Dinosaur website covering UK Dinosaur types and general popular dinosaur topics plus original dinosaur artwork

British Dinosaurs


Not listed due to
doubtful evidence:




How Another Solar System Might Form Different to Ours


Is our solar system typical of other solar systems? Well, unfortunately we do not really know because by virtue of the fact astronomers are observing very distant objects, it is much easier to detect the telltale signs of more "extreme" systems. The animations below show how the parent star is influenced by its orbiting planets. Smaller, more distant planets (like earth) exert less influence than closer, more massive planets - Think Jupiter, but only a quarter of the distance out.

Left shows an Earth-like planet exerting some gravitational tug on the parent star. Right shows a larger planet in a closer orbit which is able to create a greater wobble on its parent star. The kind of disturbance on the right is more easily detected because it is more severe but it means many Earth-like planets remain invisible to atronomers.

So, instead of looking at the known types of extra-solar planets systems which have been detected around other stars, this page examines how a more typical system might form. Planet-forming is not an exact science, so random chance always plays a part leading to curiosities which have a strange history.

When planets form close to stars there is a greater abundance of heavy elements. This leads to planets with substantial rocky cores. However, if a large planet forms at a significant distance from the star a heavy atmosphere is able to survive. Hence it is possible to have a hybrid of Venus and Jupiter. The most important question is: What planets carry water? The creation of planets in the "Goldilocks Belt" (where its not too hot or too cold) is very important. It likely that one or two bodies will occupy this space.

The closest world to the star, which we shall call "Alpha", is a giant by Earth's standards. However, unlike the giants of our system it is rock not gas, and the intense heat long ago destroyed the atmosphere leaving only its rocky surface.

Being so close to the star, "Alpha" is at the mercy of incredibly powerful gravitational forces which superheat the core and generate fantastic levels of tectonic activity. As a result the planet is covered with volcanoes which constantly stream fresh lava over the surface.

Surface temperatures are so high that some metals are vaporised which gives the planet a transient atmosphere of nickel and iron.

The Extra-Solar planet of Mu Arae d is likely to be a real example of this kind of world. Click here for more information.

The second world, "Beta", is of a similar composition to "Alpha", however it is twice the distance from the star which means that the heavy atmosphere has survived. The solar winds are gradually eroding "Beta" but much slower than "Alpha" creating a tail of streaming gas.


Beneath the dense yellow clouds, huge numbers of volcanoes jet out sulphur dioxide contributing to the already severe greenhouse effect. Sulphuric acid rains into seas of molten rock while gigantic bolts of lightning sear down.

The two large moons of this world are also volcanic nightmares tortured by the gravity of their parent planet and the nearby star.

Further out we finally find a world which we could almost call home. "Gamma" is a rocky world about twice the size of Earth. It has a molten core and quite a thick mantle but its density is a little low and consequently has a thin atmosphere.

Unlike Earth, it has no individual tectonic plates which means that there are no volcanoes.

Water is in abundance across the planet although the mean surface temperature is a little too hot to be comfortable to humans.

The high temperature also means more water vapour in the atmosphere and therefore quite a lot of cloud cover.

It has two small moons only a few hundred kilometres across.

"Delta" is the oddball of the star-system. Its basic composition is the same as "Gamma", however its orbit is massively perturbed.

Vast water oceans exist on the surface, but the ellipse of the planet's orbit takes it to massive seasonal extremes. At one point the planet passes close enough to the star for its oceans to boil off into the atmosphere, totally clouding it over, however, in the winter season temperatures drop so low that the entire world glaciates. Only during a short time in the year does the temperature balance and the planet appear Earth-like.

Very faint rings around this planet are the remnants of whatever other planet collided with "Delta" and caused it to be knocked off its orbit.

At its perihelion "Delta" passes inside the orbit of "Gamma" and at its aphelion it moves out beyond the fifth planet, "Epsilon".

Just outside the coldest fringe of the "Goldilocks Belt" we have "Epsilon", an enormous gas giant greater in diameter than Jupiter but very similar in composition.

The heat in and around "Epsilon" creates a turbulent atmosphere churning with huge storms.

Its system of moons is diverse. The closest moon is tugged by "Epsilon's" gravity, heating the interior and causing extensive volcanic activity.

A little further away the second moon is an unremarkable ball of rock, but the third moon is covered with ice. Although the star is not close enough to melt it, the effect of "Epsilon's" gravity is. The strong tidal effects cause geothermal activity which create hot underwater channels and the vast ocean beneath a surface of ice. Lines run across the moon's surface where the hot channels have reached the surface and freeze.

"Epsilon's" ring system is formed from ancient collisions between the planet's moons.

As the heating effect of the star grows weaker the further out we go, the final significant planet in our system is "Omega". It is a giant, around the size of Saturn, but it is not a true gas planet, it is an ice giant.

Its methane atmosphere lacks the energy of the inner giants and the planet's edge hazes our into space. High clouds in the atmosphere are the only surface features.

The six large moons are all cold and icy, but the one closest to "Omega" is effected by the gravity of the planet enough to cause significant geological activity. But on this frozen moon it is not lava but ice which is ejected.

Out beyond the last main planet there are three or more co-orbitals. Small, rocky bodies which are made up of the dregs of the proto-planetary disc. These objects, barely large enough to constitute planets orbit the star at the very fringes if its influence. These are merely the tip of the massive Kuiper belt of objects which extends out millions of miles.

Beyond them, the interstellar void.

Click here to read about real solar systems other than ours.

Gavin Rymill 1999