7 Dark Matter and Cosmic Structure Free Online FlashCards

What is dark matter?

Dark matter is matter inferred from its gravitational effects rather than from emitted or reflected light.

What do nearly constant outer galaxy rotation speeds suggest?

Far from many spiral galaxies’ centers, rotation speeds remain roughly constant, suggesting extended halos of unseen mass.

How does gravitational lensing help estimate mass?

Gravity bends light, so astronomers estimate a galaxy’s or cluster’s mass by measuring how it distorts images of more distant objects.

What makes the Bullet Cluster evidence for dark matter?

In the Bullet Cluster, hot gas was slowed and displaced during the collision, while lensing-inferred mass remained concentrated near the galaxies. This supports matter that interacts less with ordinary matter than the gas does.

What do cosmic microwave background patterns support?

Patterns in the cosmic microwave background, relic light from the early universe, fit a universe containing dark matter.

What role does dark matter’s gravity play in models of cosmic structure?

The observed distribution of galaxies and clusters matches models in which dark matter’s gravity helps structure grow over cosmic time.

What does “cold” mean in cold dark matter?

Cold dark matter moved slowly enough for gravity to pull it into clumps as the universe evolved.

How do dark matter halos help ordinary matter gather?

Dark matter halos provide gravitational structures that help attract ordinary matter.

When could gas gather in halos and help form stars and galaxies?

After the universe cooled enough for atoms to form, gas gathered in dark matter halos, allowing stars and galaxies to develop.

How did larger structures form within the cosmic web?

Smaller structures merged over time, building larger galaxies and clusters within a cosmic web of filaments and voids.

How does dark matter differ from dark energy?

Dark matter’s gravity helps matter clump and build structure; dark energy is associated with the accelerated expansion of the universe.

What are WIMPs, and have they been confirmed as dark matter?

WIMPs are hypothetical massive particles that would interact through gravity and only weakly with ordinary matter. No experiment has confirmed them as dark matter.