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Foundations of Astronomy (MindTap Course List)
14th Edition
ISBN: 9781337399920
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 14, Problem 16RQ
To determine
The velocity (in terms of
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What is the escape velocity Vesc of a 1.4?⊙
neutron star if its radius is 12 km? Express your answer as a multiple of the speed of light (i.e., compute Vesc/c, where c= 2.9979 x 105 km/s).
[Hint: you will need to recall the formula for escape speed from the surface of an object. This was discussed when we covered planetary atmospheres.]
A star with mass m, period Ti = 30 days, and radius ri = 1E4 km collapses into a neutron star (Links to an external site.) with a radius of rf = 3 km. Our goal will be to determine the period Tf of the neutron star. Useful formulae: Li=Lf; L=Iω; ω=2πf=2π/T; Isphere=2/5mr^2.
1.How much angular momentum Li does the star have before it collapses?
2. What is the rotation rate ωi of the star before collapsing?
3. Suppose we model the star as a solid sphere of radius ri with moment of inertia 2/5mri2 (a good assumption). What does our description of Li read now?
4.How much angular momentum Lf does the star have after it collapses?
5. What is the rotation rate ωf of the star after collapsing?
6.The new object, a neutron star, is also shaped like a sphere. What does Lf read?
Group of answer choices
7.Assuming angular momentum is conserved during collapse (also a good assumption), what is our prediction for the period of the neutron star, Tf?
8. What is Tf in units of days?
9. What…
A star with mass m, period Ti = 30 days, and radius ri = 1E4 km collapses into a neutron star (Links to an external site.) with a radius of rf = 3 km. Our goal will be to determine the period Tf of the neutron star. Useful formulae: Li=Lf; L=Iω; ω=2πf=2π/T; Isphere=2/5mr^2.
Chapter 14 Solutions
Foundations of Astronomy (MindTap Course List)
Ch. 14 - Prob. 1RQCh. 14 - Prob. 2RQCh. 14 - Prob. 3RQCh. 14 - Prob. 4RQCh. 14 - Prob. 5RQCh. 14 - Prob. 6RQCh. 14 - Prob. 7RQCh. 14 - Prob. 8RQCh. 14 - Prob. 9RQCh. 14 - Prob. 10RQ
Ch. 14 - Prob. 11RQCh. 14 - Prob. 12RQCh. 14 - Prob. 13RQCh. 14 - Prob. 14RQCh. 14 - Prob. 15RQCh. 14 - Prob. 16RQCh. 14 - If the Sun has a Schwarzschild radius, why isnt it...Ch. 14 - Prob. 18RQCh. 14 - Prob. 19RQCh. 14 - Prob. 20RQCh. 14 - Prob. 21RQCh. 14 - In what sense is a black hole actually black?Ch. 14 - If you are falling into a black hole and you point...Ch. 14 - Prob. 24RQCh. 14 - Prob. 25RQCh. 14 - Prob. 26RQCh. 14 - How Do We Know? How does peer review make fraud...Ch. 14 - Prob. 1PCh. 14 - Prob. 2PCh. 14 - Prob. 3PCh. 14 - Prob. 4PCh. 14 - Prob. 5PCh. 14 - Prob. 6PCh. 14 - Prob. 7PCh. 14 - Prob. 8PCh. 14 - Prob. 9PCh. 14 - Prob. 10PCh. 14 - Prob. 11PCh. 14 - Prob. 12PCh. 14 - Prob. 13PCh. 14 - Prob. 14PCh. 14 - Prob. 15PCh. 14 - Prob. 16PCh. 14 - Prob. 1SOPCh. 14 - Prob. 2SOPCh. 14 - Prob. 1LTLCh. 14 - Prob. 2LTLCh. 14 - Prob. 3LTLCh. 14 - Prob. 4LTLCh. 14 - Prob. 5LTL
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- The star HD 69830's mass is 1.7 ✕ 1030 kg, its radius is 6.3 ✕ 105 km, and it has a rotational period of approximately 35 days. If HD 69830 should collapse into a white dwarf of radius 7.8 ✕ 103 km, what would its period (in s) be if no mass were ejected and a sphere of uniform density can model HD 69830 both before and after?arrow_forwardInternational Astronomical Union reported on 24 Feb 1987: An object was discovered on Feb. 24.37 UT (position R.A. = 5h35m.8, Decl. = -69 18'), obtained m = 4.8 on Feb. 24.454 UT. This object proved to be the most famous supernova (SN) in the 20th Century and the brightest visible from Earth since 1604. It is classified as a SN of the type Il in the Large Magellanic Cloud (SN1987A). Its brightness peaked in May 1987, with an apparent magnitude of m = 2.8. a) Find the absolute magnitude M of the SN1987A at maximum. Distance of the LMC is 51,400 pc. b) The progenitor (before SN explosion) star was a blue supergiant of the apparent magnitude m = 12.8. How much brighter (in terms of flux density) this SN was at maximum compared to the progenitor star. Find the ratio FSN / Ebeforearrow_forwardV07arrow_forward
- what is the answer for sub-item (b) if the radius of the neutron star is 84.66 km?arrow_forwardA star has initially a radius of 660000000 m and a period of rotation about its axis of 34 days. Eventually it changes into a neutron star with a radius of only 35000 m and a period of 0.2 s. Assuming that the mass has not changed, find Assume a star has the shape of a sphere. (Suggestion: do it with formula first, then put the numbers in) [Recommended time : 5-8 minutes] (a) the ratio of initial to final angular momentum (Li/Lf) Oa. 5.22E+15 Ob. 24.2 Oc. 0.0413 Od. 1.91E-16 (b) the ratio of initial to final kinetic energy Oa. 1.3E-23 Activate V Go to Setting Ob. 607000 Oc. 1.65E-6 e here to searcharrow_forwardWhat must be the radius of a star of mass 2 x 10^30 kg so that the escape speed from this star is equal to 2 × 10^8 m/s?arrow_forward
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