Astronomy Final Exam: Chapters 13, 14, & 15 Flashcards
What are the two processes where fusion can take place?
Proton-proton chains & carbon-nitrogen-oxygen (CNO) cycle
A more massive star has what type of lifetime?
Shorter lifetime because nuclear fuel burns quicker
What is the Chandrasekhar Limit?
The maximum mass of a stable white dwarf
How many white dwarfs are out there?
8
What is the energy source of a white dwarf?
Thermal energy
What is a white dwarf?
- dense low massive object with no nuclear fuel in core
-Bigger than Earth but half as massive as the Sun
What is a planetary nebulae?
The region of cosmic gas & dust formed from the cast-off outer layers of a dying star
What is a supernova?
A colossal explosion of a star
What do supernova form?
Forms other stars due to shock wave of death collecting gas & dust
How often does a supernova happen?
3x a century
What are the types of supernovas?
Type II & Type Ia
How do Type II Supernova form?
Rapid collapse & violent explosion of a massive star
How do Type Ia Supernova form?
Binary system collision with one of the stars being a white dwarf
What is a nova?
An explosion from the surface of a white-dwarf star in a binary star system
When does a nova occur?
When a white dwarf “steals” gas from a companion star
What are event horizons?
The opening of a black hole where an observer would see time stopping & light is unable to escape
What is the Schwarzschild Radius?
The radius below which the gravitational attraction between the particles of a body must cause it to undergo irreversible gravitational collapse
How massive are black holes?
3-10 solar masses
What is a black hole?
A region of spacetime where gravity is so strong that nothing, including light or electromagnetic waves, have enough energy to escape its event horizon
What are neutron stars?
When a massive star runs out of fuel & collapses
What are pulsars?
Highly magnetized rotating neutron stars that emit beams of electromagnetic radiation out of its magnetic poles
What is the mass of neutron stars?
1.35 x the Sun’s mass usually
What is neutron degeneracy pressure?
A pressure exerted by dense material consisting of fermions (like electrons in white dwarfs)
What happens to neutron star pairs when they meet?
Merger leads to the formation of a more massive neutron star or a black hole
Can the Sun ever become a black hole?
No, it would need to be 20x more massive
What is an isolated black hole?
A black hole that traps light due to intense gravitational field & cannot be seen directly
What are accretion disks?
A disk-like flow of gas, plasma, dust, or particles around any object in which what’s orbiting in the gravitational field of the object loses energy & angular momentum as it slowly spirals inward
What are globular clusters?
Conglomeration of stars
Where are globular clusters located?
Galaxy’s halo
Why are globular clusters important?
Estimate the age of the Universe
What does the Galaxy’s disk include?
Spiral arms
What happens in the spiral arms?
Sites of ongoing star formation
OB stars are good tracers because of why?
Their short lifetimes tell astronomers where recent stars were formed
What is the Galaxy’s disk mostly made of?
gas & dust
Where is the Supermassive Black Hole?
The Galactic Center of the Milky Way
How was the Supermassive Black Hole discovered?
Radio telescopes discovered a dim speck
How many solar masses is the Supermassive Black Hole?
4.154 +- 0.014 million solar masses
What were the first stars?
Population II
What were the first stars composed of?
Hydrogen & helium
What is a cepheid variable star?
A variable star that pulses radically, varying in diameter & temperature
What do cepheid variable stars measure?
Interstellar & intergalactic distances
What is dark matter?
Nonluminous material that is postulated to exist in space (theorized to make approx. 85% of matter)
What is the Milky Way Galaxy?
Galaxy that is includes our solar system
How massive is the Milky Way Galaxy?
1.5 trillion solar masses
