<p>Historically, astronomers focused on the easier to measure conjunctions, since getting distances is very hard, so knowing exactly when greatest distance occurs was not possible.   Planets interior to the one you are on have inferior and superior conjunctions. When it is in front of the Sun, it is an inferior one, and when it is behind the Sun, it is a superior one.  Superior planets have close and distant conjunctions.</p>
<p>There is a small ambiguous issue in defining when the planet is &quot;aligned with the Sun&quot; since it is never exactly aligned.  When the planet is at the same equatorial right ascension (<span class="math-container">$\pm 12$</span> hrs) as the Sun it is a conjunction in right ascension.  When it is at the same ecliptic longitude (<span class="math-container">$\pm 180^\circ$</span>) as the Sun, it is a conjunction in ecliptic longitude.</p>

CC BY-SA 4.0
2021-02-08T20:27:51.407Z
This doesn't seem like a general answer, but it does specifically answer the paragraph starting "IIUC, in the specific case of Earth and Mars..." So we might say that for Earth and Venus their closest approach occurs (more or less) during the inferior conjunction of Venus, and their maximum separation occurs (~) during the superior conjunction of Venus. And we might say that for Earth and Mars their closest approach occurs (~) when Mars is in opposition, and their maximum separation occurs (~) when Mars is in conjunction.
Quuxplusone
CC BY-SA 4.0
2021-02-08T20:03:02.487Z
2023-06-22T14:19:39.727Z
2023-06-22T14:19:39.727Z
eshaya
<p>The term &quot;maximum separation&quot; is often used, though maximum separation can also refer to the maximum angle between two bodies in the celestial sphere.</p>
<p>Here is an example from <a href="https://arxiv.org/pdf/0705.3444.pdf" rel="nofollow noreferrer">Quintana and Lissaur</a> of the usage referring to distance:</p>
<blockquote>
<p>close binary stars with maximum separations <span class="math-container">$Q_B≤0.2 AU$</span></p>
</blockquote>
<p>and here is an example from <a href="https://www.researchgate.net/publication/257766465_On_the_Maximum_Separation_of_Visual_Binaries" rel="nofollow noreferrer">Nouh</a> of the usage referring to angle:</p>
<blockquote>
<p>In this paper, an efficient algorithm is established for computing the
maximum (minimum) angular separation ρ max(ρ min) [...] of visual
binary stars</p>
</blockquote>

CC BY-SA 4.0
2021-02-07T17:17:33.107Z
If we don't have a better answer by now, there may not be one. Many obscure concepts lack names.
Wayfaring Stranger
CC BY-SA 4.0
2021-02-06T19:44:21.167Z
2021-02-07T17:31:39.473Z
2021-02-07T17:31:39.473Z
Connor Garcia
<p>The distance from Earth to Mars, during their <strong>closest approach</strong>, is about 55 million kilometers.
At their furthest apart, that distance would be about 401 million kilometers.</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th>Distance</th>
<th>at closest approach</th>
<th>at ___________</th>
</tr>
</thead>
<tbody>
<tr>
<td>Earth–Mars</td>
<td>55 million km</td>
<td>401 million km</td>
</tr>
<tr>
<td>Earth–Jupiter</td>
<td>629 million km</td>
<td>928 million km</td>
</tr>
</tbody>
</table>
</div>
<p>Is there a standard astronomical name for &quot;their furthest apart&quot;?</p>
<p>My vague understanding is that if one body orbits <em>around</em> another, then we have words like &quot;at perigee&quot; (closest approach to Earth) &quot;at apogee&quot; (furthest apart from Earth); &quot;perihelion&quot; and &quot;aphelion&quot;; and in general <a href="https://en.wikipedia.org/wiki/Apsis" rel="nofollow noreferrer">&quot;periapsis&quot; and &quot;apsis.&quot;</a> However, it doesn't seem correct to talk about the distance from Mars to Earth &quot;at apsis&quot; because neither body orbits the other.</p>
<p>IIUC, in the specific case of Earth and Mars, we might also say that their closest approach happens (more or less) when Mars is <em>in opposition</em> (relative to the Sun, as seen from Earth); but I don't think I can infer from that any useful terminology for their maximum distance — which would happen more or less when Mars is in opposition relative to the Earth, as seen from the Sun. [<a href="https://astronomy.stackexchange.com/a/41285/37983">eshaya's answer</a> indicates that the phrase I'm looking for here is &quot;...when Mars is <em>in conjunction</em> (relative to the Sun, as seen from Earth).&quot; Contrariwise, for Venus, both extrema occur during conjunctions.]</p>
<p>(I'm interested in names for the distance and/or the position. &quot;Closest approach&quot; applies to both distance and position; &quot;apsis&quot; applies only to the position AFAIK. You wouldn't say &quot;the apsis of the Earth and the Moon is 406,000 km.&quot;)</p>

CC BY-SA 4.0
2021-02-06T17:42:31.537Z
Farthest apart?
David Hammen
CC BY-SA 4.0
2021-02-08T20:09:40.077Z
in German we can (and do) describe that with the two antonyms like Sonnenferne (max distance to sun) and Sonnennähe (minimum distance to sun). That type of word can be created for any body XXX in the form of XXXferne and XXXnähe.
planetmaker
CC BY-SA 4.0
2023-06-22T18:35:49.547Z
The term "superior conjunction" is used when an object is on the opposite side of the Sun (opposite of opposition).  But it won't necessarily be exactly the maximum distance.
Greg Miller
<solar-system><orbital-mechanics><terminology>
What is the antonym of "closest approach"?
Quuxplusone
# What is the antonym of "closest approach"?

