ASP Galaxies and Cosmology 2 — Questions and Answers
Question 1: What is dark energy?
- Energy released by black holes
- A hypothetical form of energy driving the accelerated expansion of the universe (Correct answer)
- The kinetic energy of dark matter particles
- Radiation from the early universe
Correct answer: A hypothetical form of energy driving the accelerated expansion of the universe
Dark energy is a hypothetical form of energy that permeates all of space and is the leading explanation for the observed accelerating expansion of the universe, comprising about 68% of total energy density.
Question 2: What is the Milky Way galaxy's morphological type?
- Elliptical galaxy
- Irregular galaxy
- Barred spiral galaxy (Correct answer)
- Lenticular galaxy
Correct answer: Barred spiral galaxy
The Milky Way is classified as a barred spiral galaxy (type SBbc), featuring a central bar-shaped structure from which spiral arms emerge.
Question 3: What is the Big Bang theory?
- A theory that the universe has always existed in its current state
- A theory that the universe originated from a hot dense state approximately 13.8 billion years ago and has been expanding since (Correct answer)
- A theory describing how galaxies collide and merge
- A theory explaining how stars explode
Correct answer: A theory that the universe originated from a hot dense state approximately 13.8 billion years ago and has been expanding since
The Big Bang theory states that the universe began approximately 13.8 billion years ago from an extremely hot, dense state and has been expanding and cooling ever since, supported by CMB radiation and Hubble expansion.
Question 4: What is gravitational lensing?
- The bending of light around massive objects due to their gravitational field (Correct answer)
- The magnification of stars by planetary transits
- The focusing of radio waves by stellar winds
- The distortion of spectra by stellar gravity
Correct answer: The bending of light around massive objects due to their gravitational field
Gravitational lensing occurs when a massive object bends the path of light passing near it, as predicted by general relativity, producing magnified, distorted, or multiple images of background objects.
Question 5: What is the observable universe?
- Everything we can see with current telescopes
- The spherical region from which light has had time to reach us since the Big Bang, roughly 46 billion light-years in radius (Correct answer)
- The Milky Way and all nearby galaxies
- The universe within redshift z=1
Correct answer: The spherical region from which light has had time to reach us since the Big Bang, roughly 46 billion light-years in radius
The observable universe is the spherical region centered on Earth from which light has had time to reach us given the age of the universe (~13.8 Gyr), with a current radius of about 46 billion light-years due to cosmic expansion.
Question 6: What is redshift in astronomy?
- When stars turn red as they cool
- The increase in wavelength of light from an object moving away from the observer (Correct answer)
- The reddening of light passing through dust clouds
- A type of spectral line found only in red giant stars
Correct answer: The increase in wavelength of light from an object moving away from the observer
Redshift is the increase in the wavelength (shift toward longer, redder wavelengths) of electromagnetic radiation from a source moving away from the observer, used to measure cosmic distances and expansion.
ASP Galaxies and Cosmology 2
What is dark energy?