21st Century Astronomy
6th Edition
ISBN: 9780393428063
Author: Kay
Publisher: NORTON
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Question
Chapter 13, Problem 27QP
To determine
The strength of the absorption lines in O stars, G stars and in the middle of the range of spectral types
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Choose the correct statements concerning spectral classes of stars. (Give ALL correct answers, i.e., B, AC, BCD...)
A) Neutral hydrogen lines dominate the spectrum for stars with temperatures around 10,000 K because a lot of the hydrogen is in the n=2 level.
B) Hydrogen lines are weak in type O-stars because most of it is completely ionized.
C) Oh Be A Fine Guy/Girl Kiss Me, is a mnemonic for remembering spectral classes.
D) The spectral sequence has recently been expanded to include L, T, and Y classes.
E) K-stars are dominated by lines from ionized helium because they are so hot.
F) The spectral types of stars arise primarily as a result of differences in temperature.
All massive main sequence stars reside in clouds of glowing gas. The four powerful stars in the center of the Orion Nebula are good examples. Lower mass stars like the Sun generally don't have clouds of gas around them. a. Why do powerful stars reside in gas clouds? b. What is making the gas glow exactly? For the last question, refer to the surface temperature of these stars, and to Wien's Law.
A star with a radius 1.7 times that of the
Sun has a surface temperature T=10,000
K. Calculate the luminosity of this star
and express your answer in units of the
Solar luminosity (the Solar luminosity =
3.84 x 1026 W and the Solar radius = 7 x
%3D
108 m). Choose the option below that
most closely matches your answer.
Select one:
а.
20
O b. 100.
O C.
26.
O d. 5.
O e.
1000
Chapter 13 Solutions
21st Century Astronomy
Ch. 13.1 - Prob. 13.1CYUCh. 13.2 - Prob. 13.2CYUCh. 13.3 - Prob. 13.3CYUCh. 13.4 - Prob. 13.4CYUCh. 13 - Prob. 1QPCh. 13 - Prob. 2QPCh. 13 - Prob. 3QPCh. 13 - Prob. 4QPCh. 13 - Prob. 5QPCh. 13 - Prob. 6QP
Ch. 13 - Prob. 7QPCh. 13 - Prob. 8QPCh. 13 - Prob. 9QPCh. 13 - Prob. 10QPCh. 13 - Prob. 11QPCh. 13 - Prob. 12QPCh. 13 - Prob. 13QPCh. 13 - Prob. 14QPCh. 13 - Prob. 15QPCh. 13 - Prob. 16QPCh. 13 - Prob. 17QPCh. 13 - Prob. 18QPCh. 13 - Prob. 19QPCh. 13 - Prob. 20QPCh. 13 - Prob. 21QPCh. 13 - Prob. 22QPCh. 13 - Prob. 23QPCh. 13 - Prob. 24QPCh. 13 - Prob. 25QPCh. 13 - Prob. 26QPCh. 13 - Prob. 27QPCh. 13 - Prob. 28QPCh. 13 - Prob. 29QPCh. 13 - Prob. 30QPCh. 13 - Prob. 31QPCh. 13 - Prob. 32QPCh. 13 - Prob. 33QPCh. 13 - Prob. 34QPCh. 13 - Prob. 35QPCh. 13 - Prob. 36QPCh. 13 - Prob. 37QPCh. 13 - Prob. 38QPCh. 13 - Prob. 39QPCh. 13 - Prob. 40QPCh. 13 - Prob. 41QPCh. 13 - Prob. 42QPCh. 13 - Prob. 43QPCh. 13 - Prob. 44QPCh. 13 - Prob. 45QP
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- lambdamax = 600nm (5000K/T) L ∝ R2 T 4 1. What is the peak wavelength of an O star of temperature 50,000 K? What range of the spectrum is this?arrow_forwardWhy don’t we see hydrogen Balmer lines in the spectra of stars with temperatures of 3,200 K? a. There is no hydrogen in stars this cool. b. The stars are hot enough that most of the hydrogen is ionized and the atoms cannot absorb energy. c. These stars are so cool that nearly all of the hydrogen atoms are in the ground state. d. Stars of this temperature are too cool to produce an absorption spectrum. e. Stars of this temperature are too hot to produce an absorption spectrum.arrow_forwardChoose the statements that correctly describe the characteristics of the stars located in the labeled quadrants of the H-R diagram. Luminosityarrow_forwardMany 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?arrow_forwardd²p GMp %3D dt2 (a² + p2)3/2* 2. Suppose that p < a, that is, the star is deep inside the cluster. Use a Maclaurin series to show that d²p GM d. %3D dt2 q3 +..arrow_forward"51 Pegasi" is the name of the first normal star (besides the Sun) around which a planet was discovered. It is in the constellation Pegasus the horse. Its parallax is measured to be 0.064 arcsec. a. What is its distance from us? b. The apparent brightness is 1.79 × 10-10 J/(s·m2 ). What is the luminosity? How does that compare with that of the Sun? Look up the temperature: how doarrow_forwardA main sequence star of mass, M, and radius, R, collapses to a white dwarf star with a radius 1.0% as big as the original star. If ω is the angular velocity of the original star, what is the angular velocity of the white dwarf star? Approximate the star to be a uniform solid sphere. a. 20,000ω b. 10,000ω c. 50,000ω d. 1,000ω e. 5,000ωarrow_forwardSelect all the statements below regarding spectral lines that are true. The stars with the most prominent hydrogen absorption lines are O stars. K stars have many more spectral lines than B stars. Heavy elements generally have fewer spectral lines than light elements. An absorption line is produced when a cooler gas absorbs light from a bright background continuum light source. Emission lines are produced when electrons jump from low energy levels to high ones. The longest wavelength Hydrogen Balmer line is red.arrow_forwarda) The star 58 Eridani is a feint but naked-eye star similar to the Sun. Suppose that you are observing this star in the night sky without a telescope. Ignoring any interstellar extinction or atmospheric absorption, approximately how many photons per second arrive at your retina? Show all steps in your calculation. Look up any required information about the star using Wikipedia. Use sensible approximations so your calculation is straightforward. For example you could consider only the region of the spectrum where the photon flux peaks. b) The Mid-Infrared Instrument (MIRI, camera and spectrograph) on the James Webb Space Telescope operates in the band 5 – 28 µm. For 58 Eridani, approximately how many photons per second can be used by this instrument? Assume that MIRI takes all the photons from the full JWST mirror. Show all steps in your calculation. Describe briefly two or three other factors which play a role in determining the sensitivity of an instrument such as MIRI?arrow_forwardarrow_back_iosSEE MORE QUESTIONSarrow_forward_ios
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