star clusters is the youngest
a cluster whose brightest main sequence stars are blue
Star clusters are useful to stellar astronomers because the clusters contain stars that
are all about the same age and distance
Compared to the stars in galactic clusters, globular clusters are more
likely to be ___.
older and have weaker metallic lines in their spectra
How would a flashing yellow light appear as it fell toward a black hole?
The flashes would gradually become redder.
A black hole is best defined as
any object which is smaller than its event horizon
The most important feature of binary stars is that they enable us to determine which stellar property?
Which of the following does not change during the course of a Cepheid
a star that changes from bright to dim in a pattern
That a variation in brightness of a star is observed means that ____.
the amount of energy emitted by the star varies with time
Which of these forms of radiation passes most easily through our galaxy, the Milky Way?
Planetary nebulae generally have ___ spectra because they are regions
of ___ gas.
If the sun were surrounded by a large gas and dust cloud, the cloud
would appear as a(n) _____.
emission nebula 100%
Which of the following objects would be best for estimating the distance to far-off galaxy?
a luminous OB star or supernova
How many basic types of galaxies do we observe in the Universe if we restrict ourselves to the very dominant types?
Which type of object will not be concentrated in the plane of the Milky Way?
globular star clusters
The evidence for dark matter includes
galaxies rotating faster than they should based on the matter we see
Which of these galaxies is most likely to be the oldest
a galaxy in our Local Group
When the blue light from hot O stars in very distant galaxies reaches us, it arrives at Earth in the form of
how does the habitable zone around a star of spectral type G compare to that around a star of spectral type M?
it is larger
In the Drake equation, suppose that the term f_life = 0.5. What does this mean?
half of the habitable worlds actually have life and the other half do not
Nearly all of the extrasolar planets discovered to date are most likely
Which of the following has the shortest life?
A. an isolated 8 solar mass star
B.a 1 solar mass star
C. a 1 solar mass white dwarf
What happens to the core of a high-mass star after it runs short on hydrogen?
It shrinks and heats up
As a one solar mass star evolves into a red giant, its
luminosity increases while the surface temperature decreases.
The phenomenon of global warming is attributable to
an increase of gases in the atmosphere of the earth that block radiation from escaping
Which of the following layers in the sun is the coolest?
Why do sunspots appear darker than their surroundings?
they are cooler than their surroundings
As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________.
Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case?
A. Only Mercury would be in the Sun's habitable zone.
B. Mercury and Venus would be in the Sun's habitable zone, but Earth and Mars would not.
C. Mercury, Venus, and Earth would be in the Sun's habitable zone, but Mars would not.
D. All the terrestrial planets would be in the Sun's habitable zone.
Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?
The expected lifetime of a massive star is too short to allow for the evolution of complex life
The idea that life evolves through time was first suggested in ancient Greece, and it was favored by at least some scientists of the 18th and 19th centuries even before Charles Darwin proposed the theory of evolution. What is the key observational evidence that supports the idea that life on Earth has evolved through time?
The fossil record, revealed in geological layers of different ages, shows that life on Earth has become more complex over time
Given that the fossil record provides the key evidence for evolution, what is the importance of Darwin's theory of evolution?
It represents our understanding of the process by which evolution occurs.
The first of the two "undeniable facts" is that any localized population of a species has the potential to produce far more offspring than the local environment can support. This fact is important to understanding evolution because it means that __________.
there is competition for survival among the individuals of the population
The second of the two "undeniable facts" is that individuals in a population of any species vary in many heritable traits (traits passed from parents to offspring), so that no two individuals are exactly alike. This fact is important to understanding evolution because it means that __________.
some individuals possess traits that make them better able than others to compete for food and other resources
The two facts from Parts C and D lead to the "inescapable conclusion" that individuals in a population will have unequal reproductive success, so that those whose traits best enable them to survive will leave more offspring. Therefore, in any local environment, over time, __________.
heritable traits that enhance survival will become progressively more common in succeeding generations
All stars in an open cluster are approximately the same age. T or F
Cluster ages can be determined from
main sequence turnoff
When an atom absorbs a photon containing energy, any of the following can happen except which?
An electron moves from an upper energy level to a lower one