Solar system border

[Yuri_Armstrong]

What is considered the border of our solar system? Have any of our probes passed the border yet?

 

[MeteorWayne]

There is no read "border". The sun's particle and wind environment carves out an area called the heliosheath, but the Kuiper Belt extends far beyond that. Voyager 1 and 2 are there now, 93 and 114 AU from the sun.

"On June 28, 2010, Voyager 2 completed 12,000 days of continuous operations since its launch on August 20, 1977. For nearly 33 years, the venerable spacecraft has been returning unprecedented data about the giant outer planets, the properties of the solar wind between and beyond the planets and the interaction of the solar wind with interstellar winds in the heliosheath. Having traveled more than 21 billion kilometers on its winding path through the planets toward interstellar space, the spacecraft is now nearly 14 billion kilometers from the sun. Traveling at the speed of light, a signal from the ground takes about 12.8 hours to reach the spacecraft.

Voyager 1 reached this milestone on July 13 after having traveled more than 22 billion kilometers. Voyager 1 is currently more than 17 billion kilometers from the Sun."

The sun's gravitational influence extends to the edge of the Oort Cloud, gravitationally halfway to the nearest star in any direction, 50,000 to 100,000 AU from the sun. We will certainly not visit there in my lifetime...

MW

 

[BurgerB75]

Makes you wonder if the composition of the bodies in the Oort cloud would be different that those within the heliosheath. Would the galactic radiation that the solar wind protects us from alter the bodies in the Oort cloud differently than those within?

 

[MeteorWayne]

Quite likely actually. Inside, we are protected from a majority of the cosmic rays. Objects out there are fully exposed, and such energetic radiation and particles surely cause changes to the material, even if it as created in the inner solar system as theorized.

 

[BurgerB75]

Quite likely actually. Inside, we are protected from a majority of the cosmic rays. Objects out there are fully exposed, and such energetic radiation and particles surely cause changes to the material, even if it as created in the inner solar system as theorized.

Makes me even sadder that we probably won't be able to sample them anytime soon.

By the way, I thought the Oort could was still just therorized by long period comets.

 

[MeteorWayne]

Well, of course no OCO's have been observed, but the theoretical evidence (including long period comets) is pretty strong. In any case, gravitationally halfway to the nearest star would be the limit where an object can be bound to the solar system.

Of course, the solar system's light and gravity go on forever, so in a sense, there is no border

 

[Yuri_Armstrong]

But I heard someone in the unexplained forum say that the Oort cloud doesn't even exist.

 

[MeteorWayne]

That's not what they said, and did you read my reply?
And that was in this thread BTW, so you can just scroll up to see what was said
In any case, again, that doesn't change the statement I made here that anything gravitationally bound to the solar system will be at most gravitationally halfway between the sun and the nearest star in that direction. It's the gravitational border of the solar system. Strictly speaking, whether or not anything
exists there is a moot point for this discussion about a border.

 

[Yuri_Armstrong]

Yeah, I was just wondering what astronomers consider interstellar space. But I guess using the oort cloud you could say the solar system is one light year long right?

 

[MeteorWayne]

Well 1 to 1 1/2 light years in radius, or 2-3 light years in diameter.

 

[neilsox]

If the border is where the gravity cancels, it is somewhat more than 3 light years in most directions, As most of the nearby stars have less mass than our solar system. About 2 lightyears is correct for the direction of the Centauri triple sun which has significantly more mass than our solar system. At 9.6 light years Sirius is likely far enough away that the zero gravity point is about 3 light years from here in that direction. An object that orbits a maximum of 2 light years, from the sun will likely be ejected from our solar system, eventually, as the Sun's gravity is very weak at that distance so a minor impact can push it out of orbit. Neil

 

[MeteorWayne]

Collisions would be exceedingly rare in the Oort cloud. Distances between objects will be hundreds of AU. Far more likely to cause an orbit change would be gravitational perterbations from a passing star, or galactic tides (period ~ 100,000 years) since with a semimajor axis of 0.75 LY the orbital period is over a billion years; for 1.5 LY, it's over 3 billion years, nearly the age of the solar system itself.

 

[neilsox]

If the length = circumference of an orbit is 10 light years, and the period 4.6 billion years, then objects in more distant orbits have not yet completed the first orbit, and probably won't complete one orbit, before they are perturbed into a new orbit not around the sun, so the present location of the Centauri triple sun and Sirius are almost irrelevant due to their proper motion? Neil

 

[Ace_]

Our solar system is like the outskirts of New York: There is no solid line where it ends.