles from two of the largest casinos in the world, which have consistently shown to have no regards for their surrounding communities and thus put up ridiculous amounts of light pollution. From what I hear from other stargazers, it's a pretty typical suburban sky.

I probably see 1 to 3 meteors an hour from my back yard; from New Hampshire with almost zero light pollution that goes up to about 4.
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Re: Very, very, very SLOW meteoroids.

Postby greenlimejuice » Fri Jun 09, 2017 7:58 am UTC

I know I'm late to the party but this is the greatest thread ever! The answer is so hard to find on the internet. I always assumed it was just a shooting star moving directly toward me as the user ajd007 suggested in his reply. My question is this: I get why satellites would flair into existence (coming out of earth's shadow), but why the slow fade?

The one I saw probably only lasted 2-5 seconds and only moved a couple inches horizontally from my perspective. It was quite bright as well, definitely brighter than surrounding stars.

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Re: Very, very, very SLOW meteoroids.

Postby p1t1o » Fri Jun 09, 2017 1:04 pm UTC

greenlimejuice wrote:I know I'm late to the party but this is the greatest thread ever! The answer is so hard to find on the internet. I always assumed it was just a shooting star moving directly toward me as the user ajd007 suggested in his reply. My question is this: I get why satellites would flair into existence (coming out of earth's shadow), but why the slow fade?

The one I saw probably only lasted 2-5 seconds and only moved a couple inches horizontally from my perspective. It was quite bright as well, definitely brighter than surrounding stars.


The Iridium satellites are a defunct constellation of communications satellites - these are not the only visible satellites, Im just using them as an example. They produce what is known as "Iridium flares", because they are slowly tumbling. Sometimes their solar panels will catch the sun sun and produce a bright flash, or a signature that slowly increases in brightness and then slowly fades, or any combination in between.

There are sites, IIRC, that tabulate the known orbits, and the tumbling, and various other factors, and give predictions on where+when you can spot one. I think I used to have an app that would alert me if there was going to be a flare visible at my location within a timeframe. Bit of googling, Im sure you can find the resources.

If you do it right, and are a bit lucky (sometimes they dont show up, or are obscured) you can point into the sky and say "Look!" and then a light will flare into existence, as if on command :)

Side-note: sometimes I like to randomly say dramatic things during thunderstorms, on the off-chance that it will be punctuated by a flash of lightning and a peal of thunder.

"I WILL RULE THE WORLD!!! *CRACKADOOOOOM* AHAHAHAHAHAAAA!"

So far it has never worked.


*edit*

Even if a satellite is not tumbling, its attitude is "fixed" in space - it does not remain stationary with respect to the Earths surface - unless actively controlled, which is relevant for only a few types - so from our perspective they appear to rotate, so even a non-tumbling satellite can produce variable flares.
Last edited by p1t1o on Fri Jun 09, 2017 1:32 pm UTC, edited 1 time in total.

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Re: Very, very, very SLOW meteoroids.

Postby HES » Fri Jun 09, 2017 1:13 pm UTC

p1t1o wrote:If you do it right, and are a bit lucky (sometimes they dont show up, or are obscured) you can point into the sky and say "Look!" and then a light will flare into existence, as if on command :)

Reminds me of the story about a physicist 'predicting' an earthquake from a well-timed phone call.

*googles*

Oh, of course I heard it from Randall... https://blog.xkcd.com/2011/08/24/earthquakes/
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Re: Very, very, very SLOW meteoroids.

Postby greenlimejuice » Fri Jun 09, 2017 3:46 pm UTC

I looked up some videos of Iridium flares and at first thought, "that couldn't possibly have been what I saw!"

But then I realized I was in a light polluted area and perhaps the ONLY thing I could see was at the direct time of the flare.

I used this website and it showed my location in red (second place for worst light pollution)
http://darksitefinder.com/maps/world.html

So I probably couldn't see the satellite before and after the flare because of light pollution.

Know of any other cool sites out there where I can learn more about light pollution?

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Re: Very, very, very SLOW meteoroids.

Postby Eebster the Great » Fri Jun 09, 2017 6:57 pm UTC

The "iridium flares" are specific to satellites in the iridium constellation. You probably didn't see an iridium flare, simply because other satellite flares are more numerous, but iridium flares are the brightest. You said it was dimmer than Polaris, which is pretty surprising, since a typical satellite flare would be around a thousand to a million times brighter. Are you sure you're not thinking of Venus?

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Re: Very, very, very SLOW meteoroids.

Postby gmalivuk » Mon Jun 12, 2017 3:45 pm UTC

greenlimejuice wrote:I used this website and it showed my location in red (second place for worst light pollution)
http://darksitefinder.com/maps/world.html

North Korea is so fucking creepy on light level maps.
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Re: Very, very, very SLOW meteoroids.

Postby mfb » Tue Jul 04, 2017 12:05 am UTC

greenlimejuice wrote:I get why satellites would flair into existence (coming out of earth's shadow)
That can happen, but it is not what you typically see. The satellite is in sunlight all the time. They are quite dim objects, but Iridium satellites (and a few others) have large flat areas that produce very collimated reflections with some less collimated light around it. The spots of these reflections move across the surface as the satellite orbits Earth. As seen from the ground, you have an object so dim that you probably don't see it, then the outer range of the collimated reflection reaches you but the satellite stays quite dim, then the spot approaches you and the satellite gets visible. After a few seconds you are out of the main spot and the satellite gets dimmer again. But now you know where to look, so you can follow the satellite for quite some time until the reflection doesn't hit you any more.

Iridium satellites produce the most notable flares, they can get bright enough to cast a visible shadow under very favorable viewing conditions. There are some other satellites that produce weaker flares, often shorter and sometimes irregular if the satellites tumble.

Some satellites and rocket stages can be seen without flares - they are simply like stars that move across the sky.


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