Loose Leaf For Explorations: Introduction To Astronomy
9th Edition
ISBN: 9781260432145
Author: Thomas T Arny, Stephen E Schneider Professor
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 18, Problem 1P
Until recently, experimental results for the Hubble constant ranged from about 50 to 100 km/sec/Mpc. Calculate the age of the Universe for both of these extremes. Do you see any potential conflicts with other astronomical observations if H had been either of these numbers?
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Using our example from the previous unit, let's try to determine the Hubble time for this example universe. You were given that a good representative galaxy receded at a speed of 4000 km/s and was found to be 20 Mpc away. With that in mind, what would the age of that universe be in years (aka what is that universe's Hubble time)? Go ahead and take the number of kilometers per Mpc to be approximately 3.1*10^19 km/Mpc. While this problem may look scary at first, this is really just bringing you full circle to one of the unit conversion problems you encountered at the beginning of this course.
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.
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Cosmic background
data from COBE
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Wavelength A in mm
c)
Background (CMB) undertaken by the COBE satellite. Use this diagram to estimate the
current temperature of the CMB. Based on your estimate, what would the temperature of
the CMB have been at a redshift of z = 5000?
The left hand diagram above shows the results from observations of the Cosmic Microwave
Radiated Intensity per Unit Wavelength
(16° Watts/m per mm)
Chapter 18 Solutions
Loose Leaf For Explorations: Introduction To Astronomy
Ch. 18 - Why do astronomers think that the Universe is...Ch. 18 - What is meant by the age of the Universe? How old...Ch. 18 - Prob. 3QFRCh. 18 - What is Olbers paradox?Ch. 18 - Prob. 5QFRCh. 18 - Prob. 6QFRCh. 18 - Prob. 7QFRCh. 18 - Prob. 8QFRCh. 18 - Prob. 9QFRCh. 18 - Prob. 10QFR
Ch. 18 - Prob. 11QFRCh. 18 - Prob. 12QFRCh. 18 - Prob. 13QFRCh. 18 - Prob. 14QFRCh. 18 - Prob. 15QFRCh. 18 - Prob. 16QFRCh. 18 - Prob. 17QFRCh. 18 - Prob. 18QFRCh. 18 - Prob. 19QFRCh. 18 - Prob. 20QFRCh. 18 - Prob. 1TQCh. 18 - Prob. 2TQCh. 18 - Prob. 3TQCh. 18 - Prob. 4TQCh. 18 - Prob. 5TQCh. 18 - Prob. 6TQCh. 18 - Prob. 7TQCh. 18 - Why are there points below the green line (instead...Ch. 18 - Prob. 9TQCh. 18 - Until recently, experimental results for the...Ch. 18 - The temperature of Universe at recombination was...Ch. 18 - Prob. 3PCh. 18 - Prob. 4PCh. 18 - The temperature of the Universe at recombination...Ch. 18 - One second after the Big Bang, the density of the...Ch. 18 - Prob. 7PCh. 18 - Prob. 8PCh. 18 - Prob. 1TYCh. 18 - Prob. 2TYCh. 18 - Prob. 3TYCh. 18 - Which of the following statements about the first...Ch. 18 - Prob. 5TYCh. 18 - Prob. 6TYCh. 18 - Prob. 7TYCh. 18 - Prob. 8TYCh. 18 - Prob. 9TYCh. 18 - Prob. 1EQFRCh. 18 - Prob. 2EQFRCh. 18 - Prob. 3EQFRCh. 18 - Prob. 4EQFRCh. 18 - Prob. 5EQFRCh. 18 - Prob. 6EQFRCh. 18 - Prob. 7EQFRCh. 18 - Prob. 8EQFRCh. 18 - Prob. 9EQFRCh. 18 - What is meant by the Gaia hypothesis?Ch. 18 - Prob. 11EQFRCh. 18 - Prob. 1ETQCh. 18 - Prob. 2ETQCh. 18 - Prob. 3ETQCh. 18 - Prob. 4ETQCh. 18 - Prob. 5ETQCh. 18 - Prob. 6ETQCh. 18 - Prob. 7ETQCh. 18 - Prob. 8ETQCh. 18 - Prob. 1EPCh. 18 - Prob. 2EPCh. 18 - Prob. 3EPCh. 18 - Prob. 4EPCh. 18 - Prob. 5EPCh. 18 - Prob. 6EPCh. 18 - Prob. 1ETYCh. 18 - Prob. 2ETYCh. 18 - Prob. 3ETYCh. 18 - Prob. 4ETYCh. 18 - Prob. 5ETYCh. 18 - Prob. 6ETYCh. 18 - Prob. 7ETY
