<p>How many planets do we expect, statistically, in the universe, have a sun and a moon with such a similar angular diameter as we do on earth? How many habitable planets? Is it possible to calculate this?</p>
<p>Once done, what about adding to the calculation the odds of the orbital alignment of the moon being such that there are solar eclipses.</p>

CC BY-SA 4.0
2024-04-10T13:38:20.810Z
From https://en.wikipedia.org/wiki/Exomoon "to date there have been no confirmed exomoon detections". So we have no solid data about moons outside the Solar System. But I bet the odds are very low. If aliens knew about our solar eclipses, we'd be inundated by tourists from across the galaxy. ;)
PM 2Ring
CC BY-SA 4.0
2024-04-10T13:41:23.237Z
@PM2Ring maybe that's evidence that it is not rare?  :) Well can we start with moons in our own solar system?
Rabbi Kaii
CC BY-SA 4.0
2024-04-10T13:53:09.683Z
I have some info about solar eclipses on Neptune: https://astronomy.stackexchange.com/a/55620/16685 Of course, viewing an eclipse *from* a gas / ice giant isn't easy. ;) But outside observers can watch the shadow spot. Also see https://astronomy.stackexchange.com/q/40808/16685
PM 2Ring
CC BY-SA 4.0
2024-04-10T13:58:24.257Z
I am interested more in the congruence of angular diameters. Solar eclipses don't require this so that is just tangential. Thanks though, looks interesting 
Rabbi Kaii
CC BY-SA 4.0
2024-04-10T14:58:59.577Z
I think this question has been eclipsed by a previous question (but not a dupe as that's asking about eclipses, where I am being more general about similar angular diameter) https://astronomy.stackexchange.com/questions/10208/how-rare-are-earth-like-solar-eclipses?rq=1. Would still like to see if someone will do an educated calculation!
Rabbi Kaii
CC BY-SA 4.0
2024-04-11T21:06:34.100Z
Orbital alignment isn't really an issue: an eclipse-free orbit requires the orbital period to be an exact multiple of the year.  Even the slightest deviation permits occasional eclipses.
Mark
<the-sun><the-moon><solar-eclipse>
Sun and moon same angular radius - how unlikely is this?
Rabbi Kaii
# Sun and moon same angular radius - how unlikely is this?

(Asked by: username_0 on 2024-04-10)

How many planets do we expect, statistically, in the universe, have a sun and a moon with such a similar angular diameter as we do on earth? How many habitable planets? Is it possible to calculate this?

Once done, what about adding to the calculation the odds of the orbital alignment of the moon being such that there are solar eclipses.

**Tags:** the-sun, the-moon, solar-eclipse
> **Comments:**
> **username_1**: From https://en.wikipedia.org/wiki/Exomoon "to date there have been no confirmed exomoon detections". So we have no solid data about moons outside the Solar System. But I bet the odds are very low. If aliens knew about our solar eclipses, we'd be inundated by tourists from across the galaxy. ;)  
> **username_0**: @PM2Ring maybe that's evidence that it is not rare?  :) Well can we start with moons in our own solar system?  
> **username_1**: I have some info about solar eclipses on Neptune: https://astronomy.stackexchange.com/a/55620/16685 Of course, viewing an eclipse *from* a gas / ice giant isn't easy. ;) But outside observers can watch the shadow spot. Also see https://astronomy.stackexchange.com/q/40808/16685  
> **username_0**: I am interested more in the congruence of angular diameters. Solar eclipses don't require this so that is just tangential. Thanks though, looks interesting   
> **username_0**: I think this question has been eclipsed by a previous question (but not a dupe as that's asking about eclipses, where I am being more general about similar angular diameter) https://astronomy.stackexchange.com/questions/10208/how-rare-are-earth-like-solar-eclipses?rq=1. Would still like to see if someone will do an educated calculation!  
> **username_2**: Orbital alignment isn't really an issue: an eclipse-free orbit requires the orbital period to be an exact multiple of the year.  Even the slightest deviation permits occasional eclipses.  

---

## 0 answers

