Foundations of Astronomy (MindTap Course List)
14th Edition
ISBN: 9781337399920
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Textbook Question
Chapter 25, Problem 3LTL
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.
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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.
A newly discovered orange dwarf star has a surface temperature of approximately 5185 K. How far would its Goldilocks Zone be from the star if an astrologist wanted to look for potentially habitable planets? And how wide would the zone be?
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…
Chapter 25 Solutions
Foundations of Astronomy (MindTap Course List)
Ch. 25 - Explain how astrobiology is a science and not a...Ch. 25 - Describe one special quality of water that makes...Ch. 25 - Mars and Europa are two Solar System bodies that...Ch. 25 - How does the DNA molecule produce a copy of...Ch. 25 - What would happen to a life-form if the genetic...Ch. 25 - What would happen to a life-form if the genetic...Ch. 25 - What would happen to a life-form if the...Ch. 25 - Describe an example of natural selection acting on...Ch. 25 - Prob. 9RQCh. 25 - What evidence do scientists have that life on...
Ch. 25 - Define organic, as in organic molecule. How is...Ch. 25 - Why is liquid water generally considered necessary...Ch. 25 - Some meteorites contain organic molecules. What...Ch. 25 - What is the difference between chemical evolution...Ch. 25 - Prob. 15RQCh. 25 - Why was Earths early atmosphere able to support...Ch. 25 - Molecules of which gas were needed in Earths...Ch. 25 - Does intelligence make a creature more likely to...Ch. 25 - Describe one hypothesis for how cells first...Ch. 25 - What is the evidence that the first organisms on...Ch. 25 - Name three locations in our Solar System to search...Ch. 25 - Why are upper-main-sequence (high-luminosity) host...Ch. 25 - Prob. 23RQCh. 25 - How does the stability of technological...Ch. 25 - Prob. 25RQCh. 25 - Prob. 26RQCh. 25 - Why are scientists confident Earth has never been...Ch. 25 - Why does the Drake equation implicitly assume the...Ch. 25 - A single human cell encloses about 1.5 m of DNA....Ch. 25 - If you represent Earths history by a line that is...Ch. 25 - Consider Figure 25-8. What is the ratio of the...Ch. 25 - Suppose a human generation is defined as the...Ch. 25 - If a star must remain on the main sequence for at...Ch. 25 - Prob. 6PCh. 25 - If you detected radio signals with an average...Ch. 25 - Prob. 8PCh. 25 - The first radio broadcast was made on January 13,...Ch. 25 - Prob. 10PCh. 25 - The DNA in a single cell in your body contains...Ch. 25 - Prob. 2SOPCh. 25 - Look at Figure 25-11. Since the time we sent the...Ch. 25 - The star cluster shown in this image contains a...Ch. 25 - If you could search for life in the galaxy shown...
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- 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 Skip (you cannot come back)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_forwardImagine that in the future, scientists plan on colonizing planets that orbit other stars. Based on your knowledge of the life cycle of stars, decide which type of star (High mass or Low mass) the planet should orbit that would allow for human life to safely live on that planet for the longest period of time. Explain your answer using examples from the life cycle of each star.arrow_forward
- 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?arrow_forwardSuppose 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.arrow_forwardPlanetary Nebula Age. Suppose a planetary nebula is 1 pc in radius. If the Doppler shifts in its spectrum show it is expanding at 20 km/s, how old is it? (Note that 1 pc equals 3.1x1013 km, and 1 year equals 3.2x107 seconds, to two significant figures.) Please round your answer to two significant digits. At = yearsarrow_forward
- 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_forwardConsidering what you learned from the solar nebula theory, how likely do you think it is to find habitable planets in other solar systems? Visit NASA’s Kepler mission to learn more about this search, and write a ½ page summary on the mission.arrow_forward2arrow_forward
- What evidence can you cite that the interstellar medium contains both gas and dust? (Select all that apply.) (1)The dust of the interstellar medium can be detected from the emission lines of elements heavier than iron. (2)The dust of the interstellar medium can be detected by the extinction of light from distant stars. (3)The dust of the interstellar medium can be detected by the scattering of blue light from distant or embedded objects. (4)The gas of the interstellar medium can be detected from the radiation of ultraviolet photons. (5)The gas of the interstellar medium can be detected from the radiation of photons of wavelength 21 cm. (6)The gas of the interstellar medium can be detected from the absorption lines present in the light from distant stars, which must be caused by a medium of a density and temperature other than that of the stars emitting the light.arrow_forwardIf a star must remain on the main sequence for at least 4 billion years for life to evolve to intelligence, what is the most massive a star that can form and still possibly harbor intelligent life on one of its exoplanets? (Hints: Use the formula for stellar life expectancies, Eq. 121, and data in Appendix Table A-7.)arrow_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
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