Post on 19-Jan-2016
Ordinary StarsOrdinary Stars
The Colors of Stars Color of a star is determined by the
peak wavelength of light emitted The color of a star depends on its
temperature: Low temperature: Red High temperature: Blue
Color & Temperature of Color & Temperature of StarsStars
Ordinary StarsOrdinary StarsWien’s Displacement Law
As the temperature of a star increases, the peak of its radiation is shifted toward shorter (blue) wavelengths
Stefan-Boltzmann Law As the temperature of a star increases,
the total energy output increases as the 4th power of the temperature
Ordinary StarsOrdinary Stars Example: If one star has a temperature
of 10,000 K and another a temperature of 5,000 K, how much more energy does the hotter star put out?
The first star is 2x hotter. That star puts out 24 or 16 times as much energy
Ordinary StarsOrdinary StarsSpectral LinesSpectral Lines
Emission Spectra: Certain wavelengths of light appear brighter due to the presence of certain chemicals that are excited enough to glow
Absorption Spectra: Certain wavelengths are missing due to a cool gas absorbing those wavelengths
Spectral LinesSpectral Lines
Ordinary StarsOrdinary Stars
Spectral Types Different stars show different spectra A classification scheme was soon
developed The different spectral types of stars
are classified as:
O B A F G K M
Ordinary StarsOrdinary Stars
Spectral TypesSpectral Types Type O Star: 30,000 - 60,000 K
Color = Blue
Very short life Burn out quickly Type B Star: 10,000 - 30,000 K
Color = Blue
Example: Rigel (Orion)
Ordinary StarsOrdinary StarsSpectral Types
Type A Star: 7,500 - 10,000 KColor = Blue/White Strong H, Ca, Mg linesExamples: Sirius (Canis major), Deneb (Cygnus)
Type F Star: 6,000 - 7,500 KColor = YellowExample: Polaris
Ordinary StarsOrdinary Stars
Spectral Types Type G Star: 5,000 - 6,000 K
Color = yellow Example: The Sun Type K Star: 3,500 - 5,000 K
Color = Red Example: Aldebaran Type M Star: < 3,500 K
Color = Red Example: Betelgeuse
Variable StarsVariable Stars
Long Period Variables
Cepheid Variables
RR Lyrae Variables
Binary StarsBinary Stars Pairs or groups of stars bound by
gravity Types of Binaries:
Visual
Spectroscopic
Eclipsing
Astrometric
Star Clusters:Open Star Clusters:Open (Galactic) Clusters(Galactic) Clusters
Shape: Irregular, no specific shape
Where: Galactic disk
Types of Stars:
Population I Age of Stars:
Young!
Star Clusters:Open Star Clusters:Open (Galactic) Clusters(Galactic) Clusters
Open clusters contain a few dozen to a few hundred stars
Star Clusters: Globular Star Clusters: Globular ClustersClusters
Shape:Spherical
Where found:Galactic Halo
Types of Stars:Population II
Age of Stars:Old
Star Clusters: Globular Star Clusters: Globular ClustersClusters
Globular clusters contain 50,000 to 1 million stars