Oort clound

[Jacob01]

Hi,

I have a question about the Oort cloud, which also involves Voyager 1 and interstellar space. Voyager 1 is thought to now have entered interstellar space, and therefore the Sun's SOI, I think. However, its not yet passed through, or entered, the Oort cloud. So, that means the Oort cloud is in interstellar space. But if its in interstellar space, its out of the Sun's SOI so it can't orbit the Sun. However, it supposedly orbits it anyway. So, how can it orbit the Sun when its out of its SOI?

Jacob

[andrewas]

The suns SOI continues well into interstellar space - its the region of space where the sun's gravity is the strongest influence on a body. This is well beyond most of the various points marked as the 'edge of the solar system', which are mostly to do with the interaction of the solar wind with interstellar medium. If Voyager was going to live long enough, Im sure we'd get another dozen or so reports of it leaving the solar system whenever it hits some approximation of the edge of the SOI , but it'll run out of power long before that happens.

[relin]

It's still in the SOI, but it's no longer affected by the Sun's outgoing massive particles (solar wind). I'm not actually sure if it's achieved escape velocity, but I'd imagine it has; it'll just take a while before it's actually out.

[Ralathon]

Hi,

I have a question about the Oort cloud, which also involves Voyager 1 and interstellar space. Voyager 1 is thought to now have entered interstellar space, and therefore the Sun's SOI, I think. However, its not yet passed through, or entered, the Oort cloud. So, that means the Oort cloud is in interstellar space. But if its in interstellar space, its out of the Sun's SOI so it can't orbit the Sun. However, it supposedly orbits it anyway. So, how can it orbit the Sun when its out of its SOI?

Jacob

Because in real life there are no Spheres of influence. You could feel the gravity from the sun all the way from the other side of the galaxy. Or the gravity of earth, or your own gravitational field. Of course they'd all be minuscule, but they're still there.

In KSP they use SoI to simplify the calculations and make orbiting easier. In real life the moon and the sun constantly pull on satellites causing their orbits to shift, this requires small corrections else your satellites end up deorbited or in wonky orbits. Since station keeping is rather boring they cut it out in KSP.

What they mean when Voyager 1 has reached interstellar space is that it left the heliosphere.

Basically, the sun is constantly spewing out tons of gas at very high speeds. This is the solar wind. As the gas gets further from the sun it moves slower and slower until eventually it stalls against the pressure of the interstellar gas. Voyager has crossed that barrier where the solar wind stops and is now in interstellar gas. It is the cosmic equivalent of a hydraulic jump:

Sun is the spot where the water hits the sink. Fast but shallow water is the heliosphere and the deep but slow water is the interstellar medium.

Edited January 23, 2014 by Ralathon

[andrewas]

Voyager 1 is well over escape velocity, and has been since the jupiter flyby.

[Jacob01]

Okay, I get it now. The Sun's gravity influences things well beyond into interstellar space, as do the planets. Thanks!

[nhnifong]

That is a very illustrative example!

[PakledHostage]

Something that I've always been curious about on the topic of Oort clouds is the Oort cloud surrounding Gliese 710. By some estimates, that star will pass through the outer reaches of our Sun's Oort cloud in just over a million years. How big is its own Oort cloud though? If it is of comparable size to our own Sun's, then it stands to reason that some of its Oort cloud bodies could pass through the inner solar system of our Sun.

[Jacob01]

If a star passed through/near the Oort cloud, that would be interesting to see. There would possibly be a increase in comets into the inner solar system, perhaps putting on some spectacular displays. Shame none of us will be around to see it!

[lajoswinkler]

Because in real life there are no Spheres of influence. You could feel the gravity from the sun all the way from the other side of the galaxy. Or the gravity of earth, or your own gravitational field. Of course they'd all be minuscule, but they're still there.

There are spheres of influences in real world, but they aren't perfect spheres.

SOI does not mean the gravitational influence stops. It means it's overpowered by another source.

In KSP, SOI is simplified into perfect sphere, and outside it the influence completely stops.

[Ralathon]

There are spheres of influences in real world, but they aren't perfect spheres.

SOI does not mean the gravitational influence stops. It means it's overpowered by another source.

In KSP, SOI is simplified into perfect sphere, and outside it the influence completely stops.

I know, but as you said; in real life it is more of a mathematical boundary than a physical one. You won't see any significant difference when crossing a SOI in real life. The OP clearly doesn't know much about orbital mechanics so I didn't want to scare him with a big info dump.

In the same way you don't tell a 10 year old "Everything is made of atoms. Atoms have a nucleus and electrons around it. But technically the nucleus is just a conglomeration of up and down quarks held together by constantly alternating their color charge via the exchange of virtual gluons to remain roughly in pairs of 3 but sometimes they exchange pions to create a force that binds the groups of 3 together analogous to London forces"

It's just way too much information. Gotto build it up slowly and go "Well, actually" whenever you need the more complicated stuff to explain something.