Types and Classification of Galaxies

Questions and Answers

What are the three types of galaxies?

Spiral galaxies, Elliptical galaxies, and Irregular galaxies.

How did the Milky Way form?

Galactic bars developed when stellar orbits in spiral galaxy became unstable and deviated from a circular path.

What is the Hubble Classification Scheme?

The grouping of galaxies according to their shape.

What are the three main types of galaxies that Edwin Hubble categorized?

Elliptical, barred spiral and spiral. Signup and view all the answers

What is the difference between barred spiral and spiral galaxies?

Barred spiral has a prominent bar through the nucleus, and the spiral arms emerge from the end of the bar while the spiral doesn't have these characteristics. Signup and view all the answers

What is the name of the diagram that Hubble created to classify the three different galaxies?

The Tuning Fork. Signup and view all the answers

What is the shape and structure of an elliptical galaxy?

It has no arms, or disks, and is in shape of an oval, cigar or circular shape. Signup and view all the answers

What is unique about an irregular galaxy?

They don't have any definite structure. Signup and view all the answers

What galaxy has little or no gas and dust?

The elliptical galaxy. Signup and view all the answers

What is the most popular galaxy in the universe?

The elliptical galaxy. Signup and view all the answers

What is a galaxy cluster?

A group of many different galaxies. Signup and view all the answers

What proved that there were hundreds to thousands of galactic clusters?

The Hubble Deep Field image taken by the Hubble Space Telescope. Signup and view all the answers

What super cluster is the Milky Way part of?

Virgo Super Cluster. Signup and view all the answers

What group is the Milky Way part of?

Local Group. Signup and view all the answers

What does Hubble's Law state?

Galaxies are retreating from the Milky Way and speed that is proportional to distance. Signup and view all the answers

What is the equation to get the recession speed?

Ho x distance. Signup and view all the answers

What is the evidence of the universe expanding?

Red Shift (Further the galaxy=more red shift, greater red shift= faster galaxy is receding). Signup and view all the answers

What is an active galaxy?

They have centers that emit a lot of energy. Signup and view all the answers

What are the jets of energy called that blast out from the black hole?

Quasars. Signup and view all the answers

How do you know when a galaxy is active by looking at the electromagnetic spectrum?

The emission and absorption lines are wider and gradual. Signup and view all the answers

Study Notes

Types of Galaxies

Three main types: Spiral, Elliptical, Irregular.
Spiral galaxies feature rotating disks of stars and gas with distinctive spiral arms.
Elliptical galaxies appear oval or circular and lack spiral arms.
Irregular galaxies have no defined structure.

Formation of the Milky Way

Developed from galactic bars due to instability in stellar orbits within a spiral structure.

Hubble Classification Scheme

Categorizes galaxies based on their shapes and structures.
Edwin Hubble's classification includes Elliptical, Barred Spiral, and Spiral galaxies.

Barred Spiral vs. Spiral Galaxies

Barred spiral galaxies possess a central bar structure from which spiral arms extend, unlike standard spiral galaxies.

Hubble's Tuning Fork Diagram

A visual representation created by Hubble for classifying galaxies into different categories.

Structure of Elliptical Galaxies

Characterized by the absence of spiral arms and disks, often appearing oval or cigar-shaped.
Typically contain little to no gas and dust.

Characteristics of Irregular Galaxies

Lack a fixed shape or structure, making them unique among galaxy types.

Galaxy Clusters

Groups formed by many different galaxies sharing a gravitational bond.

Evidence from Hubble Deep Field

The Hubble Deep Field image demonstrated the existence of hundreds to thousands of galaxy clusters.

Milky Way's Supercluster and Group

The Milky Way is part of the Virgo Super Cluster and belongs to the Local Group.

Hubble's Law

States that galaxies move away from the Milky Way, with their speed directly proportional to their distance.

Recession Speed Calculation

Calculated using the formula: Recession Speed = Hubble's Constant x Distance.

Evidence of Universe Expansion

Redshift observations indicate that the farther a galaxy is, the more it shifts towards red, suggesting increased speed of recession.

Active Galaxies

Defined by their high-energy centers, indicating significant emissions.

Quasars

Jets of energy that project from supermassive black holes at the centers of active galaxies.

Identifying Active Galaxies via Electromagnetic Spectrum

Active galaxies exhibit wider and gradual emission and absorption lines in their electromagnetic spectrum patterns.

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Description

Explore the fascinating world of galaxies through this quiz, which covers the main types: Spiral, Elliptical, and Irregular. Learn about the Hubble classification scheme and the differences between Barred Spiral and standard Spiral galaxies. Test your knowledge on the formation of the Milky Way and Hubble's Tuning Fork diagram.