21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Chapter 19, Problem 35QP
To determine
To compare the luminosity of
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A Type la supernova explodes in a galaxy at a
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2.07 x10 -5 years Given a Hubble constant of
74.3 km/s/Mpc, at what speed v is this galaxy
moving away from Earth? v= km/s What is
this galaxy's redshift? redshift:
An astronomical image shows two objects that have the same apparent magnitude, i.e., the same brightness. However, spectroscopic follow up observations indicate that while one is a star that is within our galaxy, at a distance dgal away, and has the same luminosity as the Sun, the other is a quasar and has 100x the luminosity of the entire Milky Way galaxy. What is the distance to the quasar? (You may assume, for this rough calculation, that the Milky Way has 1011 stars and that they all have the luminosity as the Sun.) Give your response in Mpc. Value: dgal = 49 pc
If a galaxy contains a supernova that at its brightest has an apparent magnitude of 17, how far
away is the galaxy? Assume that the absolute magnitude of the supernova is -19.
Chapter 19 Solutions
21st Century Astronomy
Ch. 19.1 - Prob. 19.1ACYUCh. 19.1 - Prob. 19.1BCYUCh. 19.2 - Prob. 19.2CYUCh. 19.3 - Prob. 19.3CYUCh. 19.4 - Prob. 19.4CYUCh. 19 - Prob. 1QPCh. 19 - Prob. 2QPCh. 19 - Prob. 3QPCh. 19 - Prob. 4QPCh. 19 - Prob. 5QP
Ch. 19 - Prob. 6QPCh. 19 - Prob. 7QPCh. 19 - Prob. 8QPCh. 19 - Prob. 9QPCh. 19 - Prob. 10QPCh. 19 - Prob. 11QPCh. 19 - Prob. 12QPCh. 19 - Prob. 13QPCh. 19 - Prob. 14QPCh. 19 - Prob. 15QPCh. 19 - Prob. 16QPCh. 19 - Prob. 17QPCh. 19 - Prob. 18QPCh. 19 - Prob. 19QPCh. 19 - Prob. 20QPCh. 19 - Prob. 21QPCh. 19 - Prob. 22QPCh. 19 - Prob. 23QPCh. 19 - Prob. 24QPCh. 19 - Prob. 25QPCh. 19 - Prob. 26QPCh. 19 - Prob. 27QPCh. 19 - Prob. 28QPCh. 19 - Prob. 29QPCh. 19 - Prob. 30QPCh. 19 - Prob. 31QPCh. 19 - Prob. 32QPCh. 19 - Prob. 33QPCh. 19 - Prob. 34QPCh. 19 - Prob. 35QPCh. 19 - Prob. 36QPCh. 19 - Prob. 37QPCh. 19 - Prob. 38QPCh. 19 - Prob. 39QPCh. 19 - Prob. 40QPCh. 19 - Prob. 41QPCh. 19 - Prob. 42QPCh. 19 - Prob. 43QPCh. 19 - Prob. 44QPCh. 19 - Prob. 45QP
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- Consider the following five kinds of objects: open cluster, giant molecular cloud, globular cluster, group of O and B stars, and planetary nebulae. A. Which occur only in spiral arms? B. Which occur only in the parts of the Galaxy other than the spiral arms? C. Which are thought to be very young? D. Which are thought to be very old? E. Which have the hottest stars?arrow_forwardFigure 2 shows the "rotation curve" of NGC 2742. It plots the “radial velocity (V)" (how fast material is moving either toward or away from us) that is measured for objects at different distances (R = radius") from the center of the galaxy. The center of the galaxy is at 0 kpc (kiloparsecs) with a speed of 9 km/sec away from us. (These velocities have been corrected for the observed tilt of the galaxy and represent true orbital velocities of the stars and gas.) 200 100 U4779 -100 As you can see, one side of the galaxy is moving with a negative velocity (spinning toward us), while the other side has a positive velocity (spinning away from us). Using Newton's gravity equation, we will be able to determine the gravitational mass of the entire galaxy and how the mass varies versus distance from the galaxy's center. -200 -8 8 -4 Radius (kpc) Read the following text carefully and follow the instructions: Select five radii spaced evenly from 0-10 kpc across the galaxy. Your selections should…arrow_forwardA Cepheid variable in the Andromeda galaxy has a period of 22 days and a mean apparent magnitude of19.5.(a) Calculate the distance modulus of the Andromeda galaxy.(b) Given that the Andromeda galaxy is approaching the Milky Way with a velocity of 119 km/s, roughlyestimate how long before these two galaxies collide? Provide your answer in years.arrow_forward