(Asked by: username_0 on 2021-02-06)

The distance from Earth to Mars, during their **closest approach**, is about 55 million kilometers.
At their furthest apart, that distance would be about 401 million kilometers.

| Distance | at closest approach | at \_\_\_\_\_\_\_\_\_\_\_ |
| --- | --- | --- |
| Earth–Mars | 55 million km | 401 million km |
| Earth–Jupiter | 629 million km | 928 million km |

Is there a standard astronomical name for "their furthest apart"?

My vague understanding is that if one body orbits *around* another, then we have words like "at perigee" (closest approach to Earth) "at apogee" (furthest apart from Earth); "perihelion" and "aphelion"; and in general ["periapsis" and "apsis."](https://en.wikipedia.org/wiki/Apsis) However, it doesn't seem correct to talk about the distance from Mars to Earth "at apsis" because neither body orbits the other.

IIUC, in the specific case of Earth and Mars, we might also say that their closest approach happens (more or less) when Mars is *in opposition* (relative to the Sun, as seen from Earth); but I don't think I can infer from that any useful terminology for their maximum distance — which would happen more or less when Mars is in opposition relative to the Earth, as seen from the Sun. [[username_4's answer](https://astronomy.stackexchange.com/a/41285/37983) indicates that the phrase I'm looking for here is "...when Mars is *in conjunction* (relative to the Sun, as seen from Earth)." Contrariwise, for Venus, both extrema occur during conjunctions.]

(I'm interested in names for the distance and/or the position. "Closest approach" applies to both distance and position; "apsis" applies only to the position AFAIK. You wouldn't say "the apsis of the Earth and the Moon is 406,000 km.")

**Tags:** solar-system, orbital-mechanics, terminology

> **Comments:**
> **username_1**: Farthest apart?  
> **username_2**: in German we can (and do) describe that with the two antonyms like Sonnenferne (max distance to sun) and Sonnennähe (minimum distance to sun). That type of word can be created for any body XXX in the form of XXXferne and XXXnähe.  
> **username_3**: The term "superior conjunction" is used when an object is on the opposite side of the Sun (opposite of opposition).  But it won't necessarily be exactly the maximum distance.  

---

## 2 answers

### Answer by username_5 on 2021-02-06. Score: 7 | Accepted answer

The term "maximum separation" is often used, though maximum separation can also refer to the maximum angle between two bodies in the celestial sphere.

Here is an example from [Quintana and Lissaur](https://arxiv.org/pdf/0705.3444.pdf) of the usage referring to distance:

> close binary stars with maximum separations $Q\_B≤0.2 AU$

and here is an example from [Nouh](https://www.researchgate.net/publication/257766465_On_the_Maximum_Separation_of_Visual_Binaries) of the usage referring to angle:

> In this paper, an efficient algorithm is established for computing the
> maximum (minimum) angular separation ρ max(ρ min) [...] of visual
> binary stars

> **Comments:**
> **username_6**: If we don't have a better answer by now, there may not be one. Many obscure concepts lack names.  

---

### Answer by username_4 on 2021-02-08. Score: 2

Historically, astronomers focused on the easier to measure conjunctions, since getting distances is very hard, so knowing exactly when greatest distance occurs was not possible. Planets interior to the one you are on have inferior and superior conjunctions. When it is in front of the Sun, it is an inferior one, and when it is behind the Sun, it is a superior one. Superior planets have close and distant conjunctions.

There is a small ambiguous issue in defining when the planet is "aligned with the Sun" since it is never exactly aligned. When the planet is at the same equatorial right ascension ($\pm 12$ hrs) as the Sun it is a conjunction in right ascension. When it is at the same ecliptic longitude ($\pm 180^\circ$) as the Sun, it is a conjunction in ecliptic longitude.

> **Comments:**
> **username_0**: This doesn't seem like a general answer, but it does specifically answer the paragraph starting "IIUC, in the specific case of Earth and Mars..." So we might say that for Earth and Venus their closest approach occurs (more or less) during the inferior conjunction of Venus, and their maximum separation occurs (~) during the superior conjunction of Venus. And we might say that for Earth and Mars their closest approach occurs (~) when Mars is in opposition, and their maximum separation occurs (~) when Mars is in conjunction.  

---

