Classifying Galaxies Flashcards

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Questions and Answers

What is a galaxy?

A collection of billions of stars, dust, and gas all held together by gravity.

In the 1920s, an astronomer named was able to gather pictures of many galaxies.

Edwin Hubble

The letter 'E' meant ____________.

Elliptical galaxies

'S' meant.

Spiral galaxies Signup and view all the answers

SB meant.

Barred Spiral galaxies Signup and view all the answers

For the 'E' or galaxies, he used the amount of flattening or .

Elliptical, Stretching Signup and view all the answers

For the S galaxies, he used how tightly the arms were wound around the bright .

Spiral, Nucleus Signup and view all the answers

For the SB or galaxies, he used to the increased openness of the .

Barred Spiral, Arms Signup and view all the answers

What is the Hubble Tuning Fork Diagram?

Signup and view all the answers

Explain the statement: 'All ellipticals are galaxies, but not all galaxies are elliptical.'

An elliptical is a sub-genre of galaxy, but not all galaxies are elliptical-shaped. Signup and view all the answers

What do you think makes an irregular galaxy irregular?

The lack of a black hole. Signup and view all the answers

What distinguishes one type of spiral galaxy from another?

Size of central bulge and tightness of arms around center. Signup and view all the answers

What does a Sa galaxy look like?

Biggest bulge with very tight arms around center. Signup and view all the answers

Describe some similarities and differences between elliptical galaxies and the halo of our galaxy.

Like the halo of our own Galaxy, ellipticals are made up of mostly old, reddish, low-mass stars. Signup and view all the answers

Describe the contents of the local group.

Local group made of Milky Way, Andromeda, and M33, along with dwarf irregulars and dwarf ellipticals. Signup and view all the answers

What is the Virgo Cluster?

A cluster of 2500 galaxies about 3 Mpc across. Signup and view all the answers

What is a normal galaxy?

A galaxy that emits visible light radiation. Signup and view all the answers

What is an active galaxy?

A galaxy that emits more radiation: infrared and radio. Signup and view all the answers

S0 galaxy is also known as _____.

Lenticular Signup and view all the answers

Describe a lenticular galaxy.

Has disk and bulge but no spiral arms. Signup and view all the answers

Describe an elliptical galaxy.

No disk or arms. Signup and view all the answers

Describe the formation of a peculiar galaxy.

Might have been a spiral galaxy but merged with another. Signup and view all the answers

What do irregular galaxies look like?

Nebulas. Signup and view all the answers

What happens when a small spiral galaxy and a large spiral galaxy merge?

They make a larger spiral galaxy. Signup and view all the answers

What happens when two large spiral galaxies of comparable size merge?

They make a large elliptical galaxy. Signup and view all the answers

What happens when a large elliptical and a small elliptical merge?

They make a large spiral and small elliptical. Signup and view all the answers

What happens when a small elliptical and a large spiral merge?

They make a larger spiral. Signup and view all the answers

What is the nearest cluster to us?

Virgo. Signup and view all the answers

What evidence is there for dark matter in galaxies?

Even rotational rates from the center of the galaxy to the outer edge. Signup and view all the answers

What is the nearest galaxy?

Andromeda. Signup and view all the answers

Study Notes

Galaxies Overview

A galaxy consists of billions of stars, gas, and dust bound by gravity.
Galaxies vary significantly in size, shape, and appearance throughout the universe.

Edwin Hubble's Contribution

Edwin Hubble classified galaxies by shape in the 1920s, emphasizing visual characteristics.
Galaxies can be categorized into different types based on their shapes and structural features.

Types of Galaxies

Elliptical Galaxies (E): Indicated by the letter "E" and classified from E0 to E7 based on flattening and stretching.
Spiral Galaxies (S): Recognized by how tightly their arms wrap around the nucleus, classified as Sa, Sb, or Sc from tightly to loosely wound.
Barred Spiral Galaxies (SB): Similar to spiral galaxies but with a bar structure; categorized as SBa, SBb, or SBc based on the openness of the arms.

Hubble Tuning Fork Diagram

Hubble created the Tuning Fork Diagram, showcasing galaxy classifications visually, where most galaxies fit into distinct categories.

Characteristics of Galaxies

Not all galaxies are elliptical; elliptical galaxies are merely one type among many within the broader galaxy classification.
Irregular galaxies lack a blackhole, distinguishing them from other types.
Variations in spiral galaxies are characterized by the size of their central bulge and the tightness of their arms.

Distinctions Among Spiral Galaxies

Sa Galaxies: Feature a large central bulge and tightly wound arms.
Sc Galaxies: Exhibit a smaller bulge with very loose arms.

Elliptical Galaxies vs. Galactic Halo

Elliptical galaxies resemble the Milky Way's halo, containing mostly old, low-mass, reddish stars and disordered star orbits with limited rotation.
Elliptical galaxies, unlike the halo, have significant amounts of very hot interstellar gas.

Local Group and Virgo Cluster

The Local Group includes the Milky Way, Andromeda, M33, and various dwarf galaxies, spanning approximately 1 Mpc in diameter.
The Virgo Cluster comprises about 2500 galaxies and measures around 3 Mpc across.

Galaxy Emission Types

Normal Galaxies: Emit visible light radiation.
Active Galaxies: Emit higher levels of radiation, including infrared and radio frequencies.

Other Galaxy Types

Lenticular (S0) Galaxies: Feature a disk and bulge but lack spiral arms.
Peculiar Galaxies: May originate from spirals that merged with others, altering their structure.
Irregular Galaxies: Resemble nebulas in appearance.

Mergers and Galaxy Formation

Mergers between small and large spiral galaxies yield larger spiral galaxies.
Two large spiral galaxies combine to form a large elliptical galaxy.
A mix of large and small elliptical galaxies can result in either large spirals or other structures depending on the sizes involved.

Clusters and Dark Matter

The nearest galaxy cluster to Earth is the Virgo Cluster, which holds significant cosmic importance.
Evidence for dark matter in galaxies is found in the consistent rotational rates maintained from the center out to the edges of galaxies.
The nearest galaxy to Earth is Andromeda.

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Description

Test your knowledge on the classification of galaxies with these flashcards. Learn about the definitions, characteristics, and historical figures involved in astronomy. This quiz will enhance your understanding of the vastness and variety of galaxies in the universe.