Astro 150 Trivia - 10/20/2023

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.

• 8 - 25 M_sun

• Neutron Stars

• >25 M_sun

• White Dwarf Stars

• < 8 M_sun

• Black Holes

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