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AST 248 - Spring 2017
Week 1 Homework Solutions
Ch 1: 4, 5, 10, 13, 14, 17
Ch 3: 4, 35, 61, 63
Ch 12: 25, 26
Chapter 1
4. Extrasolar planets are planets that orbit stars other than our Sun.
Since their discovery, it seems more likely that stars tend to have planets
orbiting them, and that there exists a greater possibility of life on these
planets.
5. A habitable world is one that may or may not have life, but has the
environmental conditions under which life (as we know it) could arise or
survive. This does not necessarily mean that life is present there, but at
least the ingredients and conditions that are needed for even simple life such
as microbes.
10. Put simply, astrobiology is the study of life in the universe. The major
areas of research in the field include the determination of the conditions
conducive to the origin and ongoing existence of life, the search for these
conditions on planets in our and other solar systems, and the search for the
actual occurrence of life other than our own.
13. By a geocentric view of the universe, we mean (a) the ancient idea
that Earth resided at the center of the universe.
14. According to current scientific understanding, life on Earth (b) arose
quite soon after conditions allowed it.
17. If we sent one of our current spacecraft to a nearby star (besides the
Sun), the trip would take about (c) 100,000 years.
Chapter 3
4. A light-year is a unit of distance which equals how far light can travel
in one year, which is approximately 10 trillion kilometers. The distances to
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AST 248 - Spring 2017
other stars are usually measured in terms of light-years, with the nearest star
system (Alpha Centauri) being about 4.4 ly away.
35. According to observations, the overall chemical composition of our solar system and other similar star systems is approximately (a) 98% hydrogen
and helium, 2% all other elements combined.
61.
km
hr
d = 4.4 ly
1 ly = 9.5 × 1012 km
d = 4.18 × 1013 km
d
t=
v
8
t = 8.36 × 10 hr ≈ 9.5 × 104 years
v = 50000
63.
1 Earth-like planet
1 million stars
100 billion stars in the Milky Way Galaxy
1
∗ 1 × 1011
6
1 × 10
= 1 × 105 Earth-like planets in the Milky Way Galaxy
Chapter 12
25. The end result of a calculation with the Drake equation is intended
to be an estimate of (c) the number of worlds in the galaxy on which civilizations are transmitting signals now.
26. Which of the following statements is true about the terms in the
Drake equation? (b) Some of the terms depend on sociology and cannot be
determined by astronomers alone.
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