ASTR Exam 2 Flashcards

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Questions and Answers

What details might we observe on the surface of a G-type star?

Sun spots

Compare an O-type main sequence star with a K-type main sequence star.

O-type: Blue color, 25,000K temp; K-type: Orange to Red color, 3,500-5,000K temp.

What is the Mass-Luminosity relationship for main sequence stars?

The greater the mass of a main sequence star, the brighter it is.

Which main sequence stars are the bluest? The reddest?

Bluest: O, B, and A; Reddest: K and M. Signup and view all the answers

What is the approximate surface temperature of a G0 type star?

5,000-6,000K Signup and view all the answers

What are the elements and stages of pre-main-sequence stellar evolution?

Protostar, main-sequence star, planetary nebula, white dwarf. Signup and view all the answers

How are Type I Supernovae produced? Type II?

Type I: Star accumulates matter from a neighbor until a runaway nuclear reaction ignites; Type II: Star runs out of nuclear fuel and collapses. Signup and view all the answers

Where were the Carbon, Nitrogen, and Oxygen atoms in your body created?

They were created in the nuclear fusion at the cores of stars and spread into the interstellar medium by supernova explosions. Signup and view all the answers

What are the stages of evolution of very massive stars?

Protostar -> Main Sequence -> Subgiant -> Red Giant -> AGB -> Supernova -> Black Hole or Neutron Star. Signup and view all the answers

What are the end-states of low-mass star evolution? Of high-mass star evolution?

Low-mass: Horizontal Branch -> Pre AGB -> AGB; High-mass: similar stages with additional nucleosynthesis. Signup and view all the answers

What causes the luminosity of a star?

Fusion Signup and view all the answers

What is hydrostatic equilibrium?

Hydrostatic equilibrium is the balance between the inward force of gravity and the pressure within the gas caused by its temperature. Signup and view all the answers

Which stars evolve the most rapidly?

The most massive stars. Signup and view all the answers

What condition keeps a white dwarf from collapsing further?

Degeneracy pressure. Signup and view all the answers

What defines a star on the main sequence?

Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. Signup and view all the answers

Where are elements heavier than Iron created?

In supernovae. Signup and view all the answers

What is a pulsar?

A pulsar is a core of neutrons that emit rapidly varying sources of low-frequency radio waves. Signup and view all the answers

What is a planetary nebula?

Gas ejected from a low-mass star in the final stage of its life. Signup and view all the answers

What stellar property determines the final stages of a star's life?

Mass Signup and view all the answers

What is a white dwarf?

A small very dense star formed when a low-mass star exhausts its central nuclear fuel. Signup and view all the answers

How can we measure a star's surface temperature?

By measuring its color and using filters of different wavelength ranges. Signup and view all the answers

Study Notes

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.

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Description

Prepare for your ASTR Exam 2 with these flashcards covering key concepts such as G-type and O-type stars. Each card presents essential details to help you understand stellar characteristics and comparisons. Test your knowledge on the different types of main sequence stars and other important astronomical phenomena.