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5/24/14 Comet 209P/LINEAR Shower - up to 1000/hr

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#1 _Z_

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Posted 09 October 2012 - 12:52 PM

S&T just put up an interesting article, every tail ejected between 1803 and 1924 from Comet 209P/LINEAR will cross the Earth's orbit on May 24, 2014. Peak would be between 7 and 8 UT, so it'll be dark in the US, and the moon is just past new.

Best model shows up to 1,000 meteors PER HOUR, another predicting 100-400 per hour.

It's being compared to the Leonids of the 1990's. Still early, but this could be a big one.

http://www.skyandtel...-173316061.html

#2 Rick Woods

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Posted 09 October 2012 - 01:19 PM

YES! This may be the one I've been waiting for!

#3 Dave M

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Posted 09 October 2012 - 02:42 PM

:cool: Thanks! for posting the link/info.

#4 bassplayer142

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Posted 09 October 2012 - 05:46 PM

Wowowow. I have no doubts that that many meteorite's would be the most amazing astronomical event I've witnessed!

#5 _Z_

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Posted 09 October 2012 - 08:40 PM

Yes if this prediction holds true, I may be putting together a mini road trip to darker skies to watch this!!

Oooo this is on a late friday night/early saturday morning. Should give a lot of people the chance to observe!

#6 krp

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Posted 09 October 2012 - 11:11 PM

Awesome, I'm looking forward to seeing it. So next year we get a great comet, the year after a meteor storm and in 2017 a total solar eclipse. What's on the calendar for 2015 and 2016?

#7 MessiToM

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Posted 10 October 2012 - 08:07 AM

i read that last night and was quite "tickled"

#8 David Knisely

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Posted 10 October 2012 - 04:05 PM

Well, if I had a dollar for every one of these "storm" predictions that didn't quite come true, I would be in more than a little money. Usually, what happens is that you don't get a storm (and in some cases, you don't get very many meteors at all when it isn't an established annual shower like the Leonids were). There are just so many variables involved that a whole bunch of things need to happen in order to get treated to a true "storm" (over 1,000 meteors per hour). I recall at an Astronomical League Mid-States convention we held in the 1990's where Jack Horkheimer was touting the possibility of a storm from the Perseids due to the recent passage of its parent comet, Comet Swift-Tuttle. We all waited on a good dark night at the predicted "peak" date to see what might happen. While the shower was good (we were seeing over 130 meteors in one hour's time around the peak), a storm never materialized. I had seen this happen a number of times with a number of minor showers (Giacobinids, Draconids, etc.) as well. These "storms" never seemed to be very long and always missed the times when I was watching for them. The second problem with these predictions is that the "hourly" rates quoted by some almost never fully reflect what an individual observer will actually see in one hour's time. Indeed, during the historic Leonid "storms" when I was observing them, the largest number of meteors I got to see in precisely a one hour interval was around 350. There were some very short intervals when the number temporarily skyrocketed, but this was always followed by a notable "meteor drouth" where few were seen. If a person limited that time interval and extrapolated that interval's number into a rate which, if maintained for a full hour's time would be the "hourly rate", then it could be in excess of 1000 per hour. However, such bursts frequently do not last anywhere near an hour. Indeed, during one particularly active minute of that extraordinary Leonid shower, I saw a whopping 19 meteors which, if extrapolated into a "number per hour" would have been 1140 meteors per hour (just into the "storm" category). However, in the next minute, that number would drop to 12 per minute and within five minutes was all the way down to a measly five per minute. When I broke my data up into 15 minute segments, I could "extend" that to an equivalent "hourly" rate of around 568/hr, but again, that isn't exactly what one might see in a one hour time interval. That Leonid shower was a truly great meteor shower (probably the best that I have ever seen), but a "storm"? Well, it missed the mark a little. Let's hope we get a "true" storm with this new one, but I am not holding my breath. Clear skies to you.

#9 Ira

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Posted 11 October 2012 - 06:03 AM

I'll take 12/minute. No problemo. :)

/Ira

#10 bassplayer142

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Posted 11 October 2012 - 11:18 AM

Agreed. The most I've counted in a night is below 50!

