COSMIC PERSPECTIVE
9th Edition
ISBN: 9780135729458
Author: Bennett
Publisher: PEARSON
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Chapter 16, Problem 39EAP
To determine
To Discuss: The possibility of existence of life in a molecular cloud.
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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.
Tutorial
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…
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
Submit
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Chapter 16 Solutions
COSMIC PERSPECTIVE
Ch. 16 - Prob. 1VSCCh. 16 - Prob. 2VSCCh. 16 - Prob. 3VSCCh. 16 - Prob. 4VSCCh. 16 - Prob. 1EAPCh. 16 - Prob. 2EAPCh. 16 - Prob. 3EAPCh. 16 - Prob. 4EAPCh. 16 - Prob. 5EAPCh. 16 - Prob. 6EAP
Ch. 16 - Prob. 7EAPCh. 16 - Prob. 8EAPCh. 16 - Prob. 9EAPCh. 16 - Prob. 10EAPCh. 16 - Prob. 11EAPCh. 16 - Prob. 12EAPCh. 16 - Prob. 13EAPCh. 16 - Prob. 14EAPCh. 16 - Prob. 15EAPCh. 16 - Prob. 16EAPCh. 16 - Prob. 17EAPCh. 16 - Prob. 18EAPCh. 16 - Prob. 19EAPCh. 16 - Prob. 20EAPCh. 16 - Prob. 21EAPCh. 16 - Prob. 22EAPCh. 16 - Prob. 23EAPCh. 16 - Prob. 24EAPCh. 16 - Prob. 25EAPCh. 16 - Prob. 26EAPCh. 16 - Prob. 27EAPCh. 16 - Prob. 28EAPCh. 16 - Prob. 29EAPCh. 16 - Prob. 30EAPCh. 16 - Prob. 31EAPCh. 16 - Prob. 32EAPCh. 16 - Prob. 33EAPCh. 16 - Prob. 34EAPCh. 16 - Prob. 35EAPCh. 16 - Prob. 37EAPCh. 16 - Prob. 38EAPCh. 16 - Prob. 39EAPCh. 16 - Prob. 40EAPCh. 16 - Prob. 41EAPCh. 16 - Prob. 42EAPCh. 16 - Prob. 43EAPCh. 16 - Prob. 44EAPCh. 16 - Prob. 45EAPCh. 16 - Prob. 46EAPCh. 16 - Prob. 47EAPCh. 16 - Prob. 48EAPCh. 16 - Prob. 49EAPCh. 16 - Prob. 50EAPCh. 16 - Prob. 51EAPCh. 16 - Prob. 52EAPCh. 16 - Prob. 53EAPCh. 16 - Prob. 54EAPCh. 16 - Prob. 55EAPCh. 16 - Internal Temperature of the Sun. The Sun is...Ch. 16 - Prob. 57EAPCh. 16 - Angular Momentum of a Close Binary. Some close...Ch. 16 - Prob. 59EAP
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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
- A radio broadcast left Earth in 1911. 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 0.20. How many possible planets with life could have heard this signal?arrow_forwardIf 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_forwardWhy are we limited to finding life on planets orbiting other stars to situations where the biosphere has created planet-scale changes?arrow_forward
- Why are upper-main-sequence (high-luminosity) host stars unlikely sites for intelligent civilizations?arrow_forwardasap pleasearrow_forwardKepler-444 is one of many stars with terrestrial planets that is over 10 billion a) What do you think the spectral type of Kepler-444 might be? b) How do stars of this spectral type end their lives? c) If evolution followed a similar course on a habitable pranet around a star similar to Kepler-444, it would be 5 billion years more advanced than we are. Let’s try to project our future and see what happens. In particular, suppose our civilization gets motivated enough to colonize another planet. Kepler indicates that most stars have potentially habitable (and colonizable) planets, so roughly how far away is the typical “nearest" planet? d) The New Horizons probe on its way to Pluto took 9 years to travel 30 AU. If we could send colony ships with the same average speed, roughly how long would it take to reach the typical nearest planet? уears old.arrow_forward
- why do scientists generally think that liquid water is necessary for the origin of life? (astronomy)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_forwardWhat evidence do scientists have that life on Earth began in the sea?arrow_forward
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