<p><a href="https://en.wikipedia.org/wiki/Neptune" rel="nofollow noreferrer">Neptune</a> has an axial tilt of 28.3 degrees and an orbital period of 164.8 Earth years; currently, the north pole is tilted away from Earth.</p>
<p>The maps in your question were each constructed from twelve exposures of Neptune: four each in 845 (red), 547 (green), and 467 nm (blue) wavelengths.  Each of the exposures was then converted from an effectively-orthographic view of a hemisphere of Neptune to the <a href="https://en.wikipedia.org/wiki/Equirectangular_projection" rel="nofollow noreferrer">equirectangular projection</a> used in the maps.  The precise technique is cited to <a href="https://iopscience.iop.org/article/10.3847/1538-3881/aaa6d6" rel="nofollow noreferrer">https://iopscience.iop.org/article/10.3847/1538-3881/aaa6d6</a> and <a href="https://iopscience.iop.org/article/10.1088/0004-637X/812/1/55" rel="nofollow noreferrer">https://iopscience.iop.org/article/10.1088/0004-637X/812/1/55</a>.</p>
<p>The bumpy appearance comes from using four discrete observations rather than a single continuous one; the black area is portions of Neptune that were never visible.  Each of those spikes is the result of projecting a single color of a single pixel on the edge of Neptune's visible disk onto an equirectangular map.</p>

CC BY-SA 4.0
2021-03-19T04:32:43.163Z
Thank you for your answer! Yes this makes total sense; each "spike" is a single color, so it originates from a single pixel of data, and the different colors will not overlap at the last pixel.
uhoh
CC BY-SA 4.0
2021-03-19T03:27:23.193Z
2021-03-19T03:27:23.193Z
Mark
<p>The open access paper <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL081961" rel="nofollow noreferrer">Formation of a New Great Dark Spot on Neptune in 2018</a> (cited in Gizmodo's <a href="https://gizmodo.com/formation-of-dark-vortex-on-neptune-captured-for-the-ve-1833555871" rel="nofollow noreferrer">Formation of Dark Vortex on Neptune Captured For the Very First Time</a> and Phys.org's <a href="https://phys.org/news/2019-03-hubble-captures-birth-giant-storm.html" rel="nofollow noreferrer">Hubble captures birth of giant storm on Neptune</a>) shows images of Neptune taken by the Hubble Space Telescope.</p>

<p>The projections are called "global cylindrical maps" and those usually result in weirdly stretched features near the poles but do not result in the spiky hairdo or <a href="https://en.wikipedia.org/wiki/Dragon%27s_Egg" rel="nofollow noreferrer">Cheela</a>-like appearance in the Hubble  images below.</p>

<p><a href="https://i.sstatic.net/TUV5G.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/TUV5G.jpg" alt="enter image description here"></a></p>

<p><a href="http://radiorobot-cnc.com/art" rel="nofollow noreferrer">Source</a></p>

<p>What causes this effect seen in these projections?</p>

<p><a href="https://i.sstatic.net/vwI86.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/vwI86.jpg" alt="enter image description here"></a></p>

<blockquote>
  <p>Individual maps from Hubble images in 2017 through 2018, in the same filters and processing as Figure 1. These maps span ±90° of latitude and longitude, and tick marks indicate 30° latitude and longitude intervals.</p>
</blockquote>

<p><a href="https://i.sstatic.net/30vBA.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/30vBA.jpg" alt="enter image description here"></a></p>

<blockquote>
  <p>False‐color global cylindrical maps from Hubble, spanning 180° of latitude and 360° of longitude, from images at 845 (red), 547 (green), and 467 nm (blue), and all use the same contrast scaling with a light unsharp mask applied. The maps are centered on 180°W longitude, except 2015, which was centered on 0° longitude. Dotted lines are shown at ~10° and 35°N to indicate the active region prior to the discovery of NDS‐2018.</p>
</blockquote>

<hr>

<p>Reference Cheela, from <a href="https://www.amazon.fr/Starquake-Robert-L-Forward/dp/0345312333" rel="nofollow noreferrer">here</a>:</p>

<p><a href="https://i.sstatic.net/bC7Eh.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/bC7Eh.jpg" alt="enter image description here"></a></p>

CC BY-SA 4.0
2019-03-27T05:43:45.793Z
moved to here from [here](https://space.stackexchange.com/q/35052/12102).
uhoh
CC BY-SA 4.0
2019-03-27T18:35:25.193Z
[Wong et al. 2018](https://doi.org/10.3847/1538-3881/aaa6d6) section 2.5 mentions an algorithm called "frydrizzle."
Mike G
CC BY-SA 4.0
2019-03-27T21:22:29.957Z
Thanks! ...which points to section 3.1 in [Fry 2012](https://iopscience.iop.org/article/10.1088/0004-6256/143/6/150/meta) which describes an implementation that unfortunately doesn't extend to the limbs where the artifact occurs.
uhoh
CC BY-SA 4.0
2021-03-22T03:05:15.690Z
Here's that map wrapped onto a globe: https://www.maptoglobe.com/r105OKBEd
PM 2Ring
CC BY-SA 4.0
2021-03-22T10:35:42.187Z
@PM2Ring sweet!
uhoh
<photography><data-analysis><hubble-telescope><neptune>
Why do these Hubble images of Neptune look like Cheela?
uhoh
# Why do these Hubble images of Neptune look like Cheela?

