final exam unit 10 Flashcards
Which of the following correctly explains the 21-cm radio emission produced by our Galaxy?
a.
It is produced from the flipping of the electrons in interstellar Hydrogen atoms, a process which emits photons because the electron’s initial state is higher in energy than its final state
b.
It is produced from the flipping of the electrons in interstellar Carbon atoms, a process which emits photons because the electron’s initial state is higher in energy than its final state
c.
It is produced from the flipping of the electrons in interstellar Carbon atoms, a process which emits photons because the electron’s initial state is lower in energy than its final state
d.
It is produced from the flipping of the electrons in interstellar Hydrogen atoms, a process which emits photons because the electron’s initial state is lower in energy than its final state
a.
It is produced from the flipping of the electrons in interstellar Hydrogen atoms, a process which emits photons because the electron’s initial state is higher in energy than its final state
Why did Einstein add the ‘Cosmological Constant’ to his equation of the Universe?
a.
To allow the Universe to expand at a rate equal to Hubble’s Constant
b.
To prevent the equation from allowing the size of the Universe to change with time
c.
To allow the Universe to expand at an accelerating rate
d.
To account for the microwave radiation left over from the Big Bang
b.
To prevent the equation from allowing the size of the Universe to change with time
According to Einstein’s Theory of General Relativity, if the Universe’s total density is found to be equal to the ‘critical density’ and the Cosmological Constant is zero, what would be the Universe’s fate?
a.
It would gradually stop expanding and freeze in size
b.
It would gradually stop expanding, after which it would contract into another Big Bang
c.
It would expand forever at an accelerating rate
d.
It would expand forever at a constant rate
a.
It would gradually stop expanding and freeze in size
What do maps of the Cosmic Microwave Background give us a picture of?
a.
The distribution of matter 400,000 years after the Big Bang, when matter and light first separated
b.
The distribution of Helium 10-32 seconds after the Big Bang, when nuclear fusion of Hydrogen began
c.
The distribution of matter 10-32 seconds after the Big Bang, when the first Hydrogen atoms formed
d.
The distribution of dark energy 400,000 years after the Big Bang, when matter and energy first separated
e.
The distribution of Hydrogen 10-32 seconds after the Big Bang, when the first Hydrogen atoms formed
a.
The distribution of matter 400,000 years after the Big Bang, when matter and light first separated
What have the distances of extragalactic supernovae revealed?
a.
Hubble’s Constant is currently less than zero, proving that the Universe’s expansion is decelerating
b.
Hubble’s Constant was lower in the past, proving that the Universe’s expansion is accelerating
c.
Hubble’s Constant was higher in the past, proving that the Universe’s expansion is decelerating
d.
Hubble’s Constant is currently greater than zero, proving that the Universe’s expansion is accelerating
e.
Hubble’s Constant has not changed since the Big Bang, proving that the Universe’s expansion is constant
b.
Hubble’s Constant was lower in the past, proving that the Universe’s expansion is accelerating
What was one of the major differences between the radio light Karl Jansky first detected, and the new sources of radio light Grote Reber detected?
a.
Jansky found signatures of pulsars
b.
Reber detected much more compact sources
c.
Janksy focussed only on daytime observations
d.
Reber found bigger sources of radio light
e.
Reber found much more spread out radio light
b.
Reber detected much more compact sources
What did Jansky determine to be the source of the cosmic radio emission he detected, and why?
a.
The Milky Way, since the radio signal was centred on the Sagittarius constellation
b.
The Sun, since the radio signal rose and fell every 24 hours
c.
Radio galaxies, since the radio signals were coming from discrete sources but were far stronger than the emission from individual stars
d.
A spinning neutron star, since the radio emission pulsed at a regular rate
a.
The Milky Way, since the radio signal was centred on the Sagittarius constellation
Dark matter…
a.
has zero gravity and does not emit light at any wavelength
b.
is believed to exist between stars because this would explain why stars have faster rotational speeds than a galaxy’s visible matter can account for
c.
is believed to compose a greater percent of the Universe than dark energy
d.
is not expected to exist in the space between galaxies because this would slow down the galaxies’ recessional motion and possibly cause the Universe to contract
e.
is believed to compose about 5% of all matter in the Universe
b.
is believed to exist between stars because this would explain why stars have faster rotational speeds than a galaxy’s visible matter can account for
Which of the following statements about dark energy is FALSE?
a.
It was first discovered by gravitational lensing
b.
It is believed to comprise approximately 73% of the Universe
c.
It is believed to be the cause of the Universe’s accelerating expansion
d.
It does not emit light at any known wavelength
a.
It was first discovered by gravitational lensing
Which of the following statements about pulsars is FALSE?
a.
When they were first detected, they were suspected to be signals from alien civilizations
b.
All neutron stars are pulsars due to their high rotation speeds
c.
They have beams of radio emission from each of their magnetic poles
d.
When in a strong gravitational field, the time between a pulsar’s pulses will lengthen due to time dilation
b.
All neutron stars are pulsars due to their high rotation speeds
What was the first radio source detected from space?
a.
Interstellar Hydrogen
b.
The Sun
c.
The Moon
d.
Interstellar Dust
e.
The Milky Way
e.
The Milky Way
What did maps of the 21-cm emission in our Galaxy reveal?
a.
Our Galaxy is a spiral galaxy
b.
Our Galaxy is filled with interstellar Carbon
c.
Our Galaxy is filled with dust
d.
Our Galaxy is filled with dark matter
a.
Our Galaxy is a spiral galaxy
The strong source of radio emission seen in the direction of the centre of our Galaxy is believed to be coming from…
a.
a gravitationally-lensed quasar
b.
the accretion disk that has begun to form as a result of the gravitational interaction between the Milky Way and the Andromeda galaxy
c.
a supermassive black hole
d.
collisions of stellar black holes, which are common at the centre of our Galaxy owing to the high density of stars in that region
c.
a supermassive black hole
Which of the following is your most accurate address in the universe?
a.
Earth, Solar System, Milky Way, Local Group, Local Supercluster
b.
Earth, Solar System, Carina Sagittarius Arm, Milky Way, Local Group, Local Super Cluster
c.
Earth, Solar System, Perseus Arm, Milky Way, Local Group, Local Super Cluster
d.
Earth, Orion Arm, Milky Way, Local Group
e.
Earth, Solar System, Orion Arm, Milky Way, Local Group, Local Supercluster
e.
Earth, Solar System, Orion Arm, Milky Way, Local Group, Local Supercluster
Which of the following is NOT a benefit of observing the sky in radio light?
a.
Radio light easily passes through the atmosphere
b.
Radio light can be detected both day and night
c.
Radio light is not affected by interstellar dust
d.
Helps us observe objects at large distances
e.
Radio light carries less energy
f.
Easy to build an observatory, because radio light bounces off most metallic surfaces
e.
Radio light carries less energy
