Three stars are moving away from the observer and their stellar spectra are shown below. 500 nm 600 nm 700 nm 400 nm 600 nm 700 nm 400 nm 500 nm 500 nm 600 nm 700 nm 400 nm 3 Arrange the stars in their velocity from fastest to slowest. Provide a reason for your answer.

Why is it difficult to study our own galaxy? O The sun obscures the view O We are within it and thus cannot see it from the outside O Earth's position is not ideal compared to other planets (within the galaxy) for viewing our galaxy O Parts of it are too far away to see

Whats the wavelength of a photon of light that permits a hydrogen atom to go from its energy level 3 to its energy level 2? 434nm 121.6nm 486.1nm O 656.3nm Whats the wavelength of a photon that could make a hydrogen atom jump from energy level 4 to energy level 2? 656.3nm 121.6nm 102.6nm 486.1nm

A He-Ne laser with wavelength 632.8 nm is fired from a great distance toward a neutron star with mass 4.5 x 1030 kg and radius 12 km. What is the wavelength of light received at the neutron star’s surface?

Please answer in Bold.

The geometry of spacetime in the Universe on large scales is determined by the mean energy density of the matter in the Universe, ρ. The critical density of the Universe is denoted by ρ0 and can be used to define the parameter Ω0 = ρ/ρ0. Describe the geometry of space when: (i) Ω0 < 1; (ii) Ω0 = 1; (iii) Ω0 > 1. Explain how measurements of the angular sizes of the hot- and cold-spots in the CMB projected on the sky can inform us about the geometry of spacetime in our Universe. What do measurements of these angular sizes by the WMAP and PLANCK satellites tell us about the value of Ω0?

A star has an element in its atmosphere that normally emits a line of frequency fs = 7.5 x 10^14 vib/s. If astronomers measure the frequency of this line to be fo = 7.7 x 10^14 vib/s, then how fast are the Earth and this star traveling relative to each other? Remember that the correct equation for the speed v is given by v = [(fo^2 - fs^2) / (fo^2 + fs^2)] c Remember fo^2 means "fo squared."