Podcast
Questions and Answers
What does our galaxy look like?
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?
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?
What is the interstellar medium?
Clouds of interstellar gas and dust that fill the galactic disk.
What is the gas-star-gas cycle?
What is the gas-star-gas cycle?
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What is a bubble in the context of our galaxy?
What is a bubble in the context of our galaxy?
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What are shock fronts?
What are shock fronts?
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What are cosmic rays?
What are cosmic rays?
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What is atomic hydrogen gas?
What is atomic hydrogen gas?
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What are interstellar dust grains?
What are interstellar dust grains?
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What are ionization nebulae?
What are ionization nebulae?
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What are spiral density waves?
What are spiral density waves?
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What is the disk population in our galaxy?
What is the disk population in our galaxy?
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What is the halo population?
What is the halo population?
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What is a protogalactic cloud?
What is a protogalactic cloud?
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How do stars orbit in our galaxy?
How do stars orbit in our galaxy?
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How is gas recycled in our galaxy?
How is gas recycled in our galaxy?
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Where do stars tend to form in our galaxy?
Where do stars tend to form in our galaxy?
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What do halo stars tell us about our galaxy's history?
What do halo stars tell us about our galaxy's history?
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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.
Studying That Suits You
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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.