ASP Galaxies and Cosmology

Question 1

What is the Hubble classification system for galaxies?

Accepted Answer

A morphological classification dividing galaxies into ellipticals, spirals, and irregulars

Answer

The Hubble tuning fork diagram classifies galaxies morphologically into ellipticals (E0-E7), lenticulars (S0), spirals (Sa-Sc), barred spirals (SBa-SBc), and irregulars.

Question 2

What is the cosmic microwave background (CMB) radiation?

Accepted Answer

The afterglow of the Big Bang permeating all of space

Answer

The CMB is the thermal radiation left over from the early universe about 380,000 years after the Big Bang, now cooled to approximately 2.73 Kelvin and permeating all of space uniformly.

Question 3

What is Hubble's Law?

Accepted Answer

The relationship showing that galaxies recede from us at a velocity proportional to their distance

Answer

Hubble's Law states that distant galaxies recede from us with velocities proportional to their distances (v = H₀ × d), providing evidence for the expanding universe.

Question 4

What is dark matter?

Accepted Answer

Matter that does not emit or absorb light but exerts gravitational effects

Answer

Dark matter is an unseen form of matter that does not interact electromagnetically (neither emitting nor absorbing light) but whose gravitational effects are evident in galaxy rotation curves and cosmic structure.

Question 5

What is a quasar?

Accepted Answer

An extremely luminous active galactic nucleus powered by a supermassive black hole

Answer

A quasar (quasi-stellar object) is an extremely luminous active galactic nucleus powered by material accreting onto a supermassive black hole, often outshining entire galaxies.

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP - Astronomical Society of the Pacific Exam Practice Test

ASP Galaxies and Cosmology