Galaxy Vocab Flashcards

Questions and Answers

What are the four classes of galaxies according to the Hubble Classification Scheme?

Barred Spirals (correct)

Irregulars (correct)

Spirals (correct)

Ellipticals (correct)

What characterizes spiral galaxies?

Twisted collections of stars and gas, often with beautiful shapes and hot young stars.

What is a barred-spiral galaxy?

A spiral galaxy with a central bar-shaped structure composed of stars.

What is an elliptical galaxy?

A type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. Signup and view all the answers

What is the definition of SBO galaxies?

A type of galaxy intermediate between an elliptical and a spiral galaxy Signup and view all the answers

What are irregular galaxies?

Galaxies that do not have a distinct regular shape. Signup and view all the answers

What are the Magellanic Clouds?

Two irregular dwarf galaxies visible in the Southern Celestial Hemisphere. Signup and view all the answers

What are standard candles in astrophysics?

A class of astrophysical objects with known luminosity due to characteristic qualities. Signup and view all the answers

What does the Tully-Fisher relation describe?

An empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation. Signup and view all the answers

What is the Local Group?

The group of galaxies that includes our galaxy, the Milky Way, with more than 50 galaxies. Signup and view all the answers

What is a galaxy cluster?

A structure consisting of hundreds to thousands of galaxies bound together by gravity. Signup and view all the answers

What does cosmologic redshift refer to?

A phenomenon where electromagnetic radiation from an object undergoes an increase in wavelength. Signup and view all the answers

What is Hubble's constant represented by?

v = H0D Signup and view all the answers

What are active galaxies?

Galaxies that emit up to thousands of times more energy than a normal galaxy. Signup and view all the answers

What are active galactic nuclei?

A compact region at the center of a galaxy with much higher-than-normal luminosity. Signup and view all the answers

What distinguishes Seyfert galaxies?

They are one of the two largest groups of active galaxies, alongside quasars. Signup and view all the answers

What is a galactic nucleus?

A compact region at the center of a galaxy with above-normal luminosity. Signup and view all the answers

What are radio galaxies?

Types of active galactic nuclei that are very luminous at radio wavelengths. Signup and view all the answers

What are radio lobes?

Large structures, hundreds of kilolight-years long. Signup and view all the answers

What is a blazar?

An active galactic nucleus with a relativistic jet. Signup and view all the answers

What are quasars?

An extremely luminous active galactic nucleus with a supermassive black hole. Signup and view all the answers

What is a quasi-stellar object?

An extremely luminous active galactic nucleus. Signup and view all the answers

What is synchrotron radiation?

Electromagnetic radiation emitted when charged particles are accelerated radially. Signup and view all the answers

Study Notes

Galaxy Classification

Edwin Hubble's Classification Scheme categorizes galaxies into four primary types: spirals, barred spirals, ellipticals, and irregulars.
Spiral galaxies feature distinctive winding structures and are predominantly composed of hot young stars; they are the most commonly observed galaxy type.
Barred-spiral galaxies possess a central bar-shaped formation of stars, found in roughly half of all spiral galaxies.

Types of Galaxies

Elliptical galaxies have an ellipsoidal shape and lack significant texture, presenting a smooth and featureless appearance.
Irregular galaxies exhibit no regular shape, differing significantly from spirals and ellipticals.
Lenticular galaxies (S0) are morphologically between elliptical and spiral galaxies, connecting E and S0 types.

Notable Galaxies

The Magellanic Clouds are two irregular dwarf galaxies orbiting the Milky Way, visible in the Southern Hemisphere and part of the Local Group.
Active galaxies emit energy at levels thousands of times greater than typical galaxies, with their centers—active galactic nuclei—showing much higher luminosity than normal stars.

Cosmic Relationships

Standard candles, such as supernovae or variable stars, have known luminosities, making them critical for distance measurements in astrophysics.
The Tully-Fisher relation links a spiral galaxy's mass or intrinsic luminosity with its rotational velocity, allowing for mass estimations based on rotation.

Galactic Structures

The Local Group consists of over 50 galaxies, with the Milky Way being a member.
Galaxy clusters contain hundreds to thousands of galaxies, bound by gravity and typically ranging in mass from 10¹⁴ to 10¹⁵ solar masses.

Cosmic Phenomena

Cosmological redshift describes the increase in wavelength of electromagnetic radiation, signaling the expansion of the universe.
Hubble's constant defines the relationship between the velocity of a galaxy's recession and its distance from us.

Active Galaxy Types

Seyfert galaxies are a prominent group of active galaxies known for high luminosity and are one of the two largest classifications alongside quasars.
Radio galaxies are distinguished by their luminosity at radio wavelengths, attributed to the synchrotron process.
Blazars are a specific type of active galactic nucleus characterized by a relativistic jet directed towards Earth.

High-Energy Astronomical Objects

Quasars are extraordinarily bright active galactic nuclei powered by supermassive black holes, with masses from millions to billions of solar masses surrounded by an accretion disk.
Quasi-stellar objects refer to extremely luminous active galactic nuclei, signaling the early stages of galaxy formation.

Emission Mechanisms

Synchrotron radiation is electromagnetic energy released when charged particles accelerate radially, often seen in active galaxies.

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Description

Test your knowledge of key terms related to galaxies with these flashcards. Learn about the Hubble Classification Scheme and various types of galaxies, including spiral galaxies. These terms are essential for understanding galactic structures and classification.