Our home
The Big Bang
The expansion (or, inflation)
of the universe can be
visualized as everything in
the system expanding
outward from everything else,
as in this simple example of a
brick of raisin bread dough
Cosmic microwave background radiation
This is a “temperature map” of the universe
Spiral galaxy NGC4414
Galaxies in the process of colliding
Barnes and Hernquist
Whirlpool M51
Recall: We Are Star Dust
The first and simplest atoms (only H &
He; some Li, Be, B) were created
during the Big Bang
When a star dies, its
atoms are expelled into
space…. to form new
stars and planets
More complex
atoms were
created in stars
Many of the atoms in our bodies were created in the cores of stars!
Formation of the Solar System
• The Solar System formed
within a giant interstellar
cloud of gas and dust.
• Solar nebula collapsed
under its own gravity.
Newborn stars in the Orion Nebula
Formation of the Solar System
• The Solar System formed
within a giant interstellar
cloud of gas and dust.
• Solar nebula collapsed
under its own gravity.
• Gravitational potential energy
converted to heat:
– Sun formed in dense, hot center.
• Shrinking nebula rotated faster.
• Collisions caused nebula
to flatten into a disk.
Protoplanetary Disks
• Protoplanetary disks (“proplyds”)
of gas and dust observed around
young stars.
• New planetary systems in
formation.
Formation of Planets
Condensation from Solar Nebula
• Condensation (solidification) of materials from solar nebula
depends on temperature:
– Planet composition depends on distance from the Sun.
• Ices condensed only beyond the frost line:
– Jovian planets formed by pulling gases onto
large icy cores in the cold outer solar system.
4 Main Ingredients of the Planets
(ices)
Accretion of Planetesimals
• Accretion: Condensed materials stick together, then attract by
gravity, to form planetesimals.
• Planetesimals collide and combine to form protoplanets.
• Only planets with "well-behaved" orbits survive!
Inner vs. Outer Solar System