ASTR 1010 / Astronomy 1010 Final HW Complete Questions & Answers.
Astronomy 1010 Final HW One of the most important earlier steps in understanding stars was to group them into classes called spectral types that could offer clues as to why they are different from one another. Shown here are spectra of some main-sequence stars. Before stars were very well understood, they were classified into an order that was based on the relative strength of hydrogen absorption lines, marked by arrows the image shown. Look at the spectra for stars of different spectral type. Choose the list of spectral types that are in order of decreasing strength of their hydrogen lines, as indicated by the arrows (strongest absorption first, weakest last). Measurements of various properties of stars allowed astronomers to determine a more physically meaningful way of ordering the different spectral types than just by the strength of their hydrogen absorption lines. Study this table of properties, and use it to determine how the stars should be ordered. Click on the spectrum for each spectral type in order of decreasing strength of whatever property or properties you choose to use from the table. Hertzsprung and Russell were the first to plot stellar luminosities as a function of their spectral type. When placed in the OBAFGKM order, an interesting pattern emerged. The following figure shows one of these plots, named a Hertzsprung-Russell, or H-R, diagram after its founders. Each dot represents a single star, with green, yellow, and red dots simply indicating regions where there are a larger number of stars in that part of the plot. The color of the stars is roughly given by the vertical colored bands in the plot background. The spectral type of a star is directly related to its color. Recall that a star emits light as a blackbody, which has a particular shape to its spectrum, as shown in this figure. Based on this, what basic property of a star determines its color (and thus its spectral type)? - The majority of stars, including the Sun, are on the main sequence. The masses and sizes of main-sequence stars in the H-R diagram are indicated in this figure. Study how the various properties of a main-sequence star are related to one another in the figure. Then select the properties in the list that would increase if the mass of a main-sequence star is increased. Spectral type correlates directly with the temperature of the star. This is not enough to completely classify stars, however, because the luminosity of a star, and thus its exact position on the H-R diagram, depends on something else in addition to temperature. This is apparent from the H-R diagram because of the different populations of stars that exist in addition to the main sequence—they may have the same temperature as a main-sequence star, but a completely different luminosity Based on the figure, what other property can we use to further classify stars? A star can be fully classified with two descriptors: its spectral type (determined by temperature) and its luminosity class (determined by size). These two together give the location of the star on the H-R diagram, and all other basic properties (except composition) follow from that. Luminosity classes are given by roman numerals I through V, plus WD. The locations of these classes are shown in the figure here, along with the terms describing what type of stars they are (i.e., main sequence, supergiant, etc.). Based on this figure, rank the following luminosity classes in order of increasing size. Based on its position in this H-R diagram, which of the following best describes the complete classification of the Sun? Note: The numbers after the letter for each spectral type run from 0 through 9 for each type (e.g., the following would read from left to right on the diagram: O0 through O9, then B0 through B9, etc.). - Both spectral type and luminosity class are needed to determine roughly where any particular star will lie on the H-R diagram. In this diagram, label where a K5 I star and a K5 V star might be located. Which of the following statements is true, based on the position of the stars in this H-R diagram? When observed from two widely separated locations, an object appears to move _____ against the background than when observed from two locations near one another. When an object is farther away, it appears to move _____ against the background than a closer object. - Astronomers cannot use parallax to find the distance to most stars. This is because the stars are From the vantage point of Earth in the diagram shown, how will the parallax of Star A compare to that of Star B? - If Stars 1, 2, and 3 all have the same apparent magnitude, rank the stars according to their size, from largest to smallest This image was taken in infrared light by Hubble's NICMOS camera in September 1997. It shows a young star cluster within the Milky Way Galaxy Why do the stars appear to be different colors? Sort each of the graphs shown into the bin describing the type of spectrum plotted. Each of the following images shows a type of spectra that can be part of a single star's complete spectrum. Match each spectrum type to the part of the star by which it is produced. Place the following spectral types of stars in order from coolest to hottest. Imagine that the binary stars in each of the pictures are observed from a telescope located somewhere below the image. Spectra of both stars are taken, and used to find radial velocities for each, which are graphed as a function of time in the plot (Star 1: pink, outer-most orbit; Star 2: blue, inner-most orbit). Label the plot with the matching orbital positions of the stars at each marked time. Match the appropriate descriptions of luminosity, temperature, and size of stars to the correct portion of the H-R diagram. Place each star at its correct position on the H-R diagram Place each star, identified by spectral type and luminosity class, in its proper place on the H-R diagram. - Rank the surface temperatures of the stars within these star systems from coolest to hottest, based on the habitable zone depicted in green. Energy stored in matter itself—mass energy—can be very powerful. Per Einstein's famous equation E = mc2, energy is equivalent to mass times a constant (the speed of light squared). The speed of light is very large, so just a small amount of mass can result in a very large amount of energy. How can mass turn into energy? Consider the two most common