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 21Q
To determine
The ratio of the luminosities for the given conditions.
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Students have asked these similar questions
Two stars have the exact same luminosity, but star Y is four times dimmer looking that star X. This means that????
1)
star Y is four times as far away as star X
2)
star Y is 16 times as far away as star X
3)
star Y is half as far away as star X
4)
star Y is twice as far away as star X
5)
we can't figure out the relative distance of the two stars from the information given
You measure a star to have a parallax angle of 0.12 arc-seconds. What fraction of a degree is this?
By how many times would you have to magnify this effect for it to be visible to the human eye? (The limit of human vision is about 1 arc-minute)
What is the distance to this star in parsecs?
What is the distance to this star in light years
What is the parallax angle of a different star that is twice as far away as the star from the previous problems? [answer in arc-seconds without including the unit]
"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
Chapter 17 Solutions
Universe: Stars And Galaxies
Ch. 17 - Prob. 1QCh. 17 - Prob. 2QCh. 17 - Prob. 3QCh. 17 - Prob. 4QCh. 17 - Prob. 5QCh. 17 - Prob. 6QCh. 17 - Prob. 7QCh. 17 - Prob. 8QCh. 17 - Prob. 9QCh. 17 - Prob. 10Q
Ch. 17 - Prob. 11QCh. 17 - Prob. 12QCh. 17 - Prob. 13QCh. 17 - Prob. 14QCh. 17 - Prob. 15QCh. 17 - Prob. 16QCh. 17 - Prob. 17QCh. 17 - Prob. 18QCh. 17 - Prob. 19QCh. 17 - Prob. 20QCh. 17 - Prob. 21QCh. 17 - Prob. 22QCh. 17 - Prob. 23QCh. 17 - Prob. 24QCh. 17 - Prob. 25QCh. 17 - Prob. 26QCh. 17 - Prob. 27QCh. 17 - Prob. 28QCh. 17 - Prob. 29QCh. 17 - Prob. 30QCh. 17 - Prob. 31QCh. 17 - Prob. 32QCh. 17 - Prob. 33QCh. 17 - Prob. 34QCh. 17 - Prob. 35QCh. 17 - Prob. 36QCh. 17 - Prob. 37QCh. 17 - Prob. 38QCh. 17 - Prob. 39QCh. 17 - Prob. 40QCh. 17 - Prob. 41QCh. 17 - Prob. 42QCh. 17 - Prob. 43QCh. 17 - Prob. 44QCh. 17 - Prob. 45QCh. 17 - Prob. 46QCh. 17 - Prob. 47QCh. 17 - Prob. 48QCh. 17 - Prob. 49QCh. 17 - Prob. 50QCh. 17 - Prob. 51QCh. 17 - Prob. 52QCh. 17 - Prob. 53QCh. 17 - Prob. 54QCh. 17 - Prob. 55QCh. 17 - Prob. 56QCh. 17 - Prob. 57QCh. 17 - Prob. 58QCh. 17 - Prob. 59QCh. 17 - Prob. 60QCh. 17 - Prob. 61QCh. 17 - Prob. 62QCh. 17 - Prob. 63QCh. 17 - Prob. 64QCh. 17 - Prob. 65QCh. 17 - Prob. 66QCh. 17 - Prob. 67QCh. 17 - Prob. 68QCh. 17 - Prob. 69QCh. 17 - Prob. 70QCh. 17 - Prob. 71QCh. 17 - Prob. 72QCh. 17 - Prob. 73QCh. 17 - Prob. 74QCh. 17 - Prob. 75QCh. 17 - Prob. 76QCh. 17 - Prob. 77QCh. 17 - Prob. 78QCh. 17 - Prob. 79QCh. 17 - Prob. 80Q
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- Star A and Star B have different apparent brightnesses but identical luminosities. If Star A is 20 light-years away from Earth and Star B is 40 light-years away from Earth, which star appears brighter and by what factor?arrow_forwardWhich of the following can you determine about a star without knowing its distance, and which can you not determine: radial velocity, temperature, apparent brightness, or luminosity? Explain.arrow_forwardTwo stars of the same diameter or observed to have surface temperatures of 4000 Kelvin and 16,000 Kelvin. Which star is probably the brighter of the two? How many times brighter?arrow_forward
- Distance from Apparent Brightness (rank; brightest, 8 = dimmest) Name of Star Earth (light years) | 1 = Sun Sirius 8.6 Canopus Arcturus 309 3. 36.7 4 Rigel Vega Alpha Centauri Bernard's Star 773 5 25.3 4.3 7 5.9 8 13 What sentence explains why a star can be much farther from Earth than the Sun, but still be bright? nida nenv A. Distance from Earth and apparent brightness are related. B. Bright stars that are farther away are larger than the Sun. C. The higher it appears in the sky, the brighter the star. D. The apparent brightness scale goes up as stars get dimmer. del sdTarrow_forwardYou measure a star to have a parallax angle of 0.12 arc-seconds What is the distance to this star in parsecs? 8.33 Hint: d = 1/p What is the parallax angle of a different star that is twice as far away as the star from the previous problems? [answer in arc-seconds without including the unit]arrow_forwardTwo stars-A and B, of luminosities 0.5 and 4.5 times the observed to have the luminosity of the Sun, respectively-are same apparent brightness. Which star is more distant, and how much farther away is it than the other?arrow_forward
- A 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_forwardThe Sun as seen from Earth has an apparent magnitude of -26 in the B-band.1. What would its apparent magnitude be as seen from Jupiter? (Jupiter is approximately 5.2 AU from theSun.)2. At a certain distance d from a Star A, its apparent brightness is f. If we were to travel at a relativisticvelocity to a point in space which is 5 times further away, how much fainter would the star appear to us?(i.e. what fraction of its original apparent brightness would it now appear to us?)arrow_forwardL = ( 0.0813 ) x (Rs) ^2 x 10-0.4m x Ls where L = luminosity of the desired star Rs = distance of the stars in light years m = apparent magnitude of star Ls = Luminosity of Sun = 1.00 The calculated value of Polaris' luminosity is: a. 2382 times Ls b. 6040 times Ls c. 5566 times Ls d. 2612 times Lsarrow_forward
- Two stars – A and B, of luminosities 0.5 and 4.5 times the luminosity of the Sun, respectively – are observed on Earth to have the same apparent brightness. Which star is more distant, and how much farther away is it than the other? [Hint: The brightness of a star is inversely proportional to the square of its distance; Week 6 slide 15]arrow_forwardA 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] What is the absolute magnitude of this star? 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) What is the luminosity of this star? (HINT: The luminosity of the Sun is 3.85×1026 W.)arrow_forwardThe origin of the above quote (with "flame" or "candle" sometimes substituted for "light") is unclear. It is often attributed to either Lao Tzu or to the character Eldon Tyrell from the 1982 movie Blade Runner. Stars follow a similar law, although the factor isn't precisely 1/2. In this problem, you will figure out the precise factor that the quote should have to apply to stars. Using the proportionality relationships for stellar luminosity as a function of mass and stellar lifetime as a function of mass, combine the two equations to arrive at a proportionality for stellar lifetime as a function of luminosity. Consider a star with luminosity twice that of the Sun's. Compute the star's main sequence lifetime as a multiple of the Sun's main sequence lifetime. Enter your result below as a decimal. For example, if you found TT⊙=0.3, enter "0.3". (Here T is the star's lifetime and T⊙ is the Sun's main sequence lifetime.arrow_forward
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