21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
6th Edition
ISBN: 9780393874921
Author: PALEN
Publisher: Norton, W. W. & Company, Inc.
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Chapter 19, Problem 30QP
To determine
To explain why astronomers think planets around stars close to the centers of galaxies is not a better place for formation of life.
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Most 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.)
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 18%. 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 8 × 1011 stars.
The Sun is moving at 220 ??/? around the Galactic Center at a more-or-less constant distance of 8.5 ???. To appreciate how remarkable this is, consider the following questions:
a) How massive would the Sun have to be for the Earth to have an orbital velocity of 220 km/s at 1 AU?
b) How fast would the Earth move if it was in orbit around the Sun at a distance of 8.5 kpc? Of course, you may ignore the effects of all other stars in this calculation.
Chapter 19 Solutions
21ST CENT.ASTRONOMY(LL)W/CODE WKBK PKG.
Ch. 19.1 - Prob. 19.1ACYUCh. 19.1 - Prob. 19.1BCYUCh. 19.2 - Prob. 19.2CYUCh. 19.3 - Prob. 19.3CYUCh. 19.4 - Prob. 19.4CYUCh. 19 - Prob. 1QPCh. 19 - Prob. 2QPCh. 19 - Prob. 3QPCh. 19 - Prob. 4QPCh. 19 - Prob. 5QP
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- I don’t understand how that it was estimated as length of a mouse is 4 to 15 cm in length. Is that a guess and the answer just varies?also where did 10^-1 come fromarrow_forwardIn 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_forwardSuppose 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_forward
- A galaxy's rotation curve is a measure of the orbital speed of stars as a function of distance from the galaxy's centre. The fact that rotation curves are primarily flat at large galactocen- tric distances (vrot(r) ~ constant) is the most common example of why astronomer's believe dark matter exists. Let's work out why! Assuming that each star in a given galaxy has a circular orbit, we know that the accelera- tion due to gravity felt by each star is due to the mass enclosed within its orbital radius r and equal to v?/r. Here, ve is the circular orbit velocity of the star. (a) Show that the expected relationship between ve and r due to the stellar halo (p(r) xr-3.5) does not produce a flat rotation curve. (b) Show that a p(r) ∞ r¯² density profile successfully produces a flat ro- tation curve and must therefore be the general profile that dark matter follows in our galaxy.arrow_forwardWhat would the universe look like if there was complete cemetery between matter and antimatter?arrow_forwardAnother explanation for the Universe is the Steady State Hypothesis. The Steady State Hypothesis says that the Universe has always existed and is infinite in extent. Which of the following supports the Big Bang Theory and which supports the Steady State Model. (Select B-Big Bang Theory, S-Steady State Model, If the first is B and the rest S, enter BSSSSS). A) An observation that some globular clusters show M-type stars that have evolved off the main sequence. B) The measurement of redshifts that show galaxies appear to be moving away from each other and the Universe is expanding. C) A measurement that shows the density of the Universe is close to the critical density. D) The measurement of the microwave background radiation. E) Observing that galaxies at very large distances look identical to those in the nearby universe.arrow_forward
- I answer is not 100, I also tried 21. I need help! Thank you!arrow_forwardAn important part of the lifecycle of galaxies like the Milky Way is the self regulation of formation of future generations of stars. Which statement best describes this process? A) Massive stars explode as Supernovae, heating nearby gas which then can't form stars, and even forcing the gas out of the galaxy in asuperbubble. B) Low mass stars like our Sun explode as Supernovae, heating nearby gas which then can't form stars, and even forcing the gas out the galaxy in asuperbubble. C) Stars fuse new elements in their cores which mix with nearby gas clouds, preventing the collapse of the clouds and hence stopping new starformation. D) The stars lock up material in their cores (like White Dwarf and Neutron Stars) meaning they can act as gravitational seeds for future starformation.arrow_forwardDo you expect that most planetary systems in the Universe have analogs to our Solar System's asteroid belt and Kuiper Belt? Would all planetary systems show signs of an age of heavy bombardment?arrow_forward
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