#11 Tonk

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Posted 13 October 2012 - 10:33 AM

Most I've actually counted in 1 hour is 108 during the supprise 1998 Leonid "fireball" display. That was 108 bright meteors, many bright as a full moon!

#12 Mike Harvey

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Posted 14 October 2012 - 04:52 AM

At it's peak, here in Central Florida during the '98 Leonids, we were counting well over 100 PER MINUTE!

Mike Harvey

#13 BillFerris

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Posted 14 October 2012 - 10:31 AM

The Leonid Meteor Storm of 2001 was simply spectacular. Early on the morning of November 18, observers in the western US were treated to a sustained display peaking at ~2,000 meteors per hour. Observing with a small group in northern Arizona, we saw a one-minute burst of activity at an awe-inspiring 7,200 meteors per hour. For that one minute, I truly appreciated the velocity with which Earth moves through space. I can only begin to imagine what people experienced during the 1966 and 1833 storms, which produced displays well in excess of 100,000 meteors per hour.

Bill in Flag

#14 krp

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Posted 14 October 2012 - 07:50 PM

The Leonid Meteor Storm of 2001 was simply spectacular. Early on the morning of November 18, observers in the western US were treated to a sustained display peaking at ~2,000 meteors per hour. Observing with a small group in northern Arizona, we saw a one-minute burst of activity at an awe-inspiring 7,200 meteors per hour. For that one minute, I truly appreciated the velocity with which Earth moves through space. I can only begin to imagine what people experienced during the 1966 and 1833 storms, which produced displays well in excess of 100,000 meteors per hour.

Bill in Flag

Wow, I can't even imagine seeing that many meteors. I wonder, when meteor storms do happen, how often are they predicted beforehand or are they often a surprise? The Leonids are only a month away, and the Orionids are next weekend but neither are predicted to produce more than 25 per hour.

#15 David Knisely

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Posted 15 October 2012 - 12:45 AM

Bill Ferris wrote:

Observing with a small group in northern Arizona, we saw a one-minute burst of activity at an awe-inspiring 7,200 meteors per hour. For that one minute, I truly appreciated the velocity with which Earth moves through space.


This again is what I get so frustrated with when it comes to meteor count rates. You clearly did not see 7,200 meteors per hour because, by your own admission, you were not observing for a one hour interval to get that 7,200 total count. You *may* have seen 120 meteors in that one minute interval (roughly two per second on average) which, if sustained, would have been the equivalent of 7,200 per hour, but that is not the actual number you saw. You clearly experienced a nice meteor storm, but it might be somewhat better to state actual meteor counts and time intervals rather than 'converting' them to an equivalent hourly rate and just stating it as "meteors per hour" with no qualification. Doing otherwise can give people the wrong idea of exactly how dense the fall rates they might observe will actually be. Clear skies to you.

#16 Jure Atanackov

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Posted 15 October 2012 - 09:09 AM

There have indeed been quite a few predictions of possible (!!) meteor storms since the Leonids of 1999 - 2002. But none, including the meteor shower from 209P were predicted as certain storms. The first prediction was for 2004 Perseids: 1-rev dust trail and a probable ZHR (Zenithal Hourly Rate) of several hundred meteors per hour, but possibly up to storm level. The actual peak ZHR was 200 which is well in line with predictions. Then there were the 2007 Alpha Aurigids, visible from North America on September 1, 2007. Predicted ZHR was about 400, possibly up to storm level. Actual peak ZHR was about 100. The last possible storm was the 2011 Draconids, with ZHR about 400 to 600, but possibly up to storm level.

