Is there momemtum in space? (1 Viewer)

[Paul Jenkins]

Here is something interesting from JPL on Schumaker-Levy-9, a comet that become orbital around Jupiter and then crashed into it...
http://www.jpl.nasa.gov/sl9/

During this close approach, the unequal Jupiter gravitational attractions on the comet's near and far sides broke apart the fragile object. The disruption of a comet into multiple fragments is an unusual event, the capture of a comet into an orbit about Jupiter is even more unusual, and the collision of a large comet with a planet is an extraordinary, millennial event.

I sure hope I don't get sucked into another hobby, home theater is expensive enough!!!

 

[Max Leung]

The 100m OWL telescope proposed a few years ago by the European Southern Observatory group (ESO) may actually be built. Currently, the largest aperture for a telescope is the Very Large Telescope (VLT) at a 'very tiny' 16.4m by comparison. This monster is predicted to have a light gathering resolution of about 40 times the Hubble Space Telescope and a sensitivity several thousand times greater. Among many other things, it should be powerful enough to detect and gather spectroscopic data of extra-solar planets in order to determine the atmospheric composition and any signatures for life, like oxygen."

 

[BrianW]

Paul, no I'm not saying that objects must be created in orbit around one another. I'm simply saying that in order for one object to capture another object in orbit, there must be some inelasticity involved that can account for the loss of kinetic energy.
However, it appears that I’m wrong.
Yeah, you heard me.
It would seem that one frame of reference is not as good as any other. How did Schumaker-Levy-9 come to crash into Jupiter, the very thing it was orbiting? From Jupiter’s reference frame, it appeared that the comet’s orbit suddenly destabilized and crashed into the very center of its universe without so much as bothering to spiral inward for even a couple of orbits. How is this possible? Simple: Jupiter is a non-inertial (accelerated) reference frame. If Jupiter were moving along in a straight line, Schumaker-Levy-9’s orbit would have no reason to destabilize. Wherever Jupiter goes, so goes the comet. But since Jupiter’s orbit is circular, not linear, Jupiter is being accelerated. It is therefore not an inertial reference frame, and where Jupiter goes, Schumaker-Levy-9 does not necessarily follow. (For the record, everything traveling in a circular or even a curved path is being accelerated, even if its actual speed doesn’t change.)
This non-inertial influence works both ways. It can work to destabilize existing orbits, causing orbiting objects to crash or to fly away, and it can act to capture approaching objects in permanent orbit.
And the Moon, also in a non inertial reference frame, even relative to the Earth, can conspire to capture another object in Earth orbit, just as Danny has stated. And the new object’s orbit need not be that elliptical, it turns out. (I can’t believe I stayed up this late to do the math. Ugh.)
Thanks for taking the time to set me straight. You guys are great.

 

[Danny R]

Objects traversing their own trajectories are captured by larger objects' gravitational pull all the time. So, yes, it can happen and does happen. Phobos and Deimos did not start out as moons of Mars, but were stray asteroids captured by the planet's gravity well.
errr, wrong answer. Its quite likely that the two moons were aerobraked in when Mars had a thicker atmosphere. Gravity alone didn't catch these two.
http://calspace.ucsd.edu/marsnow/lib...ry/moons1.html
Again, all the time.
Not that we know of without the exceptions listed above (repeated below).
If your theory were true, objects would never orbit others, unless they were "created" in orbit with one another...
Not quite... look at the exceptions. For an object to be captured, it has to be slowed down in some manner. This is accomplished via aerobraking or gravity braking. If the object is slowed down enough from its initial trajectory inward, it can form its own stable orbit.
The second way an object is found in orbit is if it strikes something. The moon/earth combo was created when a mars size body hit earth, and a large chunk of our planet spit off into space as a result. Likewise an object can strike something already in orbit, altering its trajectory enough that it sticks there.
The final way an object finds itself in orbit is if it accretes there in the first place, much as our planets formed orbiting the sun. And this exception is really just a complex version of the collision one, except involving lots of objects.

