Star Spectra Essential Question? How is information from what we see so informative about stars?

What does the light tell us? When you look at a star, the light can tell you a number of things. ▪ the distance of the star/lighted object ▪ What it’s made of relative to the elements

So what is light? Kurtzgesagt-Light Light is energy produced by a photon A photon is energy released as electrons move from different energy levels in an atom. Visible light is only a very small part of the electromagnetic spectrum Light has different frequencies but travels at the same speed (the speed of light) which is about 300,000,000 m/s

So what is light (cont)

So what is light? The Speed of light is approximately 300,000,000 m/s That’s why you see the lightning before you hear the thunder

Luminosity Actual Brightness Or Visual Magnitude of the light. Flashlight vs. Headlight of a car???

Luminosity vs. Apparent brightness Actual Brightness Or “Absolute Magnitude of the light”. It’s the total energy a star radiates per second. Think: Flashlight vs. Headlight of a car??? Apparent Brightness -what it “appears to be” Also called visual magnitude Depends on how far you are from the source. Think: 2 flashlights- different distances

Luminosity vs Apparent Brightness tells us a lot about the distance of objects.

What are spectra? Spectra are the colors of light emitted when an electron (e’) jumps from energy level to energy level within an atom. A light wave of a particular wave length is emitted. All elements have their own unique spectra. A spectra shown by a particular light tells us what it’s made of.

Absorption Line Spectra. Caused by a cold gas in front of a hot source Blackbody spectrum- produced by HOT solid/liquid or dense Gas. Bright line spectra-Produced by thin hot gasses. Colorful lines on black background. Absorption Line Spectra. Caused by a cold gas in front of a hot source

Fraunhofer Lines in the spectrum of the Sun The Solar Spectrum Fraunhofer Lines in the spectrum of the Sun

Fraunhofer Lines in the Solar Spectrum (~1817) Designation Wavelength Origin A 759.4 nm terrestrial oxygen B 686.7 terrestrial oxygen C 656.3 hydrogen (H alpha) D 589.0 neutral sodium (Na I) E 527.0 neutral iron (Fe I) F 486.1 hydrogen (H beta) G 430.3 metal blend H 396.8 ionized Calcium (Ca II) K 393.4 ionized Calcium (Ca II)

What does this tell us? ▪ the distance of Stars/lighted objects in the night sky ▪ the type of gasses the star is made of ▪ What it’s made of relative to the elements