Voyager and Comets

Sharnbrook (Mike) · #1 20-09-2008, 02:56 PM

I have a question for the knowledgeable astronomers using this forum.

Voyager 1 and 2 have now reached, and passed through, the edge of the Heliosheath, at a distance of some 100 AU, and are on their way to Outer Space, travelling at an average of approx 3 AU per year. I understand that the Heliosheath is basically the limit of the gravitational effect of the Sun.

Long Term Comets are thought to originate in the Oort Cloud which has 2 components, an inner part and an outer part. Medium term comets form in the inner cloud, whilst long term comets are formed in the outer cloud, which extends to a distance of 50,000 AU from the Sun. (Short term comets come from the Kuiper belt)

If that is so, then for the comets to be periodic, they must be within the Sun's gravitational field. They come and go, and come and go, so gravity must be the cause of this repetitive journey. If they are just one off comets, any number of events may cause the comet to enter our solar system, but it will then leave, never be seen again.

So what will happen to the Voyagers? Will they continue on their journey for ever, or until they become caught up in the gravitational field of another star, or will they eventually return to the Solar system in x thousand years time, having been to the Oort Cloud and back?

On the assumption that they will go on forever, is it possible that there may be other planets, asteroids etc that have been thrown out of a star system elsewhere in the Universe in a manner similar to the slingshot effects that were contrived by NASA to send Voyager off to oblivion? If so, can it be assumed that there may be some wandering planets in Outer Space, with no Solar system of their own?

I realise that NASA used rocket propulsion, aided by the gravity of the planets, to provide the impetus to get the satellite in the correct position to escape, but couldn't this also happen naturally, given the number of stars and planets out there?

If anyone has answers, or even hypotheses, to these question, I would be most interested in hearing them.

[1ponders] (Paul) · #2 20-09-2008, 05:06 PM

Hi Mike.

I understood the heliopause/sheath to be the point in space where the sun's solar wind is balanced by the "galactic wind" and not a point where the sun's gravity stops.

As for the Voyagers, they will still be under the major influence of the sun's gravity for some time to come, that is until they reach a point between the sun and another star who's gravitational influence becomes gradually stronger than the sun's.

Will they ever leave our system completely? I'm not sure if they have the required escape velocity, but think I did read somewhere that they did. If so they won't return.

I'd be pretty sure over time Jupiter would have played it's part in flinging objects out of the solar system.

NQLD_Newby · #3 20-09-2008, 10:24 PM

Hi Mike, being a relative newby and all I can't answer your questions directly, however regarding the question about wandering planets, the link below from another thread shows a story about the first possible photo of a planet around another sun like star. Anyway to get to the point, in that story they mention that until now the only planets that had directly been photographed were free floating planets. I presume this means that they do exist. Hope this helps.

http://www.iceinspace.com.au/forum/s...ad.php?t=35942

Sharnbrook (Mike) · #4 23-09-2008, 10:54 AM

Hi Paul,

Thanks for your input, and for correcting me on the definition of the heliopause. I must say that I had thought that it was also a point where the sun's gravity basically stopped.

As for whether the Voyagers will ever return, that surely wasn't in the minds of the scientists at NASA, as they included a plaque with details of earth, our solar system and mankind on it, just in case it was ever found by another "intelligent being". But nevertheless, COULD it be that Voyager will eventually return?

Sharnbrook (Mike) · #5 23-09-2008, 10:58 AM

Hi Rex,

Thanks for your contribution also. That article was very interesting, and it's provided an answer to one part of my question, ie, yes there are free floating planets. I had no knowledge of that, but my intuition told me that they probably had to exist.

Sorry I hadn't replied earlier, but I have been away for a few days.

Blue Skies (Jacquie) · #6 23-09-2008, 09:16 PM

I think the thing you need to know about is the escape velocity of the solar system, which is just over 73km/s (hmm, might be wrong on that but will check later, but the concept stays the same.) If the Voyagers have escape velocity, which I think they do, they'll just keep on going. Same with comets, like the speccy McNaught the other year - it looped around the sun and gained too much speed and will now just keep on heading out and not return. Other comets have been known to do that too.

Sharnbrook (Mike) · #7 23-09-2008, 10:18 PM

The 2 Voyager units have different velocities, but Voyager 1, which is faster, has a velocity of approx 3.6 AU per annum, according to NASA, (or 17.11 km/sec by my calcs), whereas the escape velocity from the Solar System, from the point of Earth's orbit, is 42.1 km/sec...... ( Wiki ) So, what do we make from that? I don't claim to know anything, other than what I have read, but these figures don't really seem to tie up. Will it escape, or will it not? I know that Wiki's facts are notoriously unreliable in some cases, but what other facts and figures are there? I shall try to research some alternatives in the next day or so, but if anyone else has any thoughts, please contribute.