The shape of the solar system?

Question

What does this article mean about the shape of the solar system? Does it mean that the shape is not spherical? If I try to visualize it, what object can be used to describe the actual shape? Does it look like a pear, or a half-moon, or what? What do they mean by "slightly dented"? Thank you.

http://news.yahoo.com/s/ap/20080702/ap_on_sc/sci_solar_system

Answer 1

"This difference proves that the heliosphere is not even close to perfectly round, but is oblong, like an egg, according to the studies, released by the British journal Nature on Wednesday." - Yahoo

"The "bottom" of the egg is flattened by a permanent clash of particles, as the outbound solar wind smashes into atomic debris hurtling in from interstellar space, the scientists theorise." - Yahoo

In other words, the sun is emitting solar rays towards the interstellar medium (space outside our little protective womb), when the solar rays meet all of the atomic particles from the interstellar medium, it's causing turbulence; dragging the heliosphere behind the solar system, denting it in. The force of the atomic particles against the solar winds is really really powerful, creating the oblong shape.

Image:

http://en.wikipedia.org/wiki/Image:Voyag...

Answer 2

They're not talking about the whole solar system, they're just talking about the shape of the boundary between the solar wind and interstellar gas.  It's dented a bit because of "ram pressure", but basically the shape is spherical.

Answer 3

http://en.wikipedia.org/wiki/Heliosheath

This is a lot more information about the phenomenon the article is discussing.

Answer 4

From what I've read, they think it is sort of egg shaped with one side being pushed in.

Answer 5

When most of us think of the solar system, we think of the Sun and 8 or 9 planets (or 12, depending on your planetary beliefs).

The planetary system extends to about 40 astronomical units (one au is the average distance from the Sun to Earth).  The 8 major planets are on almost the same plane, making the 'shape' of the solar system that of a flat disk.

Those who look at all the material bodies in the solar system will think of adding in the Kuiper objects and the Oort cloud.  The Kuiper belt is still (roughly) on the same plane but a lot thicker.  It extends to almost 60 au.

The Oort cloud is spherical (it exists in all directions, not just on the planetary plane) and it extends to almost 50,000 au.

At that distance, these objects are still (barely) in the gravitational grasp of the Sun.  Past that distance, the Sun's gravitational force is about the same as the gravitational "noise" representing the gravity of all the other stars in the neighborhood.

Energetic charged particles are expelled from the Sun in all direction.  This flow is called the Solar wind (it is different from the flow of light, which is not charged).  The solar wind keeps approximately the same speed at any distance from the Sun, until it bumps into the interstellar matter in the Galaxy.  The "shock wave" where the solar wind is suddenly stopped by the interstellar matter (gas and dust) is called the heliopause.  

When talking to those involved with the Voyager probes, this is what they see as the shape of the solar system.  The 'shape' of the heliopause was expected to be spherical, with some flattening on one side if (and only if) our Sun is moving relative to the local fluff in the Galaxy (any matter that is in orbit around the Galactic centre at the same distance as the Sun is expected to have the same orbital speed as our Sun -- but there could be a small difference which, for our Sun, is around 20 km/s, which is almost nothing).

However, the readings from the Voyager probes don't match with this picture.  Instead, it would seem that the heliopause could be dented (pushed in) on one side:  this could be due to magnetic fields from neighborhood stars or from other feature of the Galaxy.  

This makes sense as the heliopause is caused by moving charged particles.  A moving charged particle is the same as an electrical current and electrical currents are affected by magnetic field.

---

Imagine a softly inflated balloon, with a hand pushing in on one side, not enough to burst the balloon or even change the shape of the rest of the balloon, but enough so that part of the side (pushed in by the hand) is actually rounded inwards.

Mind you, the heliopause is not a thin skin but a rather thick area of turbulence and mixing.  It will still take years for the probes to cross the skin of the balloon, so that the conclusion could change again (there is nothing that says that these shock waves have to keep the same shape all the time -- if the magnetic effect changes, the shape of the heliopause could change).

I'll wait a while just to make sure.