# How big is the Solar System? **URL:** \ **Category:** Factual Questions\ **Created:** [November 18, 2003, 11:01pm UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993 "2003-11-18T23:01:31Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Earthling](https://avatars.discourse-cdn.com/v4/letter/e/90db22/32.png) [@Earthling](https://boards.straightdope.com/u/Earthling)\ **Post date:** [November 18, 2003, 11:01pm UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/1 "2003-11-18T23:01:31Z")
Does it end at the Kuiper Belt? The Oort Cloud? The Heliopause? Is there a “commonly accepted” definition? ---
**Author:** ![Coffeeguy](https://avatars.discourse-cdn.com/v4/letter/c/958977/32.png) [@Coffeeguy](https://boards.straightdope.com/u/Coffeeguy)\ **Post date:** [November 18, 2003, 11:08pm UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/2 "2003-11-18T23:08:58Z")
I think the generally accepted limit is the heliopause. The opperative word being _solar_. The end of the sun’s infuence is a good measure of where its system ends. —CoffeeGuy ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [November 18, 2003, 11:21pm UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/3 "2003-11-18T23:21:51Z")
The heliopause is the end of the sun’s radiant influence, perhaps, but the Oort cloud is gravitationally influenced by the sun. ---
**Author:** ![Earthling](https://avatars.discourse-cdn.com/v4/letter/e/90db22/32.png) [@Earthling](https://boards.straightdope.com/u/Earthling)\ **Post date:** [November 18, 2003, 11:44pm UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/4 "2003-11-18T23:44:16Z")
So…does that mean a conflicting view on where the Solar System ends? Or is that just a clarification of which “influence” we’re talking about? And now that it’s been brought up – does the Oort Cloud lie at the outer reaches of the Sun’s gravitational influence? Or does that gravity extend out farther? ---
**Author:** ![aerodave](https://avatars.discourse-cdn.com/v4/letter/a/f08c70/32.png) [@aerodave](https://boards.straightdope.com/u/aerodave)\ **Post date:** [November 19, 2003, 1:50am UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/5 "2003-11-19T01:50:40Z")
Well, technically, the sun’s gravitational influence extends out forever. All particles in the universe interact gravitationally with all other particles. The sphere of influence of a body is roughly defined as the region in which the effect it has on other, smaller bodies is the predominant force. A body in orbit around Alpha Centauri is gravitationally influenced by our sun, but the effect is negligible when compared to the nearer star. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [November 19, 2003, 6:42am UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/6 "2003-11-19T06:42:21Z")
Here’s a good recent news article on the subject. It’s of importance right bow because Voyager 1 is now at the Heliopause. [Voyager Leaves the Solar System](http://www.cbc.ca/stories/2003/11/05/voyager031105) ---
**Author:** ![cmason32](https://avatars.discourse-cdn.com/v4/letter/c/51bf81/32.png) [@cmason32](https://boards.straightdope.com/u/cmason32)\ **Post date:** [November 19, 2003, 7:49am UTC](https://boards.straightdope.com/t/how-big-is-the-solar-system/213993/7 "2003-11-19T07:49:59Z")
> [@](#): > > \*Just remember that you’re standing on a planet that’s evolving > And revolving at nine hundred miles an hour, > That’s orbiting at nineteen miles a second, so it’s reckoned, > A sun that is the source of all our power. > The sun and you and me and all the stars that we can see > Are moving at a million miles a day > In an outer spiral arm, at forty thousand miles an hour, > Of the galaxy we call the ‘Milky Way’. > Our galaxy itself contains a hundred billion stars. > It’s a hundred thousand light years side to side. > It bulges in the middle, sixteen thousand light years thick, > But out by us, it’s just three thousand light years wide. > We’re thirty thousand light years from galactic central point. > We go 'round every two hundred million years, > And our galaxy is only one of millions of billions > In this amazing and expanding universe. > \* Due credit must be given to Mr. Python