# How far out can the sun keep celestial objects revolving?

Astronomers define the Solar System as the distance under the influence of gravity from the Sun.

I read that the Oort cloud is probably the farthest object that surrounds the sun. The sphere of this icy cloud is thought to surround the Sun at up to a distance of 50,000 AU, making its total diameter nearly two light years.

How far can the sun's gravity extend to hold celestial bodies around it? The Oort cloud may be the known farthest body but its edge doesn't mark the end of the sun's effective gravitational pull.

• Looks like someone had a quick go at this, might be a start point?: forum.cosmoquest.org/… . It's a very rough estimate though; we have many stars of varying masses nearby. – user10106 May 4 '18 at 10:07
• If you rephrase this question as "where in the galaxy/universe is the Sun's gravity stronger than the gravity of any other star", you could use a Voronoi diagram to come up w/ a mathematically precise answer. As others note, it's 2.25ish ly in the direction of Alpha Centauri, but could be bigger in other directions. Someone should do the math. – user21 May 5 '18 at 16:47
• @barrycarter The Alpha Centauri trinary is a bit over 2.1 solar masses. That puts the "trojan point" if I can call it that, closer to 1.75 lya not 2.25. Small nitpick. – userLTK May 5 '18 at 18:34
• @userLTK Good point. I vaguely remember reading that Alpha Centauri is about the same size as the sun. While that's true, I forgot that it's a triple star. – user21 May 6 '18 at 16:27

• -1 This doesn't really answer the question "How far out can the sun keep celestial objects revolving?" nor does it give any information where the Oort cloud is thought to end. All this does is say it's an interesting problem and here are some things to think about if you were going to try to answer it. – uhoh May 5 '18 at 8:06