Feeding on Neighbors: Galactic Cannibalism Explained Quiz

  • 11th Grade
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1. What does the term "galactic cannibalism" refer to in the context of cosmic evolution?

Explanation

Galactic cannibalism is a primary driver of galaxy growth. According to the Big Bang model, structure forms "bottom-up," where small clumps of matter and dwarf galaxies merge over billions of years to create the massive spiral and elliptical galaxies we see today.

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About This Quiz
Feeding On Neighbors: Galactic Cannibalism Explained Quiz - Quiz

Witness the dramatic process of larger galaxies consuming their smaller neighbors. This Galactic Cannibalism Explained Quiz covers tidal stripping and the formation of stellar streams. Learn how the Milky Way is currently tearing apart the Sagittarius Dwarf Galaxy and what these interactions reveal about the history of galactic growth.

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2. Galactic cannibalism is a rare event that only happened shortly after the Big Bang.

Explanation

Galactic cannibalism is an ongoing process. The Milky Way is currently consuming several small dwarf galaxies, such as the Sagittarius Dwarf Spheroidal. This constant interaction provides evidence for the dynamic, evolving nature of matter distribution in the universe.

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3. What is a "stellar stream" in the context of a galaxy being consumed?

Explanation

As a larger galaxy’s gravity pulls on a dwarf galaxy, it strips away its stars, stretching them into long, thin arches called stellar streams. These streams act as "fossils" that allow astronomers to reconstruct the history of how our galaxy was built.

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4. The process of a galaxy's orbit decaying due to its gravitational interaction with the "dark matter sea" of a larger galaxy is called dynamical __________.

Explanation

As a dwarf galaxy moves through the dark matter halo of a larger galaxy, its gravity creates a "wake" behind it. This wake pulls back on the dwarf galaxy, slowing it down and causing its orbit to spiral inward until it is eventually merged with the host.

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5. Which of the following provide evidence that the Milky Way has "eaten" other galaxies?

Explanation

Astronomers find groups of stars moving together that have different chemical "fingerprints" than the rest of the Milky Way. These "alien" stars are the remains of devoured dwarf galaxies, providing empirical evidence of the galaxy's evolutionary history.

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6. Why do dwarf galaxies lose their gas more easily than large galaxies during a merger?

Explanation

As a dwarf galaxy falls into a larger one, it plows through the hot gas of the host's halo. This "ram pressure" strips away the dwarf's cold gas, stopping all star formation. This explains why most satellite galaxies are "red and dead" (composed only of old stars).

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7. The Milky Way and the Andromeda Galaxy are predicted to undergo a massive merger in the future.

Explanation

In about 4 billion years, the two largest members of the Local Group will collide. This is the ultimate example of galactic interaction, driven by their mutual gravitational attraction overriding the general expansion of the universe.

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8. What role does dark matter play in galactic cannibalism?

Explanation

Dark matter halos are much larger and more massive than the visible parts of galaxies. These massive "dark wells" are what first interact and collide, dragging the visible stars and gas along with them into the merger process.

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9. Astronomers use __________ to measure the "radial velocity" of stars in stellar streams to see how they are moving.

Explanation

By analyzing the Doppler shift in the light from stars within these streams, scientists can calculate their three-dimensional motion. This allows them to map out the "crime scene" of a past galactic merger and calculate the mass of the host galaxy.

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10. How does galactic cannibalism support theories of how matter is organized in the universe?

Explanation

The hierarchical model suggests that large-scale structures were built from the merger of smaller ones. Observing this process provides evidence of how the universe evolved from smooth gas to complex galaxies.

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11. When two galaxies merge, individual stars rarely collide with each other.

Explanation

Galaxies are mostly empty space. While the galaxies themselves collide and change shape due to gravity, the distances between individual stars are so vast that they pass by one another like swarms of bees, rarely ever making physical contact.

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12. What is a "fossil galaxy"?

Explanation

Some dwarf galaxies are "fossils" because they contain the same chemical ratios of hydrogen and helium predicted by Big Bang nucleosynthesis, having avoided the star-birth cycles and mergers that change the composition of larger galaxies.

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13. The __________ force is the uneven gravitational pull that stretches a dwarf galaxy as it approaches a larger host.

Explanation

Tidal forces are responsible for stretching a sphere-shaped dwarf galaxy into a long stellar stream. This is the same physics that causes tides on Earth, but on a massive, galactic scale.

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14. What type of galaxy usually results from the merger of two large spiral galaxies?

Explanation

When two spirals like the Milky Way and Andromeda merge, the organized rotation of their disks is destroyed by gravity, resulting in a randomized, "blob-like" elliptical galaxy with very little gas left for new star formation.

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15. What information can astronomers gain from studying "cannibalized" dwarf galaxies?

Explanation

By observing how the remains of dwarf galaxies are scattered, scientists can "weigh" our galaxy and map the invisible dark matter halo that surrounds us, helping to verify our current models of how the universe is structured.

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16. Which known dwarf galaxy is currently being "eaten" by the Milky Way?

Explanation

The Sagittarius Dwarf is currently passing through the disk of the Milky Way. Its stars are being stripped away, contributing to the "halo" of stars that surrounds our galaxy and providing a real-time look at galactic cannibalism.

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17. Galactic mergers can trigger a "starburst," where new stars form at a very high rate.

Explanation

As galaxies collide, their gas clouds are compressed by gravity and shockwaves. This compression causes the gas to collapse into thousands of new stars at once, creating a "starburst" galaxy that glows brightly in infrared light.

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18. Why is the study of dwarf stars in these galaxies important for understanding the Big Bang?

Explanation

Small dwarf stars can live for over 10 billion years. Because they were born early in the universe's history, their atmospheres contain the original "recipe" of elements (mostly hydrogen and helium) created during the Big Bang.

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19. The __________ Group is the local collection of galaxies where cannibalism and mergers are currently being studied.

Explanation

The Local Group is our home "neighborhood." Studying the interactions between the Milky Way, Andromeda, and their dozens of dwarf satellites allows us to observe the laws of gravity and motion in action on a cosmic scale.

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20. What is the primary evidence used to track a galaxy's merger history?

Explanation

By looking at the "kinematics" (how they move) and "metallicity" (what they are made of) of stars in the outer edges of a galaxy, astronomers can identify distinct groups of stars that were born in a different galaxy and later "cannibalized."

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What does the term "galactic cannibalism" refer to in the...
Galactic cannibalism is a rare event that only happened shortly after...
What is a "stellar stream" in the context of a galaxy being consumed?
The process of a galaxy's orbit decaying due to its gravitational...
Which of the following provide evidence that the Milky Way has "eaten"...
Why do dwarf galaxies lose their gas more easily than large galaxies...
The Milky Way and the Andromeda Galaxy are predicted to undergo a...
What role does dark matter play in galactic cannibalism?
Astronomers use __________ to measure the "radial velocity" of stars...
How does galactic cannibalism support theories of how matter is...
When two galaxies merge, individual stars rarely collide with each...
What is a "fossil galaxy"?
The __________ force is the uneven gravitational pull that stretches a...
What type of galaxy usually results from the merger of two large...
What information can astronomers gain from studying "cannibalized"...
Which known dwarf galaxy is currently being "eaten" by the Milky Way?
Galactic mergers can trigger a "starburst," where new stars form at a...
Why is the study of dwarf stars in these galaxies important for...
The __________ Group is the local collection of galaxies where...
What is the primary evidence used to track a galaxy's merger history?
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