Why these uncertainties? Because meteor streams as well as their parent comets are highly variable and inherently difficult to predict. The only meteor shower which regularly produces strong outbursts and meteor storms for which models make successful predictions are the Leonids. This is because there is a high number of observed past outburst by which the model can be calibrated. Also the parent comet (55P/Tempel-Tuttle) has a fairly stable orbit over the time span of centuries. But comets are divided into different groups depending on their orbits. Generally these are: Jupiter family comets (JFC), Halley type comets (HTC) and Long period comets (LPC). Meteor streams produced by these comets can and do make outbursts and meteor storms, but they behave in very different ways. Jupiter family comets have highly unstable orbits which change very often. This means that dust trails are deposited in slightly to very different orbits in each successive perihelion passage of the comet. Such a meteor stream is very dispersed and contains dust trails that are very far apart in significantly different orbits. There is a number of such meteor streams. The Draconids are the most well behaved meteor stream from a JFC: the orbit of their parent comet, 21P/Giacobini-Zinner is fairly stable and the meteor stream can be modeled back for at least ~200 years. The June Bootids are a very different case, with the parent comet's (7P/Pons-Winnecke) orbit having undergone very large changes in the past century due to Jupiter's graviational influence. This makes modeling of this meteor stream much more difficult. Also, because the cluster of dust trails produced in the past century is very dispersed and there have consequently been very few outbursts of this meteor shower, there is little observational data that can be used to confirm and improve the model. Both meteor showers produce strong outbursts with hundreds of meteors per hour, the Draconids have produced two major meteor storms so far.

Halley type comets are quite different. These have more stable orbits, but longer orbital periods. This also means that outbursts by their meteor showers are fewer and farther between. The Leonids are the most famous example of such a meteor shower. The parent comet's period is 33 years and has been quite stable for at least 1300 years. In this time a large number of dust trails (about 40) have been released by the comet that form a fairly compact cluster. This is why the Leonids produce quite regular outbursts every 33 years. As the outbursts are strong, often storm-level, there have been many past observations on which stream models were confirmed and refined. Leonid predictions are by far the most precise, both in terms of timing and outburst strength. The Perseids are another HTC meteor shower. However, as the parent comet's orbital period is about 130 year, much fewer outbursts have been observed, providing less data for stream model calibration. The last outbursts before the recent ones, connected with the 1992 perihelion passage of the comet, were in the 1860s, way before any standard measures of meteor shower activity were eastablished, so this data is less reliable. Go back another perihelion passage and you're almost in the dark as far as activity and exact timing is concerned. This is why Perseid predictions are less precise.

The most difficult are (Intermediate) Long Period Comets. Their orbits are quite variable from one perihelion passage to the next and even a fairly small change in orbit can translate in significant differences in dust trail locations. Furthermore, the long periods (several hundreds to several thousand years) mean that only a couple of most recent dust trails are still dense enough to produce significant outbursts. Finally, only the 1-revolution (old) trail can be modeled (to varying degrees of success) as older ones are gravitationally preturbed and the orbit of parent comet is not known for so far back in time. As far as I know only two such meteor showers have been successfully modeled and predicted in terms of the time of the outburst (not so much in terms of strength): the Alpha Monocerotids and the Alpha Aurigids. It is noteworthy that the Alpha Aurigids have produced outbursts in which the meteor rate exceeded 1000 per hour for short periods of time (~5 min). There are probably hundreds of such meteor showers, most of which are unknown and others are only known by a single outburst (e.g. September Perseids, Alpha Lyncids, Gamma Delphinids, etc). There is almost no way to predict these.

With all these factors it is no wonder that it is so difficult to accurately predict a meteor shower outburst. But, would you rather only observe when a storm will certainly occur or watch all the predicted showers just in case? I rather do the latter. Because sometimes meteor shower outbursts are stronger (much stronger) than expected. Example: this year's Draconids, a week ago. Models showed that only weak activity would occur, with perhaps 1-2 meteors per hour visible. What happened was a strong outburst with hundreds of meteors per hour (no reliable visual results yet). It is not yet known why this happened, but there is a possible simple explanation for this: the parent comet spewed out more meteoroids during the particular perihelion passage that produced this dust trail. Indeed, this dust trail was produced in the 1959 perihelion passage and as *series* of brightness outbursts of the parent comet were observed!

Now come the 209P meteors. How much we do know:

1) The comet has only been observed on two perihelion returns.
2) No meteor activity connected with this comet has been observed.
3) The comet is intrinsically very faint, with its absolute magnitude about 10 magnitudes fainter than for parent comets of the Leonids and the Draconids.

