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Analyzing Starlight & HR Diagram. Stars. Star: a ball of gases that gives off electromagnetic radiation in the form of heat and light Stars look white from Earth but can be red, blue, white, orange, or yellow. The Sun is a yellow star. Analyzing Starlight.
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Stars • Star: a ball of gases that gives off electromagnetic radiation in the form of heat and light • Stars look white from Earth but can be red, blue, white, orange, or yellow. • The Sun is a yellow star.
Analyzing Starlight • Astronomers use an instrument called at spectrograph/spectroscope • Device separates light in to different wavelengths and colors = Spectrum • All stars have dark-line spectra • Spectrum reveals a stars composition and temperature
Composition of Stars • Most common element is Hydrogen (H) • Second most common is Helium (He) • Other elements: • Carbon (C) • Oxygen (O) • Nitrogen (N)
Temp & Color • The hottest starts are BLUE • The coolest stars are RED • Average temperature starts are YELLOW, like the sun.
Stars Motion: Doppler Effect • Star moving away, spectra shifted RED • Star moving toward, spectra shifted BLUE
H-R Diagrams An H-R Diagram is… • A graph of star’s TEMPERATURE and BRIGHTNESS. • It also shows STAR’s COLOR, since color is related to temperature • Stands for Hertzsprung-Russell
Notice… • Temperature DECREASES as you move to the right () on the X-axis • Absolute Magnitude INCREASES as you move up on the Y-axis • Negative absolute magnitude values are BRIGHTER than positive absolute magnitude values
A Star… • Starts off in the lower right hand corner in THE MAIN SEQUENCE when it first becomes a star. • As it gets HOTTER and BRIGHTER, it moves up the main sequence. • Then it moves to the upper right section when it changes to GIANTS. • It ends in the lower left section when it changes to a WHITE DWARF.
Questions • Answer the question on the note guide!