Download Getting to Know: Formation of Our Solar System

Getting to Know: Formation of Our Solar System
In 1977, NASA scientists launched two probes, Voyager 1 and Voyager 2, which they hoped
would be able to visit the outer planets of the solar system and send back photographs and
other information to Earth. It took the probes a long time to reach their destination, but along
the way they have provided a great deal of information to help explain how our solar system
was formed.
What do scientists know about the
solar system’s formation?
There are several theories about the formation of the solar system. The most widely accepted of these is the nebular theory, which claims that the solar system formed approximately 5 billion years ago when a gigantic cloud of gas and dust began to collapse. The collapse of the solar nebula, as this cloud is
The Horsehead nebula is part of a
called, was caused by the force of gravity pulling
larger
nebula. The nebula got its name
particles within the nebula toward one another.
because
it looks like the head of a horse.
Once the particles were in close range, intense
pressure caused them to merge. The Sun’s great
mass was formed from the matter at the center of the collapsing clouds, and planets and
other bodies formed from matter that was farther away.
How did the Sun start to shine?
As matter at the center of the solar nebula became denser, pressures and temperatures
increased. Eventually, the intense heat and pressure caused nuclear fusion to occur and as
the atomic nuclei merged, tremendous amounts of energy were released. Nuclear fusion
continues to be the source of the Sun’s energy.
Misconception 1: The solar system will always be the same.
The solar system, just like the planets and other bodies that make it up, is always
changing. The solar system looks different than it did when it was first created
4.5 billion years ago, and it will continue to change until the Sun’s energy runs out
in approximately 5 billion more years.
Concept: Formation of Our Solar System
Getting to Know
www.discoveryeducation.com
1
© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.
Why do the planets orbit the Sun?
The matter in the solar nebula rotated around its center. As the solar nebula collapsed, matter
began rotating more quickly. Over time, this motion caused the solar nebula to flatten into
a disk-like shape with the Sun at the center. The planets formed from the matter in the diskshaped region around the center. The planets continue to orbit in the same direction that the
original solar nebula was spinning.
Misconception 2: Planets orbit the sun in a circular path.
No, the orbits of planets are elliptical, not circular. Often, models of the solar system
show the planets orbiting the Sun in circles that lie close together. This basic model
shows the relative location of all the Sun’s satellites, but it does not represent their actual
orbits or distances from one another.
Where is the edge of the solar system?
The solar system does not have a defined edge because all of the bodies it contains are constantly moving in space. Some scientists, however, point to a specific piece of debris outside the orbit of Neptune as the border of the system. Others believe the solar system extends to where the Sun no longer has a significant gravitational effect. The solar nebula
resembled a spinning
top.The larger bulge in
the middle is where the
Sun formed.
By some estimates, the solar system is at least 15,000,000,000,000
kilometers wide. Voyager 1 just reached the outer limits of the solar
system, and Voyager 2 has almost crossed this threshold. Both probes
have been traveling for over 34 years! As they move deeper into space,
it will be interesting to see what else scientists can learn about the
solar systems in our galaxy.
Concept: Formation of Our Solar System
Getting to Know
www.discoveryeducation.com
2
© Discovery Education. All rights reserved.
Discovery Education is a subsidiary
of Discovery Communications, LLC.