<p>There doesn't seem to be such a word. Interstellar space within the Solar System is still just interstellar space.</p>

<p>There doesn't seem to be a demand for the word you're looking for either. We distinguish space by its contents; the space within the heliosphere is called the interplanetary medium (it contains solar plasma, dust, etc.), while the interstellar medium comprises sparse gaseous molecules from the <a href="https://en.wikipedia.org/wiki/Interstellar_medium" rel="nofollow noreferrer">Local Fluff</a> and (if you go far enough) the rest of the <a href="https://en.wikipedia.org/wiki/Local_Bubble" rel="nofollow noreferrer">Local Bubble</a>.</p>

<p>Whereas there are about 10 oxygen molecules per cubic centimeter in the interplanetary medium, there is only 1 oxygen molecule per cubic centimeter in the interstellar medium. Seeing that there is no clear boundary for the Milky Way (nor is there any single definition for a boundary for galaxies), the intergalactic medium just vaguely describes the medium within <a href="https://en.wikipedia.org/wiki/Galaxy_filament" rel="nofollow noreferrer">galaxy filaments</a>; here, the space is so rarified that there is only 1 oxygen molecule per cubic <strong>meter</strong>.</p>

CC BY-SA 3.0
2016-10-04T06:39:51.917Z
2017-01-03T13:41:21.977Z
2017-01-03T13:41:21.977Z
Sir Cumference
<p>The Sun's Hill Sphere may be the term you're looking for. Or perhaps "within the Oort Cloud diameter" would do it for you. According to Wikipedia, the outer gravitational zero velocity distance (Hill Sphere) isn't known - it's thought to lie between 50,000 AU and 200,000 AU - or up to over 3 light years.</p>

CC BY-SA 3.0
2017-01-03T15:59:10.610Z
If you are the same Li Zhi we have had in the past, your answer is likely reliable, but since you seem to have chosen not to use a permanent account there is no way to verify that you are the same user. So, since your answer is brief and without reference, it is a target for downvotes.
called2voyage
CC BY-SA 3.0
2017-01-03T15:45:14.310Z
2017-01-03T15:45:14.310Z
Li Zhi
<p>Wikipedia says the definition of <a href="https://en.wikipedia.org/wiki/Outer_space#Interplanetary_space" rel="nofollow">interplanetary space</a> is </p>

<blockquote>
  <p>the region dominated by the interplanetary medium, which extends out
  to the heliopause where the influence of the galactic environment
  starts to dominate over the magnetic field and particle flux from the
  Sun</p>
</blockquote>

<p>While it defines the <a href="https://en.wikipedia.org/wiki/Solar_System#Boundaries" rel="nofollow">solar system</a> as the region in which the sun is the primary gravitational influence</p>

<blockquote>
  <p>The Sun's gravitational field is estimated to dominate the
  gravitational forces of surrounding stars out to about two light years
  (125,000 AU).</p>
</blockquote>

<p>So, if the region outside the heliopause but inside the solar system isn't interplanetary space, then what is it?</p>

CC BY-SA 3.0
2016-06-27T00:07:38.747Z
The way I see it, those are different definitions. The former is based on how far the Sun's plasma is sent out, while the latter is the sphere of influence of the Sun. The space within the Sun's gravitational influence but is outside of the Sun's heliosphere would then be considered interstellar space. That's just as far as I know.
Sir Cumference
CC BY-SA 3.0
2016-06-27T00:38:02.043Z
@SirCumference yes, but as came up in The Pod Bay, it is quite possible to get into a conversation where you want to specifically refer to the space outside the heliopause but inside the solar system, and if you can't refer to it, then confusion ensues. Unless you say 'interstellar space within the solar system but outside the heliopause'. Oort cloud doesn't seem to cover it...
kim holder
CC BY-SA 3.0
2016-06-27T13:29:20.663Z
IIHO the entirety of those objects bound to the Solar System barycenter as their primary is interplanetary space, and, yes that means interstellar space starts a lot farther out than the edge of the heliosphere, especially on the Vega side.
Jerard Puckett
CC BY-SA 3.0
2016-06-27T20:06:34.807Z
I am pretty sure the heliosphere is considered to be the 'range' of the solar system.
HotSaucey
CC BY-SA 3.0
2016-08-02T19:07:00.030Z
If the heliosphere has a bow shock with the interstellar medium, then the region to which you refer should be called the heliosheath.  Unfortunately, they gave that name to the region between the termination shock and the heliopause...  Maybe "interstellar sheath"?
honeste_vivere
<solar-system><interstellar-medium><oort-cloud>
What is the word for space that is in the solar system, but outside the heliopause?
kim holder
# What is the word for space that is in the solar system, but outside the heliopause?

