CHO9 - .Thishasmadea move DouglasAdams Chapter 9 The...

Info iconThis preview shows pages 1–23. Sign up to view the full content.

View Full Document Right Arrow Icon
In the beginning the Universe was created. This has made a  lot of people very angry and been widely regarded as a bad  move.    — Douglas Adams
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The Formation and Structure of Stars Chapter 9
Background image of page 2
The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of the most beautiful objects in the sky . We are interested in the interstellar medium because: 1. Dense interstellar clouds are the birth place of stars. 2. Dark clouds alter and absorb the light from stars behind them. The Interstellar Medium (ISM)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Three kinds of nebulae 1) Emission Nebulae (HII Regions) A hot star illuminates a gas cloud Excites and/or ionizes the gas (electrons kicked into higher energy states) Electrons recombining, falling back to ground state produce emission lines The Fox Fur Nebula NGC 2246
Background image of page 4
2) Reflection Nebulae Star illuminates gas and dust cloud Star light is reflected by the dust Reflection nebula appears blue because blue light is scattered by larger angles than red light Same phenomenon makes the day sky appear blue (if it’s not cloudy)
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Emission and Reflection Nebulae
Background image of page 6
3) Dark Nebulae Barnard 86 Dense clouds of gas and dust absorb the light from the stars behind; thus they appear dark in front of the brighter background.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Dark Nebulae: clouds of gas and dust which obscure background starlight.
Background image of page 8
Dark cloud
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Why is the sky blue?
Background image of page 12
Reddening
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Interstellar Reddening Blue light is strongly scattered and absorbed by interstellar clouds . Red light can more easily penetrate the cloud, but it is still absorbed to some extent. Infrared radiation is hardly absorbed at all. Interstellar clouds make background stars appear redder.
Background image of page 14
Reddening by interstellar clouds
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A dark cloud in visible light
Background image of page 16
A dark cloud in infrared light
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A dark cloud at different wavelengths
Background image of page 18
Dark Nebulae in Cygnus
Background image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Interstellar Absorption How do we know which lines are from the stellar atmosphere and which lines are from intervening gas clouds?
Background image of page 20
Spectrum of a B0 supergiant Ionized Calcium B0 stars are too hot to have CaII lines! Interpretation: absorption lines are due to an intervening gas cloud. Interstellar Absorption
Background image of page 21

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Stellar lines tend to be broader than interstellar lines. Q: Why? A: Gas in stellar atmospheres is hot,
Background image of page 22
Image of page 23
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/17/2011 for the course PHY 121 taught by Professor Weinstein during the Fall '08 term at SUNY Buffalo.

Page1 / 99

CHO9 - .Thishasmadea move DouglasAdams Chapter 9 The...

This preview shows document pages 1 - 23. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online