lect 16 - Our Galaxy: The Milky Way Chapter 23 Interstellar...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Our Galaxy: The Milky Way Chapter 23
Background image of page 1

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

View Full DocumentRight Arrow Icon
Interstellar dust obscures our view at visible wavelengths along lines of sight that lie in the plane of the galactic disk
Background image of page 2
Interstellar dust makes difficult to locate the Sun within the galaxy The Sun Herschel’s map of our galaxy • William Herschel (18 th century) counted the number of stars at different regions of the sky, and concluded we were at the center • Jacobus Kapteyn (early 1900s) came to the same conclusion by analyzing the brightness and proper motions of a large number of stars • Because of interstellar extinction they actually observed only the nearest stars, and arrived at a wrong conclusion.
Background image of page 3

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

View Full DocumentRight Arrow Icon
This dilemma was resolved by observing parts of the Galaxy outside the disk
Background image of page 4
Background image of page 5

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

View Full DocumentRight Arrow Icon
Globular clusters are a spherical distribution of roughly 10 6 stars packed in a small volume
Background image of page 6
Determining the distance and direction of the globular clusters gave us the Sun’s location In 1912, H. Leavitt discovered the period-luminosity relation for Cepheids variables. By measuring the period you can find their luminosity and calculate their distance (in order to obtain the observed brightness ). Later, Shapley studied the period-luminosity relationship for RR Lyrae variables . The importance of RR Lyrae is that they are commonly found in globular clusters .
Background image of page 7

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

View Full DocumentRight Arrow Icon
Observations of pulsating variable stars revealed the immense size of the Milky Way Our Sun lies within the galactic disk, some 8000 pc (26,000 ly) from the center of the Galaxy
Background image of page 8
Observations at non-visible wavelengths reveal the shape of the Galaxy IRAS COBE • Interstellar extinction is maximum for the blue end of the spectrum
Background image of page 9

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

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/06/2011 for the course ASTR 113 taught by Professor Geller during the Spring '08 term at George Mason.

Page1 / 41

lect 16 - Our Galaxy: The Milky Way Chapter 23 Interstellar...

This preview shows document pages 1 - 10. Sign up to view the full document.

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