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# Schwassmann-Wachmann 73P; Here's what I learned about its trajectory

ScienceOnly

User ID: 84962
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04/25/2006 07:28 AM
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Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
I have spent time studying the trajectory of 73P using my "Starry Night" planetarium software. I will share with you some information about it, and perhaps we can theororize a bit.

I haven't been reading too much lately because I have been out of pocket. Please share information about any of the fragments' positions relative to the published path of the comet itself, and I will attempt to input it into the software program to see how close it might get.

Of all the comets we have looked at over time here on GLP, I would give this one the highest probability of affecting Earth. Let me explain.

The Trajectory

The best way to explain the trajectory is to build a visual analogy. Imagine you are in a race car (Earth) and are traveling on a circular racetrack, going counter-clockwise at a constant speed. At the center of the track is the sun.

73P is moving at a higher speed, and is going to pass you on the right. Thinking only in two dimensions for the moment. As 73P overtakes you, it passes in front of you from right to left, almost clipping your front-right bumper as it does. It continues across your lane and off to the left.

Now let's take it to 3-D. The approach of 73P is from slightly above, so you would have to adjust your side-view miror up just a bit to see it coming up on your right side. It is getting lower and lower as it overtakes you but does not get to your level until after it passes you way ahead and on the left.

The view would be like seeing it pass by you on the right and a little above you. As it gets directly in front of you (in your lane), it is about as high as the windshield. It continues to speed away to the left and keeps descending until it gets to ground-level, but that's a ways ahead and also a bit to the left.

To imagine the angles involved here, imagine that you are on a five lane highway, and you are driving down the middle lane. Thinking again in two-dimensions. It would be like 73P begins to move out of the far-right-hand lane about ten car-lengths back. If it wasn't for the fact that it was moving faster than you, it would side-swipe you, but since it is moving faster, it just misses your front bumper. Taking it to 3-D again, it would appear that the 73P is traveling above the ground about 20 feet off the ground. As it overtakes you because of its speed, it is about 10 feet off the ground as it gets even with you, about five feet as it crosses in front of you, and gets to ground level up ahead about ten car-lenghts ahead and in the far left lane.

I hope I have explained the trajectory sufficiently. There is cause to watch this closely.

More in a moment...
Unsure(c)

User ID: 15255
United Kingdom
04/25/2006 07:34 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Good description !

Are you indicating that the fragments might be moving slower than the main body and therefore will rear end us or be in our path when we move into that bit of space ??

Also from what you calculate what side of the earth will be most at risk of any rougue pieces and what are we talking about ? baseballs or houses ??
Unsure(c) - Why i am uncertain - that's for sure !!!
ScienceOnly  (OP)

User ID: 84962
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04/25/2006 07:50 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Continuing,

If this comet was in one piece, we would have to conjer up all the GLP teotwawki spirit we could in order to get that comet to veer off its course and strike us.

But is not in one piece, it has broken apart. Instead of a rifling effect of a .22 bullet, it has become the scatter-shot as though fired from a shotgun. Remembering the "spread pattern" produced by a shotgun (remembering the Chaney mishap on the ranch in Texas), the farther it gets from the barrel of the gun, the wider the spread pattern.

Could we get hit by one of fragments? How about the moon?

more in a moment...
ScienceOnly  (OP)

User ID: 84962
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04/25/2006 07:54 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Unsure,

Exactly. If any fragment is lagging behind, impact could occur (moon or Earth).

If we expand the analogy above to being planes flying in the air, with long banners attached at the tail, then it becomes well within the realm of reason that the banner attached to the passing plane would slap us before it got clear of us.
Unsure(c)

User ID: 15255
United Kingdom
04/25/2006 07:57 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Science what size are we talking about ?

As i asked is it baseballs or houses ?

Also what do you suppose the fragments are made of, will these be able to get past earths atmosphere ?

Also by striking the moon surely it would require a massive strike to have any effect on lunar orbit ??
Unsure(c) - Why i am uncertain - that's for sure !!!
Anonymous Coward
User ID: 85458
Taiwan
04/25/2006 08:08 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Pin this, Trinity!
Anonymous Coward
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04/25/2006 08:17 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
ScienceOnly  (OP)

User ID: 84962
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04/25/2006 08:26 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Unsure,

My Starry Night program lists 73P as being 20km in diameter.

As far as striking the Earth or the moon, let's forget for a moment "why" the comet has fragmented and "why" the comet fragments have seperated from each other a bit. I'll come back to that once I have studied it a bit more.

For now, we know we are looking at several objects coming in with a wider footprint than a single 20 km object. In other words, the path of destruction is wider for anything in its way.

With respect to the timing of the passage, here's what I derived from the software visually.

As 73P moves to overtake the Earth, it gets even with, and slightly above, on May 5. At that time the difference between the two bodies is about 0.1 au.

