Planetary Orbits, an open discussion

This thread is more of a means to answering a question for me. I found myself wondering why the planetary orbits of our solar system are not experiencing some form of degradation towards the gravity well that is our sun. After some brief research, I may have a well encompassing answer.

The planetary orbits are not stable and increase with time. For the beginning of the solar systems, all planets were closer to the Sun, and will be more distant in the future. The cause is the relative instability of the planetary orbits and solar mass loss by radiation and solar wind. The potential energy of planetary orbits relative to the solar escape energy (escape velocity) determines the stability of planetary orbits.

Link to harvard paper -->Link


My interpretation of the above is, that due the continuous reduction in mass of our sun, the gravitational pull of our sun is slowly but surely weakening and over time will eventually fling our solar systems planetary bodies off into deep space.
The reason this topic entered my mind was because I was thinking of satellites and how they require bursts of energy to maintain their orbits as a result of orbital degradation. Further to this, what will happen to the moon?


Just a thought on this topic, from a non-expert, is that the whole relationship between mass and gravitation pull seems ironic. Ironic in the sense that within the context of our solar system, the Sun is the gravitational pinnacle and that similar stars (of greater mass then our own) have the potential to be the gravitation beast known as a black hole.

Day dreaming about the unique processes of our universe is sometimes quite hard to comprehend, but quite fun to do.

Sort of Just taking out loud here and would love to read anyone’s input on the topic.

reply to post by MDDoxs


Weird. We usually interpret planets as having a spiralling down (towards the Sun) orbit, not outward. I see the guy's point, but It looks weird nevertheless.

reply to post by swan001


Yea I thought it was very interesting. I guess the misconception, in my case anyways, was that the suns mass is in a state of decline. I have a basic understanding that as the sun uses up its nuclear fuel it's mass would decrease, but I did not imagine it would be one such a scale that its grip on the planets is loosening.

reply to post by MDDoxs


Me neither.

But it does make sense.

Yet, a star like the Sun will expand into a giant star in 5 billion years. It will be so energetic it will produce carbon. Only then will the sun shrink into a white dwarf.

I thought our sun was fairly new or a baby in comparison to the suns in surrounding solar systems. Which in turn will grow and become a red giant about 8 billion years from now swallowing earth etc...

Here's an scientific website with an explanation opposing what you have posted...

www.scientificamerican.com...

Interesting thread. Thank you. S&F for you

reply to post by Xquizit


Yeah, that's the classical view, which assumes the Sun is not losing mass. But if it's leaking energy, then it's leaking mass. And I know it's leaking energy, especially when I get sunburned on summers.

reply to post by Xquizit


I didn't mean to say opposing... Lol. Total error. I meant to say that this website (posted in my above post) is similar. My bad

reply to post by Xquizit


Human specie will have colonized the Galaxy long before that happens. No problem for us...

reply to post by Xquizit


Guess it could be a matter of timing. Which will happen first perhaps? Will the sun lose enough mass to eject the planets from the solar system before it collapses in on itself and explodes? I do not have the answers

The above poster is right. We will be well out of our solar system when this actually becomes an issue for the human species.

reply to post by MDDoxs


Our star will not nova, it lacks the minimum required mass to achieve such a fate, it will slowly fade and die quietly, it wont burn out it will fade away.

Also your missing a key factor in your thinking, the sun every single day, pulls in more mass with its gravity than the earth, just as the earth, grows by many tone from meteors and dust. So too does the sun, so its not losing mass in proportion to its energy release. It is losing much mass per "day" in the form of energy release, but it always gaining mass also, do to its massive size and gravity.

The moon is actually moving away from the Earth at something like 1.4-1.5 inches every year, I guess it is only a matter of time before it breaks free (many billions of years).


As for the Earths orbit around the sun? I honestly don't know, probably similar to the moon.

reply to post by inverslyproportional


Yeah, that's true. Space is full of hydrogen, if the Sun passes through this (well actually, it is in some sort of a thin nebula) it'll give it more fuel. Well, I guess. That's how stars get formed in the first place anyway.

reply to post by woogleuk


Hm. Last itime I checked, the Moon was said to spiral down. What is causing it to spiral up? It can't gain speed up on its own, and I doubt NASA's shuttle departure from Earth contributed to diminish Earth's mass.

