astronomy 123 modules 5-8 summary exam
If our Sun were to become a black hole, the radius of its event horizon would be about:
3 kilometers
Roughly what percent of the mass and energy contents of the universe is made up of ordinary (atomic) matter?
5%
Why did Einstein introduce the cosmological constant into the equations of his General Theory of Relativity when describing the universe?
Einstein's equations required the universe to expand or contract; he could not imagine or accept it doing either one, so he put a factor in to stop it from moving
Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:
a distortion in spacetime caused by the gravity of the Sun
The object(s) created by the merger of two black holes is:
a single black hole with mass slightly lower than the sum of the merging ones
Factoring in everything we currently know about the history of the universe, our best estimate for the age of the universe is:
about 13.8 billion years
When laser beams in an interferometer combine,
an interference pattern of bright and dark light is formed
When laser beams in an interferometer combine:
an interference pattern of bright and dark light is formed
General Relativity predicts that light passing near a massive object like the sun will:
appear bent when observed from Earth
After traveling 140 million light years from the 170817 neutron star merger, gravitational waves and gamma rays:
arrived at earth at almost exactly the same time
The gravitational wave signal from merging black holes is called a "chirp" because:
as the black holes get closer, the signal frequency and amplitude increase
The three observational pillars of cosmology are the expanding universe, the cosmic microwave background, and:
big bang nucleosynthesis
According to the General Relativity, the presence of mass:
causes a curvature (or warping) of spacetime
According to the general theory of relativity, the presence of mass:
causes a curvature (or warping) of spacetime
If the universe consisted only of matter and its density were equal to critical, the universe would:
continue expanding, eventually slowing down to zero
When the age of the universe was about 10 seconds, it had cooled sufficiently for neutrons and protons to bind together and form the key nuclear species which allows production of helium to proceed. This key nucleus is called:
deuterium
Current measurements of the Hubble constant H0:
disagree depending on the method used
Where in space did the expansion of the universe begin?
everywhere at once
Based on cosmic microwave background (CMB) data, astronomers now conclude that the average density of the universe is:
exactly equal to the critical density
What do the surveys of the three-dimensional distribution of groups of galaxies reveal about how groups and clusters of galaxies are organized?
galaxy groups are organized into huge filaments with great voids between them
What is a key reason that gravitational waves are so much harder to detect than electromagnetic waves?
gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect
According to the Cosmological Principle, the universe:
is isotropic and homogeneous over large distances
After a star collapses to form a black hole, the only information we can measure is:
its mass and spin
Which of the following does NOT happen when two galaxies collide?
many of the stars in one galaxy collide with the stars in the other
To predict whether a star will ultimately become a black hole, what is the key property of the star we should look at?
mass
A gravitational lens is formed by:
mass between the source and earth
Special relativity gives a "speed limit", meaning that:
objects cannot move faster than the speed of light
Spacetime effects like time dilation are only noticeable when:
objects move close to the speed of light
Merging black holes can be observed
only by their gravitational wave emission
Protons and neutrons are composed of other more elementary particles known as:
quarks
Galaxies that we see as they were 11 billion years ago or more, as compared to galaxies today, are generally:
redder and smaller
Which of the following did NOT happen during the first few minutes after the Big Bang?
some very massive early stars formed
When astronauts aboard the International Space Station (ISS) in space let go of an orange, it just floats there. Why is that?
the ISS is falling around the Earth, and in free fall, things feel no weight
How do astronomers currently think the amount of detectable (observable) matter in the universe compares to the amount of dark matter?
the amount of detectable matter is about 1/5th the amount of dark matter
The three observational pillars of cosmology are the expanding universe, big bang nucleosynthesis, and:
the cosmic microwave background
The region around a black hole where everything is trapped, and nothing can get out to interact with the rest of the universe, is called:
the event horizon
The region around a black hole where everything is trapped, and nothing can get out:
the event horizon
The redshift observed in the light emitted by distant galaxies is due to:
the expansion of space
With enormous effort, a team of astronomers manages to collect enough light from a galaxy far, far away to produce a spectrum. That spectrum has lines from the elements carbon, silicon, and sulfur. This tells the team that:
the galaxy must have had an entire generation of stars that was born, lived, and died
A student shines a flashlight out the window of a very fast rocket. If the normal speed of light is c, then:
the light always travels at speed c
Recent observations indicate that the universe is expanding faster today than it was a few billion years ago (that, in other words, the expansion of the universe is accelerating.) What kind of observations have led astronomers to this surprising conclusion?
the measurement of galaxy distances using Type Ia supernovae
In the first direct detection of gravitational waves by LIGO in 2015, the waves came from:
the merger of two black holes
The first time that astronomers observed both gravitational waves and electromagnetic waves from the same event, what they were observing was:
the merger of two neutron stars
Observations of the spectra of the afterglow of the binary neutron star merger revealed:
the presence of newly created heavy elements
The speed that gravitational waves travel is:
the speed of light
The main postulate of special relativity is that:
the speed of light is an absolute constant
In the observation of galaxies, astronomers refer to look-back time, which means:
the time it took for the observed light from a galaxy to reach us
What happened when the age of the universe was 380,000 years which allows us to observe the cosmic microwave background?
the universe cooled sufficiently to allow neutral hydrogen to form
The reason nucleosynthesis stopped when the age of the universe was about 3 minutes was because:
the universe was cooling too fast to produce elements beyond helium
According to General Relativity, in a freely falling reference frame, light:
travels in a straight line
In the 2015 gravitational wave discovery event, the two black holes:
were each about 30 solar masses
