Astronomy Astronomy Galaxies and the Milky Way 2 — Questions and Answers
Question 1: What will eventually happen when the Milky Way and Andromeda galaxies collide?
- They will merge into a large elliptical galaxy (Correct answer)
- They will pass through each other with no effect
- They will destroy each other's stars in collisions
- One will capture the other as a satellite galaxy
Correct answer: They will merge into a large elliptical galaxy
In approximately 4-5 billion years, the Milky Way and Andromeda will merge to form a large elliptical galaxy, sometimes called 'Milkomeda.'
Question 2: What is a galaxy cluster?
- A gravitationally bound group of hundreds to thousands of galaxies (Correct answer)
- A dense region of stars within a single galaxy
- A cloud of gas and dust that forms galaxies
- A group of spiral galaxies with similar rotation rates
Correct answer: A gravitationally bound group of hundreds to thousands of galaxies
A galaxy cluster is a large, gravitationally bound structure containing hundreds to thousands of galaxies, hot gas, and dark matter.
Question 3: What is the Local Group of galaxies?
- The gravitationally bound group containing the Milky Way and its neighbors (Correct answer)
- All galaxies within 100 million light-years
- The cluster of galaxies nearest to our solar system
- The group of stars orbiting the Milky Way's center
Correct answer: The gravitationally bound group containing the Milky Way and its neighbors
The Local Group is the galaxy group containing the Milky Way, Andromeda, Triangulum, and over 50 smaller galaxies, spanning about 10 million light-years.
Question 4: What causes the spiral arm structure seen in galaxies like the Milky Way?
- Density waves that compress gas and trigger star formation (Correct answer)
- The rotation of the galactic disk ejecting stars outward
- Magnetic fields aligning star orbits
- Dark matter concentrations forming arm-like structures
Correct answer: Density waves that compress gas and trigger star formation
Spiral arms are caused by density waves rotating through the galactic disk, compressing gas and dust to trigger enhanced star formation that illuminates the arms.
Question 5: What is the difference between a Type I and Type II galaxy classification (de Vaucouleurs)?
- This is not the correct classification system; Hubble tuning fork uses elliptical vs spiral vs irregular (Correct answer)
- Type I are spiral and Type II are elliptical
- Type I are barred and Type II are unbarred spirals
- Type I have old stars and Type II have young stars
Correct answer: This is not the correct classification system; Hubble tuning fork uses elliptical vs spiral vs irregular
The Hubble classification system (tuning fork diagram) classifies galaxies as elliptical (E0-E7), lenticular (S0), spiral (Sa-Sd), barred spiral (SBa-SBd), or irregular.
Question 6: What is an active galactic nucleus (AGN)?
- An extremely luminous core powered by a supermassive black hole accreting matter (Correct answer)
- The bright central bulge of stars in an elliptical galaxy
- A young star-forming region at a galaxy's center
- A neutron star remnant at the galaxy center
Correct answer: An extremely luminous core powered by a supermassive black hole accreting matter
An AGN is an extremely luminous galactic core where a supermassive black hole is actively accreting infalling matter, releasing enormous amounts of energy.
Astronomy Astronomy Galaxies and the Milky Way 2
What will eventually happen when the Milky Way and Andromeda galaxies collide?