<p><a href="https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies" rel="noreferrer">https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies</a> gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ?</p>
<p>I guess it's &quot;easy&quot; for Mars, Jupiter and Saturn (thanks to the rings ?) but how was it measured for Venus under its clouds, or Uranus + Neptune that are so far away ?</p>
<p>Links to scientific publications would be appreciated.</p>
<p>Thanks</p>

CC BY-SA 4.0
2021-02-10T16:40:20.633Z
You can identify features in Venus' clouds as well as in the atmospheres of the other planets even with amateur equipment - and track them if you get a long enough sequence. Their rotation axis gives the tilt.
planetmaker
CC BY-SA 4.0
2021-02-10T16:56:59.413Z
With Venus you can also do earth-based radar measurements of the solid surface (or could until Arecibo crashed). And of course everything can be measured in-situ by orbiters.
planetmaker
CC BY-SA 4.0
2021-02-10T17:54:43.610Z
The gas giants have powerful magnetospheres that can be observed by radio astronomy.  Though in the case of Uranus, it isn't aligned with the spin axis, hehe: https://physicsworld.com/a/nightmare-geometry-of-uranus-creates-tumbling-magnetosphere/ . Luckily Uranus also has observable rings.
Connor Garcia
CC BY-SA 4.0
2021-07-09T05:18:17.723Z
See: https://astronomy.stackexchange.com/questions/11182/what-is-the-axial-tilt-of-a-planet-measured-relative-to
Nilay Ghosh
CC BY-SA 4.0
2021-08-14T00:31:21.150Z
The values are available with greater than two decimals of precision on these sub-pages: https://nssdc.gsfc.nasa.gov/planetary/planetfact.html - found by following the reference on Wikipedia.
Rob
<planet><rotation><observational-astronomy>
How was the axial tilt of planets measured?
Dr. Goulu
# How was the axial tilt of planets measured?

(Asked by: username_0 on 2021-02-10)

<https://en.wikipedia.org/wiki/Axial_tilt#Solar_System_bodies> gives the axial tilt of all planets with two decimal precision, but how and when were they measured so precisely ?

I guess it's "easy" for Mars, Jupiter and Saturn (thanks to the rings ?) but how was it measured for Venus under its clouds, or Uranus + Neptune that are so far away ?

Links to scientific publications would be appreciated.

Thanks

**Tags:** planet, rotation, observational-astronomy

> **Comments:**
> **username_1**: You can identify features in Venus' clouds as well as in the atmospheres of the other planets even with amateur equipment - and track them if you get a long enough sequence. Their rotation axis gives the tilt.  
> **username_1**: With Venus you can also do earth-based radar measurements of the solid surface (or could until Arecibo crashed). And of course everything can be measured in-situ by orbiters.  
> **username_2**: The gas giants have powerful magnetospheres that can be observed by radio astronomy.  Though in the case of Uranus, it isn't aligned with the spin axis, hehe: https://physicsworld.com/a/nightmare-geometry-of-uranus-creates-tumbling-magnetosphere/ . Luckily Uranus also has observable rings.  
> **username_3**: See: https://astronomy.stackexchange.com/questions/11182/what-is-the-axial-tilt-of-a-planet-measured-relative-to  
> **username_4**: The values are available with greater than two decimals of precision on these sub-pages: https://nssdc.gsfc.nasa.gov/planetary/planetfact.html - found by following the reference on Wikipedia.  

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## 0 answers

