Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Question
Chapter 17, Problem 31Q
To determine
The star which appears brighter.
Whether or not, the luminosities of the given stars can be concluded from the given information.
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"51 Pegasi" is the name of the first normal star (besides the Sun) around which a planet was discovered. It is in the constellation Pegasus the horse. Its parallax is measured to be 0.064 arcsec.
a. What is its distance from us?
b. The apparent brightness is 1.79 × 10-10 J/(s·m2 ). What is the luminosity? How does that compare with that of the Sun? Look up the temperature: how do
Star A has an apparent magnitude of –1.5 and is 12.6 light-years from Earth. Star B has an apparent magnitude of 0.4 and is 15.6 light-years from Earth.
Why should apparent magnitude NOT be used to determine which star is brighter? What information could help you determine which star is brighter?
. A star"s position in the sky against distant background objects has shifted by 0.4" in 6 months it returned where it was. what is the stellar parallax p of this star?
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Chapter 17 Solutions
Universe: Stars And Galaxies
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- The apparent magnitude of a star on earth was measured to be +2. The zenith angle was 45° and the optical depth TO = 0.14. What is the apparent magnitude of the star above the earth's atmosphere? Round your answer to three significant figures. %3Darrow_forwardIn the parallax method of determining stellar distances, the angle to a star is measured while the earth is on one side of the sun and then again six months later, as in the diagram below. Assume the earth-sun distance is 1 Astronomical Unit. The parallax angle of Alpha Centauri is 0= 2.1 x 10-4 ° . Find the distance from the sun to a Centauri in light years. Assume a circular orbit for the Earth. a Centauri Earth (June) Earth (December) Sunarrow_forwardStar A and Star B are a bound binary at a distance of 20 pc from the Earth. Their separation is 30 AU. Star A has a mass twice that of Star B. The orbital period of the binary is 100 years. Assume the stars orbit in circular orbits. a. What is the parallax of Star A, in units of arcsec? Assume parallax is measured from the Earth. For part a, ignore the presence of the binary companion. b. What is the angular separation we would observe between Star A and Star B, in units of arcsec? If we compare multiple images of this star system taken across different months and years, which source of motion will be the dominant effect? What is the total mass of the binary system (combined mass of Star A and Star B)? Provide your answer in both kg and solar masses. c. d. What is the distance from Star A to the center of mass of the binary system?arrow_forward
- 15: A star has a parallax angle of 0.0270 arcseconds and an apparent magnitude of 4.641. What is the distance to this star? Answer: 37 16: What is the absolute magnitude of this star? Answer:1.8 17: Is this star more or less luminous than the Sun? Answer "M" for More luminous or "L" for Less luminous. (HINT: the absolute magnitude of the Sun is 4.8) Answer: M 18: What is the luminosity of this star? (HINT: The luminosity of the Sun is 3.85×1026 W.) Please answer question #18, #15-17 are correct, the photos provide the work for them.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_forwardA brand new telescope has been named after you. It is therefore only fitting that you get to make the very first set of observations. During your first night observing, you first measure the apparent brightness and spectrum of a group of stars that appear close to each other within the telescopes field of view. From a separate set of observations 6 months later, you are able to measure each star’s parallax. Next you plot the luminosity and temperature of each star in a Hertzsprung-Russell Diagram What features below help you conclude that the group of stars is a star cluster? Explain Approximately how old do you think this star cluster is? Explain How do you expect the spectrum of the most luminous and least luminous main sequence stars in the cluster to differ? Explain why these differences occur in terms of the star’s properties and any measured absorption lines. A year after your discovery, another new star cluster has been found by the same telescope, but its distance is too far…arrow_forward
- A star has a parallax angle of 0.0270 arcseconds and an apparent magnitude of 4.641. What is the distance to this star? [Answer in parsecs] 37 What is the absolute magnitude of this star? 1.8 Is this star more or less luminous than the Sun? Answer "M" for More luminous or "L" for Less luminous. (HINT: the absolute magnitude of the Sun is 4.8) M What is the luminosity of this star? (HINT: The luminosity of the Sun is 3.85×1026 W.)arrow_forwardProblem 5. Imagine that you observe a star field twice, with a six-month gap between your observations, and that you see the two sets of stars shown below. Which do you think is closest to the observer? Figure 1: Schematic of image of stars A,B, and P taken six months apart. Problem 6. Suppose the angular separation between stars A and B is 0.5 arcseconds. How far would you estimate star P to lie from the observer?arrow_forwardConsider two stars with mV = 2.2 and mV = −1.5. What is their combined visual magnitude? Is the answer plausible.arrow_forward
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