AS101 ExAm QuEStionS with AnSwErS 100% CorrECt
What are the traits of a neutron star? ✔✔ Its radius would be 10km, the star would be hot,
extremely dense, have high spin, and have strong magnetic fields
What are Cepheid variable stars? ✔✔ Variable stars with pulsation periods of 1 to 60 days and
whose period of variation is related to luminosity
What did Harlow Shapley do? ✔✔ He calibrated Cepheid variable stars to find the distance to
globular clusters, he showed that our galaxy is much larger than the region we can easily see,
and that the sun is not at the centre
Why are Cepheid variable stars the most important variable stars? ✔✔ Because their periods of
variability are related to their absolute luminosity, making them invaluable contributors to
astronomical distance measurement
How long is a Cepheid variable star's period of variability? ✔✔ They range from 1 to 100 days
and are very regular
What does the disk component consist of? ✔✔ All matter confined to the plane of the galaxy
What are spiral arms? ✔✔ Features of the disk component, they extend from the centre to the
edge of the disk of spiral galaxies and are composed of star clusters and gas/dust
Evidence suggests that the spiral arms are irregular and interrupted by branches, gaps, and
spurs
What is the spherical component? ✔✔ The part of the galaxy that includes all matter in a
spherical distribution around its centre
,What is the halo? ✔✔ The spherical region of a spiral galaxy containing a think scattering of
stars, star clusters, and small amounts of gas
What is the central bulge? ✔✔ The dense cloud of stars that surround the centre of our galaxy
How can the mass of the galaxy be found? ✔✔ By studying orbital motions of the stars within
the galaxy
What do astronomers estimate the mass of the Milky Way to be? ✔✔ About 100 billion solar
masses
What does the rising rotation curve indicate? ✔✔ That the halo contains much more mass
What is the dark halo? ✔✔ The low density extension of the halo of our galaxy, believed to be
composed of dark matter
What is dark matter? ✔✔ The nonluminous matter that is detected only by its gravitational
influence, it is a hypothetical form of matter that is thought to account for approximately 85% of
the matter in the universe and about a quarter of its total energy density
What are spiral tracers? ✔✔ Objects used to map the spiral arms
What instruments are used to map the milky way? ✔✔ Infrared and radio telescopes
What was the density wave theory proposed for? ✔✔ To account for the spiral arms as
compressions of the interstellar medium in the disk of the galaxy, in this region of gas cloud
compression, star formation occurs
, What are self sustaining star formations? ✔✔ The process by which the birth of stars
compresses the surrounding gas clouds and triggers the formation of more stars
How old is the disk of our galaxy? ✔✔ At least 9 billion years old as the oldest open clusters
have ages of about 9 to 10 billion years
When did our galaxy begin forming? ✔✔ At least 13 billion years ago since the oldest globular
clusters are a little over 13 billion years old
Which stars are rich in atoms heavier than helium? ✔✔ Population I stars, they are nearly
always relatively young stars found in the disk of the galaxy
Which stars are poor in atoms heavier than helium? ✔✔ Population II stars, they are nearly
always relatively old stars that are found in the halo, globular clusters, or the central bulge
What is the monolithic collapse model? ✔✔ An early hypothesis that states that the galaxy
formed from the collapse of a single large cloud of turbulent gas over 13 billion years ago
Who was John Michell? ✔✔ An English clergy scientist who was the first person to propose the
existence of black holes
He suggested that there might be many dark stars in the universe
According to Newton, what is light made up of? ✔✔ Tiny particles that when emanated from a
star, slow down because of the star's gravitational pull
What are the traits of a neutron star? ✔✔ Its radius would be 10km, the star would be hot,
extremely dense, have high spin, and have strong magnetic fields
What are Cepheid variable stars? ✔✔ Variable stars with pulsation periods of 1 to 60 days and
whose period of variation is related to luminosity
What did Harlow Shapley do? ✔✔ He calibrated Cepheid variable stars to find the distance to
globular clusters, he showed that our galaxy is much larger than the region we can easily see,
and that the sun is not at the centre
Why are Cepheid variable stars the most important variable stars? ✔✔ Because their periods of
variability are related to their absolute luminosity, making them invaluable contributors to
astronomical distance measurement
How long is a Cepheid variable star's period of variability? ✔✔ They range from 1 to 100 days
and are very regular
What does the disk component consist of? ✔✔ All matter confined to the plane of the galaxy
What are spiral arms? ✔✔ Features of the disk component, they extend from the centre to the
edge of the disk of spiral galaxies and are composed of star clusters and gas/dust
Evidence suggests that the spiral arms are irregular and interrupted by branches, gaps, and
spurs
What is the spherical component? ✔✔ The part of the galaxy that includes all matter in a
spherical distribution around its centre
,What is the halo? ✔✔ The spherical region of a spiral galaxy containing a think scattering of
stars, star clusters, and small amounts of gas
What is the central bulge? ✔✔ The dense cloud of stars that surround the centre of our galaxy
How can the mass of the galaxy be found? ✔✔ By studying orbital motions of the stars within
the galaxy
What do astronomers estimate the mass of the Milky Way to be? ✔✔ About 100 billion solar
masses
What does the rising rotation curve indicate? ✔✔ That the halo contains much more mass
What is the dark halo? ✔✔ The low density extension of the halo of our galaxy, believed to be
composed of dark matter
What is dark matter? ✔✔ The nonluminous matter that is detected only by its gravitational
influence, it is a hypothetical form of matter that is thought to account for approximately 85% of
the matter in the universe and about a quarter of its total energy density
What are spiral tracers? ✔✔ Objects used to map the spiral arms
What instruments are used to map the milky way? ✔✔ Infrared and radio telescopes
What was the density wave theory proposed for? ✔✔ To account for the spiral arms as
compressions of the interstellar medium in the disk of the galaxy, in this region of gas cloud
compression, star formation occurs
, What are self sustaining star formations? ✔✔ The process by which the birth of stars
compresses the surrounding gas clouds and triggers the formation of more stars
How old is the disk of our galaxy? ✔✔ At least 9 billion years old as the oldest open clusters
have ages of about 9 to 10 billion years
When did our galaxy begin forming? ✔✔ At least 13 billion years ago since the oldest globular
clusters are a little over 13 billion years old
Which stars are rich in atoms heavier than helium? ✔✔ Population I stars, they are nearly
always relatively young stars found in the disk of the galaxy
Which stars are poor in atoms heavier than helium? ✔✔ Population II stars, they are nearly
always relatively old stars that are found in the halo, globular clusters, or the central bulge
What is the monolithic collapse model? ✔✔ An early hypothesis that states that the galaxy
formed from the collapse of a single large cloud of turbulent gas over 13 billion years ago
Who was John Michell? ✔✔ An English clergy scientist who was the first person to propose the
existence of black holes
He suggested that there might be many dark stars in the universe
According to Newton, what is light made up of? ✔✔ Tiny particles that when emanated from a
star, slow down because of the star's gravitational pull
