UNIVERSE (LOOSELEAF):STARS+GALAXIES
6th Edition
ISBN: 9781319115043
Author: Freedman
Publisher: MAC HIGHER
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Chapter 25, Problem 15Q
To determine
The wavelength at which we detect the Lyman alpha photons from the galaxy and in which
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The Andromeda Galaxy, M31, is the closest large spiral galaxy to our Milky Way. When we look at its chemical spectrum, we see that its hydrogen alpha emission line (Hα) has an observed wavelength of λobs = 655 nm.-Calculate z, being careful with the sign.-How fast is it moving in km/s?-Is it redshifted or blueshifted? Is it moving towards or away from us?
answer to three significant figures.
Imagine that you are observing the light from a distant star that is located in a galaxy 100 million lightyears
away from you. By analysis of the starlight received, you are able to tell that the image we see is of a 10-
million-year-old star. You are also able to predict that the star will have a total lifetime of 50 million years, at
which point it will end in a catastrophic supernova.
a) How old does the star appear to be to us here on Earth now?
b) How long will it be before we receive the light from the supernova event?
c) Has the supernova already occurred? If so, when did it occur?
Problem 2: Black hole – the ultimate blackbody
A black hole emits blackbody radiation called Hawking radiation. A black hole with mass
M has a total energy of Mc², a surface area of 167G²M² /c*, and a temperature of
hc³/167²KGM.
a) Estimate the typical wavelength of the Hawking radiation emitted by a 1 solar
mass black hole (2 × 103ºkg). Compare your answer to the size of the black hole.
b) Calculate the total power radiated by a one-solar mass black hole.
c) Imagine a black hole in empty space, where it emits radiation but absorbs nothing.
As it loses energy, its mass must decrease; one could say "evaporates". Derive a
differential equation for the mass as a function of time, and solve to obtain an
expression for the lifetime of a black hole in terms of its mass.
Chapter 25 Solutions
UNIVERSE (LOOSELEAF):STARS+GALAXIES
Ch. 25 - Prob. 1QCh. 25 - Prob. 2QCh. 25 - Prob. 3QCh. 25 - Prob. 4QCh. 25 - Prob. 5QCh. 25 - Prob. 6QCh. 25 - Prob. 7QCh. 25 - Prob. 8QCh. 25 - Prob. 9QCh. 25 - Prob. 10Q
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Analyzing the spectrum of a distant galaxy, you discover evidence that a type la supernova is occurring in that galaxy. A type la supernova has a peak luminosity of about 1010 solar luminosities (1 solar luminosity = 3.8e26 Watts). Looking at an image of the galaxy, you estimate that here on earth your telescope only sees a brightness of 8.45E-10 Watts/m². Using this information and the brightness equation, how distant is the galaxy in which the supernova is occurring? Give your answer in It yrs.arrow_forwardAssuming stars to behave as black bodies stefan-boltzmann law to show that the luminosity of a star is related to its surface temperature and size in the following way: L = 4(3.14)R^2oT^4 where o= 5.67 ×10^-8 Wm^-2 K-4 is the stefan- boltzmann constant. Then use this expression together with the knowledge that the sun has a surface temperature of 5700k and radius 695 500km to calculate the luminosity of the Sun in units of Wattsarrow_forwardThe Andromeda Galaxy, M31, is the closest large spiral Galaxy to our Milky Way. When we lookat its chemical spectrum, we see that it's hydrogen alpha emission line has an observed wavelength of 655nm. a. Calculate z, being careful with the sign b. How fast is it moving in km/s c. Is it redshifted or blueshifted? Is it moving toward or away from us?arrow_forward
- The 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_forwardWhat is the wavelength in micrometers of peak emission for a black body at 33.5°C? (c = 3.0 × 108 m/s, Wien displacement law constant is 2.9 × 10-3 m ∙ K, σ = 5.67 × 10-8 W/m2 ∙ K4). Please give your answer with one decimal place.arrow_forwardUse Wien's Law to calculate the peak wavelength of light coming from the Sun. Assume T=5800 K for the surface temperature of the Sun. Wein's displacement law says that the blackbody temperature and peak wavelength multiplied together give a constant of 0.29 cm-K. (K is degrees Kelvin). Convert the wavelength from part A into a frequency. The product of wavelength and frequency for electromagnetic radiation is a constant, the speed of light (c), 3 x 10^10 cm/s.arrow_forward
- You observe the H-alpha line of Hydrogen in a distant galaxy to have a wavelength of 754.4 nm. What is the radial velocity of the galaxy? Hint: The rest wavelength of H-alpha is 656 nm.arrow_forwardWhat is the peak wavelength (in nm) of a neutron star's luminosity if its temperature is 106 K?arrow_forwardWhy would we not expect to detect X-rays from a disk of matter about an ordinary star?arrow_forward
- In the Check Your Learning section of Example 27.1, you were told that several lines of hydrogen absorption in the visible spectrum have rest wavelengths of 410 nm, 434 nm, 486 nm, and 656 nm. In a spectrum of a distant galaxy, these same lines are observed to have wavelengths of 492 nm, 521 nm, 583 nm, and 787 nm, respectively. The example demonstrated that z=0.20 for the 410 nm line. Show that you will obtain the same redshift regardless of which absorption line you measure.arrow_forwardWhy is Hubble’s law considered one of the most important discoveries in the history of astronomy?arrow_forwardWould you expect to be able to detect an H II region in X-ray emission? Why or why not? (Hint: You might apply Wien’s law)arrow_forward
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