UNDERSTANDING THE UNIVERSE(LL)-W/CODE
3rd Edition
ISBN: 9780393869903
Author: PALEN
Publisher: NORTON
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Chapter 14, Problem 43QAP
To determine
To estimate the quasar’s lifetime.
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Suppose a quasar is shining with a luminosity L. What is the approximate minimal mass of the black hole? (If the black hole had a lower mass than this, the pressure in the material would overcome the gravity of the black hole and the material would be blown apart.) Give your answer in solar masses, in scientific notation to one significant figure (no decimal places).
Value:
L=1×10^12Lsun
Suppose the quasar in the previous problem is 10% efficient at turning rest mass into energetic photons, according to Einstein's equation E=mc2. What is the necessary rate of accretion of mass onto this black hole, to sustain its luminosity of 1* 1012 solar luminosities -- i.e. how much mass must be 'fed' to this black hole to keep the AGN shining so brightly?
Give your response in units of solar masses of material per year, with one decimal place.
A galaxy is found to be receding at a velocity of 3.0 x 104 km-s-1. Calculate the distance to the galaxy.
Suppose 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.
Chapter 14 Solutions
UNDERSTANDING THE UNIVERSE(LL)-W/CODE
Ch. 14.1 - Prob. 14.1CYUCh. 14.2 - Prob. 14.2CYUCh. 14.3 - Prob. 14.3CYUCh. 14.4 - Prob. 14.4CYUCh. 14 - Prob. 1QAPCh. 14 - Prob. 2QAPCh. 14 - Prob. 3QAPCh. 14 - Prob. 4QAPCh. 14 - Prob. 5QAPCh. 14 - Prob. 6QAP
Ch. 14 - Prob. 7QAPCh. 14 - Prob. 8QAPCh. 14 - Prob. 9QAPCh. 14 - Prob. 10QAPCh. 14 - Prob. 11QAPCh. 14 - Prob. 12QAPCh. 14 - Prob. 13QAPCh. 14 - Prob. 14QAPCh. 14 - Prob. 15QAPCh. 14 - Prob. 16QAPCh. 14 - Prob. 17QAPCh. 14 - Prob. 18QAPCh. 14 - Prob. 19QAPCh. 14 - Prob. 20QAPCh. 14 - Prob. 21QAPCh. 14 - Prob. 22QAPCh. 14 - Prob. 23QAPCh. 14 - Prob. 24QAPCh. 14 - Prob. 25QAPCh. 14 - Prob. 27QAPCh. 14 - Prob. 28QAPCh. 14 - Prob. 29QAPCh. 14 - Prob. 30QAPCh. 14 - Prob. 31QAPCh. 14 - Prob. 32QAPCh. 14 - Prob. 33QAPCh. 14 - Prob. 34QAPCh. 14 - Prob. 35QAPCh. 14 - Prob. 36QAPCh. 14 - Prob. 37QAPCh. 14 - Prob. 38QAPCh. 14 - Prob. 39QAPCh. 14 - Prob. 40QAPCh. 14 - Prob. 41QAPCh. 14 - Prob. 43QAPCh. 14 - Prob. 44QAPCh. 14 - Prob. 45QAP
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- What would be your estimate for the age of the universe if you measured Hubbleʹs constant to be 33 km/s/Mly? You can assume that the expansion rate has remained unchanged during the history of the universe.arrow_forwardDescribe a quasar.arrow_forwardTwo galaxies are moving away from each other at 8000 km/sec and are 4x103 light-years apart. It was observed that their speed is constant. Calculate the time taken by them to move 4x103 light-years in years.arrow_forward
- Observations of quasars have shown us that many are extremely _________, emitting more energy than all the stars in a galaxy. The energy they give off comes from a very small volume, typically about the size of ___________. Some have long ______, shooting off in opposite directions. Today, astronomers understand that all the properties of quasars can be explained if they are __________ at the centers of galaxies. Astronomers can use _____________ to study images and spectra of the central regions of galaxies more clearly than earlier instruments.arrow_forwardThe most distant quasar is "J0313-1806". Its redshift is z = 7.64. [ z = (femitted - fobserved)/ fobserved] Assume that the redshift is due to relative motion. Then how fast is the quasar moving away from Earth? (speed as the fraction of c = ) | .704 According to Hubble's Law, the distance (r) depends on the speed of recession (v) according to v = Hor where Ho~ 20km/s Mly How many years are required for light to travel from the quasar to Earth? (years = )arrow_forwardIf a galaxy is receding at 0.05 c, how far away is the galaxy if the Hubble parameter is 70 km/s/Mpc. О а. 23 Мрс Ob.7.0x 10 LY О с. 7 Мрс O d. 76 MLYarrow_forward
- The hydrogen Balmee lime Hb has a wavelength of 4.86.1 nm. It is shifted to 55.8 nm in a quasar's spectrum. What is the redshift of the quasar?arrow_forwardThe Lyman alpha line (Kα) of hydrogen is measured in the laboratory to have a wavelength of 121.6 nm. In the quasar PKS 2000-330 the same line is determined to have a wavelength of 580.0 nm. What is its redshift and recession velocity?arrow_forwardCalculate how far the quasar is in light years by knowing that distance = velocity/Ho. Make the appropriate units conversions.arrow_forward
- A galaxy is observed to be at 10.0 Mpc from Earth. If it is receding at 520 km/s, calculate the Hubble's constant.arrow_forwardConsider a Schechter luminosity function of the form where a = 0.9, ΦΣ = -0 (L)dL = D(+) L e-(L/Lx)dL, L 0.012h3 Mpc3 and L - 1010h Lo. Calculate the total number density. Express the final answer in terms of h where h = Ho/(100 km s−¹Mpc¯¹) (Ho is the Hubble constant).arrow_forwardProblem 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.arrow_forward
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