Astronomy Lecture Notes on Distance Measurement and Galaxy Dynamics

These flashcards cover key concepts from the lecture notes related to the distance measurement methods in astronomy, Hubble's law, supermassive black holes, and active galactic nuclei.

What is the main method used to measure distances within the Solar System?

Radar and signals from space probes.

What is parallax used for in astronomy?

To find distances to nearby stars by measuring their shift against distant backgrounds.

What are standard candles?

Objects like Cepheid variables used to measure distances to nearby galaxies.

How far can Cepheid variables measure distances?

Up to 30 million parsecs (30 megaparsecs).

What type of supernova is used as a standard candle for measuring larger distances?

Type Ia supernovae, which have well-defined peak luminosities.

What is Hubble's Law?

An observation about the universe that indicates galaxies are moving away from each other, with farther galaxies moving faster.

How does Hubble's Law demonstrate that the universe is isotropic?

Because it applies the same in every direction, indicating uniform expansion.

Why are gravitationally bound galaxies an exception to Hubble's law?

Their gravitational attraction can overcome the expansion of space, causing them to move closer together.

What is the look-back time in astronomy?

The time it takes for light from a distant object to reach us, allowing us to observe the universe at different stages.

What significant discovery was made about quasars in the late 1950s?

They are bright, compact radio sources that correspond to very blue, starlike objects.

What is an active galactic nucleus (AGN)?

A supermassive black hole surrounded by an accretion disk that emits radiation due to gravitational energy conversion.

What causes the emission of different types of radiation from an AGN?

The conversion of gravitational energy into thermal energy as material falls into the black hole.

What relationship exists between a supermassive black hole and the bulge of a galaxy?

The mass of the supermassive black hole is related to the mass of the bulge of its host galaxy.

What triggers the activity of AGNs in galaxies?

The availability of gas and stars being funneled into the accretion disk of the black hole.

What happens to galaxies that interact with each other?

They can be pulled into distorted shapes, which may trigger AGN activity.