Transcript solar system formation and gal

THE FORMATION OF THE
SOLAR SYSTEM
Its all about gravity
• Gravity can set the particles and dust in a
nebula into motion
• The core of a young star (protostar) acts as
an anchor being the largest mass in the
nebula
• The protostar is hot and dense and particles
from the nebula begin to gather around itgravity
• The spinning nebula begins to contract and
smaller pieces build up, if they avoid impact
the planetismals can develop to full planets.
How it
works
Evidence to support this
theory
• Think back to the lab we did and think
about the disorganized formation this
and a
theory implies.QuickTime™
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anything that can support it
• The many craters on the moon and
other planets indicate many collisions
occurred in the formation of the
universe.
What happens to the Nebula?
• Over time it flattens into a disc-like shape
while spinning in one direction
• Astronomers theorize that any planets
forming during this phase would form in the
same flat plane and would rotate and revolve
around the star in the same way
• Using technology, astronomers have
discovered flattening nebulas of young stars
outside our solar system to support the solar
nebula theory
Extrasolar planets
• This theory suggests that planets are byproducts
of star formation, so planets should be common
since we have a sky filled with stars
• Astronomers have discovered over 300 planets
that are orbiting other stars and these are called
extrasolar planets
• Astronomers have used star light level changes
to determine the existence of planets-when
viewing the star with the planet in-between the
viewer and the star, the brightness is changed.
• In 2008 the first image was taken of extrasolar
planets orbiting HR 8799 in the Pegasus
constellation
HR 8799
GALAXIES
The Discovery
• William Herschel (1738-1822) discovered that
the milky way was a huge system of stars that
today we know is a galaxy
• Every star that you see on a clear night is part
of the milky way
• A galaxy is a collection of stars, gas dust and
planets held together by gravity
Galaxy Shapes
• Spiral
• Elliptical
• irregular
Understanding the Milky Way
• Star Clusters
– Open clusters--50-1000 stars along main band of
the Milky way
– Globular clusters--100000 - 1 000 000 stars
arranged in a spherical shape around the centre of
the Milky way
• The diameter of the Milky Way
– Around 100 000 light years and the shape is disclike
– We know this from radio waves being able to
travel through dust and gas between stars of the
Milky way
– Recall the distance of 1 light year is 9.5 x 1012 km
Star Clusters
The Centre of the Milky Way
Galaxy
• Using radio waves again, astronomers
discovered that the centre of the Milky Way is
surrounded by a bulge of stars (a sphere of
globular clusters)
• The shape of the Milky way galaxy was
determined based on its disc-like shape and
central bulge of stars, astronomers concluded
it is a spiral galaxy.
• The Sun is approximately 28 000 light years
away from the centre region of the galaxy
• The visible mass estimate is 200 billion solar
masses
The Local Group
• The Milky Way belongs to about 40
galaxies called the Local group.
• The diameter of this group is about 10
million light years
• The milky way and Andromeda galaxies
are the larges galaxies in the group
• Most of the galaxies in this group are
small elliptical
Homework
• Pg 336 #1-3
• Pg 366 #1-3
• Pg 367 #1-5