AST101H1 Lecture Notes - Lecture 12: Interstellar Cloud, Orion Nebula, Oort Cloud

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST101H1
• Professor: Bryan Gaensler

Document Summary

Lecture 12: doppler shifts & origin of the solar system. Nebular hypothesis: proposed by german philosopher immanuel kant around 1755, popular in 19th century, rejected in 20th and resurrected now and highly favoured. Oxygen to silicon silicon to sulphur, etc: heavy elements mixed with other interstellar gas and formed new generations of stars. The interstellar medium: the gas between the stars is called the interstellar medium, most of it is invisible but there are isolated dense (cid:498)molecular clouds(cid:499) of gas and dust (e. g. orion nebula) A cloud collapses: something starts a cloud to collapse, gravity continues to drag the gas inwards, this squeezing motion makes the gas (cid:498)in(cid:499) the cloud hot. Thus, causes of orderly motion and circular orbits are established. Formation of planets: tiny small objects stick together to form planetesimals, these are seeds (cores) of what will become planets. The frost line: disk is 98% hydrogen & helium; 2% other atoms/molecules.