There are no X-ray telescopes on Earth because:
A) they are too expensive to build.
B) no one has yet invented an X-ray telescope that works.
C) we can't figure out how to direct an X-ray beam through space.
D) X-rays don't penetrate Earth's atmosphere.
E) there are no astronomical objects that emit X-rays.
Question 2
The largest known black holes:
A) create the dark nebulae in the plane of the Milky Way.
B) can be no more than 1.4 solar masses, according to Chandrasekhar.
C) lie in the cores of the most massive galaxies.
D) can be no bigger than a small city, just like neutron stars.
E) can be no bigger than the Earth, like white dwarfs.
Speed of Earth
The Tilt of Earth’s Axis
Reflecting Telescopes
Heaven or earth?
Earth 430 Million Years Ago
Earth 65 Million Years Ago