# Is my solar system even remotely plausible?

I've sketched out a solar system for my science-fantasy setting. In the interest of hand-waving only when necessary, I'm reality checking my idea to see what needs to be tweaked or changed outright, so that it works.

Here's my system.

Glimmer: Is the first planet in the system a Gas-Dwarf. Its name comes from the fact that its atmospheric composition causes it to sparkle like a jewel in space.

Tempest: The second planet smaller than earth around the size of Venus. Pre Terraforming it was planet covered with steam storms. Extreamophiles were the only inhabitants. Post Terraforming it's a tropical paradise, covered with archipelagos.

Viridian: The third planet named for its green skies. A super-terrestrial world thrice the size of earth, however its low density give the planet only slightly higher gravity, about 1.2gs.

Tellus Alpha and Beta: The forth planet and its moon. Tellus-Alpha and Beta required minimal Terraforming. Tellus-Beta while refereed to as the moon, would better be described as a sister planet. As a result of their sizes and proximity Tellus-Alpha and Beta both experience massive tides.

Sojourn: The fifth planet so named because the gravitational influence of the sixth planet a Gas-giant perturbs the orbit, which gives the world long, cold, dark winters.

Regis: The sixth, so named because it is the largest planet in the system and its many satellites which are refereed to as vassals; of which twelve were deemed worth the effort of Terraforming. It is also the last planet of the inner system.

The Gulf: Lies between the Inner and Outer and planets. In is composed of five asteroid belts and a number of dwarf planets and planetoids. It is believed that a massive cataclysm in the early years of the system shattered the planets whose material now composes the belts.

Ember: The seventh planet in the system, a gas giant half the size of Regis. Its name comes from the fact that the planet faintly glows. Reactions deep with in the planet cause it radiate heat. The planet possess a number of moons, five of which were Terraformed; the heat that Ember gives off reduced the amount effort required for certain aspects of the Terraforming.

Aegis: The eighth and last planet in the system. Its name comes from its pre Terraforming appearance and orbital position. Do to the abundance of metallic elements in its thin atmosphere the planet seemed to gleam like polished armor. People thought of it as the guardian or protect of the system.

                               ***


To the inquisitive minds: Self-replicating Biots played a part in the Terraforming of the planets. They remain active in the atmospheres of the outer planets, acting as heat insulators and lenses that amplify light.

• ...The first planet of your solar system is a gas giant? By which you mean it is the closest planet to the system's star? Right off the bat, that's already not plausible. – AngelPray Jul 31 '17 at 23:34
• @AngelPray Why not? We've found oodles of hot gas giants in orbits that get even smaller than Mercury's in real life. So that detail alone I would say is extremely plausible. – Logan R. Kearsley Aug 1 '17 at 0:28
• Logan is quite correct, gas giant planets have been detected in very close orbits around stars, and even have been nicknamed "roasters". It is quite plausible that eons of exposure to the stellar wind and heat energy of the star have stripped away a large portion of the atmosphere, creating a gas dwarf. – Thucydides Aug 1 '17 at 2:38
• @AngelPray Google "hot jupiters". Gas giants that close are real. Not sure about gas-dwarfs though. – a4android Aug 1 '17 at 2:50
• To be pedantic.. 'A Solar System' doesn't make sense, there is only one Solar System; the one that we are in. You describe a 'Planetary system' – JeffUK Aug 1 '17 at 8:13

For a reality-check, you've not given us enough information. Gravitation must be balanced in a system. Without the balance planets either collide, spiral into the sun, or spin off into space. My gut tells me you didn't consider this. So I'm going to go with no, it's not plausible.

HOWEVER, plausible is in the eye of the beholder. If you think the people most exposed to your idea will be astronomers, you should spend a bit of time looking into the science behind solar system development (or expect them to point out why it's not plausible). If you're marketing to young adults or a more general market, your solution won't be noticed as off base (we happily believe the Death Star can enter planetary orbits and not wreak havoc with tidal conditions or orbital perturbations...). Therefore, I'd focus more on writing a cool story. Your basic premise is close enough to believable that I'd happily suspend my disbelief for a good story.

I'd like to ask after the planetary names. If the system was colonized, then they're cool. If the system inhabitants are native, the names make very little sense and stick out to me. Historically, heavenly objects are named religiously or scientifically --- not artistically. But if it were colonized, then everything's cool.

