Cosmic Car Crashes: Galaxy Collisions Quiz

  • 12th Grade
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| Questions: 20 | Updated: Feb 16, 2026
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1. Why do individual stars rarely collide during a galaxy merger?

Explanation

Although galaxies contain billions of stars, the space between them is enormous. If a star were the size of a marble, the nearest star would be hundreds of miles away. Consequently, during a collision, the galaxies pass through each other like ghosts; however, their gravitational fields and gas clouds interact violently.

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About This Quiz
Cosmic Car Crashes: Galaxy Collisions Quiz - Quiz

Witness the violent and creative dances of merging star systems. The Galaxy Collisions quiz explores how gravity pulls galaxies together, triggering massive bursts of star formation. Learn about the future fate of the Milky Way and Andromeda as they prepare for their inevitable, multi-billion-year cosmic encounter.

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2. A "starburst" is a period of intense star formation often triggered by a galaxy collision.

Explanation

When galaxies interact, the interstellar gas clouds are compressed by shockwaves and gravitational tidal forces. This compression causes the gas to collapse rapidly, leading to a massive increase in the birth rate of new stars.

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3. Which of the following are common structural features observed in interacting galaxies?

Explanation

As galaxies approach each other, mutual gravity pulls long streamers of stars and gas into space, known as tidal tails. A "bridge" can also form if matter is pulled from one galaxy toward the other. These features are the visual signatures of the gravitational "tug-of-war."

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4. The eventual merger of the Milky Way and Andromeda will likely result in a large ______ galaxy.

Explanation

Computer simulations show that when two large spiral galaxies collide, the organized rotation of their disks is destroyed. The stars eventually settle into a randomized, three-dimensional swarm characteristic of an elliptical galaxy.

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5. What happens to the supermassive black holes at the centers of two merging galaxies?

Explanation

As the galaxies merge, the two central black holes sink toward the new common center due to dynamical friction. They form a binary pair, spiraling closer until they merge into a single, even more massive black hole, releasing gravitational waves.

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6. Galaxy collisions can strip a galaxy of its gas, "killing" its ability to form new stars.

Explanation

In high-speed collisions or when a galaxy falls into a dense cluster, its gas can be "stripped" away by the pressure of the surrounding medium. Once the gas is gone, the galaxy can no longer create new stars and is considered "quenched."

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7. Which factors determine the outcome of a galaxy collision?

Explanation

The dynamics of a merger depend on whether it is a "minor merger" or a "major merger." The speed determines if they merge or simply "fly by," while gas content determines how much star formation the collision will produce.

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8. The process by which a large galaxy absorbs a smaller satellite galaxy is called galactic ______.

Explanation

Galactic cannibalism is common; the Milky Way is currently "eating" several small dwarf galaxies. The smaller systems are torn apart by tidal forces, and their stars are incorporated into the halo or disk of the larger galaxy.

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9. What is "Dynamical Friction" in the context of galaxy interactions?

Explanation

As a massive object moves through a sea of smaller stars, its gravity creates a "wake" behind it. The pull of this wake acts as a drag force, slowing the object down and causing it to sink toward the center of the gravity well.

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10. The "Antennae Galaxies" are a famous example of two spiral galaxies currently merging.

Explanation

The Antennae (NGC 4038/4039) provide a spectacular look at a mid-stage merger. Their long, curved tidal tails resemble the antennae of an insect, helping astronomers verify mathematical models of how gravity reshapes galaxies.

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11. Why do some galaxy collisions result in "ring galaxies" like the Cartwheel Galaxy?

Explanation

If a smaller galaxy passes directly through the center of a larger disk galaxy, it creates a ripple effect. This gravitational wave pushes gas and dust outward in a circle, triggering a ring of intense star formation moving away from the impact site.

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12. Gravitational ______ are ripples in spacetime produced when massive objects like black holes merge.

Explanation

Predicted by Einstein, gravitational waves are ripples in spacetime. As the central black holes of two colliding galaxies spiral together, they emit these waves, carrying away orbital energy until they finally join.

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13. How does a galaxy collision affect the orbits of stars already present in the galaxies?

Explanation

Before a collision, stars in a spiral galaxy move in organized, circular orbits. The chaotic gravitational changes during a merger "scatter" these stars into randomized, three-dimensional paths, which is why mergers often produce puffy elliptical galaxies.

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14. Most of the stars in the universe were likely part of a galaxy interaction at some point.

Explanation

In the early universe, galaxies were closer together and collided much more frequently. This "hierarchical" model suggests large galaxies like ours are built from the pieces of many smaller ones through constant interaction.

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15. What are the primary indicators that a galaxy has undergone a recent merger?

Explanation

Even after a merger is complete, evidence remains. Some elliptical galaxies show "shells" of stars. If the central black holes haven't merged yet, a galaxy might appear to have two distinct centers or "nuclei."

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16. The "Local Group" is currently dominated by the impending merger between the Milky Way and ______.

Explanation

Andromeda (M31) is currently moving toward the Milky Way. In about 4 to 5 billion years, the two will begin a merger that will fundamentally change the structure of both galaxies.

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17. What is the fate of the gas that isn't used up in a starburst during a collision?

Explanation

The intense star formation triggered by a collision leads to many supernovae. The collective energy of these explosions can create a "galactic wind" that pushes remaining gas into intergalactic space, halting further star formation.

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18. Galaxy interactions are responsible for the various shapes seen in the Hubble Sequence.

Explanation

While some shapes are determined at birth, many are the result of environment. Elliptical galaxies are most common in dense clusters where collisions are frequent, suggesting the Hubble Sequence is partly a map of historical interactions.

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19. Which telescopes are best suited to see details of merging galaxies shrouded in dust?

Explanation

Collisions stir up dust that blocks visible light. Infrared telescopes (like JWST) peer through the dust, radio telescopes track cold gas, and X-ray telescopes detect super-heated gas and central black hole activity.

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20. Roughly how long does a "major merger" between two large galaxies take to complete?

Explanation

Galaxy collisions happen on a truly cosmic timescale. Because galaxies are so large and move relatively slowly on that scale, the process from first interaction to final settling into a single galaxy takes a massive amount of time.

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Why do individual stars rarely collide during a galaxy merger?
A "starburst" is a period of intense star formation often triggered by...
Which of the following are common structural features observed in...
The eventual merger of the Milky Way and Andromeda will likely result...
What happens to the supermassive black holes at the centers of two...
Galaxy collisions can strip a galaxy of its gas, "killing" its ability...
Which factors determine the outcome of a galaxy collision?
The process by which a large galaxy absorbs a smaller satellite galaxy...
What is "Dynamical Friction" in the context of galaxy interactions?
The "Antennae Galaxies" are a famous example of two spiral galaxies...
Why do some galaxy collisions result in "ring galaxies" like the...
Gravitational ______ are ripples in spacetime produced when massive...
How does a galaxy collision affect the orbits of stars already present...
Most of the stars in the universe were likely part of a galaxy...
What are the primary indicators that a galaxy has undergone a recent...
The "Local Group" is currently dominated by the impending merger...
What is the fate of the gas that isn't used up in a starburst during a...
Galaxy interactions are responsible for the various shapes seen in the...
Which telescopes are best suited to see details of merging galaxies...
Roughly how long does a "major merger" between two large galaxies take...
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