ASTR Exam 2 Flashcards

G-Type Stars

• Surface features include sunspots, which are cooler and darker areas caused by magnetic activity.

Comparison of Main Sequence Stars

• O-type stars: Blue, temperature around 25,000K, characterized by singly ionized helium lines and strong ultraviolet emissions.
• K-type stars: Orange to red, with temperatures between 3,500-5,000K, dominated by metallic lines and weak blue continuum.

Mass-Luminosity Relationship

• Higher mass in main sequence stars correlates with increased brightness.

Color of Main Sequence Stars

• Bluest stars: O, B, and A types.
• Reddest stars: K and M types.

G0 Type Stars

• Approximate surface temperature ranges from 5,000 to 6,000K.

Pre-Main-Sequence Stellar Evolution

• Stages include protostar, main-sequence star, planetary nebula, and white dwarf.

Supernova Types

• Type I: Occurs when a star accrues matter from a companion, leading to a runaway nuclear reaction.
• Type II: Results from a star exhausting its nuclear fuel and collapsing under gravity.

Element Formation

• Carbon, nitrogen, oxygen, and calcium atoms are formed through nuclear fusion in stars, later dispersed by supernovae.

Evolution of Very Massive Stars

• Progression: Protostar → Main Sequence → Subgiant → Red Giant → Asymptotic Giant Branch (AGB) → Supernova → Black Hole or Neutron Star.

End-States of Star Evolution

• Low-mass stars evolve to a horizontal branch with a helium burning core, progressing through a red giant phase and ending as a white dwarf.
• High-mass stars undergo similar stages but with additional nucleosynthesis creating heavier elements before collapsing.

Luminosity Source

• Stars gain luminosity primarily through nuclear fusion processes.

Hydrostatic Equilibrium

• A balance between gravitational force and internal gas pressure maintains stability within a star.

Stellar Evolution Rate

• The most massive stars evolve at the fastest rates.

White Dwarf Stability

• Degeneracy pressure prevents further collapse of a white dwarf.

Main Sequence Definition

• Main sequence stars actively fuse hydrogen into helium in their cores.

Formation of Heavier Elements

• Elements heavier than iron are primarily produced during supernova events.

Pulsars

• Pulsars are rapidly spinning neutron stars, emitting low-frequency radio waves after a supernova explosion.

Planetary Nebula

• A planetary nebula consists of gas expelled from a low-mass star nearing the end of its life, often showing a bipolar shape.

Final Stages Determined by Mass

• The mass of the star is a critical factor in determining its final evolutionary stages.

White Dwarf Characteristics

• A white dwarf is a dense remnant of a low-mass star, roughly planetary sized, that results from the loss of outer layers after nuclear fuel depletion.

Measuring Surface Temperature

• Surface temperature can be gauged by analyzing a star's color using filters at different wavelengths to compare light intensity.

Star Formation

• Stars originate from dense regions within molecular clouds in space.