Lecture 22 - Star Formation from Molecular Clouds

Gravitational contraction of gas clumps (like balloons) can’t happen in the atmosphere because you can’t get as big as the Jeans Length. But in interstellar space, it’s a different story

Term: the Interstellar Medium- material in space between the stars

A Star is born….

A Star is born (Part 2) …

Forming stars eventually rip up the molecular cloud in which they formed. The molecular

cloud is dissipated after about 30 million years. (How can we know

that?)

Star formation and the conservation of angular momentum

You can see these phenomena in stars in the sky (T Tauri stars, Herbig-

Haro objects, etc)

jet

Accretion disk

Question:

• We see these processes occurring in young protostars.

• We understand the physics of these processes (at least partially)

• We believe the Sun formed like this.• What characteristic of the solar system can we see

that is an indicator of the processes of contraction, jet formation, accretion disk formation, etc?

Young Stars with Accretion Disks

Beta Pictoris Fomalhaut

Artist’s Conception of Fomalhaut System

Summary of what we know about the formation of stars

• Stars form from the massive amounts of material in cold, dark molecular clouds

• Contraction from the low density molecular cloud to a dense, compact, shining star occurs through gravitational contraction (Jeans Length)

• As the star contracts and “spins up”, it sheds a disk of matter, from which planets form.

Where do we see this occurring?

Everywhere in the sky. Particularly in the Milky Way. Check the Skalnate Pleso charts for Taurus and Auriga