Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 5, Problem 50Q
To determine
The sensitivity of the eyes of creatures born on a planet orbiting a star hotter than the sun.
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Students have asked these similar questions
You record the spectrum of a distant star using a telescope on the ground on Earth. Upon
analysing the spectrum, you discover absorption lines spaced at intervals typical of oxygen
atoms. Which of the following are possible interpretations of this evidence? Select all that
apply.
The width of the spectral lines gives the diameter of the star
The star is likely orbited by habitable planets with breathable atmospheres.
The height of the spectral lines above the star's general blackbody spectral curve tells us how much
oxygen is in the star
The atmosphere of Earth contains oxygen
The red or blueshift of the set of lines can tell us the speed of the star's motion toward or away from us
Voyager 2.
When the Voyager 2 spacecraft was approaching towards its Neptune encounter in
1989, it was 4.5 × 10° km away from the earth. Its radio transmitter, with which it
communicated with us (and we communicated with it), broadcast with a mere 22 Watt
of power at the S-band (2.1 GHz). (Your home wi-fi router emits around 2 Watt at 2.4
GHz wi-fi band). Assuming the Voyager transmitter broadcast equally in all directions,
(a) What signal intensity was received on the earth?
(b) What electric and magnetic field amplitudes were detected?
(c) How many 2.1 GHz photons were arriving per second on a radio-receiver antenna
with a circular cross-section of diameter 34 meters?
Two counter-propagating plane waves
(a) Let E(z, t) = E0 cos(kz – wt)â + E, cos(kz + wt)x. Write E(z, t) in simpler form
and find the associated magnetic field.
(b) For the fields in part (a), find the instantaneous and time-averaged electric and
magnetic field energy densities.
(c) Let E(z, t) = E, cos(kz – wt)x + E,…
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.
Chapter 5 Solutions
Universe: Stars And Galaxies
Ch. 5 - Prob. 1QCh. 5 - Prob. 2QCh. 5 - Prob. 3QCh. 5 - Prob. 4QCh. 5 - Prob. 5QCh. 5 - Prob. 6QCh. 5 - Prob. 7QCh. 5 - Prob. 8QCh. 5 - Prob. 9QCh. 5 - Prob. 10Q
Ch. 5 - Prob. 11QCh. 5 - Prob. 12QCh. 5 - Prob. 13QCh. 5 - Prob. 14QCh. 5 - Prob. 15QCh. 5 - Prob. 16QCh. 5 - Prob. 17QCh. 5 - Prob. 18QCh. 5 - Prob. 19QCh. 5 - Prob. 20QCh. 5 - Prob. 21QCh. 5 - Prob. 22QCh. 5 - Prob. 23QCh. 5 - Prob. 24QCh. 5 - Prob. 25QCh. 5 - Prob. 26QCh. 5 - Prob. 27QCh. 5 - Prob. 28QCh. 5 - Prob. 29QCh. 5 - Prob. 30QCh. 5 - Prob. 31QCh. 5 - Prob. 32QCh. 5 - Prob. 33QCh. 5 - Prob. 34QCh. 5 - Prob. 35QCh. 5 - Prob. 36QCh. 5 - Prob. 37QCh. 5 - Prob. 38QCh. 5 - Prob. 39QCh. 5 - Prob. 40QCh. 5 - Prob. 41QCh. 5 - Prob. 42QCh. 5 - Prob. 43QCh. 5 - Prob. 44QCh. 5 - Prob. 45QCh. 5 - Prob. 46QCh. 5 - Prob. 47QCh. 5 - Prob. 48QCh. 5 - Prob. 49QCh. 5 - Prob. 50QCh. 5 - Prob. 51Q
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- Suppose astronomers discover a radio message from a civilization whose planet orbits a star 35 lightyears away. Their message encourages us to send a radio answer, which we decide to do. Suppose our governing bodies take 2 years to decide whether and how to answer. When our answer arrives there, their governing bodies also take two of our years to frame an answer to us. How long after we get their first message can we hope to get their reply to ours? (A question for further thinking: Once communication gets going, should we continue to wait for a reply before we send the next message?)arrow_forwardWhy is traveling between the stars (by creatures like us) difficult?arrow_forwardhello, how we solve this problem?arrow_forward
- The angular separation in degrees of two objects is (physical separation × 360°) / (2 π × distance). If an individual was observing our solar system from Castor at a distance of 7.6 light years. What angular resolution, in arcsecond, is needed to resolve the Sun-Earth system as distinct points of light?arrow_forwardThe angular separation in degrees of two objects is (physical separation × 360°) / (2 π × distance). If an individual was observing our solar system from Castor at a distance of 7.6 light years. What angular resolution, in arcsecond, is needed to resolve the Sun-Jupiter system (5.46 AU) as distinct points of light?arrow_forwardWhy do we think we would be able to decode a message deliberately sent to us by an alien civilization? Group of answer choices The message will probably be in video format, allowing us to watch it even without knowing the alien language. We can assume that aliens will also have 10 fingers and 10 toes and therefore that they can send a message that relies on this fact. They undoubtedly have already received our television broadcasts and would therefore be likely to send the message in English. The aliens presumably know the same laws of mathematics and physics as we do and therefore could develop a simple code based on these laws.arrow_forward
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