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Name: Heather Lucero Date: 04-03-2022 Student Exploration: Star Spectra Directions: Follow the instructions to go through the simulation. Respond to the questions andprompts in the orange boxes. 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? White light divides into several wavelengths andhues, including red, orange, yellow, and green. 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? The absence of light is depicted by the dark line. Red, green, yellow, orange, blue, purple,and black lines are all over the place. 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? 10 lines 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? Some of them do, but not all of them. 3. Drag the Helium spectrum next to the Star spectrum. Do some lines match? Helium does match thespectrum of stars. 4. Try out the other available spectra. Do any others have lines that match? No, nobody else does. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
5. Which elements have contributed to the spectrum of star 1? Hydrogen and Helium Note: The elements in a star’s spectrum do not necessarily reflect what the star is made of. The absorptionspectrum is mostly determined by the surface temperature of the star. Activity A: Classifying stars Get the Gizmo ready: ● Check that Show labels is on and Neutral spectra is selected. Question: How are stars classified? Introduction: Late in the 19 th 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 dothe work, paying them 25 cents a day. The most prominent of these women was Annie Jump Cannon, whodevised 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, ionizedcalcium 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, ionizedcalcium, ionized iron, ionized magnesium 5,000 – 6,000 K Orange Neutral calcium, neutral iron, neutralmagnesium 3,500 – 5,000 M Red Neutral iron, neutral magnesium, andneutral titanium oxide (not shown) < 3,500 1. Classify: Use the Gizmo to find the elements that are present in the spectra of stars 1 through 4. Remember to check both the Neutral spectra and the Ionic spectra . Then use the table above to classify each star and describe its surface temperature. (Note: A star spectrum may not display lines of all of theelements typical of its spectral class.) Star Color Elements in spectrum Class Surface Temperature (K) 1 Blue Ionized Helium, Ionized Hydrogen O > 25,000 2 Orange Neutral Iron, Neutral Calcium, Neutral Magnesium K 3,500 - 5,000 3 Blue Ionized Hydrogen, Ionized Helium O > 25,000 4 White Hydrogen, Ionized calcium, Ionized sodium A 7,500-11,000 Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
2. On your own: Look up Annie Jump Cannon on the Internet or in a library and read her story. Share your discoveries with your classmates and teacher. The creation of modern star classification was made possible by the cataloging work of Americanastronomer Annie Jump Cannon. Activity B: Unusual stars Get the Gizmo ready: ● Select star 5 . Question: What else can we learn from stellar spectra? 1. Observe: Observe the spectra of stars 5 – 10. Identify the elements in each spectrum, and try to classify each star. If you notice unusual features in these spectra, describe them. Star Color Elements in spectrum Class Unusual features 5 Yellow None of the elements match G Similar to sodium's double line, howeverthey are displaced 6 Red Neutral titanium oxide andneutral iron (not shown) M The neutral magnesium does not fitsince it has some more pronouncedblack lines than the original magnesium. 7 Blue- White Hydrogen, Neutral helium B Normal 8 Yellow Calcium, Neutral sodium G The light flickers, moves up and down,and there are some unfamiliar dark linesin the neutral sodium. 9 Withe Ionized calcium, Hydrogen,Neutral sodium F Calcium did not match neither ionized orneutral, besides moving sometimes 10 Yellow Calcium, Neutral sodium G Normal Match: Write the number of the star or object that matches each description. Then use this information to helpyou identify the elements and reclassify the stars in the table above. 3 High atmospheric pressures in a star cause spectral lines to be broadened, or “smeared out.” Giant stars , which have relatively low atmospheric pressures, are characterized by narrow spectral lines. 2 If a star is moving away from an observer, spectral lines are redshifted , or shifted toward the red end of the spectrum. An approaching star is blueshifted . 8 A star orbited by a large planet will move in a small circle. This will cause its spectrum to be slightlyredshifted part of the time and blueshifted at other times. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
4 Binary stars are pairs of stars that orbit one another. Their presence is indicated by two spectra that shift in opposite directions. 6 Cepheid variable stars change their brightness in a regular cycle. Gas pressure builds up, causing the stars to expand quickly. When the pressure is released, the star contracts, and the intensity ofsome spectral lines may decrease. 7 A nebula is an enormous cloud of gas and dust in which stars are born. Most nebulae produce an emission spectrum , which is characterized by bright lines of color against a dark background. The bright lines in an emission spectrum correspond to the dark lines in an absorption spectrum. Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved
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Star Spectra Gizmo Answer Key