Astronomy Unit 4: Galaxies Flashcards

Questions and Answers

Astronomers estimate that 50 billion to 1 trillion galaxies exist within our universe.

True

What are the 4 main parts of a spiral galaxy?

A halo, bulge, dish, and arms

The Milky Way galaxy is home to our Solar System.

True

How do scientists know that dark matter exists?

Gravitational lensing Signup and view all the answers

Edwin Hubble used a telescope and observed fuzzy blobs of light off in the distance; he realized that these lights were what?

Galaxies Signup and view all the answers

Closed clusters are groups of closely grouped stars that are located along the spiral disk of a galaxy.

False Signup and view all the answers

Galaxies are classified by their shape and size into 5 major groups.

False Signup and view all the answers

Accretion is defined as what?

Gravity that pulls matter in a spiraling matter Signup and view all the answers

Which type of galaxy is a spherical cluster of stars with extraordinary brightness and little dust and gas?

Elliptical galaxies Signup and view all the answers

What best describes the black hole status within the Milky Way?

There is a supermassive black hole that is about 15 million miles across Signup and view all the answers

Many galaxies' gravity source is in the form of black holes.

True Signup and view all the answers

Redshifts are what?

Galaxies that are moving farther apart Signup and view all the answers

Black holes have the strongest force of gravity in the universe.

True Signup and view all the answers

A cluster of galaxies containing very few galaxies is known as what?

Poor cluster Signup and view all the answers

A globular cluster is a group of older stars that cluster together.

True Signup and view all the answers

Describe the Milky Way. What does it contain?

The Milky Way is a 13.5 billion-year-old, average-sized, barred spiral galaxy. It contains four main spiral arms (Perseus, Cygnus, Centaurus, Sagittarius) and approximately 500 billion stars. Signup and view all the answers

How are galaxies organized and distributed within the universe?

Galaxies are typically organized into clusters and distributed across the universe. In clusters, galaxies are held together by the force of gravity. If a cluster contains numerous galaxies, then it is a supercluster. The Milky Way is a part of the Local Group cluster which contains more than 50 other galaxies. Signup and view all the answers

How is gravity important to the galaxies within our universe?

Gravity binds everything together; it keeps galaxy clusters intact. Gravity also forms galaxies into different shapes: spiral, elliptical, and irregular. Signup and view all the answers

How do galaxies vary?

Galaxies vary in many ways. They come in different shapes: spiral, elliptical, and irregular. Spiral galaxies look like flying saucers; elliptical galaxies are circular; irregular galaxies do not have a defined shape. Spiral galaxies contain nebulae; elliptical galaxies do not. Spiral galaxies are constantly making new stars, whereas elliptical galaxies do not make new stars. Galaxies also come in different colors. Spiral galaxies are blue; elliptical galaxies are red. Signup and view all the answers

What forces shape the stars in galaxies?

Gravity is what causes stars to form. During accretion, gravity pulls matter into a core, which can be a star, planet, or black hole. Signup and view all the answers

How do galaxies change over time?

Galaxies change as time passes. Young galaxies are not well organized, but eventually become organized into different clusters. Young galaxies are spiral-shaped; older galaxies are elliptical shaped. Additionally, galaxies change colors, from blue to red, as they get older. The color change is because younger galaxies form new stars (giving off ultraviolet and blue light), whereas older galaxies contain old stars (giving off red light) and create fewer new stars. Signup and view all the answers

How are galaxies created?

There are two theories about how galaxies were formed after the Big Bang. According to one theory, gravity pulled gas and dust together to make stars and planets, which were drawn together to create galaxies. According to the second theory, the universe already contained 'clumps' of matter, that gathered together to form galaxies. This second theory is supported by Hubble Space Telescope photographs of 'clumps' which may be developing into new galaxies. Additionally, small galaxies are often consumed up by larger ones, including the Milky Way. Signup and view all the answers

Study Notes

Overview of Galaxies

Estimated existence of 50 billion to 1 trillion galaxies in the universe.
Galaxies are categorized by shape and size with specific classifications.

Structure of Spiral Galaxies

Composed of a halo, bulge, disk, and spiral arms.
The Milky Way is classified as a barred spiral galaxy containing about 500 billion stars and four main spiral arms (Perseus, Cygnus, Centaurus, Sagittarius).

Dark Matter and Gravity

Dark matter is inferred from gravitational lensing phenomena.
Gravity plays a crucial role in maintaining galaxy structure and formation, shaping galaxies into spiral, elliptical, or irregular forms.

Edwin Hubble's Contributions

Hubble identified distant "fuzzy blobs" as galaxies, expanding our understanding of the universe.

Black Holes

The Milky Way houses a supermassive black hole approximately 15 million miles across.
Many galaxies contain black holes as a source of significant gravitational force.

Galaxy Clusters

A 'poor cluster' refers to a cluster with very few galaxies.
Superclusters contain numerous galaxies and are held together by gravity.
The Milky Way is part of the Local Group, consisting of over 50 other galaxies.

Star Formation and Accretion

Accretion refers to the gravitational process where matter spirals inward, potentially forming stars, planets, or black holes.
Stars form through gravitational forces, with newer stars typical of spiral galaxies and older stars prevalent in elliptical galaxies.

Galactic Evolution

Galaxies evolve over time, starting as less organized and developing into structured clusters.
Young spiral galaxies may transition into older elliptical galaxies, with color changes from blue (indicating active star formation) to red (indicating older, less active stars).

Theories of Galaxy Formation

Two primary theories exist regarding galaxy formation post-Big Bang:
- Gravity attracted gas and dust to form galaxies.
- Pre-existing "clumps" of matter coalesced into galaxies, supported by Hubble Space Telescope images showing these clumps.
Smaller galaxies often merge into larger ones, such as the Milky Way.

Galaxy Movement

Redshifts indicate that galaxies are moving farther away from each other, a key observation in understanding the expanding universe.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge of galaxies with these flashcards from Astronomy Unit 4. Learn about the structure of spiral galaxies, the existence of dark matter, and fascinating facts about the Milky Way. Perfect for students reviewing key concepts in astronomy.