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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Question
Chapter 18, Problem 7ETQ
To determine
To find any place in the Milky Way would be more or less likely to find a civilization and the parts of the Galaxy that a message can send.
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Suppose that stars were born at random times over the last 1010 years. The rate of star formation is simply the number of stars divided by 1010 years. The fraction of stars with detected extrasolar planets is at least 11 %. The rate of star formation can be multiplied by this fraction to find the rate planet formation. How often (in years) does a planetary system form in our galaxy? Assume the Milky Way contains 3 × 1011 stars.
Tutorial
A radio broadcast left Earth in 1925. How far in light years has it traveled?
If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast
reached?
Assume that the fraction of these star systems that have planets is 0.30 and that, in a given planetary
system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.85. How
many possible planets with life could have heard this signal?
Part 1 of 3
To figure out how many light years a signal has traveled we need to know how long since the signal left Earth.
If the signal left in 1925, distance in light years = time since broadcast left Earth.
d = tnow - tbroadcast
d =
light years
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Suppose that stars were born at random times over the last 10e10 years. The rate ofstar formation is simply the number of stars divided by 10e10 years. The fraction ofstars with detected extrasolar planets is at least 9 %. The rate of star formation can bemultiplied by this fraction to find the rate planet formation. How often (in years) doesa planetary system form in our galaxy? Assume the Milky Way contains 7 × 10e11 stars.
I've done this problem 3 different times from scratch and looked at similar problems here. Each time my answer is 1.587 (1.59 rounded to 2 significant figures), but when I submit, it says the answer is wrong. What do you think?
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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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
- If you could search for life in the galaxy shown in this image, would you look among stars in the disk, in the central bulge, in the halo, or in all of those places? Discuss the factors that influence your decision.arrow_forwardWhat evidence can you give that we live in a galaxy?arrow_forwardWould a human have been possible during the first generation of stars that formed right after the Big Bang? Why or why not?arrow_forward
- In a globular cluster, astronomers (someday) discover a star with the same mass as our Sun, but consisting entirely of hydrogen and helium. Is this star a good place to point our SETI antennas and search for radio signals from an advanced civilization? Group of answer choices No, because such a star (and any planets around it) would not have the heavier elements (carbon, nitrogen, oxygen, etc.) that we believe are necessary to start life as we know it. Yes, because globular clusters are among the closest star clusters to us, so that they would be easy to search for radio signals. Yes, because we have already found radio signals from another civilization living near a star in a globular cluster. No, because such a star would most likely not have a stable (main-sequence) stage that is long enough for a technological civilization to develop. Yes, because such a star is probably old and a technological civilization will have had a long time to evolve and develop there.arrow_forwardTutorial A radio broadcast left Earth in 1923. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.50 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.40. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1923, distance in light years = time since broadcast left Earth. d = tnow - broadcast d = 97 97 light years Part 2 of 3 Since the radio signal travels in all directions, it expanded as a sphere with a radius equal to the distance it has traveled so far. To determine the number of star systems this signal has reached, we need to determine the volume of that sphere. V, = Vb…arrow_forwardImagine that you have achieved immortality and you used it to travel outside of the Milky Way (you will be leaving today and you will be traveling with the speed of 1/10th of the speed of light). Describe how the Milky Way would look from the outside if you could watch it for the next 100 billion years.arrow_forward
- Suppose there are 9000.0 civilizations broadcasting radio signals in the Milky Way Galaxy at the moment. On average, how many stars would have to be searched before a signal is heard? Assume that there are 8 × 1011 stars in the Galaxy and one civilization per star.arrow_forwardMost of the stars we can see with the unaided eye in our night sky are hundreds or even thousands of lightyears away from Earth. (The very closest ones are only a few dozen lightyears away, but most are much further.) The vast majority of stars in our galaxy are many tens of thousands of lightyears away. IF intelligent life existed on planets orbiting some of these stars – and that’s a huge IF! – comment on the likelihood and practicality of (a) visiting, (b) communicating with, or (c) verifying the existence of those life forms. Describe how you might go about approaching EACH of these three tasks, or if you think they are even possible. (One or two sentences for each part would be appropriate.)arrow_forwardThink of our Milky Way Galaxy as a flat circular disk of diameter 100,000 light-years. Suppose we are one of 1000 civilizations, randomly distributed through the disk, interested in communicating via radio waves. How far away in light years would the nearest such civilization be from us on average? Show your working. (Hint: Begin by calculating the area of the disk. Find the area of one of a 1,000 squares. Consider the separation of the centres of two adjacent squares.)arrow_forward
- Suppose three stars lie in the disk of the Galaxy at distances of 20,000 light-years, 25,000 light-years, and 30,000 light-years from the galactic center, and suppose that right now all three are lined up in such a way that it is possible to draw a straight line through them and on to the center of the Galaxy. How will the relative positions of these three stars change with time? Assume that their orbits are all circular and lie in the plane of the disk.arrow_forwardThe Milky Way galaxy has about 5 x 10⁹ solar masses of gas in total. If 13 solar masses of that gas is turned into stars each year, how many more years could the Milky Way keep up with such a star formation rate? years (Note for comparison that the age of the universe is about 13.5 billion years, which can be written 1.35e10 years. Also, the value given is in the ballpark of how much gas in the Milky Way is used to make new stars each year.)arrow_forward
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