ISP chapter 15 - Chapter 15 15.1- know the different types...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 15 15.1- know the different types of galaxies 15.2 HOW DO WE KNOW UNIVERSE IS EXPANDING? Edwin Hubble was the first to measure the distances to other galaxies 1. We determine the size of our solar system using radar 2. We determine distances to stars out to a few hundred light-years using parallax o ? If you went to Mars and measured the parallax angles of nearby stars from there (it would take at least ½ a Martian year) they would be: i. Larger Luminosity passing through each sphere is the same o Area of sphere: 4pi (r) 2 o Divide luminosity by area to get brightness A standard candle is an object whose luminosity we can determine without measuring its distance ? suppose you measured the apparent brightness of one star just like the sun, you find that it is 10^20 times fainters than the sun: o Star A is 10^10 Au away ? How far is 10 10 AU? o 1.5x10 18 km (=10^5 light years) Sun is 150 million kilometers 3. Apparent brightness of star clusters main sequences tells distance
Background image of page 1

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

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 2

ISP chapter 15 - Chapter 15 15.1- know the different types...

This preview shows document pages 1 - 2. Sign up to view the full document.

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