Analyzing cepheid variables in a giant elliptical galaxy m87 determine it's distance. one cepheid, that was somewhat of an outlier, gave a period 72 days, and had an apparent magnitude mv = 24.70
using the more accepted distance of 16.4 mpc:
a) what is the smallest angle resolvable with the event horizon telescope (eht), operating at a wavelength of 1.3 mm if its diameter is that of the earth?
b) what physical size, in au, would barely be resolved at m87's distance?
c) if the resolution limit were the schwarzschild radius, what is the mass of the black hole?

In the image, the arrow is pointing to a celestial object. which attribute disqualifies the object from being a planet?

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?