The Ha line of a star is received on Earth at a wavelength of 656 nm. What is the star's radial velocity relative to Earth?

The spectra of most galaxies show redshifts. This means that their spectral lines
(a) always are in the red part of the visible spectrum.
(b) have wavelengths that are longer than normal.
(c) have a higher intensity in the red part of the spectrum.
(d) have wavelengths that are shorter than normal.

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

A) New telescopes incorporate new technology to increase their efficiency.

B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths.

C) Photons of different energy behave differently and require different collection strategies.

D) Light pollution is worse at radio wavelengths than visible wavelengths.

E) Astronomers and engineers enjoy the challenge of making new telescope designs.

Which of the following statements about the celestial sphere is not true?

a. The celestial sphere does not exist physically.
b. When we look in the sky, the stars all appear to be located on the celestial sphere.
c. The Earth is placed at the center of the celestial sphere.
d. The "celestial sphere" is another name for our universe.