The total mass of the pair of stars in spectroscopic binaries are difficult to estimate because
a. we can't measure the radial velocities of each star in the system.
b. we can't see the shape or tilt of the orbit.
c. we can't find the diameters of the stars.
d. we can't determine the luminosities of the stars.
e. the Doppler shift is not measurable.
Question 2
The optical shape of segmented mirrors is controlled by computer-driven thrusters under the mirrors in what is called
a. an achromatic lens.
b. active optics.
c. a Schmidt-Cassegrain design.
d. a Newtonian design.
e. interferometry.
The reflection nebula NGC 1999 is brilliantly illuminated by V380 Orionis (center), a variable star
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