elements in the universe: hydrogen and helium. As shown in this figure, a hydrogen nucleus (where most of its mass is contained) is made of one proton (p). A helium nucleus is made of two protons and two neutrons (n). Nuclear reactions can change what a nucleus is made of. The mass of hydrogen is 1.6726 x 10-27 kg, and the mass of helium is 6.6465 x 10-27 kg. Given this, which of the following nuclear reactions would result in a decrease of total mass, and thus a release of energy, while keeping the same number of particles involved? Why don't nuclear fusion reactions, which combine smaller nuclei into a larger nucleus, happen all around us every time atoms come in contact with one another? Gravity attracts particles with mass to one another, but it is extremely weak compared to the electromagnetic force. The strength and direction of the electromagnetic force depends on the charge of the particle. Particles with the same charge repel each other, and particles with opposite charges attract each other. Sort each of the following particles into the appropriate bin according to the electromagnetic force it would feel in the presence of a hydrogen nucleus. The relative charge of each particle is displayed on it. - How do protons ever fuse together in the presence of the electromagnetic force? There is another force involved here called the nuclear strong force. It is the strongest of all the forces, but it only acts over extremely small distances before it becomes too weak to matter. If protons and neutrons are able to get close enough to one another, the strong force provides a powerful attractive force that can bind them together in a nucleus, despite the electromagnetic force. -. At the densities of the Sun, hydrogen nuclear fusion can occur at temperatures greater than about 10 million degrees Kelvin (K). Based on these graphs of the Sun's pressure, density, and temperature in its interior, where are the nuclear reactions occurring? In the Sun, four hydrogen nuclei do not fuse directly into a helium nucleus. The overall reaction involves several steps, and other particles are also produced in the process. The Sun's interior is extremely dense, so as soon as a photon is produced inside the Sun, it is almost instantly absorbed by matter. It is then emitted in a random direction and possibly at a different wavelength, only to be absorbed again and reemitted. This results in a random walk of the photons as they move toward the surface, where they can escape into space. This situation may sound familiar: it is the effect of a blackbody, which is similar to the simplified view of light bouncing around in a box until it is able to randomly escape from a tiny hole, as shown in the figure. Say you are trying to study the nuclear reactions in the Sun's core by observing photons coming off its surface. How will this random walk affect your results? There is a particle produced in the Sun's nuclear reactions that we can use to directly study what is happening in the interior. Neutrinos are weakly interacting particles, and they have almost no mass and no charge. They are not affected at all by the nuclear strong force. As neutrinos travel through the Sun's dense interior, how will their path change due to the presence of the gravitational, electromagnetic, and nuclear strong forces around them? - Neutrinos pass straight through solid matter, making them difficult to detect. Luckily, they do react with one type of force—the nuclear weak force. For instance, on extremely rare occasions, a neutrino may interact via the nuclear weak force with a chlorine atom, turning it into a radioactive argon isotope. However, this is rare enough that we would almost never witness this type of reaction in the natural world. Which of these actions would improve our chances of seeing this reaction and thus detecting the presence of a solar neutrino? The first neutrino detector (Homestake, shown in this image) consisted of a 100,000 gallon tank of a chlorine-containing liquid, built 1,500 meters underground to block out particles other than neutrinos that might affect the results. Calculations from the model of the nuclear reactions expected to occur in the Sun predicted that it would detect about 1 neutrino every day as it turned a chlorine atom into argon. In actuality, only 1 neutrino was detected about every 3 days. This was referred to as the solar neutrino problem. What might this problem imply? It was discovered that there are three different types of neutrinos, called flavors, and that neutrinos can spontaneously change from one type to another. Electron neutrinos are produced in the Sun's core, but they can change into a muon or tau neutrino during their trip to Earth. The first detectors were built only to detect electron neutrinos. Can this new information solve the neutrino problem and confirm that our models of nuclear reactions in the Sun are correct? To consider the possibility of life on other planets, we must look at the only example we have—life on Earth. We can then apply what we learn there to other worlds to determine the likelihood that life could have arisen there as well. There is no life on the surface of Mars or Venus, which are lacking one very important substance that Earth has in large quantities: liquid water. The following plot shows the conditions necessary for water to exist in the solid, liquid, or vapor (gas) phase. On the basis of your observations of the plot, which of the following things are absolutely necessary for a world to have for liquid water to exist on its surface? Which of the following statements about the habitable zone is correct? One of the requirements for habitability for humans is a sufficient level of oxygen in the atmosphere to breathe. The table at right shows the percentage of oxygen in the atmospheres of Venus, Earth, and Mars. Oxygen is continuously removed from the atmosphere by oxidation reactions that combine it with other molecules, such as those in surface rocks. On the basis of this information, and your observations of the data in the table, which of the following is correct? Oxygen exists in our atmosphere as O2 (two oxygen atoms bonded together) and O3 (three oxygen atoms bonded together, known as ozone). Both can absorb ultraviolet light from the Sun, through the reactions shown in the following figure. Oxygen and an ozone layer surrounding a planet help to prevent ultraviolet radiation from reaching the ground. We know that high-energy