FOUNDATIONS OF ASTRONOMY-WEBASSIGN
14th Edition
ISBN: 9780357135655
Author: Seeds
Publisher: CENGAGE L
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Chapter 14, Problem 7P
To determine
Luminosity of Neutron star in units of Watts and solar luminosity.
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Assuming stars to behave as black bodies stefan-boltzmann law to show that the luminosity of a star is related to its surface temperature and size in the following way:
L = 4(3.14)R^2oT^4
where o= 5.67 ×10^-8 Wm^-2 K-4 is the stefan- boltzmann constant. Then use this expression together with the knowledge that the sun has a surface temperature of 5700k and radius 695 500km to calculate the luminosity of the Sun in units of Watts
If the hottest star in the Carina Nebula has a surface temperature of 51,000 K, at what wavelength (in nm) does it radiate the most energy?
Hint: Use Wien's law:
?max =
2.90 ✕ 106 nm · K
T
How does that compare with 91.2 nm, the wavelength of photons with just enough energy to ionize hydrogen?
-The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen.
-The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will have more than enough energy to ionize hydrogen.
-The wavelength calculated above is shorter than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.
-The wavelength calculated above is longer than 91.2 nm. Photons at this calculated wavelength will not have enough energy to ionize hydrogen.
What are the on the axes of a Hertzsprung-Russell diagram? (b) Name one thing you can tell about a star from its location in an H-R diagram (Other than luminosity & temperature!) c) Where are most stars located in the diagram?
Chapter 14 Solutions
FOUNDATIONS OF ASTRONOMY-WEBASSIGN
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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- At the average density of the interstellar medium, 1 atom per cm3, how big a volume of material must be used to make a star with the mass of the Sun? What is the radius of a sphere this size? Express your answer in light-years.arrow_forwardA star with spectral type A0 has a surface temperature of 9600 K and a radius of 2.2 RSun. How many times more luminous is this star than the Sun? (if it is less luminous enter a number less than one) This star has a mass of 3.3 MSun. Using the simple approximation that we made in class, what is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr. Compare this to the lifetime of a A0 star listed in Table 22.1 (computed using a more sophisticated approach). Is the value you calculated in the previous problem longer or shorter than what is reported in the table? (L for longer, S for shorter) (You only get one try at this problem.)arrow_forwardIf a neutron Star has a radius of 12 km and a temperature of 8.0 x 10^6 K, how luminous is it? Express your answer in watts and also in solar luminosity units. (Hint: Use the relation L/L= (R/R)^2(T/T)^4 . Use 5,800 K for the surface temperature of the Sun. The luminosity of the sun is 3.83 x 10^26W) luminosity in watts ________ W luminosity in solar luminosity units ______ Larrow_forward
- Using solar units, we find that a star has 4 times the luminosity of the Sun, a mass 1.25 times the mass of the Sun, and a surface temperature of 4090 K (take the Sun's surface temperature to be 5784 K for the sake of this problem). This means the star has a radius of.................... solar radii and is a .................... star (use the classification).arrow_forwardFor a main sequence star with luminosity L, how many kilograms of hydrogen is being converted into helium per second? Use the formula that you derive to estimate the mass of hydrogen atoms that are converted into helium in the interior of the sun (LSun = 3.9 x 1026 W). (Note: the mass of a hydrogen atom is 1 mproton and the mass of a helium atom is 3.97 mproton. You need four hydrogen nuclei to form one helium nucleus.)arrow_forwardLet us imagine that the spectrum of a star is collected and we find the absorption line of Hydrogen-Alpha (the deepest absorption line of hydrogen in the visible part of the electromagnetic spectrum) to be observed at 656.5 nm instead of 656.3 nm as measured in a lab here on Earth. What is the velocity of this star in m/s? (Hint: speed of light is 3*10^8 m/s; leave the units off of your answer) Question 4 of 7 A Moving to another question will save this response. 1 6:59 & backsarrow_forward
- Let us imagine that the spectrum of a star is collected and we find the absorption line of Hydrogen-Alpha (the deepest absorption line of hydrogen in the visible part of the electromagnetic spectrum) to be observed at 656.5 nm instead of 656.3 nm as measured in a lab here on Earth. What is the velocity of this star in m/s? (Hint: speed of light is 3*10^8 m/s; leave the units off of your answer)arrow_forwardAs a star runs out of hydrogen to fuel nuclear fusion in its core, changes within the star usually cause it to leave the main sequence, expanding and cooling as it does so. Would a star with a radius 12 times that of the Sun, but a surface temperature 0.5 times that of the Sun, be more, or less luminous than the Sun? Show and explain your reasoning. You may assume the surface area of a sphere is A = 4πr2.arrow_forwardFinally estimate the lifetime of an M0 spectral type star if the total mass of the star is M = 0.51M⊙ , and it has a total luminosity L = 7.7× 10−2L⊙. Make the same assumptions as the previous two problems. How does your calculated Main Sequence lifetime for the M0 type star compare to the Main Sequence lifetime you calculated for the Sun?arrow_forward
- For the PP chain 0.7% of the mass participating in nuclear fusion is liberated as energy which produces a star's luminosity. Assume that the core of a main sequence star consists of 10% of its total mass. Hence, estimate the lifetime of a star on the main sequence in terms of its luminosity L/L. Give your answer in years. You may use the observed mass-luminosity relation L x M³.5, where M is the star's total mass. Using typical values, calculate estimates for the main sequence lifetime of a KO star and a 05 star. Describe briefly why your estimate might be more accurate for K stars compared to O stars.arrow_forwardUsing the HR diagram, what is the approximate range of relative luminosities covered for a main sequence star at 10 000 K? Would this star be most like Rigel or Sirius?arrow_forwardThe figure above shows a track on the H-R diagram corresponding to the evolution of a star like the one you’ve just considered. Six stages are numbered. Six stages of stellar evolution are listed below – for each stage, write the number corresponding to its position on the diagram (four of these stages are the same stages you considered in the first part of this tutorial). Horizontal branch: Asymptotic giant branch: White dwarf: Main sequence: Planetary nebula: Red giant branch: What is the approximate mass of this star, in solar masses? Explain how you can tell.arrow_forward
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