3 Different Types of Stars Giants D. SupergiantsWhite Dwarfs E. SunMain Sequence
4 Sagittarius Star Cloud, HST Star ColorStars have different colorsSome look red (like Betelgeuse), somelook more yellow (like the Sun), and somelook blue or blue-white (like Sirius)Color is directly related to temperatureLight is not sensitive to the details ofthe star's composition but to itstemperature(according to which law?)Astronomers can determine:1. the surface temperature of a star bymeasuring its color2. the composition of its outer layers bylooking at its spectral linesWien’s law: T=k/lambda(max)Sun
5 Star color and brightness Is a star’s color (temperature) related to its size?Is the relation the same for all stars?Are there different kinds of stars?
6 Electromagnetic Radiation Energy that travels through space in wavesStars give off electromagnetic radiation in different formsEach form has its own wavelengthRadio WavesInfrared RaysVisible LightUltraviolet LightX-RaysGamma Rays
7 Continuous spectrum and Absorption spectrum A Any visible white light consists of millions of colors, including the seven very obvious colors: red – orange – yellow – green – blue – indigo and violet.A hot glowing object like a wire inside the bulb gives off a continuous spectrum.A continuous spectrum is a spectrum that shows all colors.
8 Continuous SpectrumA rainbow is an example of a continuous spectrum. Most continuous spectra are from hot, dense objects like stars, planets, or moons.. Any solid, liquid and dense (thick) gas at a temperature above absolute zero will produce a thermal spectrum.
9 Absorption SpectrumBecause each element in this world absorbs a color or more of the continuous spectrum, the elements in the atmosphere of a star emits an absorption spectrum rather than a continuous spectrum.A absorption spectrum is produced when light from a hot solid or dense gas passes through a cooler gas (which is the atmospheric gases of the star in this case)
10 Measuring the chemical composition of a star from its absorption spectrum
11 Identifying the composition of star’s atmosphere using its absorption spectrum
13 Here are spectra for some elements common in the atmospheres of stars: In a star, these elements absorb light at their special frequencies. On the following pages, you will see both the elements for comparison and a star's spectrum. Your job is to identify all the elements you can detect in the star's atmosphere.
14 Here are spectra for some elements common in the atmospheres of stars: Here is the spectrum of a mystery star:Which elements are present?
15 Yes, you are correct!The mystery star:has the following elements.HydrogenIron
16 Here is the spectrum of a mystery star: Here are spectra for some elements common in the atmospheres of stars:Here is the spectrum of a mystery star:Which elements are present?
17 Yes, you are correct!The mystery star:has the following elements.CalciumHydrogenMagnesiumYou have identified all the elements
18 Assignment 1What is the supernova and how does it differ from the black hole?