(Asked by: username_0 on 2016-06-26)

Wikipedia says the definition of [interplanetary space](https://en.wikipedia.org/wiki/Outer_space#Interplanetary_space) is

> the region dominated by the interplanetary medium, which extends out
> to the heliopause where the influence of the galactic environment
> starts to dominate over the magnetic field and particle flux from the
> Sun

While it defines the [solar system](https://en.wikipedia.org/wiki/Solar_System#Boundaries) as the region in which the sun is the primary gravitational influence

> The Sun's gravitational field is estimated to dominate the
> gravitational forces of surrounding stars out to about two light years
> (125,000 AU).

So, if the region outside the heliopause but inside the solar system isn't interplanetary space, then what is it?

**Tags:** solar-system, interstellar-medium, oort-cloud
> **Comments:**
> **username_1**: The way I see it, those are different definitions. The former is based on how far the Sun's plasma is sent out, while the latter is the sphere of influence of the Sun. The space within the Sun's gravitational influence but is outside of the Sun's heliosphere would then be considered interstellar space. That's just as far as I know.  
> **username_0**: @SirCumference yes, but as came up in The Pod Bay, it is quite possible to get into a conversation where you want to specifically refer to the space outside the heliopause but inside the solar system, and if you can't refer to it, then confusion ensues. Unless you say 'interstellar space within the solar system but outside the heliopause'. Oort cloud doesn't seem to cover it...  
> **username_2**: IIHO the entirety of those objects bound to the Solar System barycenter as their primary is interplanetary space, and, yes that means interstellar space starts a lot farther out than the edge of the heliosphere, especially on the Vega side.  
> **username_3**: I am pretty sure the heliosphere is considered to be the 'range' of the solar system.  
> **username_4**: If the heliosphere has a bow shock with the interstellar medium, then the region to which you refer should be called the heliosheath.  Unfortunately, they gave that name to the region between the termination shock and the heliopause...  Maybe "interstellar sheath"?  

---

## 2 answers

### Answer by username_1 on 2016-10-04. Score: 3

There doesn't seem to be such a word. Interstellar space within the Solar System is still just interstellar space.

There doesn't seem to be a demand for the word you're looking for either. We distinguish space by its contents; the space within the heliosphere is called the interplanetary medium (it contains solar plasma, dust, etc.), while the interstellar medium comprises sparse gaseous molecules from the [Local Fluff](https://en.wikipedia.org/wiki/Interstellar_medium) and (if you go far enough) the rest of the [Local Bubble](https://en.wikipedia.org/wiki/Local_Bubble).

Whereas there are about 10 oxygen molecules per cubic centimeter in the interplanetary medium, there is only 1 oxygen molecule per cubic centimeter in the interstellar medium. Seeing that there is no clear boundary for the Milky Way (nor is there any single definition for a boundary for galaxies), the intergalactic medium just vaguely describes the medium within [galaxy filaments](https://en.wikipedia.org/wiki/Galaxy_filament); here, the space is so rarified that there is only 1 oxygen molecule per cubic **meter**.


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### Answer by username_5 on 2017-01-03. Score: 1

The Sun's Hill Sphere may be the term you're looking for. Or perhaps "within the Oort Cloud diameter" would do it for you. According to Wikipedia, the outer gravitational zero velocity distance (Hill Sphere) isn't known - it's thought to lie between 50,000 AU and 200,000 AU - or up to over 3 light years.

> **Comments:**
> **username_6**: If you are the same Li Zhi we have had in the past, your answer is likely reliable, but since you seem to have chosen not to use a permanent account there is no way to verify that you are the same user. So, since your answer is brief and without reference, it is a target for downvotes.  

---

