Understanding Our Universe
3rd Edition
ISBN: 9780393614428
Author: PALEN, Stacy, Kay, Laura, Blumenthal, George (george Ray)
Publisher: W.w. Norton & Company,
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Chapter 10.2, Problem 10.2CYU
To determine
The significance of star having weak hydrogen lines and blue in colour.
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Many of the bright stars in the night sky are highly luminous normal blue stars (such as Acrux), and others are blue giants (such as Rigel) or red giants (such as Betelgeuse). Generally, such stars have a luminosity of 103 to 105 times that of our Sun!
Ignoring any effects from our atmosphere, how bright would a star with a luminosity of 8380 solar luminosities be if it were located 620 light years from Earth?
(You will need to convert some values.)
W/m²
For comparison, if you were 1 meter from a regular 100 W light bulb, the brightness would be 7.96 W/ m². (Since stars are not this bright, your answer should be considerably less!) Kind of amazing you can see these things, isn't it?
If a star has a surface temperature of 18,000 K (1.80 ✕ 104 K), at what wavelength (in nm) will it radiate the most energy? Is this a cool or hot star? (Give your answer relative to the Sun.)
As 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 6 times that of the Sun, but a surface temperature 0.4 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.
Chapter 10 Solutions
Understanding Our Universe
Ch. 10.1 - Prob. 10.1CYUCh. 10.2 - Prob. 10.2CYUCh. 10.3 - Prob. 10.3CYUCh. 10.4 - Prob. 10.4CYUCh. 10 - Prob. 1QAPCh. 10 - Prob. 2QAPCh. 10 - Prob. 3QAPCh. 10 - Prob. 4QAPCh. 10 - Prob. 5QAPCh. 10 - Prob. 6QAP
Ch. 10 - Prob. 7QAPCh. 10 - Prob. 8QAPCh. 10 - Prob. 9QAPCh. 10 - Prob. 10QAPCh. 10 - Prob. 11QAPCh. 10 - Prob. 12QAPCh. 10 - Prob. 13QAPCh. 10 - Prob. 14QAPCh. 10 - Prob. 15QAPCh. 10 - Prob. 16QAPCh. 10 - Prob. 17QAPCh. 10 - Prob. 18QAPCh. 10 - Prob. 19QAPCh. 10 - Prob. 20QAPCh. 10 - Prob. 21QAPCh. 10 - Prob. 22QAPCh. 10 - Prob. 23QAPCh. 10 - Prob. 24QAPCh. 10 - Prob. 25QAPCh. 10 - Prob. 26QAPCh. 10 - Prob. 27QAPCh. 10 - Prob. 28QAPCh. 10 - Prob. 29QAPCh. 10 - Prob. 31QAPCh. 10 - Prob. 32QAPCh. 10 - Prob. 33QAPCh. 10 - Prob. 34QAPCh. 10 - Prob. 35QAPCh. 10 - Prob. 36QAPCh. 10 - Prob. 37QAPCh. 10 - Prob. 38QAPCh. 10 - Prob. 39QAPCh. 10 - Prob. 40QAPCh. 10 - Prob. 41QAPCh. 10 - Prob. 42QAPCh. 10 - Prob. 43QAPCh. 10 - Prob. 44QAPCh. 10 - Prob. 45QAP
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- Many of the bright stars in the night sky are highly luminous normal blue stars (such as Acrux), and others are blue giants (such as Rigel) or red giants (such as Betelgeuse). Generally, such stars have a luminosity of 103 to 105 times that of our Sun! Ignoring any effects from our atmosphere, how bright would a star with a luminosity of 60900 solar luminosities be if it were located 532 light years from Earth? (You will need to convert some values.) W/m² For comparison, if you were 1 meter from a regular 100 W light bulb, the brightness would be 7.96 W/m². (Since stars are not this bright, your answer should be considerably less!) Kind of amazing you can see these things, isn't it?arrow_forwardA star such as our Sun will eventually evolve to a “red giant” star and then to a “white dwarf” star. A typical white dwarf is approximately the size of Earth, and its surface temperature is about 2.4 × 104 K. A typical red giant has a surface temperature of 3.2 × 103 K and a radius ~90000 times larger than that of a white dwarf. Take the radius of the red giant to be 6 × 1010 m. What is the average radiated power per unit area of the red giant?_________W/m2 What is the average radiated power per unit area of the white-dwarf?________W/m2 What is the total power radiated by the red giant? _________W What is the total power radiated by the white dwarf? ________W Please show full work! Thank you!arrow_forwardImagine a planet orbiting a star. Observations show a Doppler shift in the star's spectrum of 66 m/s over the 4.5 day orbit of the planet. What is the mass of the planet in kg? Assume the star has the same mass as the Sun (2.0 x 1030 kg), there are 365.25 days in a year, and 1AU = and 1.5 x 1011 m.arrow_forward
- A star is moving toward Earth with a radial velocity (speed directly toward or away from Earth) of 40,000 km/s. If we take a spectrum of this star’s light, will we find it to be red shifted or blue shifted? By what fraction are the wavelengths in this star’s spectrum shifted? [Answer: λ0/λ = 0.88]arrow_forwardUsing 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_forwardIf the surface Temperature of a star was about 11000.0 K instead of 7000.0 K what is the ratio of power per square meter of the 11000.0 K star compared to power per square meter of the 7000.0 K star? How many times greater is the magnitude of power per square meter of the 11000.0 K star compared to the 7000.0 K stararrow_forward
- = A star population is composed of stars with masses in the range between 1M and 150M. The initial mass function is = 0 (M/M)-2.3, where o (Mo). The luminosity of a star = (M/M) 3.3. Calculate the percentage of the total luminosity of the stars in the population which is produced by stars with mass between 120M and 150M. scales with its mass as L/Larrow_forward(a) The surface temperature of a star is 25,000 K and it has a luminosity about 1% that of our Sun. What kind of star is it? (B) The surface temperature of a star is 3,000 K and it has a luminosity about 104 time that of our Sun. What kind of star is it?arrow_forwardIf a star has M = 100Msun and L = 10^6Lsun, how long can it shine at that luminosity if it started as pure hydrogen and is able to convert 10% of its H to He? If a star has M = 0.5Msun and L = 0.1Lsun, how long can it shine under the same conditions?arrow_forward
- A star has the peak of its blackbody spectrum occur at a wavelength of 284 nm. What is its temperature? Hint: The rest wavelength of H-alpha is 656 nm.arrow_forwardWe will take a moment to compare how brightly a white dwarf star shines compared to a red giant star. For the sake of this problem, lets assume a white dwarf has a temperature roughly twice as large as a red giant star. As for their stellar radii, the white dwarf has a radius about 1/10000th that of a red giant star. With this in mind, how does the luminosity of a red giant star compare to that of a white dwarf? (Put differently, find the ratio of their luminosities a.k.a. how many times more luminous is the red giant than the white dwarf? An answer of less than 1 means the white dwarf is more luminous, an answer of 1 means they have the same luminosity, and an answer greater than 1 means the red giant is more luarrow_forwardThe Hα spectral line has a rest wavelength of 6562.8 ˚A (remember: 1 ˚A = 10−10 m). In star A, the lineis seen at 6568.4 ˚A, in star B it’s seen at 6560.3 ˚A, and in star C it’s seen at 6562.8 ˚A. Which star ismoving the fastest (along the line of sight) and what is the radial velocity of each star?arrow_forward
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