Celestia Forums

I'm doing a new add-on with a F8V star and this star have 15 planets. Only 1 planet is gaseous, the others are rocky worlds. Some planets are quite big and denser than our planet and many of them have about the size between Earth and Mars. A big system is more interesting than small system.
I've read that F stars can have more and denser planets than G and K stars.
A F8V star offer sufficient time to develop complex file in a planet? I think yes, because it's said that F2V stars don't offer sufficient time to complex life develop on a planet, but a F8V star have a "life" time between a G2V and F2V stars, and I think that it would be OK. 7 to 9 billion years are sufficient for complex life develop in planets.

Also, i'm doing a K0V star with it's system.

I think that the best type of star to develop life are K stars, because it produces less ultraviolet radiation and offer more time for complex life develop in planets. The only problem is that a planet to have a temperature that permit liquid water must be near enough to the planet be tidely locked. A planet would be at a distance of about 0.5 AU.

Or the star could be a K0V and the planet be at a distance about 0.6 or 0.7 AU. And at these distances the planet is not tidely locked yet.

I will create a new system in a M8V star. This M8V star is near the K0V star. And the F8V star is the most distant of the group. I'm going to add more and more stars.
And finally, how many planets A, F, G, K and M stars can have more or less?

Honest answer? No idea.

I'm guessing that A will have less planets, F and G will have the most planets, and then K will have less and M will have the least. Smaller stars should (I think) have smaller protoplanetary discs.

That said, it all kinda depends on planet formation. We've got four largeish terrestrial worlds in our inner system, but in that same space we could have ended up with six smaller ones, or 8 or 10 much smaller ones, or one or two really big ones...

I'd say M V stars should have the smallest systems in terms of maximum orbital distance. They'd probably have the fewest planets too.

This may be a little off topic:
After I've finished the Lera Solar System, I'm doing my next solar system on the M V star Proxima Centauri, and I'm not worrying about maximum orbital distances, the farthest planets are going to be about 50 AU from the star, in the real universe these planets would probably be cold and boring, but I will most likely make them more colourful.

What would a planet be like if it was orbiting around Proxima Centauri at 50 AU? I would prefer the most interesting case scenario.

Michael Kilderry

Michael Kilderry wrote:What would a planet be like if it was orbiting around Proxima Centauri at 50 AU? I would prefer the most interesting case scenario.

"Most interesting" would probably be "frozen solid" .

At 50 AU, it would have a blackbody temperature of just over 4 K. The orbital period would be 1012.14 years. For comparison, Pluto's temperature at that distance around our own sun is about 40 K. So this planet really would be utterly frozen - almost every gas (Helium is the only exception I think) would be solid at that temperature. To get as cold as this in our solar system, you'd have to be 4250 AU from the Sun! In fact, it's barely warmer than the microwave background radiation of the universe!

It'd be unlikely to be a gas giant at that distance - that's about as far as Pluto gets from the sun, and there's just too little material out there even around our own star to have formed a small gas giant like Uranus or Neptune. So it would probably be a small ice/rock object like Pluto or one of the other Kuiper Belt objects, but frozen absolutely solid.

Not that this has any bearing on what you're likely to put in your solar system, of course...

So an ice-ball with a helium atmosphere, got it. The outermost gas giant is at about 30 AU, any suggestions on what that would look like? It has rings and is about Saturn's diameter and mass.

Michael Kilderry

Michael Kilderry wrote:So an ice-ball with a helium atmosphere, got it.

No, the Helium would be liquid (superfluid too, possibly). But it has to hold onto Helium in the first place... though it's not beyond the realms of possibility that it could have liquid Helium lakes...

The outermost gas giant is at about 30 AU, any suggestions on what that would look like? It has rings and is about Saturn's diameter and mass.

Not much warmer... only 5.5 K!

You would choose one of the most feeble red dwarfs known to stick your planet around... ! Proxima isn't much in the way of being a star as it is. Quite astoundingly, to get a planet with the same blackbody temperature as Pluto, it would have to be located at only 0.55 AU from Proxima (i.e. between Mercury and Venus's orbits in our own solar system). See what I mean about it having a somewhat smaller system?

I would stick all of the planets inside Proxima to give the worlds sufficent heat, but they wouldn't all fit into that tiny star.

Helium lakes just makes the planet even more interesting, it would be Proxima's Titan.

Do you actually have any suggestions about what that 30 AU Saturn giant would look like?

And also, if you had a tidally locked Earth-Like planet around Proxima, could a small gas giant fit into an even tighter orbit with everything still being ok? I got the idea off 55 Cancri b and e.

I picked Proxima Centauri beacause it is the closest star to the Sun and no other Celestia solar systems seem to have been done around it, but now I know why.

Michael Kilderry

Michael Kilderry wrote:Do you actually have any suggestions about what that 30 AU Saturn giant would look like?

No idea. Assuming it could even exist... it could look like any of our current gas giants really. Or any of ther ones that other people have made.

And also, if you had a tidally locked Earth-Like planet around Proxima, could a small gas giant fit into an even tighter orbit with everything still being ok? I got the idea off 55 Cancri b and e

Definitely not. For starters, a tidelocked earthlike planet would have to be at about 0.012 AU from Proxima, or only 2.25 million kilometres. For comparison, that's about twice as far from Jupiter as Ganymede is.

So in other words, I can use my imagination on what a 30 AU Proxima Saturn would look like, that's even better.

How far would you have to put the Earth sized planet form Proxima to be able to fit the minature gas giant inbetween? Since I am planning to be a liitle bit more realistic with my Proxima Centauri system, and I want to include this gas dwarf, I could just change my Proxima Earth into a Proxima Mars if neccessary.

