1) The constellation Canis Major is prominent in the evening sky at 10pm tonight.

a) (8 pts) Draw a simple star chart, name a bright star in Canis Major and give an approximate location (altitude and azimuth) for this constellation at 10pm tonight.

b) (6 pts) The bright star in Canis Major is about 10 times more massive than our own Sun. Explain why we expect this star to have a much shorter lifetime than our Sun (don't answer with an equation ... give an explanation).

2) The parallax technique enables us to use geometry to find the distances to many stars that are relatively close to the Earth.

a) (8 pts) Explain (a simple diagram may help) why the parallax angle is inversely related to distance. As part of your answer, briefly state why we cannot reliably use the parallax method for stars at very great distances.

b) (6 pts) Suppose we find a star for which we lack a comparable "standard candle". This star is close enough, however, to measure its parallax angle. How could we find the absolute luminosity of this target star?

3) Our earliest understanding of the nature of atoms and electrons was facilitated by Ernest Rutherford, who found that atoms consist of a dense nucleus surrounded by a diffuse cloud of relatively light weight electrons.

a) (8 pts) In the space to the right of the diagram below describe Rutherford's experiment that led to this discovery.

b) (6 pts) The diagram below represents the energy levels of a particular atom. The arrows represent possible transitions (where D represents the electron leaving the atom, the process of ionization). Circle the letter next to the arrow that represents the electron in level E=4 emitting the longest possible wavelength of light. No explanation is needed here.

4) In the Sun's corona, gases reach temperatures of millions of degrees or higher. We can track temperatures in the corona by observing which ionization species are present for certain elements.

a) (10 pts) Explain why higher ionization species are associated with higher temperatures.

b) (4 pts) Some of the first Astronomers to survey the corona found patterns of unfamiliar spectral lines that they dubbed "coronium". Name one of the elements that makes up coronium.

5) We explain the Sun's energy generation with the theory of nuclear fusion. Our understanding of nuclear physics also has other applications here on Earth.

a) (6 pts) We use Positron Emission Tomography to help detect cancerous tissue in some patients. Explain how and why a PET scanner can distinguish cancerous tissue from normal tissue.

b) (8 pts) Once energy is generated in the core of the Sun, it travels outward through the envelope. Explain why energy travels differently in the radiative and the convective zone.

6) In the film we viewed, "Where Are the Aliens?", scientist Peter Ward talked about why he feels life similar to life on Earth will be extremely hard to find.

a) (6 pts) Why does Ward think that Earth-like life will be extremely difficult to develop on some other Earth-like planet orbiting a distant star?

b) (8 pts) Some believe in the existence of extraterrestrial life so strongly that it is virtually indistinguishable from an irrefutable belief! Briefly describe the major benefit and the major drawback to systems of thought based on irrefutable beliefs.

7) Telescopes enable Astronomers to gather in light from extremely faint objects, and Astronomers use many different types.

a) (5 pts) Briefly explain why Astronomers tend to prefer reflecting over refracting telescopes.

b) (4 pts) Why do Astronomers use instruments such as cameras and spectroscopes to observe stars rather than observing through an eyepiece with their own eyes?

c) (5 pts) Explain why radio telescopes, despite being hundreds of times larger than most optical telescopes, have worse resolution.

8) Stellar spectra can reveal much about the properties of stars, if properly interpreted. For example, some stars have very weak Hydrogen lines despite having a large abundance of Hydrogen, so relying on line strength to tell us how much Hydrogen is present can be misleading.

a) (8 pts) Name and briefly explain two reasons (related to temperature) why a star with lots of Hydrogen present might have very weak Hydrogen line strength.

b) (3 pts) In the spectral classification system OBAFGKM, developed and interpreted in part by Cecilia Payne, what stellar property is this scheme based on? No explanation needed.

c) (3 pts) In the spectral classification system ABCDEFG, what stellar property is this scheme based on? No explanation needed.