21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Question
Chapter 20, Problem 45QP
To determine
The fraction of milkyway’s disk lying in the habitable zone.
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Let us assume that our galaxy consists of 2.5 × 1011 stars each of one solar mass. How long will a star at a distance of 50,000 ly from the galactic centre take to complete one revolution ? Take the diameter of the Milky Way to be 105 light year.
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 10 %. 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 9 × 1011 stars.
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 20 Solutions
21st Century Astronomy
Ch. 20.1 - Prob. 20.1CYUCh. 20.2 - Prob. 20.2CYUCh. 20.3 - Prob. 20.3CYUCh. 20.4 - Prob. 20.4CYUCh. 20 - Prob. 1QPCh. 20 - Prob. 2QPCh. 20 - Prob. 3QPCh. 20 - Prob. 4QPCh. 20 - Prob. 5QPCh. 20 - Prob. 6QP
Ch. 20 - Prob. 7QPCh. 20 - Prob. 8QPCh. 20 - Prob. 9QPCh. 20 - Prob. 10QPCh. 20 - Prob. 11QPCh. 20 - Prob. 12QPCh. 20 - Prob. 13QPCh. 20 - Prob. 14QPCh. 20 - Prob. 15QPCh. 20 - Prob. 16QPCh. 20 - Prob. 17QPCh. 20 - Prob. 18QPCh. 20 - Prob. 19QPCh. 20 - Prob. 20QPCh. 20 - Prob. 21QPCh. 20 - Prob. 22QPCh. 20 - Prob. 23QPCh. 20 - Prob. 24QPCh. 20 - Prob. 25QPCh. 20 - Prob. 26QPCh. 20 - Prob. 27QPCh. 20 - Prob. 28QPCh. 20 - Prob. 29QPCh. 20 - Prob. 30QPCh. 20 - Prob. 31QPCh. 20 - Prob. 32QPCh. 20 - Prob. 33QPCh. 20 - Prob. 34QPCh. 20 - Prob. 35QPCh. 20 - Prob. 36QPCh. 20 - Prob. 37QPCh. 20 - Prob. 38QPCh. 20 - Prob. 39QPCh. 20 - Prob. 40QPCh. 20 - Prob. 41QPCh. 20 - Prob. 42QPCh. 20 - Prob. 43QPCh. 20 - Prob. 44QPCh. 20 - Prob. 45QP
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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 our solar system is 4.6 billion years old, how many galactic years has planet Earth been around?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_forwardWhat evidence can you give that we live in a galaxy?arrow_forward
- Stars form in the Milky Way at a rate of about 1 solar mass per year. At this rate, how long would it take for all the interstellar gas in the Milky Way to be turned into stars if there were no fresh gas coming in from outside? How does this compare to the estimated age of the universe, 14 billion years? What do you conclude from this?arrow_forwardWhat will be the long-term future of our Galaxy?arrow_forwardThink of our Milky Way Galaxy as a flat 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 would the nearest such civilization be from us (on average)?arrow_forward
- Suppose no stars more massive than about 2 MSunhad ever formed. Would life as we know it have been able to develop? Why or why not?arrow_forwardSuppose there are l0,000 civilizations broadcasting radio signals in the Milky Way GaIaxy right now. On average, how many stars would we have to search before we would expect to hear a signal? Assume there are 500 billion stars in the galaxy. How would the answer change if there were only 100 civilizations instead of 10,000?arrow_forwardA 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_forward
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