Gizmos Student Exploration: Star Spectra

Name: Date: Student Exploration: Star Spectra Vocabulary: absorption spectrum, binary star, blueshift, Cepheid variable, emission spectrum, giant star, nebula, redshift, spectrum, star Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. What happens when light goes through a prism? This band of colors is called a spectrum. 2. A rainbow is an example of a spectrum. What is the sequence of colors in a rainbow? Gizmo Warm-up The interior of a star produces a continuous spectrum of light, like a rainbow. Cooler gases in the outer layers of the star absorb certain wavelengths of light, causing dark lines to appear in the spectrum. The resulting absorption spectrum can tell astronomers a great deal about the star. 1. On the Star Spectra Gizmo™, turn on Show labels. Select star 1 to see its absorption spectrum. How many lines do you see in the spectrum? 2. Drag the Hydrogen spectrum next to the Star spectrum so that the edges line up. Do some of the lines on the two spectra match up? 3. Drag the Helium spectrum next to the Star spectrum. Do some lines match?. 4. Try out the other available spectra. Do any others have lines that match? 5. Which elements have contributed to the spectrum of star 1?, Note: The elements in a star’s spectrum do not necessarily reflect what the star is made of. The absorption spectrum is mostly determined by the surface temperature of the star. Question: How are stars classified? Introduction: Late in the 19th century, Harvard astronomer Edward Pickering wanted to sort and catalog the thousands of star spectra that had been collected by the Harvard Observatory. He hired several women to do the work, paying them 25 cents a day. The most prominent of these women was Annie Jump Cannon, who devised a classification system still used today. Harvard Classification Scheme Class Color Prominent spectral lines Surface Temp. (K) O Blue Ionized helium, hydrogen > 25,000 B Blue-white Neutral helium, hydrogen 11,000 – 25,000 A White Hydrogen, ionized sodium, ionized calcium 7,500 – 11,000 F White Hydrogen, ionized sodium and calcium; neutral sodium and calcium 6,000 – 7,500 G Yellow Neutral sodium and calcium, ionized calcium, ionized iron, ionized magnesium 5,000 – 6,000 K Orange Neutral calcium, neutral iron, neutral magnesium 3,500 – 5,000 M Red Neutral iron, neutral magnesium, and neutral titanium oxide (not shown) < 3,500 ....................................................continued.......................................................