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− | ==题目==
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− | 1. On December 21, 2020, Jupiter was at $$(\alpha,\delta)=(20^{h}10^{m},-20°34′)$$. Which constellation was Saturn in?
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− | (a) Capricornus
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− | (b) Aquarius
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− | (c) Pisces
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− | (d) Aquila
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− | 2. What is the spectral type of a star with a luminosity of 5.86 * 10<sup>26</sup> W and radius of 8.51 * 10<sup>8</sup> m?
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− | (a) A
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− | (b) F
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− | (c) G
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− | (d) K
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− | (e) M
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− | 3. The exoplanet HD 209458b has a mass of 0.71 Jupiter masses and orbits HD 209458 with an orbital period of 3.53 days. HD 209458 has a mass of 1.15 Solar masses. Assuming that the orbit of HD 209458b is circular (which is a good approximation here) and that its orbit lies perfectly in our line of sight, what is the radial velocity semi-amplitude of HD 209458 due to the orbital motion of HD 209458b, in m/s?
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− | (a) 69.6 m/s
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− | (b) 85.9 m/s
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− | (c) 94.2 m/s
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− | (d) 120.8 m/s
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− | 4. The photon number density of a blackbody depends on temperature as $$nd = a(\frac{k_{B}T}{\hbar_{c}})^{n}$$ where $$k_{B}$$ is the Boltzman constant, $$\hbar$$ is the reduced Planck’s constant, $$c$$ is the speed of light and $$T$$ is the blackbody temperature. Here, $$a$$ is a dimensionless numerical constant. What is the value of $$n$$?
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− | (a) 1
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− | (b) 2
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− | (c) 3
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− | (d) 4
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− | 5. HD 209458b has a radius of 1.35 Jupiter radii, while the radius of HD 209458 is 1.20 Solar radii. What is the transit depth of HD 209458b, in percent?
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− | (a) 0.013%
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− | (b) 0.13%
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− | (c) 1.3%
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− | (d) 13%
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− | 6. Which of the following is a problem of the conventional Big Bang theory that is resolved by the theory of inflation?
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− | (a) Under the conventional Big Bang theory, it is extremely unlikely for our universe to be flat or nearly flat today, contrary to observation.
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− | (b) Under the conventional Big Bang theory, it is impossible for the Cosmic Microwave Background to have come into thermal equilibrium by the time of recombination, despite its observed uniform temperature.
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− | (c) The conventional Big Bang theory predicts a huge abundance of magnetic monopoles, while no magnetic monopoles have ever been discovered.
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− | (d) All of the above
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− | 7. Comet C/2020 F3 (NEOWISE) last reached perihelion on July 3, 2020. Comet NEOWISE has an orbital period of ≈ 4400 years and its eccentricity is 0.99921. What is the perihelion distance of Comet NEOWISE, in AU?
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− | (a) 0.0123 AU
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− | (b) 0.212 AU
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− | (c) 2.69 AU
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− | (d) 26.8 AU
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− | 8. An astronomer detected a galaxy and decided to analyze its different parts and physical aspects. The frequency generated by a “spin-flip” transition of atomic hydrogen is $$v_{0} = 1420.406MHz$$, however it was detected on the galaxy as $$v = 1422.73$$. He finds that:
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− | 1. Population I stars are (1) and are metal-(2).
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− | 2. The galaxy is (3) from us with a speed of (4) $$km * s^{-1}$$.
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− | Choose the alternative that correctly completes sentences above.
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− | (a) (1) young; (2) poor; (3) distancing; (4) 245
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− | (b) (1) old; (2) rich; (3) approaching; (4) 490
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− | (c) (1)old; (2) poor; (3) distancing; (4) 490
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− | (d) (1) young; (2) rich; (3) approaching; (4) 490
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− | (e) (1) young; (2) rich; (3) approaching; (4) 245
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− | 9. A stable open cluster of about $$N = 1000$$ sun-like stars has an angulardiameter of $$\theta$$ = 30 arc minutes and distance of $$d$$ = 500 pc. Assuming the cluster can be approximated by a sphere of uniform density, estimate the average velocities of stars in the cluster. The gravitational potential energy of a sphere of uniform density and radius $$r$$ is
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− | $$U_{sphere} = -\frac{3}{5}\frac{GM^{2}_{sphere}}{r}$$
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− | (a) 507 m/s
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− | (b) 643 m/s
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− | (c) 894 m/s
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− | (d) 1021 m/s
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− | (e) 771 m/s
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− | 10. What would happen to the analemma of the Sun if the obliquity of the Earth’s orbit suddenly went to zero degrees and its eccentricity remained unchanged?
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− | (a) The anallema would be perfectly symmetric in both axes and would have the shape of an“8”.
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− | (b) The analemma would look like a dot.
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− | (c) The analemma would be the arc of a great circle.
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− | (d) The analemma would look like a circle.
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− | (e) The analemma would be a spherical triangle.
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− | 11. Let $$T_{{\odot},C}$$ and $$T_{{\odot},S}$$ be the temperatures at the core and the surface of the sun, respectively. Similarly, let $$T_{A,C}$$ and $$T_{A,S}$$ be the temperatures at the core and surface of the red giant Arcturus, and let $$T_{S,C}$$ and $$T_{S,S}$$ be the temperatures at the core and surface of the white dwarf Sirius B. Which of the following inequalities is true?
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− | (a) $$\frac{T_{{\odot},C}}{T_{{\odot},S}} < \frac{T_{A,C}}{T_{A,S}} < \frac{T_{S,C}}{T_{S,S}}$$
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− | (b) $$\frac{T_{{\odot},C}}{T_{{\odot},S}} < \frac{T_{S,C}}{T_{S,S}} < \frac{T_{A,C}}{T_{A,S}}$$
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− | (c) $$\frac{T_{A,C}}{T_{A,S}} < \frac{T_{{\odot},C}}{T_{{\odot},S}} < \frac{T_{S,C}}{T_{S,S}}$$
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− | (d) $$\frac{T_{S,C}}{T_{S,S}} < \frac{T_{{\odot},C}}{T_{{\odot},S}} < \frac{T_{A,C}}{T_{A,S}}$$
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− | (e) $$\frac{T_{S,C}}{T_{S,S}} < \frac{T_{A,C}}{T_{A,S}} < \frac{T_{{\odot},C}}{T_{{\odot},S}}$$
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− | 12. The spectral line $$H_{\alpha}$$ in the spectrum of a star is recorded as having displacement of $${\Delta}{\lambda} = 0.043 {\times} 10^{-10}$$ m. At rest, the spectral line has a wavelength of $${\lambda}_{0} = 6.536 {\times} 10^{-7}$$ m. Calculate the period of rotation for this star, if it is observed from its equatorial plane. We also know: $$R_{star} = 8 {\times} 10^{5}$$ km.
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− | (a) 29.59 days
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− | (b) 14.63 days
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− | (c) 21.15 days
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− | (d) 34.39 days
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− | 13. The reflector telescope built by Sir Issac Newton was a f{5 telescope and had a primary mirror of diameter 30mm. He used an eyepiece with a focal length of 5mm. What is the focal length and magnification obtained by this telescope?
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− | (a) 150mm, 30ˆ
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− | (b) 300mm, 15ˆ
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− | (c) 300mm, 30ˆ
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− | (d) 150mm, 15ˆ
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