21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 15, Problem 31QP
To determine
Determine whether interstellar reddening affect the observation of star’s temperature.
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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 5,000 K and Star B has a temperature of 6,000 K. At what wavelengths (in nm) will each of these star's intensity be at its maximum?
If the temperatures of the stars increase, the wavelength of maximum intensity.
What is the temperature (in K) of a star that appears most intense at a wavelength of 829 nm?
Part 1 of 4
Wien's Law tells us how the temperature of a star determines the wavelength of maximum intensity or at what wavelength the star appears brightest.
2.90 x 106
TK
If the temperature is in kelvin (K) then A is in nanometers (nm).
Anm
^A =
AB =
=
Part 2 of 4
To determine the wavelengths of maximum intensity for the two stars:
2.90 x 106
2.90 x 106
K
nm
nm
If the surface Temperature of a star was about 11000.0 K instead of 7000.0 K what is the ratio of power per square meter of the 11000.0 K star compared to power per square meter of the 7000.0 K star? How many times greater is the magnitude of power per square meter of the 11000.0 K star compared to the 7000.0 K star
Chapter 15 Solutions
21st Century Astronomy
Ch. 15.1 - Prob. 15.1CYUCh. 15.2 - Prob. 15.2CYUCh. 15.3 - Prob. 15.3CYUCh. 15.4 - Prob. 15.4CYUCh. 15 - Prob. 1QPCh. 15 - Prob. 2QPCh. 15 - Prob. 3QPCh. 15 - Prob. 4QPCh. 15 - Prob. 5QPCh. 15 - Prob. 6QP
Ch. 15 - Prob. 7QPCh. 15 - Prob. 8QPCh. 15 - Prob. 9QPCh. 15 - Prob. 10QPCh. 15 - Prob. 11QPCh. 15 - Prob. 12QPCh. 15 - Prob. 13QPCh. 15 - Prob. 14QPCh. 15 - Prob. 15QPCh. 15 - Prob. 16QPCh. 15 - Prob. 17QPCh. 15 - Prob. 18QPCh. 15 - Prob. 19QPCh. 15 - Prob. 20QPCh. 15 - Prob. 21QPCh. 15 - Prob. 22QPCh. 15 - Prob. 23QPCh. 15 - Prob. 24QPCh. 15 - Prob. 25QPCh. 15 - Prob. 26QPCh. 15 - Prob. 27QPCh. 15 - Prob. 28QPCh. 15 - Prob. 29QPCh. 15 - Prob. 30QPCh. 15 - Prob. 31QPCh. 15 - Prob. 32QPCh. 15 - Prob. 33QPCh. 15 - Prob. 35QPCh. 15 - Prob. 36QPCh. 15 - Prob. 37QPCh. 15 - Prob. 38QPCh. 15 - Prob. 39QPCh. 15 - Prob. 40QPCh. 15 - Prob. 41QPCh. 15 - Prob. 42QPCh. 15 - Prob. 43QPCh. 15 - Prob. 44QPCh. 15 - Prob. 45QP
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- In a laboratory, the Balmer-beta spectral line of hydrogen has a wavelength of 486.1 nm . If the line appears in a star’s spectrum at 485.8 nm , what is the star’s radial velocity? Is it approaching or receding? Is this a blueshift or a redshift?arrow_forwardMany of the bright stars in the night sky are highly luminous normal blue stars (such as Acrux), and others are blue giants (such as Rigel) or red giants (such as Betelgeuse). Generally, such stars have a luminosity of 103 to 105 times that of our Sun! Ignoring any effects from our atmosphere, how bright would a star with a luminosity of 8380 solar luminosities be if it were located 620 light years from Earth? (You will need to convert some values.) W/m² For comparison, if you were 1 meter from a regular 100 W light bulb, the brightness would be 7.96 W/ m². (Since stars are not this bright, your answer should be considerably less!) Kind of amazing you can see these things, isn't it?arrow_forwardA star has a measured radial velocity of 300 km/s. If you measure the wavelength of a particular spectral line of Hydrogen as 657.18 nm, what was the laboratory wavelength (in nm) of the line? (Round your answer to at least one decimal place.) nm Which spectral line does this likely correspond to? Balmer-alpha (656.3 nm) Balmer-beta (486.1 nm) Balmer-gamma (434.0 nm) Balmer-del ta (410.2 nm)arrow_forward
- Let’s say you’re looking for extrasolar planets. You observe a star that has a spectral shift in the line that is supposed to be at at 656.28011 nm – this star shows this line at 656.28005 nm. What is the radial velocity of star (in m/s) and in what direction in relation to you? a) 27.4 m/s, towards b) 27.4 km/s, away c) -27.4 m/s, toward d) -27.4 km/s, awayarrow_forwardAs a star runs out of hydrogen to fuel nuclear fusion in its core, changes within the star usually cause it to leave the main sequence, expanding and cooling as it does so. Would a star with a radius 6 times that of the Sun, but a surface temperature 0.4 times that of the Sun, be more, or less luminous than the Sun? Show and explain your reasoning. You may assume the surface area of a sphere is A = 4πr2.arrow_forwardIn a laboratory, the Balmer-beta spectral line of hydrogen has a wavelength of 486.1 nm. If the line appears in a star's spectrum at 486.7 nm, what is the star's radial velocity (in km/s)? (Enter the magnitude.) Is it approaching or receding? Is this a blueshift or a redshift?arrow_forward
- Using solar units, we find that a star has 4 times the luminosity of the Sun, a mass 1.25 times the mass of the Sun, and a surface temperature of 4090 K (take the Sun's surface temperature to be 5784 K for the sake of this problem). This means the star has a radius of.................... solar radii and is a .................... star (use the classification).arrow_forwardA star has a surface temperature of T = 10,000 K and a radius three times that of the Sun, R = 3R (recall that symbolizes the Sun). What is its luminosity, L, in units of solar luminosities, L ? Give your answer to three significant figures. answer, expressed in solar luminosities, tells how many times more luminous this star is than the Sun.arrow_forwardIf a star has a surface temperature of 3000 K but a luminosity 150 times greater than our Sun, what size is this star? Give your answer in units of the solar radius, R .arrow_forward
- If a star has a radius 2 times larger than the Sun's and a luminosity 1/4th that of the Sun, how many times higher is the star's temperature than that of the Sun? (If it is smaller by a factor of 8, you would write 0.125 because 1/8=0.125)arrow_forwardWhat elements are stars mostly made of? How do we know this?arrow_forwardOur Sun, a type G star, has a surface temperature of 5800 K. We know, therefore, that it is cooler than a type O star and hotter than a type M star. Given what you learned about the temperature ranges of these types of stars, how many times hotter than our Sun is the hottest type O star? How many times cooler than our Sun is the coolest type M star?arrow_forward
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