Download document 8902000

Name: ___________________________________ uNID: _______________
Foundations of Astronomy ASTR/PHYS 2500
Midterm 3 *
Physical Constants Gravitational constant Elementary charge Vacuum permittivity Electron Volt Speed of light in vacuum Planck constant Reduced Planck constant Boltzmann constant Stefan-­‐Boltzmann constant Proton mass Electron mass Atomic mass unit Mass of an iron atom Astronomical Constants
G e ε0 eV c h h/2π k σSB mp me u or amu mFe -­‐11
6.673 x 10 -­‐19
1.602 x 10 -­‐12
8.854 x 10 -­‐19
1.602 x 10 8
2.998 x 10 -­‐34
6.626 x 10 -­‐34
1.055 x 10 -­‐23
1.381 x 10 -­‐8
5.670 x 10 -­‐27
1.673 x 10 -­‐31
9.109 x 10 -­‐27
1.6605 x 10 -­‐26
9.2731 x 10 3
-­‐1 -­‐2
m kg s C 2 -­‐1
-­‐1
C J m J -­‐1
m s J s J s -­‐1
J K -­‐1
-­‐2 -­‐4
J s m K kg kg kg kg * Mass of Earth Mass of Sun Mass of Moon Equatorial radius of Earth Mean radius of Earth Equatorial radius of Sun Equatorial radius of Moon Mean density of Earth Mean density of Sun Mean density of Moon Jupiter radius Jupiter mass Luminosity of Sun Effective temperature of Sun Light-­‐year Astronomical Unit Parsec Length of solar day Length of sidereal day Length of a year (Julian) 24
5.974 x 10 30
1.989 x 10 22
7.36 x 10 6378 6371 5
6.955 x 10 1737 5515 1408 3346 10.97 317.8 26
3.839 x 10 5778 12
9.461 x 10 8
1.496 x 10 13
3.086 x 10 24 hours = 86400 seconds 23hours 56 minutes = 86160 s 8
3.15576 x 10 kg kg kg km km km km -­‐3
kg m -­‐3
kg m -­‐3 kg m
Mean Earth radii Mean Earth masses W K km km km s ASTR/PHYS 2500 Final Exam ii
1a. What are “reddening” and “extinction” in observational astronomy? 1b. Explain what the Jeans’ mass is. On what quantities does it depend? 1c. What is meant by the Chandrasekhar limit for white dwarfs? 1d. What length scale characterizes the “size” of a black hole? 1e. List the major components of our Galaxy, the Milky Way.
ASTR/PHYS 2500 Final Exam iii
(L¤)
2. Sketch the evolutionary track of the Sun in the above HR diagram. Label the following items in the diagram and write out the full name of each: ZAMS: _____________________________________________ [Hint: ZA=”zero-­‐age”] RGB: _______________________________________________ He Flash: ____________________________________________ HB: _________________________________________________ AGB: ________________________________________________ [Hint: L rises to ~ 104 L¤ in this phase] PN: _________________________________________________ WD: _________________________________________________ ASTR/PHYS 2500 Final Exam iv
3a. The Hubble Space Telescope detected Cepheid variables as part of its Key Project to accurately determine distances on cosmological scales (Freedman et al. 1994, Nature, 371, 757). Typical values of P (period of pulsation) and m (apparent magnitude) of Cepheids in one galaxy, M100, are P = 50 days and mV = 25. From these values, estimate the distance d to M100. d [Mpc]: ______________ 3b. X-­‐ray absorption lines of ionized oxygen from the surface of a neutron star show a gravitational redshift of Δυ⁄υ = 0.35 (Cottam, Paerels & Mendez, 2002, Nature, 420, 51). Assuming a mass of 2 M¤ for the star, what is its radius r? r [km]: _______ 3c. The rotation curve of spiral galaxy NGC 3198 is shown below (Begeman, 1989, A&A, 223, 47), along with a telescope image of the galaxy (approximately on the same scale as the x-­‐axis in the plot). Estimate the mass M of this galaxy inside of R=30 kpc, assuming a spherical mass distribution. M(R<30 kpc) [M¤]: ____________________