Galaxies and the Expanding Universe

posted March 26, 2001, jeb

WEB PAGE:

http://physics.uoregon.edu/~jimbrau/astr123

Course Outline

lectures

Exam Schedule

exams

Grading

you only have to take two of three)

extra credit

Quizzes can increase your grade by a total of about two percent

The Sky

The full night sky reveals a concentration of stars (the "Milky Way")

Galaxies

	Sprinkled around the sky are objects that look like collections of stars
	Many of these collections have spiral shapes, which are revealed when magnified by powerful telescopes
	The deepest region of space ever explored (galaxies are denser there). (from the Hubble Space Telescope)

Constellations

A natural human tendency is to see patterns and relationships between objects even when no true connection exists, and people long ago connected the brightest stars into configurations called constellations, which ancient astronomers named after mythological beings, heroes, and animals - whatever was important to them.

Early astronomers had very practical reasons for studying the sky.
Some constellations served as navigational guides. For example, the star Polaris, part of the Little Dipper, indicates north, and the near-constancy of its location in the sky, from hour to hour and night to night, has aided travelers for centuries.

Other constellations served as primitive calendars to predict planting and harvesting seasons. For example, many cultures knew well that the appearance of certain stars on the horizon just before daybreak signaled the beginning of spring and the end of winter.

	In the southern winter sky, a collection of stars form a pattern that can be interpreted as the image of a hunter, Orion By connecting the stars with lines, the hunter's image appears But these stars are not really associated with one another
	Many such constellations were defined