Week 11 - Stars & Stellar Evolution

Evolution

Changing over time

Stellar

Starlight

Blackbody radiation

How stars emit light and energy

Stellar spectra

The rainbow of a star

Stellar spectral classes

OBAFGKM temperature

Apparent magnitude

How bright a star looks as viewed on Earth

Absolute magnitude

How bright a star looks at 10 paraseconds

Parsec

3.27 light years

Luminosity

Power of a star

Solar units

Units we use for power

Doppler Effect

Used to figure out the velocity of stars

Eclipsing binary stars

Stars that pass in front of each other as viewed from Earth

Hertzsprung-Russell Diagram

Graph of temperature and luminosity

Main sequence stars

Most stars most of the time are sequence stars

Red giants

Cool stars that are very big and very powerful

White dwarfs

Hot stars that are small and low power

Stellar mass units

Units we use for masses of stars

Star cluster

Group of stars made from the same cloud and same time

Protostar

Baby star

Stellar mass limits

Range of star masses

“carbon ash”

Carbon that is formed from helium fusion

Cepheid Variable Stars

Allows to measure distances

How do we measure these aspects of stars?

Distance, temperature, composition, luminosity, size, velocity

What are the stellar spectral classes, and what do they designate?

O, B, A, F, G, K, M - organized by temperature from highest to lowest. Students remember this as "Oh, be a fine girl, kiss me." 

What is a H-R diagram, and what does it show?

Stellar temperature (or spectral class) versus luminosity (or absolute magnitude). A plot of star temperatures versus luminosity that identifies star types (red giants, white dwarfs) and shows most stars along the main sequence diagonal.

What are the general relationships between mass, temperature, color, luminosity, and size of stars?

They help measure the aspects of stars.

How do we identify red giants

Bright but cool stars that must be very large.

How do we identify white dwarfs?

Dim but hot stars that must be very small.

What are the stages of stellar evolution?

Mass is the primary factor determining a star's fate and evolution timeline.

How does a star remain stable during its life?

Inward gravitational force and outward pressure from nuclear fusion.

What are variable stars, and how are they useful?

Stars that pulse regularly, becoming brighter and dimmer as they expand and contract. Their pulse periods correlate with luminosity, making them crucial for measuring distances to far galaxies.

What one factor is most important in determining the fate of a star?

Mass