Ast 105 Chapter 15: Our Galaxy Flashcards

Questions and Answers

What does our galaxy look like?

The Milky Way Galaxy is a spiral galaxy consisting of a thin disk about 100,000 light years in diameter with a central bulge and a spherical halo that surrounds the disk.

What is a spiral galaxy?

Our galaxy, the Milky Way, is a spiral galaxy named because of the spiral arms.

What is the interstellar medium?

Clouds of interstellar gas and dust that fill the galactic disk.

What is the gas-star-gas cycle?

The galactic recycling process which begins with the star's formation. Signup and view all the answers

What is a bubble in the context of our galaxy?

Hot, ionized gas ejected from supernovae or powerful stellar winds that sweeps up interstellar material. Signup and view all the answers

What are shock fronts?

Abrupt, high gas pressure walls that move faster than the speed of sound waves in interstellar space. Signup and view all the answers

What are cosmic rays?

Rays produced by supernovae that may affect life on Earth by causing genetic mutations. Signup and view all the answers

What is atomic hydrogen gas?

Gas that is cool enough that hydrogen atoms remain neutral rather than being ionized. Signup and view all the answers

What are interstellar dust grains?

Tiny, solid flecks of carbon and silicon materials that resemble smoke particles. Signup and view all the answers

What are ionization nebulae?

Colorful, wispy blobs of glowing gas often found near hot stars. Signup and view all the answers

What are spiral density waves?

Disturbances in the spiral pattern of star formation in the gaseous disk of a spiral galaxy. Signup and view all the answers

What is the disk population in our galaxy?

Stars that follow orderly orbital patterns, consisting of both young and old stars with heavy element proportions near 2%. Signup and view all the answers

What is the halo population?

Stars that orbit the galaxy's center with varied inclinations, consisting of old and low-mass stars. Signup and view all the answers

What is a protogalactic cloud?

The beginning of our galaxy, composed of hydrogen and helium. Signup and view all the answers

How do stars orbit in our galaxy?

Stars in the disk all orbit the galactic center in about the same plane and direction. Signup and view all the answers

How is gas recycled in our galaxy?

Stars are born from gas clumps in molecular clouds, explode as supernovae, and recycle gas into new stars. Signup and view all the answers

Where do stars tend to form in our galaxy?

Active star forming regions, primarily in the spiral arms. Signup and view all the answers

What do halo stars tell us about our galaxy's history?

They provide insights into the older, low-mass star population and the galaxy's formation. Signup and view all the answers

Study Notes

Overview of the Milky Way Galaxy

The Milky Way is a spiral galaxy with a diameter of about 100,000 light years.
It consists of a thin disk, a central bulge, and a surrounding spherical halo.
The disk contains an interstellar medium made up of gas and dust, while the halo includes minimal hot gas and no cold gas.

Spiral Galaxy

Characterized by its distinctive spiral arms.

Interstellar Medium

Composed of clouds of gas and dust in the galactic disk.
This medium obscures visibility when observing with visible light.

Gas-Star-Gas Cycle

A cyclical process involving star formation and the recycling of gas emitted from dying stars.

Bubbles

Formed by hot, ionized gas ejected from supernovae and stellar winds.
These bubbles gather interstellar material and are prevalent in the galactic disk but can be difficult to detect.

Shock Fronts

High-pressure gas "walls" moving faster than the speed of sound through interstellar space.

Cosmic Rays

Produced by supernovae, these rays consist of electrons, protons, and atomic nuclei.
They can influence life on Earth by causing genetic mutations.

Atomic Hydrogen Gas

Composed of cool hydrogen atoms that are not ionized, becoming prevalent after gas cools from bubbles.

Interstellar Dust Grains

Tiny particles of carbon and silicon that form in the winds of red giant stars, resembling smoke.

Ionization Nebulae

Also known as emission nebulae (H II regions), these are glowing gas clouds that emit light when electrons in atoms are energized by ultraviolet light from nearby hot stars.

Spiral Density Waves

Disturbances that propagate through the gaseous disk, influencing patterns of star formation.

Disk Population (Population I)

Comprises stars following orderly orbits within the disk, including both young and old stars, with approximately 2% heavy elements relative to the sun.

Halo Population (Population II)

Composed of old, low-mass stars with randomly inclined orbits that cross the disk.
These stars have lower heavy element proportions, as low as 0.02%.

Protogalactic Cloud

The initial stage of galaxy formation made of hydrogen and helium, providing foundational differences between halo and disk stars.

Star Orbits in the Galaxy

Disk stars orbit in a consistent plane and direction, while halo stars have randomly inclined orbits.
Orbital motions provide insight into the mass distribution of the galaxy.

Gas Recycling Process

Begins with star formation from gas clumps in molecular clouds.
Dying massive stars explode as supernovae, forming hot bubbles that mix elements with the interstellar medium to create atomic hydrogen gas.
This gas can cool further to form molecular clouds, leading to new star formation.

Star Formation Locations

Active star-forming regions are mostly located in spiral arms where spiral density waves compress gas clouds to foster star formation.

Halo Stars and Galactic History

The halo contains predominantly old, low-mass stars, which provide clues about the early history and evolution of the galaxy.

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Description

Test your knowledge of the Milky Way Galaxy with these flashcards. This quiz covers the structure and components of our galaxy, including its spiral shape, central bulge, and surrounding halo. Perfect for students of Astronomy 105.