Parallels: Proto-Planetary Disks and rings

30 November 2015

Origin of the Solar System

• It’s a fundamental problem in astronomy• We must explain the characteristics of our own

system, and of planets around other stars• Elements were made inside stars• Stars formed from giant molecular clouds• Planets form in a disk around the protostar• Giant planets form from accretion onto cores• Terrestrial planets are only the cores

Characteristics of our Solar System

• Regular planet orbits• Planets are closely spaced• Terrestrial and Jovian planets• Asteroids and comets leftover• Satellites and rings imitate a miniature Solar

System

Stages in planet formation• Dust collects in the mid-plane of the

protoplanetary disk• Grows by mutual collisions: ‘accretion’• Planetesimals (about 1km across) grow and collide• Giant collisions are the final stage• Giant planet cores are bigger outside the frost-line:

they attract gas to become gas giants like Jupiter• Star ignites: the gas and dust blown away

Leftovers

• Near the Sun (inside frost-line, also known as snow line or ice line) rocky objects become asteroids

• Far from the Sun (outside frost-line) icy objects form the comets and Kuiper Belt Objects

Density waves andpropellers in a forming disk