H-R diagram

Stellar life recap• Stars begin as a

• If they reach ___________________

• They move onto the ________ __________

• They spend most of their lives here burning _________

Nebula

Critical Temperature

MainSequence

Hydrogen

Dying stars• Stars start to die when they run out of hydrogen

• As they age into ___________giants, they cool down but get larger.

• They then begin to burn

• The __________stars burn much hotter and brighter, but are then much ___________ as they have collapsed into a white dwarf or supernova. These oldest stars are _________ or ____________.

Red

Helium

Older Smaller

Blue White

Stars the Size of the Sun

• Die as

• Stars larger than the sun die as

White Dwarves

Supernova, neutron stars or black holes

Reading the H-RThe H-R diagram classifies stars by

Surface Temperature

ColorLuminosity Spectral Class

DefinitionsLuminosity – how truly bright it is based on the sun

Ex: it is 100,000 brighter than the sun–It is as bright at 7598 sunsStars can be hundreds of times brighter or dimmer than our sunThey are so far away that they appear dimThis is also calledAbsolute Magnitude

Spectral ClassesTemperature (may vary on HR)O > 20,000K Blue StarsB 10,000 - 20,000 K Blue - whiteA 7,500 - 10,000 K White stars F 6,000 - 7,500 K Yellow-white stars G 5,000 - 6,000 K Yellow stars (like the Sun)

K 3,500 - 5,000K Yellow-orange stars M < 3,500 K Red starsOh, Be a Fine Girl/Guy, Kiss Me

Spectral classes

O ,B, A, F, G, K, M Means absolutely

nothing.

Other things we can determine

• Age• Is it burning hydrogen, helium or carbon

• Size compared to the sun

Read the H-R diagram• Which stars are the

hottest?– Blue and white stars

• Which are the coolest?– Red and Orange Giants

• Which are the oldest– White dwarfs.– Which star is older:

Sirius or Betelguese– Which star is more

luminous: Sirius or Betelguese?

Star Life Cycles – RecapStars begin asProtost

ars

Main Sequence

Critical Temperature

Helium

Hydrogen

Oldest

Red

Smaller Blue White

If they reach, they move onto the

Where they spend most of their lives burning

As they age into giants, they cool down but get larger. At this point they are burning

The stars burn much hotter and brighter but are then much as they have collapsed into white dwarfs or supernova. These oldest stars are or in color.

SuperNOVA in M82

What is the H-R Diagram

• http://aspire.cosmic-ray.org/Labs/StarLife/hr_diagram.html

• Follow the above link to learn about the HR Diagram

• Complete the activity online and show your teacher your work.