 

[Max Leung]

Oh BTW, here's a few links showing pictures of the M42 nebula, made by ground telescopes:
http://www.astropix.com/HTML/B_WINTER/M42.HTM
http://www.seds.org/messier/m/m042.html
Some amateur images: http://www.seds.org/messier/more/m042-043_m1.html
Lots more from a Google search can be found!

 

[BrianW]

Its quite likely that the two moons were aerobraked in when Mars had a thicker atmosphere.

Wow, that's cool! What fun it would have been to have been a Martian at the time this was happening!

Edit - Danny and I are trampling each other addressing the same stuff. Suffice to say that Danny has been way more eloquent in describing the mechanisms responsible for orbital capture than I have been. However, I didn't buy into notion that gravity braking alone could ever account for orbital capture. But the mention of comet SL-9 got me to thinking, and I cracked a few books and drew a few pictures only to discover that Danny is right on that count, too.

Must sleep now.

 

[MarkJAstro]

Hi All,
Paul's brother here. I am one of the amateur astronomers (astrophotographers actually) that is responsible for the photo that Paul posted earlier. Please don't confuse me with a Astrophysicist!
Three of us worked on this project. I assure you it was taken with amateur, ground based telescopes, albeit expensive ones! (i.e. no Meade, Tasco or Celestron at work here! Of the three telescopes used, none of them are larger than 10" in diameter. One is a 7" the second a 9.25" and the third a 10".
This project consists of over 500 individual exposures. The "RGB" composites from each telescope are taken through Red, Green, Blue filters. My telescope, a 9.25" Maksutov Newtonian also contributed a narrow band component taken with a 656nm wavelength / ~3nm spread Hydrogen-Alpha filter.
We use cooled, CCD digital cameras designed expressly for astronomical use. They are not color cameras. We must shoot several exposures through each color filter and combine them to produce an RBG composite.
All three telescopes also exposed a Lumenence or "L" layer that is shot unfiltered and provides a full spectrum high resolution component of the composite.
I see that Max has posted links to other photographs of M42. That's great! M42 is one of the most photographed astronomical objects ever. What makes our version of this object so unique is the fact that until very recently, Jack was correct and for the most part still is about the performance of ground based telescopes. Especially in the amateur realm. Most amateurs are not as nutz as we are about this stuff and will stop after only a few hours of work on each subject. This project took the combined effort of 3 people over a 4 month period (part time of course!) of late nights (early mornings) and countless hours sitting behind a computer screen doing the processing. One has to dedicate an extraordinary amount of time and effort to obtain the results you see in our M42.
We have searched the web exhaustively and to date have not found a photograph of M42 with as much detail. The Trapezium region (central stellar nursery) is of particular interest. The HST imaged this region a while ago and there is a comparison of the level of detail we obtained between the two here:
http://www.astro-physics.com
Click on the Gallery link then the "Artists of the Night Sky" scroll down until you find
M42 Core of the Orion NebulaRoland Christen Overlay with HST Image
You may need to stretch the window that opens up to get the overlay to work.
You will see that a 10" telescope (designed and manufactured by Roland by the way) actually outperforms the HST!
Feel free to browse through the gallery. It is one the best showcases of astrophotography anywhere.
The company's web site that you will be on is Astro-Physics. They make all of our telescopes and mounts. You can get a feel for what some of our equipment costs. The CCD cameras we use range in price from $3,000 (mainly used as just an auto-guider) to the $7,500 - $10,000 range for the main imaging camera complete with filter wheel and filters. Add to that a dedicated computer for each camera and software of course!
Our websites: http://www.bigcigarastronomy.com and Link Removed
Oh yeah, I do have an ad-hoc home theater too! It's probably laughable by your standards but I can project my DVD and Satellite dish signal onto a wall that is 8' x 17' using my lowly Telex FireFly. I use my very humble home stereo system for sound and we do the popcorn thing and....
I have a room in my basement all picked out to be used as a "real" home theater and Paul knows which one I'm talking about.
Someday!

 

[Danny R]

I think I may have come upon a slight alternative to the collision means of capture as well.

What if a large asteroid enters, and then due to tidal stresses breaks apart? Could it be possible for one portion of the asteroid to remain, with the excess energy travelling with a fragment that escapes? Sort of the opposite dynamics of a collision.