Originally posted by MDDoxs
Just a thought on this topic, from a non-expert, is that the whole relationship between mass and gravitation pull seems ironic. Ironic in the sense that within the context of our solar system, the Sun is the gravitational pinnacle and that similar stars (of greater mass then our own) have the potential to be the gravitation beast known as a black hole.

Just because our sun isn't a black hole doesn't mean that it also doesn't gobble up cosmic debris. When asteroids or Kupier belt objects get perturbed from their orbits, they can potentially slam into any planet, but since the sun has the bulk of the solar system's gravity, they are most likely to end up in the sun, and next most likely to end up in Jupiter.

So the sun is gobbling things up, but not as fast as a higher mass black hole would. However it's losing more mass than it's gaining so there is a net loss.

In a few billion years if humans still exist we need to move to Mars or eventually the moons of Jupiter/Saturn because Earth will become too hot to sustain life as the sun expands. Yes this is a paradox, that as it loses mass, it will actually become bigger (and less dense) and boil away all the water in the Earth's oceans. All this will happen long before any planets get flung away, so don't worry too much about planets flinging away, that's the least of our worries.

What is uncertain is if the Earth orbit will move far away enough from the sun so that the sun won't swallow it up or not. The sun is expected to expand to the Earth's present orbit in maybe 5 billion years, but of course when that happens Earth's orbit will be further out, so it might be a close call, but even if the Earth isn't swallowed by the sun, it still won't be habitable, even by extremophiles. It will likely appear as ball of molten lava on the surface if it survives at all.

Originally posted by swan001
reply to post by woogleuk

 

Hm. Last itime I checked, the Moon was said to spiral down. What is causing it to spiral up? It can't gain speed up on its own, and I doubt NASA's shuttle departure from Earth contributed to diminish Earth's mass.

I think your last check was in error. It was never said to spiral down. The Earth's rotation is slowing down and some of the energy is being imparted to the moon, speeding it up, making it spiral up. This is due to Earth-moon interaction (tides, etc).

reply to post by Arbitrageur


Further to this, the Moon is receding at a rate 1.48 inches per year. Here's an interesting article...

Why the Moon is Getting Further Away From Earth

reply to post by Insomniac


The time scale is something hard to grasp with the cosmic occurances. I have difficulty comprehending 1 Billion years beyond the purely numerical context

reply to post by MDDoxs


Vast expanses of space and extremely long periods of time are way outside our ability to comprehend. Michael Moorcock wrote this poem and it was used by the band to my left. I guess it's not entirely relevant to thread, but if the OP and the Mods will permit me, it does give a feel for the incomprehensible...

The Black Corridor (Moorcock)

Space is infinite.
It is dark.

Space is neutral.
It is cold.

Stars occupy minute areas of space. They are clustered a few billion here. A few billion there. As if seeking consolation in numbers.

Space does not care.

Space does not threaten.

Space does not comfort.

It does not sleep; it does not wake; it does not dream; it does not hope; it does not fear; it does not love; it does not hate; it does not encourage any of these qualities.

Space cannot be measured. It cannot be angered, it cannot be placated. It cannot be summed up. Space is there.

Space is not large and it is not small. It does not live and it does not die. It does not offer truth and neither does it lie.

Space is a remorseless, senseless, impersonal fact.

Space is the absence of time and of matter

Originally posted by Arbitrageur

I think your last check was in error. It was never said to spiral down. The Earth's rotation is slowing down and some of the energy is being imparted to the moon, speeding it up, making it spiral up. This is due to Earth-moon interaction (tides, etc).

It seemed that this interaction would make the Moon lose energy too, making it slow down, just like the Earth is doing with the sun. They lose energy just by staying in orbit. Kinetic energy is transferred through gravitational pull, from both sides. Is there databases showing the annual Moon distance to Earth that I could check out?


Ah, never mind, I saw the link the next gentlemen posted, from BBC news:

The Moon continues to spin away from the Earth, at the rate of 3.78cm (1.48in) per year, at about the same speed at which our fingernails grow.

Without the Moon, the Earth could slow down enough to become unstable, but this would take billions of years and it may never happen at all.

Hm. It seems you are right after all. So smaller planets and moon will be the first to go in the distant future, due to gravity which is imparted.

Thanks for the correction, mate.