Planetary System Formations
To understand how planetary systems
form I will focus on the Solar system because it is the most widely
studied system. Astronomers believe the nebular hypothesis when it
comes to the solar system. They believe that the solar system formed
from the collapse (gravitationally) of a portion of a very big
molecular cloud. The formation of the Solar system occurred about
4.55 billion years ago
The molecular cloud was most likely
about 20 pc and the part that actually collapsed to form the solar
system was about 1 pc or 20,000 AU in size.
Here is a picture of a molecular cloud:
The 1 pc region included a mass of a
little bit more than the Sun (around 1.98*10^30 kilograms). Hints: the
sun is the most massive object in the Solar system. This region was
composed of primarily Hydrogen and Helium with very tiny amounts of
lithium.
The molecular cloud at a certain point
began to spin very fast because of angular momentum. The atoms
inside cloud began to collide and they
converted their kinetic energy into heat. As it continued to collapse
the center of it was much hotter than is surrounding disk. After
about 100,000 years the forces of gas pressure and gravity competing
led to the formation of a protostar . After 50 million years the
protostar became hot enough to fuel itself through nuclear fusion and
the protostar became what is known as the Sun.
The planets in the solar system formed
from the disc shaped cloud containing dust and gas that the sun left
after its formation. Astronomers believe that the planets (like the earth) began as
grains of dust and accumulated matter over years until they became
planets. This process is very inefficient according to Astronomers
when compared to star formation. While the gas giants in the solar
system formed much farther out.
"While the gas giants in the solar system formed much farther out."
ReplyDeleteI thought the leading hypothesis is that gas giants form closer to the star. For example, a lot of the gas giant exoplanets are typically found orbiting their star rather closely. And isn't there a theory that states Jupiter (and Saturn?) may have been ejected into the outer solar system early in its formation?
~ Chris Lindsay
Ann Arbor Science & Skeptics
www.annarborscienceskeptic.com
https://www.facebook.com/AnnArborScienceSkeptics
Chris, that is a great question. Firstly I would like to say that this particular post focused primarily on the solar system's formation that has been studied for years. Also par my research Jupiter can been deemed a "failed star" because it did not have enough mass to start nuclear fusion, but that does not specifically tell us that it formed close to the sun. Now with that begin said in the initial stages of planet formation all of the planets appear to have formed the same way, however, the outer planets are much further from the Sun, so they formed in a colder environment. Gravity in the outer (colder) part of the system attracts and holds gas together that would have been lost from the planets that are closer to the sun because of their warmer temperatures. The gaseous planets also gain mass when strong solar winds blow most of the gas and dust from the inner planets (hints another reason why most of the gaseous planets are larger than the inner planets). As for the theory that Jupiter and Saturn may have been ejected into the outer solar system, I am not familiar with it but I would love for you to post a think so i can read up on it.
ReplyDeleteAs far as your statement "a lot of the gas giant exoplanets are typically found orbiting their star rather closely". This is correct for "some" of the exoplanets we have discovered but over time they go through mass loss and end up earth like and as "land" planets. For more info on this here is an interesting article I read: http://www.nasa.gov/centers/goddard/news/topstory/2010/earthlike-exoplanet.html
Talor, thanks for the reply. I'll definitely check out the link.
ReplyDeleteRegarding what I wrote about Jupiter having been closer to the Sun, I did some checking and can't seem to find a link. However, I did find a story about a theory stating that Jupiter may have moved in then back out again.
http://michastrostudent.blogspot.com/2012/11/planetary-system-formations.html
So it's entirely possible that I am mis-remembering what I had read, and it's more to do with this. If I do find something that's more directly related to what I had written, I'll let you know.