Stellar Evolution of Single Stars
Stellar evolution can be divided into 3 distinct phases: 1)Pre-main sequence evolution: a relatively short (~ 107-8 yrs) phase, but involving many complex processes. An active research area. 2)Main sequence phase: the lon
Evolution of High Mass Stars
No Helium Flash: The pressure and temperature are higher initially, so He
burning starts before the core becomes degenerate. The descent from the giant branch is slower (and smaller). More massive stars go further to the blue
The Hertzsprung-Russell diagram and star clusters
There are few direct tests of stellar structure models. However, they can be generalized to models of stellar evolution (later). There are many tests of these. Some derive from applications to star cluster
Cosmology: Building the Universe.
The term has several different meanings. We are interested in physical cosmology the study of the origin and development of the physical universe, and all the structure within it. Important questions: How was the large-sc
Types of Binary Stars (the majority of stars may be in binaries)
Optical doubles - Two stars in nearly the same line-of-sight, but at very different distances. Not true binaries. Gravitationally associated systems: Visual binaries - can resolve the 2 star
What Powers the Stars?
In brief, nuclear reactions. But why not chemical burning or gravitational contraction?
Bright star Regulus (& Leo dwarf galaxy).
Basic Principle: conversion of mass to energy according to Einstein: E = mc2.
Single star evolution continued
Complications on the Asymptotic Giant Branch
A more detailed look at some of them.
The large amplitude of AGB pulsations changes the structure of the outer atmospheres. Momentum input from the pulsations drives s
Variable Stars and Pulsation
Why do Stars Vary?
Fact: variations of 1 magnitude (2.5x) are common, variations of > 3 mag. (>20x) in Miras. Pulsations are the best explanation. We can determine the radius increase directly from observation. I.e., R <v> (Do
Whats inside the stars?
We have found a plausible power source - nuclear fusion. But in discussing it we have already made some assumptions about the thermal conditions in the cores of stars. How do we know? We have only 2 ways to look inside of stars: As
Basic Stellar Properties
Weve already discussed several, but have a few more to do, and a few loose ends.
Clusters M46 and M47 (from APOD).
1. How far? Distances.
Weve already covered most of the important methods. However, now that weve covered thermal r
Introduction to Astrophysics
Whats the difference between astronomy and astrophysics? No very great formal difference. The core of astronomy is traditionally seen as observing the positions and brightnesses of astronomical objects. Now brightnesses can be