PCS 181 Midterm: ASTRONOMY TEST 2
Document Summary
Astronomy test #2: the celestial sphere is a representation of the sky around the entire earth, the earth is the center of this sphere. The earth goes around the sun once per year (orbits) Star formation: why do these clouds of gas and dust collapse due to gravity. As they collapse they form together (nuclear fusion) 4h he + energy four hydrogen are fused into a single helium. Energy is released in this process: eventually, clouds of gas become very dense and very hot. The chemical composition of the sun 3 billion years ago was different from what it is now in that it had: more hydrogen. Star brightness: as the sun sets, some stars are visible. These are the first magnitude stars: later, when twilight is over, more stars are visible. These are the second magnitude stars, and so on. Apparent magnitude: how bright something appears to us from.
