In the 1800s, scientists did not know that these lines were chemical in origin. These lines are now known collectively as the fraunhofer lines. Interstellar dust absorbs light, especially blue light, making stars look dimmer and redder than they really are. The stars spectrum, shown at the left, has a valley in the red area. Spectral lines of atomic hydrogen chemistry libretexts. This figure illustrates one difference in the spectral lines from stars of the same temperature but different pressures. Long books and computer databases have been compiled to show. Spectral line s are produced by transitions of electrons within atoms or ions.
Not only is this a good read for any observer thinking of taking up spectroscopy, but its also suitable for high school or firstyear college students in astronomy and physics. This will be used as a model for how nasa uses spectroscopy to determine the nature of elements found on earth and other planets. If the spectrum of the white light from the sun and stars were simply a. This lab will allow you to gain experience with measuring stellar spectral lines to identify the elements that are being created in stars. When seen through a spectroscope, stars reveal their. Blackbody radiation as we saw in the activity magnitudes and colours of stars, it is assumed that a star behaves like a blackbody1 and emits a spectrum that is well described by various equations and laws of thermal physics. We can learn a lot more from the spectral lines than from the continuum the motion of stars and galaxies in such an analysis of chemical abundances, the wavelength of each line is treated as fixed. Learning about stars from their spectra page 11 of 29 assumption 1. The spectra of stars including the sun show many spectral features this tells us that the photospheres are composed of many elements. In a single atom, emission occurs when an electron lowers its energy by ejecting. Spectral classification of stars 43 space math at nasa. Traditionally, spectral images are two dimensional, and related to text. Name date class 2 activity spectral analysis handson. Having read this much, please answer the first three questions, and write your answer in the space provided on your report sheet.
Spectral classification of stars 43 the advent of the spectroscope in the 1800s allowed astronomers to study the temperatures and compositions of stars, and to classify stars according to their spectral similarities. However, this is not true when the star is moving towards us the lines are observed at shorter wavelengths, or blueshifted, than those measured in the laboratory or moving away. A traditional mnemonic for the sequence is oh, be, a fine girlguy, kiss me. Explain how this effects the position of your pleiades data on your graph, and how that changes the distance. Bohrs model explains the spectral lines of the hydrogen atomic emission spectrum. Each element makes a unique pattern of lines, which helps us determine which elements are present. Thus, the spectral sequence includes b8, b9, a0, a1, etc. A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Chromospheric activity of periodic variable stars including eclipsing.
Thus a b5 star is cooler than a b0 star but hotter than a b9 star. Spectral classification and the pleiades worksheets. Nobody knew that emission and absorption lines depended on the orbital structure of electrons in atoms. In this lab you will use a visual spectroscope to observe the spectra of several bright stars, identify spectral features, and determine their spectral classes.
Most curricular materials in teachengineering are hierarchically organized. Stellar spectroscopy and the hr diagram,stellar masses this subject is one of the keys to modern astronomy. While the electron of the atom remains in the ground state, its energy is unchanged. This shifts the stars spectral lines toward the blue end of the spectrum. Two very important things we can learn from spectral lines is the chemical composition of objects in space and their motions. When the atom absorbs one or more quanta of energy, the electron moves from the ground state orbit to an excited state orbit that is further away. Spectral line definition of spectral line by the free. Using their data, they make comparisons between different light sources and make conjectures about the composition of a mystery light source. In this activity, students will build a spectrometer using basic materials to observe the light emitted and absorbed by several sources.
For most elements, there is a certain temperature at which their emission and absorption lines are strongest. If the star is moving away from us, its waves are effectively stretched out when they reach. These activities were designed to aid student understanding of spectral analysis, what the patterns mean, how elements are involved, and how this relates to stars. A look at spectral lines from different elements and molecules, and from a thermal emitter.
This is an advanced lab activity which requires familiarity with the telescope, precise focusing, and careful observing. Hydrogen will only absorb light if the star is at the right temperature. Thus, the letters used by fraunhofer to identify the lines have no relation to chemical symbols nor to the symbols used to. Stars and galaxies name date class spectral analysis handson activities the photograph of the spectrum of a star, sorted by color across a plate, will reveal spectral lines upon close examination. Eclipsing binaries in which we can see the spectral lines of both stars have played a crucial role in establishing the masses and the radii of different types of stars. In a rainbow, the colors of light go from purple to red. Activity guide for science, mathematics, and technology education1 introduction if you go to the country,far from city lights,you can see about 3,000 stars on a clear night. Find spectral lines lesson plans and teaching resources. If the star is too hot or too cool, the hydrogen will not absorb this light.
Eclipsing binaries in which we can see the spectral lines of both stars have played a. In the coolest m stars below 3500 k, absorption bands of titanium oxide and other molecules are very strong. An art activity book for creative kids of all ages. These spectral lines can be used to determine an incredible amount of information about the star, including its temperature, composition, size, velocity and age, as well as many other properties. Spectral lines are often used to identify atoms and molecules. Spectral line definition is one of a series of linear images formed by a spectrograph or similar instrument and corresponding to a narrow portion of the spectrum of the radiation emitted or absorbed by a particular source.
