# If the Earth was part of an ultimate solar system, what would the sky look like?

I once show a picture depicticting the idea of an ultimate solar system:

In this solar system there are 8 planetary orbits, each containing 52 equal-mass, evenly-spaced planets all in the habitable zone.

Now, imagine that in the far far future, humanity has the energy and resources to engineer such a solar system. If we succeded, (assuming that this solar system really is stable and there won't be any catastrophic collisions between the earth and any other planet) how would the sky be different. What I mean is, would the planets that are at the same orbit as Earth or beyond the earth's orbit be visible during the night or the day? And what about the planets that are in front of the Earths orbit, would they be visible during the day? Could they cause minor eclipses when passing in front of the Earth or they wouldn't be visible at all to our eyes.

Also another question about this solar system is, would the Earth be capable of holding it's moon? Would the neighboring planets be too close to the moon when it rotates around the earth, or would there be enough space for the moon's orbit around the earth be unaffected?

Edit:If the planets beyond Earth were visible by night how would they look like to the human eye? Assuming that the Earth was located at the fifth orbit (I'm not exactly sure which of these orbits represents the Earth's orbit, please correct me if it is) how visible would the planets be? Would they seem, like stars like venus or mars, or would they look like smaller versions of the moon?

• Please credit the creator of this work, Sean Raymond, who also showed the stability of this system. His website: planetplanet.net/author/snraymond – AtmosphericPrisonEscape Jan 27 '19 at 13:06
• The Ultimate Solar system was designed as a model of what a super advanced civilization might create using science and technology advanced thousands or millions of years beyond ours. Sean Raymond never specified that the ultimate engineered solar system would be built using our solar system as one of the components. You are the source of the idea that our planet Earth might be orbiting in some version of the ultimate engineered solar system. You can put Earth in such a system in your story if you want to, or not if you don't want to. – M. A. Golding Jan 27 '19 at 20:41

## Edit

According to AlexP Venus is visible during the day so This changes my answer about day visibility to yes. Sorry for the mistake.

Visible by Night?

According to Wikipedia the most common estimate for the habitable zone is from 0.95 to 1.37 AU (Astronomical Units: average distance between Earth and sun) so we have $$6.283 \cdot 10^{10}m$$ of room to fit 8 Earths into. This means in most cases the planets will be way closer than even Venus (which is the third most bright object after sun and moon)

So the answer is easily YES (every Planet that is in line of sight).

Visible by Day?

For this we assume the moon is about 1 cm big for the naked human eye. (If you haven't noticed the moon is visible during the day)

So the moon has a diameter of 3 476 000 m and is 384 400 000 m apart from our earth so the size reduction per meter is about 9 times smaller.

To get the distance to Planets are apart from each other (at least) we simply divide our habitable zone length by 8 for each orbit circle. Which we get 7 853 888 175meters for. Multiplied by our shrinking factor we get a size reduction to the eye of $$7.068 \cdot 10^{10}$$ which for a planet the size of the earth means it would be around the size of a dust particle. YES

What about planets in the same orbit?

First we will take a look at the smallest orbit (0.95 AU).

The orbit length can be calculated by this Formula: $$Ol = 2\pi \cdot r$$ Ol = Orbit length. With this we get a length of $$8.9295 \cdot 10^{11}m$$ when we divide this by 52 we get the distance between two planets in the same orbit with: $$1.717 \cdot 10^{10}m$$ which is far grater than the distance between two planets in different orbits but still closer than Venus most of the time so YES

Eclipses?

Due to their small size there wouldn't be any noticeable effect. So NO

Could earth keep its moon?

Due to the Planets on other orbits constantly the moons orbit wouldn't be as predictable as it is in our solar system and its orbit would resemble more that of Hyperion than that of our current moon. Basically it would wiggle in its orbit. So the answer is YES

• Venus is visible with the naked eye in the day sky. A planet the size of Earth closer than Venus would also be visible in the day sky, obviously. – AlexP Jan 27 '19 at 15:23
• @AlexP OK thanks for the info didn't know that. – Soan Jan 27 '19 at 15:26
• @AlexP But Venus is only so bright because it's so close to the sun. The brightness of a planet is basically proportional to the inverse square of the both the distances to the sun and the astronomer. Basically $\approx \frac{1}{d_{sun}^2}\cdot r^2\cdot\frac{1}{d_{astronomer}^2}$, where $d_{sun}$ is the distance to the sun, $d_{astronomer}$ is the distance to the observer, and $r$ is the radius of the planet (so $r^2$ is proportional to its surface area). – cmaster - reinstate monica Jan 28 '19 at 1:20
• @cmaster Thanks for the info I will include another edit adjusting for this formula. – Soan Jan 28 '19 at 5:26