The moon is also moving in a counter-clockwise motion around the Earth, and at this time the moon is moving up in between the Earth and 73P. Keeping with the race-car analogy, on May 5 you could look out your right window and you would see 73P along side but a bit higher. Coming up quickly in between would be the moon.

By May 12, the moon is basically right outside your right window. This is also the time when the moon will be full, since the sun is always out your left window (remember we are on a circular racetrack representing the Earth's orbit). To add to this, it just so happens that Jupiter is right out your right window as well...way out there, but basically in line. So what I am outlining is a line-up of the sun, Earth, moon, and Jupiter. By May 12-13, 73P has moved ahead a bit and is directly in front of you but a little higher, in what appears to be a successful move to pass you out.

On May 13, 73P is crossing the orbital path of the Earth but slightly higher...so in reality, 73P never actually crosses a point where Earth will travel. On that day the distance between 73P and Earth is 0.079 au.

More to follow...
Anonymous Coward
User ID: 85463
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04/25/2006 08:31 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Science Only, keep studying and posting your highway analogies provide an excellent way to understand what's likely to occur.
ScienceOnly  (OP)

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04/25/2006 08:31 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Continuing,

On May 24, comet 73P has finally reached the Earth's orbital plane. The point where it would "Disappear into the ground" is farther ahead and off to the left. The distance between Earth and 73P is .13 au.

With respect to the moon, the moon is orbiting the Earth counter-clockwise. From May 5 through May 20, the moon is outside the Earth's orbit. Per the analogy, it moves from behind the back bumper, up to the right side, and crosses the front bumper from right to left during this timeframe.

It is only logical to assume then, if some kind of "lagging fragment" is going to cause trouble, it would be more dangerous for the moon, since the moon is a little closer to 73P's path. Although it is only .002 au away from the Earth, it could act in a fashion similar to a "Block" in a game of American football.

So, how high is 73P when it is out in front of the Earth? Will we have to "Duck" to get under the path of the comet's many fragments?

Let me look...
Halcyon Dayz

User ID: 84549
Netherlands
04/25/2006 08:44 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
How the comet broke up back in '95 is important.
If it was thermal stress, the pieces will
be a lot closer together then when it was
caused by something more violent (collision).
The further out, the smaller the fragments,
in either scenario.

1 AU = 150,000,000 km.
Reaching for the sky makes you taller.

Hi! My name is Halcyon Dayz and I'm addicted to morans.
ScienceOnly  (OP)

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04/25/2006 09:01 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Continuing,

From the viewpoint of the center of the sun, looking out directly at Earth, 73P is 5 degrees above Earth's orbital plane on May 4. It takes 20 days for the comet to move down to Earth's orbital plane, crossing it on May 24.

So, during this timeframe 73P moving down towards the Earth's orbital plane at about .25 degrees per day (5 divided by 20).

Using the distance to Earth as a constant (1 au), 5 degrees of seperation from the vantage point of the sun equates to a distance of 0.087156 au. The "Drop per day," then, is 0.004363 au per day.
Dee
User ID: 536
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04/25/2006 09:11 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory

Thank you for the great analogy Science Only..

ScienceOnly  (OP)

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04/25/2006 09:20 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Using Halycon Dayz information above,

on or about May 4, 73P is about 13 million kilometers "above" the Earth as seen from the vantage point of the center of the sun...dropping at about 654,500 kilometers per day.

On May 13, about the time the comet crosses to the inside of Earth's orbit (directly in front of our race car, the elevation of the comet will be roughly 7 million kilometers above the Earth. The distance seperating the Earth and 73P at that time will be roughly 12 million kilometers.

****----****----****----****

Combining all the information above, if there are pieces of this comet that are trailing, then the most dangerous pieces will be those that are farther behind, below, and to the right of the comet's published path.

If a fragment is not too far behind, then it is going to have to be a fairly good amount below the published path, or a fair way to the right.

If a fragment was going to hit the Earth or moon, then:

If the fragment is not too far behind, but much lower, impact would occur in the first half of May.

If the fragment is not too far behind, but much to the right, then impact would occur in the second half of May.

If the fragment is a good ways back, but more aligned with the normal path of the comet, then impact would occur between the middle of May and the middle of June.

So, now we can look at the distribution of the fragments to see if any of the above scenarios are worth studying.

Does anyone know anything about the distribution of the fragments?
ScienceOnly  (OP)

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04/25/2006 09:21 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Dee
Anonymous Coward
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04/25/2006 09:48 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Anonymous Coward
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04/25/2006 09:51 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
UPCOMING CLOSE APPROACHES TO EARTH

Anonymous Coward
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04/25/2006 09:53 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
ScienceOnly  (OP)

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04/25/2006 09:59 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
I must run out for a bit. If someone can dig up a little information on the relative positions of the fragments (if known), when I get back I'll run it against the software and see if things are looking better or worse.

peace.
Anonymous Coward
User ID: 74098
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04/25/2006 10:02 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Yeah, and with Earth's ever increasing gravitational pull (like a bowling ball spinning in molasses constantly gathering more material as one scientist put it) It will be interesting to see if Earth get's skinned during this freak encounter.