Observe the change in a stars spectrum as its motion changes. Others, like helium, appear only in the spectra of very hot stars. The visible portion of the total spectrum of energy received can be analyzed by using a spectroscope. Stars with strong hydrogen lines, the a stars, had intermediate temperatures around 10,000 o k. Ionized metals provide the most conspicuous lines in stars with temperatures from 6000 to 7500 k spectral type f. You will see two kinds of spectra, a continuous spectrum rainbow and a. This figure illustrates one difference in the spectral lines from stars of the. Although based on the absorption lines, spectral type tells you about the surface temperature of the star. The lines you see in a star s spectrum act like thermometers. Your knowledge of the laws of star spectra can be tested using this interactive worksheet and quiz. Thermal sources such as stars produce continuum spectra, sometimes with the addition of emission or absorption lines at more discrete wavelengths. Several hundred years ago, the famous scientist isaac newton did an experiment where he showed that even white light from the sun was made up of. Guide to spectroscopy and spectral lines astrobites. This is the cause of the valleys you saw in the spectra in the last exercise.
When acquiring a spectrum of an astronomical object, astronomers rely upon spectral lines to determine a myriad of physical properties, such as composition, temperature, ionization state, velocity, redshift and more. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Vega for example, is a very hot star in the constellation lyre and a pair of binoculars will easily show it glowing with a bluish tinge. The spectral classification system used today is a refinement called the mk system, introduced in. The photograph of the spectrum of a star, sorted by color across a plate, will reveal spectral lines upon close examination. The observed spectral lines of a star are all shifted towards the red end of the spectrum. As the electrons move closer to or farther from the nucleus of an atom or of an ion, energy in the form of light or other radiation is emitted or absorbed.
The auditory activity allows students to hear differences in patterns of various elements. Hydrogen lines are strongest in a stars with atmospheric temperatures of about 10,000 k. Energy comes to us from our sun and other stars in the form of electromag netic energy. An art activity book for creative kids of all ages lee nemmers on. The spectral lines of two stars in a particular eclipsing binary system shift back and forth with a period of 10 months. The red giant star mira a right and its companion, a close binary pair. This paper aims to provide teachers with a range of ideas and activities plus some.
Schedule this lab is to be completed in two lab sessions. Every element produces a unique fingerprint of spectral lines. Chromospheric activity and lithium line variations in the spectra of. If your eyes were bigger, you could see many more stars. The spectra of stars and brown dwarfs astronomy openstax. Students compare the spectral lines to the temperatures of the stars. One can see that there are few spectral lines in the early spectral types o and b. Spectral lines are atom specific as to the pattern produced on the spectrum. The lines you see in a stars spectrum act like thermometers. Using spectra to measure stellar radius, composition, and. Absorption lines are seen when electrons absorb photons and move to higher energy levels. When we observe the spectra of other stars we find that some are like the sun and others are very different. With a pair of binoculars, an optical device that effectively enlarges the pupil of your eye by about 30. This has been accounted for in the standard stars, but not the pleiads.
A giant star with a verylowpressure photosphere shows very narrow spectral lines bottom, whereas a smaller star with a higherpressure photosphere shows much broader spectral lines top. The decimal divisions of spectral types followed the same pattern. Some compounds, like titanium oxide, only appear in the spectra of very cool stars. The key to the stars, keith robinson makes spectroscopy approachable for those who are interested in expanding their observational repertoire. Teach astronomy solar spectrum showing the dark absorption lines. In order to understand spectral lines, color has to be understood. Spectral order of stars hottest to coolest o, b, a, f, g, k, m, l, t. This allows astronomers to determine what elements are present in the stars and in the clouds of gas and dust among the stars. Atoms and molecules can emit and absorb radiation at distinct wavelengths, causing the appearance of spectral lines. The triplet has a strong emission, and is most prominently observed in the absorption of spectral type g, k and m stars. Using spectra to measure stellar radius, composition, and motion.
Students use the spectrographs from the building a fancy spectrograph activity to gather data about light sources. Spectral line definition of spectral line by merriamwebster. Identifying elements in the sun using spectral lines. Spectral classification hertzsprungrussell diagram naap. These lines represent the chemical composition of the star. Since each atom has its own characteristic set of energy levels, each is associated with a unique pattern of spectral lines.
Some activities or lessons, however, were developed to stand alone, and hence, they might not conform to this strict hierarchy. By identifying the spectral features in stellar spectra, we can determine the composition and temperature of stars. Dark absorption lines can be observed which can be used to identify a. Being the sun the only star whose magnetic activity phenomena can be truly. Our stars spectrum is crossed by dark lines produced by atoms in the. Spectral lines generally occur when there is an interaction between an atom and a photon. Hydrogen energy diagramastronomers learn a lot about the universe from the complimentary processes of emission and absorption of radiation. An isolated bright or dark line in a spectrum produced by emission or absorption of light of a single wavelength.