2. A spaceship orbits a black hole at a safe distance of 45,000 km. At this distance the escape velocity is 2,000 km/s. The spaceship decides to take a closer look, and approaches to a distance of 5,000 km. What is the escape velocity at this new distance? O 222 km/s QO 667 km/s (O 2,000 km/s @ 6,000 km/s (O 9,000 km/s (O 18,000 km/s 3. Astar with a surface temperature of T=2900K is moving towards us with a radial velocity of 3 x 10 m/s. What is the peak wavelength of its spectrum? (O 900 nm @ 990 nm (O 1000 nm O 1010 nm (O 1100 nm (O not enough information to determine 4. Polaris (the \"North Star\") has a surface temperature of 6000 K, and has a radius of 730,000 km. How much power does each square meter of its surface radiate? @ 7.3x 10" W/m? O 4.9x10* W/m? O 1400 W/m? O 2 W/m? O 1.3x10" W/m? O 49x10W/m