Shared Flashcard Set

Details

Final: Astro 101
for the final
64
Astronomy
06/07/2010

Additional Astronomy Flashcards

 


 

Cards

Term
In the asteroid impact theory of the extinction of the dinosaurs some 65 million years ago, the dinosaurs (and over half of all the other species on the earth at that time) died off largely because
Definition
dust injected into the stratosphere from the impact absorbed visible light from the Sun, causing global temperatures to plummet.
Term
A typical shooting star in a meteor shower is caused by a ________ entering the earth's atmosphere.
Definition
pea-size (or smaller) particle from a comet
Term
Why was the Shoemaker-Levy 9 impact so important to astronomers?
Definition
It dredged up material that gave us our first direct look at Jupiter's interior composition
Term
What part of a comet points most directly away from the Sun?
Definition
the plasma tail
Term
What is a meteorite?
Definition
a fragment of an asteroid from the solar system that has fallen to the earth's surface
Term
Why isn't there a planet where the asteroid belt is located?
Definition
Gravitational tugs from Jupiter prevented material from collecting together to form a planet.
Term
An icy leftover planetesimal orbiting the Sun is
Definition
a comet.
Term
Why aren't small asteroids spherical in shape?
Definition
The strength of gravity on small asteroids is less than the strength of the rock.
Term
Comets with extremely elliptical orbits, like comets Hyakutake and Hale-Bopp,
Definition
come from the Oort cloud.
Term
Which of the following statements about comets and asteroids is true?
Definition
Comets are balls of ice and dust.
Term
The first planets around other Sun-like stars were discovered:
Definition
About a decade ago.
Term
What defines the habitable zone around a star?
Definition
the region around a star where liquid water can exist on planetary surfaces
Term
Stephen J. Gould said evolution is based on two undeniable facts and one inescapable conclusion. Fact 1 is that species produce more offspring then can possible survive (based on the limits of ecosystems). Fact 2 is that offspring posess variations in heretable traits. The inescapable conclusion is:
Definition
All of the above
Term
The analysis of certain Martian rocks on Earth show that they contain
Definition
tantalizing hints of life.
Term
How do we think the "hot Jupiters" around other stars were formed?
Definition
They formed as gas giants beyond the frost line and then migrated inwards.
Term
In the search for extrasolar planets, gravitational tugs can be detected by measuring:
Definition
Red shifting and blue shifting of the star
Term
Why do some scientists think that Jupiter's existence may have been critical for life to evolve on Earth?
Definition
It kicked out many comets from the inner solar system through gravitational encounters, thus ending the heavy bombardment phase of the solar system.
Term
The earliest evidence for life on Earth dates to
Definition
about 3.8 billion years ago.
Term
Extrasolar planets can be detected through:
Definition
Answers 1 and 2 only.
Observing planets directly through images or spectra

Observing gravitational tugs exerted on the star by the orbiting plane
Term
After Mars, the next most likely candidates for life in the solar system are
Definition
the large moons of the jovian planets.
Term
Imagine having a very powerful telescope through which you could vaguely observe an extrasolar planet. Using spectrosopy, which of the following would most strongly suggest the presence of life?
Definition
Molecular oxygen (O2), which only persists in the presence of photosynthesis.
Term
Generally speaking, what is (are) considered necessary for life anywhere in the universe?
Definition
Liquid water

Chemical reaction, sunlight, or some other energy source.

organic molecules or some other source of nutrients that can be used to build cells
Term
Why are hydrothermal vents (black smokers) useful in the study of early life on earth?
Definition
The primary producers of life around these structures use chemosynthesis to obtain energy

They are found on the deep ocean floor, which would have been a location protected from sterilizing uv radiation on the earth's surface

Prokaryotic archaea are living there in modern times, but their genetic material indicates they are evolutionarily ancient
Term
Natural selection:
Definition
assumes some individuals will possess traits that make them live longer

a particular environment cannot support 100% of the offspring that individual organisms produce

organisms best adapted for the conditions of a particular environment will thrive

