<p>"<a href="https://en.wikipedia.org/wiki/Primary_(astronomy)" rel="nofollow noreferrer">Primary</a>" is quite a common term for this.</p>

CC BY-SA 4.0
2018-06-14T23:32:20.723Z
It's a shame I can only choose one accepted answer - this is excellent thanks, I thought primary referred only to the central body of a solar system (IE, the primary star), but it looks as though it can be used in any system or subsystem - so the Earth can be the primary body in the earth-moon system.
Frater
CC BY-SA 4.0
2018-06-14T10:28:35.973Z
2018-06-14T10:28:35.973Z
Steve Linton
<p>When one body has a much larger mass, so it's motion is negligable, it can be called the <em>central body</em> (even for eccentric orbits, where the central body is a the focus of the ellipse, and far from the centre)</p>

<p>This is the terminology used by Wikipedia editors</p>

<blockquote>
  <p>The central body in an orbital system can be defined as the one whose mass (M) is much larger than the mass of the orbiting body (m)...</p>
</blockquote>

<p>Also by <a href="http://radio.astro.gla.ac.uk/a1dynamics/twobody.pdf" rel="noreferrer">Glasgow university</a></p>

<blockquote>
  <p>The most straightforward orbit calculations occur when the central body is much more massive than the orbiting body.</p>
</blockquote>

<p>and <a href="https://books.google.co.uk/books?id=COgDAAAAMBAJ&amp;pg=PA1582&amp;lpg=PA1582&amp;dq=orbit%20central%20body&amp;source=bl&amp;ots=M6Qwsa8yzQ&amp;sig=eBD-uyvTJCsf_3mElv-3nlOokcM&amp;hl=en&amp;sa=X&amp;ved=0ahUKEwiHs9q5w9LbAhVOYsAKHQ3pBT8Q6AEInQEwDQ" rel="noreferrer">elsewhere</a></p>

<blockquote>
  <p>The angular momentum of a satellite depends on both the mass of orbiting satellite and central body as well as the radius of the orbit.</p>
</blockquote>

<p>Normally, in a specific situation "planet", or "star" can be used.</p>

CC BY-SA 4.0
2018-06-14T06:58:56.423Z
Thanks, that's helpful.  The specific names don't work as i'm trying to abstract out from specific, but central body could work.
Frater
CC BY-SA 4.0
2018-06-14T06:40:16.103Z
2018-06-14T06:40:16.103Z
James K
<p>A hopefully simple terminology question:  When you have an object that orbits another object in space, what do you call the object being orbited in relation to the object orbiting?</p>

<p>For instance, you might call the object orbiting the "satellite" of the orbited object, but what would you call the object being orbited?  </p>

<p>Orbitee is all i've been able to come up with but it doesn't seem quite right ;)</p>

<orbit><terminology>
Terminology of Orbits
Frater
# Terminology of Orbits

(Asked by: username_0 on 2018-06-14)

A hopefully simple terminology question: When you have an object that orbits another object in space, what do you call the object being orbited in relation to the object orbiting?

For instance, you might call the object orbiting the "satellite" of the orbited object, but what would you call the object being orbited?

Orbitee is all i've been able to come up with but it doesn't seem quite right ;)

**Tags:** orbit, terminology


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## 2 answers

### Answer by username_2 on 2018-06-14. Score: 5 | Accepted answer

When one body has a much larger mass, so it's motion is negligable, it can be called the *central body* (even for eccentric orbits, where the central body is a the focus of the ellipse, and far from the centre)

This is the terminology used by Wikipedia editors

> The central body in an orbital system can be defined as the one whose mass (M) is much larger than the mass of the orbiting body (m)...

Also by [Glasgow university](http://radio.astro.gla.ac.uk/a1dynamics/twobody.pdf)

> The most straightforward orbit calculations occur when the central body is much more massive than the orbiting body.

and [elsewhere](https://books.google.co.uk/books?id=COgDAAAAMBAJ&pg=PA1582&lpg=PA1582&dq=orbit%20central%20body&source=bl&ots=M6Qwsa8yzQ&sig=eBD-uyvTJCsf_3mElv-3nlOokcM&hl=en&sa=X&ved=0ahUKEwiHs9q5w9LbAhVOYsAKHQ3pBT8Q6AEInQEwDQ)

> The angular momentum of a satellite depends on both the mass of orbiting satellite and central body as well as the radius of the orbit.

Normally, in a specific situation "planet", or "star" can be used.

> **Comments:**
> **username_0**: Thanks, that's helpful.  The specific names don't work as i'm trying to abstract out from specific, but central body could work.  

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### Answer by username_1 on 2018-06-14. Score: 4

"[Primary](https://en.wikipedia.org/wiki/Primary_(astronomy))" is quite a common term for this.

> **Comments:**
> **username_0**: It's a shame I can only choose one accepted answer - this is excellent thanks, I thought primary referred only to the central body of a solar system (IE, the primary star), but it looks as though it can be used in any system or subsystem - so the Earth can be the primary body in the earth-moon system.  

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