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- The best parallaxes obtained with Hipparcos have an accuracy of 0.001 arcsec. If you want to measure the distance to a star with an accuracy of 10%, its parallax must be 10 times larger than the typical error. How far away can you obtain a distance that is accurate to 10% with Hipparcos data? The disk of our Galaxy is 100,000 light-years in diameter. What fraction of the diameter of the Galaxy’s disk is the distance for which we can measure accurate parallaxes?arrow_forwardWhat is the estimated age of the Universe (in years) if the Hubble constant is 60 km/s/Mpc?arrow_forwardHow would I calculate the age of the universe in billions of years from the Hubble constant (73.48 +/- 1.66 km/s/Mpc)? I know I need to use basic unit conversion but I’m not sure which numbers to use.arrow_forward
- Explain how the Hubble constant, H0, can be used to make an estimate for the age of the Universe. Use the value of H0 = 0.07×103 kms-1/Mpc to estimate the Universe’s age. Comment on the significance of your answer.arrow_forwardRecall that Hubble’s Law is given by V=HR; this means that H has units of inverse seconds (1/sec). A convenient laboratory set of units is to give H in km per sec per megaparsec. A parsec is 3.26 light years and the speed of light is 3 X 105 km/sec. Use 3.156 X 107 sec/yr. The first data off the then new Hubble Space telescope suggested a value of H equal to 108 km per sec per megaparsec. What is H in inverse seconds? Hint divide by the number of km in a megaparsec.arrow_forwardmathematician Archimedes, responding to a claim that the number of grains of sand was infinite, calculated that the number of grains of sand needed to fill the universe was on the order of 1063. Our understanding of the size of the universe has changed since then, and we now know that the observable universe alone is a sphere with a radius of 1026 m. Estimating the size of a grain of sand, A) Approximately how many grains of sand would fill the observable universe? B) How many times larger or smaller is this number than Archimedes' result?arrow_forward
- In the reading, you were told that there were roughly 10,000 galaxies in the image of the Hubble Ultra Deep Field alone. The image is roughly 10 square arcminutes and there are roughly 1.5*10^8 square arcminutes composing the entire sky. With that in mind and assuming that the Hubble Ultra Deep Field represents an average part of the sky, roughly how many galaxies may exist in the observable universe? (Please include commas for every factor of 1,000; for example 2,343,567,890)arrow_forwardAssume the observable Universe is charge neutral, and that it contains n nuclei (hydrogen plus helium nuclei, ignoring other elements). Take the helium mass fraction as 1/4. How many electrons are there in the observable Universe? Enter your answer in scientific notation with one decimal place. Values: n = 1*10^80arrow_forwardAssume the observable Universe is charge neutral, and that it contains n nuclei (hydrogen plus helium nuclei, ignoring other elements). Take the helium mass fraction as 1/4. How many electrons are there in the observable Universe? Enter your answer in scientific notation with one decimal place. Value: n = 4*1080arrow_forward
- If a galaxy is 8.8 Mpc away from Earth and recedes at 498 km/s, what is H0 (in km/s/Mpc)? _______ km/s/Mpc What is the Hubble time (in yr)? _______ yr How would acceleration change your answer? A: If the expansion of the Universe has been accelerating, the Universe could be substantially younger than the value entered above. B: If the expansion of the Universe has been accelerating, the Universe could be substantially older than the value entered above.arrow_forwardIt is possible to derive the age of the universe given the value of the Hubble constant and the distance to a galaxy, again with the assumption that the value of the Hubble constant has not changed since the Big Bang. Consider a galaxy at a distance of 235 million light-years receding from us at a velocity, v. If the Hubble constant is 20.5 km/s per million light-years, what is its velocity? (Enter the magnitude in km/s.) _________ km/sarrow_forwardCalculate the number of miles in a light-year, using 1.86 105 mi/s as the speed of light. (Hint: The number of seconds in a year, 365 days, will be useful.)arrow_forward
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