the individuals that are most successful in a given environment will have at least some offspring with the same traits that made them successful
Term
In 1974, a radio message was sent out from the Arecibo observatory in Puerto Rico. How far has it gotten, approximately?
Definition
just a miniscule fraction of the distance across the Milky Way
Term
On a Hertzsprung-Russell diagram, where would we find stars that have the largest radii?
Definition
upper right
Term
Which of the following characteristics of stars has the greatest range in values?
Definition
luminosity
Term
The overall fusion reaction by which the Sun currently produces energy is
Definition
4 H --> 1 He + energy.
Term
The spectral sequence sorts stars according to
Definition
70 percent hydrogen, 28 percent helium, 2 percent other elements
Term
What observations characterize solar maximum?
Definition
We see many sunspots on the surface of the Sun.
Term
What do we mean when we say that the Sun is in gravitational equilibrium?
Definition
There is a balance within the Sun between the outward push of pressure and the inward pull of gravity.
Term
Why are Cepheid variables so important for measuring distances in astronomy?
Definition
Their luminosity can be inferred from their period.
Term
Suppose you measure the parallax angle for a particular star to be 0.1 arcsecond. The distance to this star is:
Definition
10 parsecs.
Term
Which of the following is true about low-mass stars compared to high-mass stars?
Definition
Low-mass stars are cooler and less luminous than high-mass stars.
Term
Since all stars begin their lives with the same basic composition, what characteristic most determines how they will differ?
Definition
Mass they are formed with.
Term
A star's luminosity is the
Definition
total amount of light that the star radiates each second.
Term
At the center of the Sun, fusion converts hydrogen into
Definition
helium, energy, and neutrinos.
Term
Hydrogen fusion in the Sun requires a temperature (in Kelvin) of
Definition
millions of degrees.
Term
Which of the following statements about apparent and absolute magnitudes is true?
Definition
The magnitude system that we use now is based on a system used by the ancient Greeks over 2,000 years ago that classified stars by how bright they appeared.

A star with apparent magnitude 1 is brighter than one with apparent magnitude 2.

A star's absolute magnitude is the apparent magnitude it would have if it were at a distance of 10 parsecs from Earth.

The absolute magnitude of a star is another measure of its luminosity.
Term
From the center outward, which of the following lists the "layers" of the Sun in the correct order?
Definition
core, radiation zone, convection zone, photosphere, chromosphere, corona
Term
Which of the following is closest in size (radius) to a neutron star?
Definition
a city
Term
What types of stars end their lives with supernovae?
Definition
stars that are at least several times the mass of the Sun
Term
What did Carl Sagan mean when he said that we are all "star stuff"?
Definition
that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores
Term
Which of the following is closest in size (radius) to a white dwarf?
Definition
the earth
Term
Which of the following sequences correctly describes the stages of life for a low-mass star?
Definition
protostar, main-sequence, red giant, white dwarf
Term
After a supernova event, what is left behind?
Definition
either a neutron star or a black hole
Term
Compared to the star it evolved from, a red giant is
Definition
cooler and brighter.
Term
From an observational standpoint, what is a pulsar?
Definition
an object that emits flashes of light several times per second or more, with near perfect regularity
Term
When does a star become a main-sequence star?
Definition
when the rate of hydrogen fusion within the star's core is high enough to sustain gravitational equilibrium
Term
Compared to the star it evolved from, a white dwarf is
Definition
hotter and dimmer.
Term
What is the basic definition of a black hole?
Definition
any compact object from which the escape velocity is greater than the speed of light
Term
What do we mean by the singularity of a black hole?
Definition
D) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.
Term
What are the two key observational facts that led to widespread acceptance of the Big Bang model?
Definition
the cosmic background radiation and the high helium content of the universe
Term
What makes up the interstellar medium?
Definition
gas and dust
Term
What kinds of objects lie in the halo of our galaxy?
Definition
globular clusters
Term
What kinds of atomic nuclei formed during the era of nucleosynthesis?
Definition
hydrogen and helium and trace amounts of lithium, beryllium, and boron
Term
What is the diameter of the disk of the Milky Way?
Definition
100,000 light years
Term
Which of the following types of galaxies are most spherical in shape?
Definition
ellipticals
Term
What happened to the quarks that existed freely during the particle era?
Definition
They combined in groups to make protons, neutrons, and their antiparticles.
Term
Why do we expect the cosmic background radiation to be almost, but not quite, the same in all directions?
Definition
The overall structure of the universe is very uniform, but the universe must have contained some regions of higher density in order for galaxies to form.
Term
The disk component of a spiral galaxy includes which of the following parts?
Definition
spiral arms
Term
What is the major difference between an elliptical galaxy and a spiral galaxy?
Definition
An elliptical galaxy lacks a disk component.
Term
Which of the following is true about irregular galaxies?
Definition
They were more common when the universe was younger.
Term
Currently, we have direct experimental evidence on the behavior of matter and energy well enough to describe generally what was happening in the universe ________ after the Big Bang.
Definition
10^ -10 (ten to the minus tenth) second