<p>It's partly the class width that defines &quot;Neptune class&quot; planets, but it also the detection bias.</p>
<p>Kepler depends on transits to detect planets. This means it is much better at detecting large planets that transit in front of the star than small ones. Small planets may not block enough light to cause a significant dip in the star's brightness.</p>
<p>The nomenclature is solar-system biased, but there is some sense to it. The division into &quot;rocky, terrestial&quot; planets, &quot;icy&quot; planets and &quot;giant gaseous planets&quot; makes sense in our solar system.  The division into &quot;super&quot; and &quot;sub&quot; Earths seems more arbitrary.</p>

CC BY-SA 4.0
2022-12-17T10:02:07.840Z
2022-12-17T10:02:07.840Z
James K
<p>The data from Kepler has taught us that there is a much larger number of "Neptune-class" planets out there than we previously thought. I wonder, however, if this "dominance" of Neptunes is because of the wide range of radii we use to define this class. If I'm not mistaken, we classify a planet as "Earth-like" when it is in the range 0.75 to 1.25 R(Earth), "Super-earth" from about 1.25 to 2.0 R(Earth) and "Neptune class" from 2.0 to 6.0 R(Earth) (a much larger range which would stand out even more if we knew masses). Are we maintaining the nomenclature to classify planets of different characteristics or are we just "solar system biased"?</p>

CC BY-SA 3.0
2016-04-26T08:54:32.267Z
You've probably already seen this, but FYI:  https://en.wikipedia.org/wiki/List_of_planet_types    and this one, focuses more on mass:  http://phl.upr.edu/library/notes/amassclassificationforbothsolarandextrasolarplanets
userLTK
CC BY-SA 3.0
2016-05-01T14:58:10.207Z
Embarrassingly, no I didn't look at this. I see that our solar system objects are boundaries for the terminology rather than mid-points. However, I think this shows my point that we shouldn't be surprised at the discovery of so many "mini-Neptunes" by Kepler since there is a much wider "radius range" with this "mass range" than super-Earths or sub-Earths.
Jack R. Woods
<data-analysis><kepler>
Classification of Planets?
Jack R. Woods
# Classification of Planets?

(Asked by: username_0 on 2015-09-14)

The data from Kepler has taught us that there is a much larger number of "Neptune-class" planets out there than we previously thought. I wonder, however, if this "dominance" of Neptunes is because of the wide range of radii we use to define this class. If I'm not mistaken, we classify a planet as "Earth-like" when it is in the range 0.75 to 1.25 R(Earth), "Super-earth" from about 1.25 to 2.0 R(Earth) and "Neptune class" from 2.0 to 6.0 R(Earth) (a much larger range which would stand out even more if we knew masses). Are we maintaining the nomenclature to classify planets of different characteristics or are we just "solar system biased"?

**Tags:** data-analysis, kepler
> **Comments:**
> **username_1**: You've probably already seen this, but FYI:  https://en.wikipedia.org/wiki/List_of_planet_types    and this one, focuses more on mass:  http://phl.upr.edu/library/notes/amassclassificationforbothsolarandextrasolarplanets  
> **username_0**: Embarrassingly, no I didn't look at this. I see that our solar system objects are boundaries for the terminology rather than mid-points. However, I think this shows my point that we shouldn't be surprised at the discovery of so many "mini-Neptunes" by Kepler since there is a much wider "radius range" with this "mass range" than super-Earths or sub-Earths.  

---

## 1 answers

### Answer by username_2 on 2022-12-17. Score: 2

It's partly the class width that defines "Neptune class" planets, but it also the detection bias.

Kepler depends on transits to detect planets. This means it is much better at detecting large planets that transit in front of the star than small ones. Small planets may not block enough light to cause a significant dip in the star's brightness.

The nomenclature is solar-system biased, but there is some sense to it. The division into "rocky, terrestial" planets, "icy" planets and "giant gaseous planets" makes sense in our solar system. The division into "super" and "sub" Earths seems more arbitrary.


---