(Asked by: username_0 on 2019-03-27)

The open access paper [Formation of a New Great Dark Spot on Neptune in 2018](https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL081961) (cited in Gizmodo's [Formation of Dark Vortex on Neptune Captured For the Very First Time](https://gizmodo.com/formation-of-dark-vortex-on-neptune-captured-for-the-ve-1833555871) and Phys.org's [Hubble captures birth of giant storm on Neptune](https://phys.org/news/2019-03-hubble-captures-birth-giant-storm.html)) shows images of Neptune taken by the Hubble Space Telescope.

The projections are called "global cylindrical maps" and those usually result in weirdly stretched features near the poles but do not result in the spiky hairdo or [Cheela](https://en.wikipedia.org/wiki/Dragon%27s_Egg)-like appearance in the Hubble images below.

[![enter image description here](https://i.sstatic.net/TUV5G.jpg)](https://i.sstatic.net/TUV5G.jpg)

[Source](http://radiorobot-cnc.com/art)

What causes this effect seen in these projections?

[![enter image description here](https://i.sstatic.net/vwI86.jpg)](https://i.sstatic.net/vwI86.jpg)

> Individual maps from Hubble images in 2017 through 2018, in the same filters and processing as Figure 1. These maps span ±90° of latitude and longitude, and tick marks indicate 30° latitude and longitude intervals.

[![enter image description here](https://i.sstatic.net/30vBA.jpg)](https://i.sstatic.net/30vBA.jpg)

> False‐color global cylindrical maps from Hubble, spanning 180° of latitude and 360° of longitude, from images at 845 (red), 547 (green), and 467 nm (blue), and all use the same contrast scaling with a light unsharp mask applied. The maps are centered on 180°W longitude, except 2015, which was centered on 0° longitude. Dotted lines are shown at ~10° and 35°N to indicate the active region prior to the discovery of NDS‐2018.

---

Reference Cheela, from [here](https://www.amazon.fr/Starquake-Robert-L-Forward/dp/0345312333):

[![enter image description here](https://i.sstatic.net/bC7Eh.jpg)](https://i.sstatic.net/bC7Eh.jpg)

**Tags:** photography, data-analysis, hubble-telescope, neptune

> **Comments:**
> **username_0**: moved to here from [here](https://space.stackexchange.com/q/35052/12102).  
> **username_1**: [Wong et al. 2018](https://doi.org/10.3847/1538-3881/aaa6d6) section 2.5 mentions an algorithm called "frydrizzle."  
> **username_0**: Thanks! ...which points to section 3.1 in [Fry 2012](https://iopscience.iop.org/article/10.1088/0004-6256/143/6/150/meta) which describes an implementation that unfortunately doesn't extend to the limbs where the artifact occurs.  
> **username_2**: Here's that map wrapped onto a globe: https://www.maptoglobe.com/r105OKBEd  
> **username_0**: @username_2 sweet!  

---

## 1 answers

### Answer by username_3 on 2021-03-19. Score: 2 | Accepted answer

[Neptune](https://en.wikipedia.org/wiki/Neptune) has an axial tilt of 28.3 degrees and an orbital period of 164.8 Earth years; currently, the north pole is tilted away from Earth.

The maps in your question were each constructed from twelve exposures of Neptune: four each in 845 (red), 547 (green), and 467 nm (blue) wavelengths. Each of the exposures was then converted from an effectively-orthographic view of a hemisphere of Neptune to the [equirectangular projection](https://en.wikipedia.org/wiki/Equirectangular_projection) used in the maps. The precise technique is cited to <https://iopscience.iop.org/article/10.3847/1538-3881/aaa6d6> and <https://iopscience.iop.org/article/10.1088/0004-637X/812/1/55>.

The bumpy appearance comes from using four discrete observations rather than a single continuous one; the black area is portions of Neptune that were never visible. Each of those spikes is the result of projecting a single color of a single pixel on the edge of Neptune's visible disk onto an equirectangular map.

> **Comments:**
> **username_0**: Thank you for your answer! Yes this makes total sense; each "spike" is a single color, so it originates from a single pixel of data, and the different colors will not overlap at the last pixel.  

---

