NATS 1740 Chapter Notes - Chapter 15: Inverse-Square Law, Binary Star, Ellipse

• School: York University
• Department: Natural Science
• Course: NATS 1740
• Professor: Tatiana Paulin

Document Summary

The apparent brightness of a star declines with the square of it"s distance. It follows the inverse square law (ex. Binary star systems- systems in which 2 stars continually orbit each other. Visual binary- both stars can be resolved with a telescope. Spectroscopic binary- we detect the spectral lines of one or both stars alternately becoming blue and red shifted as they orbit each other. Eclipsing binary- 2 stars happen to be orbiting in the plane of our line of sight so that each star will periodically ellipse each other. Most of the very brightest stars are red in colour. Brighter stars are white with blue tint, middle are yellow/white, and dimmest are small red dots. Hr diagram- surface temp(x) and stellar luminosity(y) Main-sequence lifetime- the length of time for which a star of a particular mass can shine by fusing h into he in it"s core. Less massive stars have longer life times than high mass stars.