What would the minature gas giant and Proxima Mars look like?

Added note: One other reason I picked Proxima to be the center of my new system is because I've drawn a number of pictures of the planets and moons of Proxima and I want to base a Celestia system on that. Interestingly, the small planet at 50 AU is a bit pluto like with mysterious purple lakes on it, I never made up anything about what they'd be made of, but now I know that they would be made of helium. How many colours can helium lakes be?

Michael Kilderry

I have been doing a bit of research about what my Proxima planets may be like, and here's what I found:

A Saturn-sized planet at 30au away from Proxima is possible, since helium would be a gas (just barely) at the temperature this world would have (5.5 K). Helium would be the only gas in this planet's atmosphere though, as everything else would be solid at these temperatures.

Since Helium is colourless, the planet would be blue in color due to Raleigh scattering. So what we have so far is a featureless Uranus-like planet, but I don't think that the planet would be this boring.

Ice particles could exist in this helium atmosphere and could form white cloud bands, and possibly have a bit of a brownish shine to it due to dust in the atmosphere.

This planet also has rings. I would make the rings black and white in colour, as Uranus is another cold planet and it has very dark black rings, and white for the ice in the rings. I would also put some red ring bands in because that's the colour of Sedna, the most distant world from our Sun.

For the 50 AU planet which is 6 Earth masses, I would put Helium oceans on it, with a bit of a bluish tinge to them, again due to Raleigh Scattering, and make them shiny. Since the liquid helium is likely to be superfluid, which can seep through the most minute cracks, the continents will have cracks and rivers running through them to try and demonstrate this.

The 50 AU planet will also have a moon, this moon won't have as much liquid helium on it, just a few large lakes. But it will have liquid helium volcanoes, driven by the tidal pull of it's planet. Droplets of liquid helium would then probably create a slight atmosphere after a volcano, and possibly helium rain?

Is this still realistic? Or am I getting a little off track with my Proxima Centauri planets?

Michael Kilderry

The gas giant might actually be normal, since it's generating its own heat through slow gravitational collapse (like Jupiter and Saturn are). That'd keep the atmosphere warm enough to have gaseous hydrogen and helium and other gases.

The problem is in forming it out there - there probably wouldn't be enough material to form a gas giant that far from the star.

I was about to make the same comment as Evil Dr. Ganymede... most Gas giants actually radiate more heat than they recieve, though its not a great deal. The bigger the Gas Giant, the more heat it radiates. It all comes from radioactives in the core and heat generated by Gravitational contraction.

On the subject of how many worlds a given class of star would have, I usually consider the age of the star more than the type. If its young, its likely that there would be a greater density of heavier elements in the protostellar cloud. Also, I would have thought that planetary formation is highly chaotic, and thus seemingly random.

I suppose the question would be, 'How does one work out the maximum orbital distance of a planet orbiting a star of a given mass?'. I would assume the proximity of nearby stars would be a factor for the really distant bodies.

Cheers,

Cormoran

The fact that gas giants produce most of their heat changes what my planet would look like entirely. Taking into consideration gravitational collapse, how warm would Proxima Saturn at 30AU be? Could the heat effect the temperature of any moons the world may have?

What do you think of the other world and it's moon?

Michael Kilderry

Michael,

I'm no scientist, but I'd say that there are more factors than the planet's proximity to Proxima at work here.

Firstly, if your planet were quite dense (unlike Saturn, which is about as dense on average as a milkshake), the thermal difference may be quite significant to the appearance of the planet's outer layers. Heat drives weather, such as storms. The more heat, the more interesting the surface will be. Note, however, that this heat will have no noticeable effect on the moons.

On the subject of moons, there's two more factors that affect overall temperature. Both are related to Tidal stress. Io, for example, is close to Jupiter, and the tidal stresses are high. However, Io is also stressed by conjunctions with its companion Galilean Moons (Europa, Callisto and the Evil Doctor's)... The result is extreme tidal flexing, which has generated enough heat to disperse any ices on the surface, and made the mantle extremely active.

To a lesser extent, the liquid oceans of Europa, and possibly Ganymede and Callisto, are maintained in the same way, with the tidal stress being high enough to generate heat to keep the subsurface layers of water liquid.

Thus distance from the primary is just PART of the story...

Evil Dr. G could elucidate much further on this subject. He does it for a living, after all.

Cheers,

Cormoran

How about a gas giant in an eccenrtic orbit far from Proxima? Assuming that Proxima is part of the Alpha Centauri multiple star system, it will have been formed in the same stellar nursery;

Proxima might have been thrown out of the nursery during the complex gravitational collapse of the original cloud,
and perhaps there were other smaller locations of disk instability that formed gas giant sized bodies...

the two main stars are too close together to keep a family of gas giants, but if one (or more gas giants) followed Proxima out into the darkness it need not be in a close orbit.

The sort of thing I am talking about is shown in this simulation (which you might have seen already).
http://www.astro.ex.ac.uk/people/mbate/Research/pr.html

My F8V star have a radius of 0.90 Rsun and have 20 planets. The K0V star have a radius of 0.65 Rsun and the M8V star have 0.37 Rsun. The K0V and M8V stars are at a distance of 10000 AU. It is possible in the real universe?

My F8V star have 20 planets, 5 inner planets ( too hot for life can develop ) 7 medium planets ( planets that have temperatures that life can develop ) and 8 outer planets ( planets that are too cold for life can develop ). There are also some comets.
Do you think that all these planets can form in such star?

What do you think of the text above?

kikinho wrote:What do you think of the text above?

English, 3 sentences, 62 words, 249 characters.

maxim

Do what you want, Kikihno. You really do not need to ask for our approval at every step.