| Last: 9. How Far the Stars? | Next: 11. Origin of the Elements |
Stars are born inside great clouds of cool gas and dust. Such a cloud may contain thousands of denser lumps of gas; some of these lumps collapse under their own weight. This gravitational compression heats the gas until thermonuclear reactions can occur. When the production of nuclear energy matches the rate at which energy escapes into space, the collapse halts and a main-sequence star is born.
Topics:
Reading:
| Ch. 9 | PROTOSTARS AND PRE-MAIN-SEQUENCE STARS (p. 182) |
| Ch. 9-1 | Stars condense from clouds of gas and dust |
| Ch. 9-2 | Supernova explosions in cold, dark nebulae trigger the birth of stars |
| Ch. 9-3 | When a protostar ceases to accumulate mass, it becomes a pre-main-sequence star |
| Ch. 9-4 | The evolutionary track of a pre-main-sequence star depends on its mass |
| Ch. 9-5 | H II regions harbor young star clusters |
| Ch. 9-6 | Plotting a star cluster on an H-R diagram reveals its age |
| Ch. 9 | MAIN-SEQUENCE STARS AND GIANT STARS (p. 191) |
| Ch. 9-7 | Stars spend most of their life cycles on the main sequence |
Web Resources:
A very large star-formation region in a neighboring spiral galaxy.
A small cloud of molecular gas and dust is silhouetted against a background of stars.
A spectacular emission nebula with a central cluster of bright young stars. The X-ray images shows the hot gas produced by winds from these stars.
Anoter beautiful emission nebula.
Animation showing a nearby star-formation region in the constellation of Orion.
A famous dark nebula in belt of Orion.
Close-ups of the star-formation region in Orion. The visible light image emphasizes the glowing gas, while the infrared light image shows the cluster of young stars.
An extremely active star-forming region in the Orion Nebula.
Dense clouds of gas `boiling off' due to radiation from massive stars.
In order from left to right, a dying star with a ring around it, a brilliant cluster of young stars, and gas clouds forming the next generation of stars.
As protostars collapse, they often generate ``jets'' of fast-moving gas.
This double cluster of young stars is faintly visible to the even without a telescope.
Orbital motion of stars in a small cluster. Color indicates stellar mass; red is low-mass, blue is high-mass. Notice that the high-mass stars tend to collect in the center of the cluster, while smaller stars are pushed to the fringes or even ejected.
Faint praise for astronomy lectures...
From a website on running toilets and how to fix them.
Homework 10: Main-Sequence Stars, due 11/06.
Quiz 10: How Hot The Sun?, given 11/01.
Last modified: November 13, 2001
http://www.ifa.hawaii.edu/~barnes/ast110/sn.html
