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WorksheetsAstro 150 Trivia - 10/20/2023
Total questions: 17
Worksheet time: 15mins
Roughly 98% of all main sequence stars in our galaxy have masses _____ and will ultimately become white dwarf stars.
less than 8 solar masses
8 to 25 solar masses
greater than 25 solar masses
Which element(s) are massive (M > 8 Msun) stars able to fuse up to?
Helium
Carbon and Oxygen
Iron
Uranium
How are Neutron Stars formed?
Normal evolution of a sun-like star.
Merging white dwarf stars.
Collapsing stars with masses between 8-25 solar masses.
Collapsing stars with masses above 25 solar masses.
Neutron stars have masses above 1.4 solar masses, yet they are roughly the size of Ames! If there is no nuclear fusion to counteract gravity in these stars, what supports them from collapse?
Nuclear fission
Thermal pressure
Electron degeneracy pressure
Neutron degeneracy pressure
Though because of their small size, neutron stars are not very bright. However some do emit radio pulses with very short intervals (milliseconds), which can be detected with radio telescopes on Earth. What causes these so-called 'pulsars' to pulse?
They are physically pulsating.
Their magnetic field axis and rotation axis are misaligned.
Like the sun, they have star spots and are rotating.
Pulses are caused by transiting planets.
What object is left behind following the explosion of a star more massive than 25 Msun?
White Dwarf Star.
Neutron Star.
Black Hole.
There is no remnant object.
Why don't stars fuse elements heavier than iron?
It takes more energy to fuse iron than you'd get out of fusing iron
No star can be massive enough to get iron to fuse
Stars actually do fuse elements heavier than iron
The pressure it takes to fuse iron actually causes the iron core to collapse before it can start fusing
Match the final evolutionary states with their progenitor star masses.
White Dwarf Stars
< 8 Msun
Neutron Stars
8 - 25 Msun
Black Holes
>25 Msun
Black holes don't emit their own light, so what is one way that astronomers can observe them?
We see stars disappear as black holes swallow them
21 cm emission
Black holes do emit their own light!
Iron Kα Line
How does a black hole produce x-rays?
Hawking radiation
The x-rays are residual energy from when the black hole was still a star
Although black, black holes are hot enough to produce x-rays
Extreme friction between particles in the accretion disk
What would happen to the Earth if you replaced the Sun with a black hole of the same mass?
Earth would spiral into the black hole
Earth would be pushed away from the black hole
Earths orbit would remain unchanged
Earth would be ripped apart to form an accretion disk around the black hole
What's the escape velocity from a black hole?
Depends on the mass
The speed of light
2/3 the speed of light
11.3 km/s
Label the parts of the X-ray Binary.
Accretion Disk
Black Hole
Companion Star
Jet
Rank in order of increasing size (smallest first)
Black hole event horizon, neutron star, white dwarf
White dwarf, black hole event horizon, neutron star
Neutron star, black hole event horizon, white dwarf
Not enough information
Supermassive Black Holes are thought to have formed in the early universe. How do we think that they may have formed?
Collapsing material from a gas cloud
A small black hole devours an entire galaxy
Merging of smaller black holes
Collapsing galactic superclusters
How do we know there is a supermassive black hole at the center of our galaxy? (Hint: See Image)
All the stars in the field move radially towards the center
Some of the stars in the field are orbiting apparently nothing
Some of the stars are periodically swallowed by the central black hole
This image does not provide any evidence to there being a SMBH at the center of our Galaxy
What happens when black holes collide?
A kilo-nova occurs
They don't; black holes that get too close repel each other
They merge and make a larger black hole
They merge and form a new star