They can't even keep the space station in proper orbit because Earth is constantly reeling it in.

And losing the moon an inch a year with it's eliptical orbit? I don't think so. More like it will gain 2 inches a year on the low side.

Smacko!
Anonymous Coward
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04/25/2006 10:02 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
supposedly the trail of dust and fragments is 4 million miles long
Anonymous Coward
User ID: 75343
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04/25/2006 10:03 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Your search string '73P' matched the following 38 records:
Please select from the list below.

Comet 73P/Schwassmann-Wachmann 3 [1995]
Comet 73P/Schwassmann-Wachmann 3-B [2006]
Comet 73P/Schwassmann-Wachmann 3-C [2006]
Comet 73P/Schwassmann-Wachmann 3-E [2001]
Comet 73P/Schwassmann-Wachmann 3-G [2006]
Comet 73P/Schwassmann-Wachmann 3-H [2006]
Comet 73P/Schwassmann-Wachmann 3-J [2006]
Comet 73P/Schwassmann-Wachmann 3-K [2006]
Comet 73P/Schwassmann-Wachmann 3-L [2006]
Comet 73P/Schwassmann-Wachmann 3-M [2006]
Comet 73P/Schwassmann-Wachmann 3-N [2006]
Comet 73P/Schwassmann-Wachmann 3-P [2006]
Comet 73P/Schwassmann-Wachmann 3-Q [2006]
Comet 73P/Schwassmann-Wachmann 3-R [2006]
Comet 73P/Schwassmann-Wachmann 3-S [2006]
Comet 73P/Schwassmann-Wachmann 3-T [2006]
Comet 73P/Schwassmann-Wachmann 3-U [2006]
Comet 73P/Schwassmann-Wachmann 3-V [2006]
Comet 73P/Schwassmann-Wachmann 3-W [2006]
Comet 73P/Schwassmann-Wachmann 3-X [2006]
Comet 73P/Schwassmann-Wachmann 3-Y [2006]
Comet 73P/Schwassmann-Wachmann 3-Z [2006]
Comet 73P/Schwassmann-Wachmann 3-AA [2006]
Comet 73P/Schwassmann-Wachmann 3-AB [2006]
Comet 73P/Schwassmann-Wachmann 3-AC [2006]
Comet 73P/Schwassmann-Wachmann 3-AE [2006]
Comet 73P/Schwassmann-Wachmann 3-AF [2006]
Comet 73P/Schwassmann-Wachmann 3-AG [2006]
Comet 73P/Schwassmann-Wachmann 3-AH [2006]
Comet 73P/Schwassmann-Wachmann 3-AI [2006]
Comet 73P/Schwassmann-Wachmann 3-AJ [2006]
Comet 73P/Schwassmann-Wachmann 3-AK [2006]
Comet 73P/Schwassmann-Wachmann 3-AL [2006]
Comet 73P/Schwassmann-Wachmann 3-AM [2006]
Comet 73P/Schwassmann-Wachmann 3-AN [2006]
Comet 73P/Schwassmann-Wachmann 3-AO [2006]
Comet 73P/Schwassmann-Wachmann 3-AP [2006]
ScienceOnly  (OP)

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04/25/2006 10:03 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
In an above post I wrote incorrectly that my software had 73P listed as 10 km in diameter. The actual number is 20 km; I updated the post.

Anonymous Coward
User ID: 85478
Taiwan
04/25/2006 10:05 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
20 km
Mrdjs7

User ID: 79015
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04/25/2006 10:05 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Wouldn't it be nice if it hit the white house when all "Relevent" people are there?

Sorry, off topic a bit. I can dream.

Thanks for the thread! Informative! At least someone is keep track of this!
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Anonymous Coward
User ID: 84505
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04/25/2006 10:07 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
SO, did you factor in the near earth asteroid 2006 GY2

closest approach to earth on:

May 16
6.7 Lunar distances
Anonymous Coward
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United States
04/25/2006 10:08 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
the problem is not moving the moon out of it's orbit
the problem would be scattered debris from whatever impacted the moon
Anonymous Coward
User ID: 85435
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04/25/2006 10:09 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
You can get the general idea of what the OP is saying here [link to neo.jpl.nasa.gov]

Choose the comet
Zoom all the way in
Center Comet/Asteroid
Anonymous Coward
User ID: 75343
Guatemala
04/25/2006 10:11 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
Remember
" should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstances"

Mrdjs7

User ID: 79015
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04/25/2006 10:12 AM
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Re: Schwassmann-Wachmann 73P; Here's what I learned about its trajectory
O.K., what about "Gravity Pull" put on these things as they pass through our solar system? Wouldn't that change the trajectory?
.........This Space For Rent.........
Anonymous Coward
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Australia
04/25/2006 10:13 AM
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