- The gas in the outer region of the Andromeda galaxy is found to be orbiting the galaxy with a velocity of 250 km/s. The gas is at a distance of 35 kpc from the center of the galaxy. The total mass of the galaxy is _______ solar masses.arrow_forwardSuppose that a galaxy has 109 M⊙ of neutral HI gas with a temperature of about 10 K. Estimate the luminosity of the 21 cm wavelength radiation that is expected from the galaxy. Answer in watts.arrow_forwardQuestion 3: (a) A Type la supernova is seen to occur in the central bulge of a spiral galaxy. At its peak, the total apparent magnitude of the bulge plus the supernova is V= 13.68. Pre-explosion images reveal the bulge alone to have a magnitude V= 14.21. Assuming that all Type Ia supernova have peak absolute visual magnitudes of My = -19.30, calculate the distance to this galaxy, assuming there is no extinction in the direction of the supernova.arrow_forward
- If a galaxy contains a supernova that at its brightest has an apparent magnitude of +15, how far away is the galaxy? Assume that the absolute magnitude of the supernova is −17. Use the magnitude-distance formula: d = 10(mV − MV + 5)/5 .arrow_forwardQuestion 3: (a) A Type la supernova is seen to occur in the central bulge of a spiral galaxy. At its peak, the total apparent magnitude of the bulge plus the supernova is V= 13.68. Pre-explosion images reveal the bulge alone to have a magnitude V= 14.21. Assuming that all Type Ia supernova have peak absolute visual magnitudes of My = -19.30, calculate the distance to this galaxy, assuming there is no extinction in the direction of the supernova. (b) Estimate the observed wavelength of the Hẞ line (rest-frame wavelength 486.1 nm) in this galaxy. Assume the Hubble constant has the value 67.4 kms ¹Mpc-¹.arrow_forwardIf a galaxy has a radial velocity of 21,641 km/s, what is its expected distance from the Hubble Law? Assume that the Hubble Constant is 71 km/s/Mpc. Answer in Mpcarrow_forward
- If a galaxy has an apparent radial velocity of 2000 km/s and the Hubble constant is 70 km/s/Mpc, how far away is the galaxy?arrow_forwardn(r) = 1ge where r represents the distance from the centre of the Galaxy, Ro is the distance of the Sun from the centre of the Galaxy, Ra is the typical size of disk and no is the stellar density of disk at the position of the Sun. All distances are expressed in kpc. An astronomer observes the center of the Galaxy within a small field of view. We take a particular type of Red giant stars as the standard candles for the observation with approximately constant absolute magnitude of M = -0.2, (a) A telescope has a limiting magnitude of m = 18. Calculate the maximum distance to which this telescope can detect these red giant stars. For simplicity we ignore the presence of interstellar medium so there is no extinction. (b) Assume an extinction of 0.7 mag/kpc for the interstellar medium. Repeat the calculation as done in the part 5a and obtain a rough number for the maximum distance these red giant stars can be observed. (c) Give an expression for the number of these red giant stars per mag-…arrow_forwardThe quasar that appears the brightest in our sky, 3C 273, is located at a distance of 2.4 billion lightyears. The Sun would have to be viewed from a distance of 1300 light-years to have the same apparent magnitude as 3C 273. Using the inverse square law for light, estimate the luminosity of 3C 273 in solar units.arrow_forward
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