• The system was settled and has no native inhabitants. While names I gave are place holders they are not that far from what Intend to call them. – Trismegistus Aug 1 '17 at 12:04

With the information given and what we know about planets, there are a couple issues that I know of.

Ember Based on current scientific knowledge, it is unrealistic to say that the planet glows in the visible spectrum. The closest equivalent that I could find is that of a brown dwarf, which glows faintly in the red and infrared. The only problem is that brown dwarfs tend to be bigger than gas giants, as they cover the gap between gas giants and stars. While there is much overlap in the size, the largest planets are about twice the diameter of Jupiter, while the smallest brown dwarfs are slightly larger than Jupiter. This directly conflicts with the information that Ember is only half the size of Regis, though this is close to the limit.

Tellus Alpha and Beta While it is be possible for two planets to orbit each other as you described, the tidal effects described would cause both planets to become tidally locked to each other, as the Earth is to the moon. This is occurring currently with Earth, on a slow scale. For planets as you described, it would occur on a much faster timescale, with the locking likely occurring before the terraforming even began. There are inherent issues with terraforming tidally locked planets, mostly temperature-related. Of all the issues detailed here, this is the only one that I would consider an absolute impossibility.

Aegis This is not an impossibility, just an improbability. Most models of star system formation concentrate metals in inner planets. There is a scientific reason for this, partially based on our observations of existing systems, and partially based on what we know about science. It is unlikely to have such a metal rich planet so far from the center.

Regis Jupiter has a large effect on the orbits of the other planets in the solar system. You are right to assume that Sojourn's orbit would be largely affected by this. However, I would think that more than this would be affected by such a large planet, especially with so many planets spaced in such a small area. This is only a gut feeling, not a fact. (I am assuming that Regis's orbital distance is similar to Jupiter, by your descriptions.)

Glimmer As mentioned in a comment, a gas dwarf orbiting close to the sun would be unlikely to retain its atmosphere for any length of time. This due to a couple of factors, including the increased heat.

None of these issues should be glaring to the general public, and we really do not know enough about star systems to say that most of these are absolute impossibilities.

• Brown dwarfs are more massive than gas giants, but they aren't bigger, only denser. From Jupiter mass to red dwarf stars, the diameter pretty much stays the same, and even decreases ever so slightly. But this does mean that it cannot be smaller than another planet indeed. The only exception would be if Regis was massive enough and very, very close to the star, whose massive heat can cause a gas giant to swell up. – Eth Dec 1 '17 at 13:52

Glimmer: As far as we can tell, gas giants cannot form near the star since star ignition tends to blow the gas away. So, Glimmer had to travel inward from the outer reaches. I find it unlikely that it could have made it that close without disrupting the other inner planets. If it was off the plane of the ecliptic it could be a capture (either an outside planet or a planet that was thrown out by another gas giant and then recaptured).

Sojourn: I find it unlikely that it could be that affected by Regis without getting kicked out completely. An interesting possibility would be for it to orbit Regis' L1 point.

The Expanse: for multiple rings, you would have to have shepherd planitoids look at Saturn's rings. Also, I find it to be less plausible for it to occur outside Regis' orbit than inside. It is just that an asteroid belt inside of Regis would make Sojourn too far away to be influenced that much. So, given how many odd things we've seen in the planetary systems that we have seen, you are probably safe in leaving it as is and just having the observers say, "well, lookit that."

You've got a big problem with Glimmer.

First, it can't have formed there. Nor can it have spiraled in there as it would take out every planet between it's original orbit and it's current orbit. Also, planets that spiral in are in retrograde orbits.

The only scenario I see that could make it is an insane longshot--there were two rogue planets that came through the system at the same time. They went SPLAT (We are talking a kaboom worthy of the Death Star) and what was retained became Glimmer. This not only requires the two rogues to meet at just the right spot, but with the correct energy levels that the remains go into a reasonable orbit.

You also have a big problem holding onto the mass--more later.

Second, in Glimmer's orbit you're going to need an awfully big planet to hold onto hydrogen (and gas worlds are mostly hydrogen.) A gas dwarf is rapidly going to bleed it's mass into space and be reduced to a rocky core.

Now, surviving becomes a bit more possible if we replace Glimmer with a superjovian. It also makes it much more able to hold onto it's mass when things went splat. It does nothing about the insane odds against just the right splat, though.