--

Another alternative I was considering is that of a comet. If it came in at just the right angle and speed, the gaseous venting might slow it down just enough to also be captured.

In a simular vein, particles that are light enough could slowed by solar wind/photon force.

 

[MarkJAstro]

Just for grins here is the latest project we are working on.
http://www.bigcigarastronomy.com/M16Ha1SmallCol1.jpg
It is a false colored version but consists of over 10 hours of initial exposures including Hydrogen -Alpha lines using a 7" Apochromatic Refractor.
That's all for me unless anyone has any questions.
I certainly do not want to take this forum in a direction that is contradictory with its intended purpose.
I will retain my registration as I do have an interest in building a home theater.

 

[MarkJAstro]

One more thing.


All the images I have posted references to including the in-line image that Paul posted are copyrighted by their respective owners and may not be used without permission.

Thanks.

 

[Julie K]

I think the issue has been dealt with pretty well, but just a couple of things. The original post had:

stopped by our gravitational rotation and become a part of our solar system?

A minor nitpick, but perhaps it will help to illustrate some concepts...

The objects flying by us are already in the solar system. They are in orbit about the Sun as we are. However, relative to the Earth, they are on escape trajectories. These are generally hyperbolic, which mean they have a velocity relative to Earth at infinity of greater than 0 km/s. There are also parabolic trajectories which have an Earth relative velocity at infinity of 0 km/s. However, in the solar reference frame, they are all on good elliptical trajectories. For instance, a good first order approximation to an interplanetary trajectory can be made by breaking the trajectory into three parts: a hyperbolic escape trajectory from Earth, an elliptical transfer orbit centered on the Sun, and an incoming hyperbolic trajectory at the other planet. As for orbit capture, there are ideas for using aerocapture (aerobraking usually refers to changing a highly ellliptical orbit to a circular one) instead of large propulsive maneuvers. However, heating rates can be pretty high and I could imagine a lot of natural objects breaking up.

BTW, there was an interesting article I read recently that proposed that the Eocene extinction event (1 of 5 species went extinct when Antartica froze at the end of the Eocene) was due to a slight decrease of solar radiation due to a temporary ring about the Earth. This ring was proposed to be caused by an asteroid collision that threw material back up into orbit. I'm don't totally buy it, but it was interesting. Whether or not this was the cause of the cooling of the Earth in the Eocene, it does show that here is another way to get material into orbit.

 

[Max Leung]

That's really good stuff Mark! Imagine if you were as dedicated to home theater as you were to that project...

 

[Holadem]

Hey Jack! You want some salt with that foot?
I have been waiting all day for your reply and now I have to go home
--
Holadem

 

[KyleS]

Well Jack we all learn something every day in our lives but sounds like you will have to pony up dinner for Paul if/when he ever gets out to LA. Mark those are some fantastic pictures that you guys have taken A+
KyleS

 

[John Stone]

Extremely impressive work, Mark! I'm somewhat of an astronomy buff, so I know how difficult it can be to take really BAD pictures of deep sky objects! Thanks for taking the time to post, that was really interesting stuff. Good luck with your HT!

 

[Jack Briggs]

Crow is a dish best served ... cold.
Mark, I want to discuss this image further, but I must leave the office presently. I will return to this thread tonight. (Does your brother like his steak medium or well done?)

 

[MarkJAstro]

Thank you for all of your kind words.
I will be around here tonight for Q&A as the clouds have rolled in. It looks like I will not be catching any photons for the next couple of nights.
It figures. It's a new moon after all!
The formula goes:
New Moon = clouds
Full Moon = clear skies!
Arrrrggghhhh!
Hey maybe a movie!

 

[BrianW]

Mark, thanks for stopping by. I wish I were in a position to hire you and your fellow astrophotographers. I've never seen such (non-Hubble) pictures.
Do you have a shot of that nebula from a different angle?

 

[MarkJAstro]

Hey Brian,
Thanks!
Let's see, if you can let me borrow that faster than light speed space ship I could get that other camera angle for you!
Or I could just skew it in photoshop!

 

[Paul Jenkins]

hey, come on now, can't you do that wonderful Matrix-like effect where you go AROUND the nebula
I thought you Mac guys could do anything!!