ultraviolet radiation kills most living cells. Now, think about the oxygen content Earth had in the past. Which of the following would be the most likely place that life would first form on Earth? - This radio message was beamed toward globular star cluster M13 in the year 1974, for a total broadcast of less than three minutes. Assume M13 is exactly 25,000 light-years away from us. If life within the globular cluster received our message and immediately sent back a response, in what year would we receive it? Life continuously supplies oxygen to Earth's atmosphere. While we breathe in oxygen and expel carbon dioxide, some species, such as some bacteria and plants, expel oxygen. However, it took time for the amount of oxygen in the air to build up to the levels with which we are now familiar. The following figure shows the oxygen levels that existed in the Earth's atmosphere throughout its 4.5-billion-year history. Choose the letter closest to the point on the graph that marks the borderline beyond which a human with time-travel technology would begin to have trouble breathing. You may assume that a human can only breathe comfortably if the atmosphere contains nearly the same level of oxygen that it does now. - Extremophiles exist on Earth. These organisms can withstand conditions that would kill most other creatures. The figures below demonstrate some examples. This blind cave salamander lives in caverns below the surface. Giant tube worms near volcanic vents at the bottom of the deep ocean. The tardigrade, or "water bear," can survive the vacuum of space, extremely high pressures, temperatures above the boiling point and below the freezing point of water, high doses of radiation, and extremely dry conditions. The discovery of life on another world would be even more exciting if that life were intelligent and technologically advanced enough to communicate with us or visit our planet. How feasible would a long-distance communication be between us and life on a world around another star? The nearest star to us is Proxima Centauri, which is 4.24 light-years away. How many conversational exchanges—including a message and a reply—could occur between Alpha Centauri and the Sun within a 70-year lifetime? ____ messages - Answer: - 8 Select the statements below that are among the possible reasons we might not receive any response from the message we sent to M13 in 1974. - Photons and particles that originate in the Sun reach Earth in a wide range of time intervals. Place these in order of their travel times. Sort the particles into the categories describing whether they are input particles that get used up in the reaction, new output particles persisting after the reaction, or intermediate particles that exist only temporarily during the reaction. Hydrostatic equilibrium in the Sun means that Nuclear fusion of hydrogen to helium involves a number of steps; one type is called the proton-proton chain. Place the forms of the elements involved in order from first to last. (Variations occur; use the sequence that is most common and thus produces most of the energy.) - Label each region of the Sun with the most important process that is happening there. - When hydrogen is fused into helium, energy is released from Label the layers of the Sun as represented in this graph of density and height above the solar surface The Sun's atmosphere produces different types of spectra depending on the conditions of the layer. This graph shows how the temperature changes at different heights above the Sun's surface. Match the types of spectra to the layer in which they are produced. - Answer: - Continuous, Absorption, Emission, X-ray emission Sunspots appear dark because Examine the following images that were taken simultaneously of the same part of the Sun but at different wavelengths. What do the images tell you about the relationship between sunspots and solar flares? The following graph shows the number of sunspots counted on the Sun as a function of time over 40 years. How does the solar minimum that occurred around 2008 compare to those in the previous solar cycles? The following graphs plot the number and latitude of sunspots. The top graph shows the number of sunspots counted on the Sun as a function of time. The bottom graph plots individual sunspot latitudes on the Sun as a function of time. It is sometimes called a "butterfly diagram" because of its shape. Identify the statement that best describes how the latitude of sunspots varies over a sunspot cycle, which is defined to begin at solar minimum. As shown in the figure, the interior structure of the Sun is divided into zones on the basis of where energy is produced and how it is transported outward. part 1 Rank the layers of the Sun in order from highest to lowest temperature. part 2 Rank the layers of the Sun in order from lowest to highest density. In the phrase "theory of evolution," the word theory means that evolution The Urey-Miller experiment produced ______ in a laboratory jar. Using the graph, sort the organisms according to whether or not they need oxygen to survive. - Life first appeared on Earth ___________ of years ago. Extremophiles are organisms that Carbon is a favorable base for life because Scientists look for water to indicate places where life might exist because These three bodies are known to have significant amounts of liquid water. Rank them from least to greatest amount of water. Astronomers think that intelligent life is more likely to be found around stars of types F, G, K, and M because The Drake equation enables astronomers to The following figure shows the estimated relative amounts of water on the moons Europa and Titan and on Earth. These moons in our Solar System likely have more liquid water than all the oceans on Earth. How can this be true when the moons are so much smaller than Earth? - Craters on planet surfaces are the result of impacts by large objects such as asteroids and comets. The impact of a 10-km diameter asteroid that struck Earth 65 million years ago is believed to have caused the mass extinction of over 70 percent of all living species at that time. Place these results in sequence as they occurred.
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astronomy 1010 final
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one of the most important earlier steps in understanding stars was to group them into classes called spectral types that could offer clues as to why they are different f