Currently the parent comet is intrinsically very faint. Scaling its activity with absolute magnitudes, a 10 magnitude difference would mean that 209P produces a single meteoroid for every ~4000 meteoroids produced by parent comets of the Leonids or the Draconids. This would mean that even a central passage through one of the dust trails produced by the comet would produce only a moderate meteor shower. But the absolute magnitude is not the best measure of dust production of a comet. A gas-rich comet might have a brighter absolute magnitude and still low dust production and vice versa. The afrho value, calculated from images through R filter, is a much better proxy for dust production. Current peak afrho values for 209P are only about 10 times lower than for 21P. This would suggest 'only' 10 times lower meteoroid spatial densities and 'only' 10 times lower meteor activity. A central passage through such a dust trail could produce a very strong meteor shower, perhaps even a minor storm at best, but nowhere near 10 000+ meteors per hour that the Draconids (21P shower) produced. Howeverm the Earth encounters no less than 20+ (!!) piled up dust trails, from perihelion passages from the late 18th to the early 20th century. Also, as activity of JFCs does vary over decades and centuries, it is quite possible than during that time period 209P was much more active. But with no observed past outbursts of the 209P meteor shower we have no way to see how active the comet really was and how dense the dust trails might be.

So as far as the potential 209P meteor storm is concerned, my opinion is that:

1) The possible activity range is from a moderate meteor shower with only several tens of meteors per hour to possibly a significant meteor storm.
2) There is very little that can be done to refine the model and make more precise predictions.
3) 209P predictions are almost incomparably more difficult than predictions for more frequent and well-observed meteor showers such as the Leonids.

Just my 2 cents :)
Clear skies
Jure

#17 Jure Atanackov

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Posted 15 October 2012 - 09:15 AM

A short comment about meteor rates. It is true what Mr. Knisely says about meteor rates: no meteor shower outburst produces as many meteors per hour as the peak rates suggest. The number is always lower. But for meteor shower research the meteor rate over shorter time scales is very important as it shows small variations in spatial density of meteoroids in the meteoroid stream and dust trails. As most such outburst last several tens of minutes up to a couple of hours, the true hourly rate would smear out any structure (even the general activity profile of the outburst).

BillFerris: where did you observe the storm from? I was with the NASA 2001 Leonid MAC ground team on Mt. Lemmon. I saw a peak rate of 70 meteors per minute. But as I drove through northern Arizona a couple of days later (Kaibab national forest) I wondered how many meteors would have been seen from there as the sky there is much darker!

Clear Skies!
Jure

#18 derangedhermit

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Posted 16 October 2012 - 07:22 PM

We should shoot rockets full of stuff into space just so we can run into it later and enjoy the show. Use different ingredients so we get different colors, like fireworks.

#19 BillFerris

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Posted 17 October 2012 - 10:48 PM

Don't be frustrated, Dave. Just be happy for those of us who enjoyed the show.

Bill in Flag

Bill Ferris wrote:

Observing with a small group in northern Arizona, we saw a one-minute burst of activity at an awe-inspiring 7,200 meteors per hour. For that one minute, I truly appreciated the velocity with which Earth moves through space.


This again is what I get so frustrated with when it comes to meteor count rates. You clearly did not see 7,200 meteors per hour because, by your own admission, you were not observing for a one hour interval to get that 7,200 total count. You *may* have seen 120 meteors in that one minute interval (roughly two per second on average) which, if sustained, would have been the equivalent of 7,200 per hour, but that is not the actual number you saw. You clearly experienced a nice meteor storm, but it might be somewhat better to state actual meteor counts and time intervals rather than 'converting' them to an equivalent hourly rate and just stating it as "meteors per hour" with no qualification. Doing otherwise can give people the wrong idea of exactly how dense the fall rates they might observe will actually be. Clear skies to you.



#20 bassplayer142

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Posted 22 October 2012 - 07:29 PM

Brilliant. This is how the 4th of July will be celebrated in a few hundred years. Unfortunately I won't be around.






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