CHANCES OF LIFE BEYOND THE SOLAR SYSTEM - PART 1
Throughout the years, science fiction has given us reason to believe that our galaxy is filled with planets that are just like our own. Through movies such as Star Wars and shows like Star Trek, we have been able to experience many different and unique worlds. Is this possible? Perhaps, but it is hard to say for sure. I will first try to explain what is needed for these planets to form.
In order for rocky Earthlike planets to form, there needs to be certain elements present. These elements include the heavy elements of iron, carbon, nitrogen and oxygen. Unfortunately, 99.8 percent of the atoms that make up the universe are comprised of the lighter elements of hydrogen and helium. This is great for creating stars but not planets with complex life forms. These heavier elements did not even exist at the beginning of the universe and were not created until they were released by the nuclear fusion reaction within stars, which gives them their brilliant light.
In fusion, the energy is produced when two lighter elements are combined to form the heavier elements. When the stars exhaust their fuel and die, either by exploding or ejecting its outer layers, the heavier elements are released into space. A supernova would be able to create even more of these heavier elements considering its incredible energy.
If this star lies within a large galaxy such as the Milky Way, the ejecting elements are held within the galaxy by gravity, creating large clouds of dust and gas. This dust and gas can eventually be used to form new stars and planets. The new younger stars can potentially have Earthlike planets, since the heavier elements necessary for the formation of planets is leftover by the older generation of stars.
Once the heavy elements required are acquired for the formation of planets, this debris forms a rotation cloud around the new star. This cloud will collapse into a thin layer much like a pizza would if it were spun around in the air. The inner section of the cloud first forms a star. Then the solid particles within the disk stick together to form large grains of dust. As these grains of dust collide with each other, they become larger and grow into small bodies called planetesimals. These planetesimals may be only a few inches across of become the size of the moon. The larger ones tend to continue colliding with all the material that is that the same orbital distance from the star. As the planetesimal collects all the material in a band around the sun, it becomes a planet. The closer the band is to the star, the smaller the planet will be since the circumference of the band is smaller as you move closer to the star. This is why smaller planets tend to form closer to the star.
The distance from the star also affects the composition of the planet. As you move closer to the star, the disk becomes increasingly hot. Therefore, the planets that close will need to be made up of elements that would be able to withstand the heat and not break apart, such as iron and rock. The four planets closest to our Sun - Mercury, Venus, Earth and Mars - are made up of dense rock and iron. As you move further from the sun, there are additional materials that solidify such as water, methane and ammonia, that become a part of the core of the outer planets. The larger the planet, the larger the gravitational field, which allows gas giants like Jupiter and Saturn to attract hydrogen to form large atmospheres. Therefore, each planet is a product of the unique conditions of its formation.
Within the last eight years, discoveries have led to the theory of planet formation to be put into doubt. We have found that there are numerous planets out there, but they do not support our theory of planet formation. These are actually quite different from those that we see in our own solar system. Due to the presence of these planets that do not follow our rules, many new theories are being suggested. Although they all begin with the same disk of material orbiting a forming star. This just goes to show that the universe can be a much stranger and more varied place that we ever imagined.