Astronomy
1st Edition
ISBN: 9781938168284
Author: Andrew Fraknoi; David Morrison; Sidney C. Wolff
Publisher: OpenStax
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Textbook Question
Chapter 17, Problem 21E
Appendix I lists some of the nearest stars. Are most of these stars hotter or cooler than the Sun? Do any of them emit more energy than the Sun? If so, which ones?
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Astronomers use two basis properties of stars to classify them. These two properties are luminosity and surface temperature. Luminosity usually refers to the brightness of the star relative to the brightness of our sun. Astronomers will often use a star’s color to measure its temperature. Stars with low temperatures produce a reddish light while stars with high temperatures shine with a brilliant blue—white light. Surface temperatures of stars range from 3000o C to 50,000o C. When these surface temperatures are plotted against luminosity, the stars fall into groups. Using the data similar to what you will plot in this activity, Danish astronomer Ejnar Hertzsprung and United States astronomer Henry Norris Russell independently arrived at similar results in what is now commonly referred to as the HR Diagram.
Procedures:1. Read the Background Information
2. On the graph paper provided. Place a number next to the star according to its luminosity and surface temperature listed in the data…
Tutorial
Star A has a temperature of 6,000 K. How much energy per second (in J/s/m²) does it radiate onto a square meter of its surface?
If the temperature of Star A decreases by a factor of 2, the energy will decrease by a factor of
Star B has a temperature that is 5 times higher than Star A. How much more energy per second (compared to Star A) does it radiate onto a square meter of its surface?
Part 1 of 4
The energy of a star is related to its temperature by
E = OTA
where o = 5.67 x 10-8 J/s/m²/K4.
Part 2 of 4
To determine how much energy Star A is radiating, we just plug in the temperature to solve for EA.
EA
J/s/m²
Tutorial
Star A has a temperature of 5,000 K. How much energy per second (in J/s/m2) does it radiate from a square meter of its surface?
If the temperature of Star A decreases by a factor of 2, the energy will decrease by a factor of
Star B has a temperature that is 5 times higher than Star A. How much more energy per second (compared to Star A) does it radiate from a square meter of its surface?
Part 1 of 4
The energy of a star is related to its temperature by
E = GT4
where σ = 5.67 x 10-8 J/s/m2/K4.
Part 2 of 4
To determine how much energy Star A is radiating, we just plug in the temperature to solve for EA.
EA =
J/s/m²
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Chapter 17 Solutions
Astronomy
Ch. 17 - What two factors determine how bright a star...Ch. 17 - Explain why color is a measure of a star’s...Ch. 17 - What is the main reason that the spectra of all...Ch. 17 - What elements are stars mostly made of? How do we...Ch. 17 - What did Annie Cannon contribute to the...Ch. 17 - Name five characteristics of a star that can be...Ch. 17 - How do objects of spectral types L, T, and Y...Ch. 17 - Do stars that look brighter in the sky have larger...Ch. 17 - The star Antares has an apparent magnitude of 1.0,...Ch. 17 - Based on their colors, which of the following...
Ch. 17 - Order the seven basic spectral types from hottest...Ch. 17 - What is the defining difference between a brown...Ch. 17 - If the star Sirius emits 23 times more energy than...Ch. 17 - How would two stars of equal luminosity-one blue...Ch. 17 - Table 17.2 lists the temperature ranges that...Ch. 17 - Suppose you are given the task of measuring the...Ch. 17 - Star X has lines of ionized helium in its...Ch. 17 - The spectrum of the Sun has hundreds of strong...Ch. 17 - What are the approximate spectral classes of stars...Ch. 17 - Look at the chemical elements in Appendix K. Can...Ch. 17 - Appendix I lists some of the nearest stars. Are...Ch. 17 - Appendix J lists the stars that appear brightest...Ch. 17 - What star appears the brightest in the sky (other...Ch. 17 - Suppose hominids one million years ago had left...Ch. 17 - Why can only a lower limit to the rate of stellar...Ch. 17 - Why do you think astronomers have suggested three...Ch. 17 - Sam, a college student, just bought a new car....Ch. 17 - Would a red star have a smaller or larger...Ch. 17 - Two stars have proper motions of one arcsecond per...Ch. 17 - Suppose there are three stars in space, each...Ch. 17 - What would you say to a friend who made this...Ch. 17 - In Appendix J, how much more luminous is the most...Ch. 17 - Verify that if two stars have a difference of five...Ch. 17 - As seen from Earth, the Sun has an apparent...Ch. 17 - An astronomer is investigating a faint star that...Ch. 17 - The center of a faint but active galaxy has...Ch. 17 - You have enough information from this chapter to...Ch. 17 - Do the previous problem again, this time using the...Ch. 17 - Star A and Star B have different apparent...Ch. 17 - Star A and Star B have different apparent...Ch. 17 - The star Sirius A has an apparent magnitude of 1.5...Ch. 17 - Our Sun, a type G star, has a surface temperature...
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- Answer these questions for celestial bodies at each of the following temperatures and then draw a conclusion about the relationship between temperature and wavelength of maximum intensity. What is the wavelength of maximum intensity? In which part of the electromagnetic spectrum (gamma-ray, X-ray, UV, visible light, IR, microwave, or radio) does this peak wavelength lie? Give an example of an object that might have this temperature. a. 50 K b. 500 K c. 5000 K d. 50,000 Karrow_forwardExplain how we use spectral absorption and emission lines to determine the composition of a gas.arrow_forwardThe edge of the Sun doesn’t have to be absolutely sharp in order to look that way to us. It just has to go from being transparent to being completely opaque in a distance that is smaller than your eye can resolve. Remember from Astronomical Instruments that the ability to resolve detail depends on the size of the telescope’s aperture. The pupil of your eye is very small relative to the size of a telescope and therefore is very limited in the amount of detail you can see. In fact, your eye cannot see details that are smaller than 1/30 of the diameter of the Sun (about 1 arcminute). Nearly all the light from the Sun emerges from a layer that is only about 400 km thick. What fraction is this of the diameter of the Sun? How does this compare with the ability of the human eye to resolve detail? Suppose we could see light emerging directly from a layer that was 300,000 km thick. Would the Sun appear to have a sharp edge?arrow_forward
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