FORMATION OF THE SOLAR SYSTEM The Stellar Nebula Hypothesis

Any theory on the formation of the solar system MUST explain these four characteristics of our solar system

The Stellar Nebula Hypothesis #1 – All the objects in the solar system are about the same age – So, all objects must have formed at the same time

The Stellar Nebula Hypothesis #2 – All the planets orbit the sun in the same direction and in the same plane – The solar system must have formed from a swirling disc of material

The Stellar Nebula Hypothesis #3 – The inner planets are rocky and the outer planets are gaseous – Shows that there is an orderly arrangement to the solar system

The Stellar Nebula Hypothesis #4 – The outer planets have more in common with the sun than the inner planets – Seems contrary to logic! – Some process must have affected only the inner solar system

So What Happened? Prior to the development of the solar system, this area of space contained an interstellar cloud of dust and gas produced by an ancient supernova We know a supernova existed here because of the abundance of heavy elements like gold, silver, and uranium

So What Happened? Gravity caused the cloud to begin to collapse in on itself As the cloud collapsed, two important things happened… – #1- the cloud flattened into a disk (like pizza dough spun on your finger) – #2 – the center of the cloud heated up due to collisions and friction

So What Happened? Center of cloud gradually heats to 15 million degrees C – Forms the “protosun” Heat from the protosun vaporizes the ices and gases nearby so that only rock and metal remain in the inner solar system The outer solar system remains cooler and can maintain gases and ices

Beginnings of Planets Once the sun formed, the disc began to spin faster due to the increased gravity at the center – This created disturbances in the dust grains orbiting the sun – These disturbances caused collisions in the orbiting dust – Eventually, the dust “clumps” together, forming boulders

Beginnings of Planets The boulders begin colliding and sticking together in a process known as accretion – Planets close to the sun did not grow as large since there was less material in the inner solar system – Planets in the outer solar system were able to attract more ices and gases and grow larger

The Great Bombardment Final stage in the development of the solar system – “Rain” of remaining debris on the planets of the solar system – Heated the planets up and brought additional material (like water) to the inner planets – Evidence is clearly seen on the Moon, Mercury, and Mars – Continues today!!

Summarize…