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SYRACUSE / Astronomy / ASTR 104 / What are the major components of a galaxy?

What are the major components of a galaxy?

What are the major components of a galaxy?

Description

School: Syracuse University
Department: Astronomy
Course: Stars, Galaxies & Universe
Professor: Saulson
Term: Spring 2019
Tags: astronomy
Cost: 25
Name: AST 104 Exam 3 Study Guide
Description: enjoy :)
Uploaded: 04/07/2019
4 Pages 23 Views 12 Unlocks
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Study Guide © Alyeska Dronsfield 2019. For personal use only, not for redistribution. Study Guide for Exam 3


What are the major components of a galaxy?



What was Harlow Shapley’s conclusion about the distribution of stars in the Milky Way and  the Sun’s place in it? What observations led him to reach this conclusion?  Shapley, by measuring and mapping out globular clusters as well as Cepheid stars, was able to  determine the approximate layout of the Milky Way galaxy and our solar system's position in it. He  found Cepheid stars in each nearby cluster or assumed the brightness of a hypothetical one where none  were found, and used the inverse-square law to find distances.  

(If that sounds confusing af it's because it is lol)

What are the major components of a galaxy?  

Spiral galaxy: flat, white disks with yellowish bulge at center. Spiral "arms" extend out. Cool gas and  dust.

Elliptical galaxies: redder, rounder, longer in one direction. Hot ionized gas.


What is a “standard candle” in astronomy?



Irregular galaxies: neither disk-like nor rounded.

Where do younger, hot, blue stars occur?

Spiral galaxies

Where is the majority of the gas and dust in a spiral galaxy found?  

The disk

Where are open and globular star clusters found?  

Open found in disk, globular found in bulge and halo.

How do elliptical galaxies differ from spiral galaxies?  

Elliptical galaxies have only a spheroidial component and lack a significant disk component.

What are the major classes of galaxies and what are their distinguishing characteristics?  Elliptical galaxies:

E0

E5

E7

etc

Lower numbers have a rounder appearance.


How does hubble’s law relate to the distance and recession velocity of galaxies?



Spiral galaxies:

S0 If you want to learn more check out What makes good traits for candidates?

Sa

Sb

Sc

SB0

SBa

SBb

SBc

Sa & SBa galaxies have a larger buldge, less dusty gas, and tighter spiral arms. This decreases as the  letters descend from b to c, etc. We also discuss several other topics like B-cells make antibodies (ab) also called what?

S0 & SB0 galaxies are lenticular galaxies.  

Irregular galaxies:

Irr

What is a “standard candle” in astronomy?

A light source of a known, standard luminosity. An astronomical object that we have some way of  knowing its true luminosity without measuring apparent brightness and distance.  

What are some examples discussed in lecture?

Street lamps, for on-Earth. Main-sequence stars with spectral type G2 have about the same luminosity  as the sun, so we can use those to determine distances.

How large is the Milky Way galaxy?  

100,00 light years in diameter, 1,000 light years thick.

What type of galaxy is it and where are various components located?  Don't forget about the age old question of Mass disasters means what?

It's a spiral galaxy. Halo is outside the disk. The disk is the dense "swirling" part. The bluge is the bright  circle in the middle. The spiral arms are the pieces of the spiral that spread out into the halo on the  edges of the disk.

Where is the Sun located in the Milky Way?

The Sun is about halfway between the bulge and the edge of the disk. This tends to be where yellowish  stars like ours hang out, the "disk population."

Where is the Milky Way located in the universe?  

The Milky Way galaxy is in the Local Group, which resides just on the edge of the Virgo Supercluster.

To what collections of galaxies does the Milky Way belong?  

The Milky Way is in the Local Group.

What is the Doppler shift phenomenon?  

Doppler shift is how wavelengths change relative to the direction they are going toward or away from an  object.  

What does this phenomenon do to light?  

The Doppler shift changes the "tint" of light emitted by an object to either be redder or bluer.  Don't forget about the age old question of What are some key characteristics of human developmen?

How can we measure a Doppler shift, and what does it tell us about the motion of the light  source?

We can measure doppler shift by comparing the visible light spectra of a certain light source or gas with  a standard candle. Whichever way the absorption lines shift, either more toward the red side of the  spectra, or more toward the blue side, we can determine if redshift or blueshift occurred. Don't forget about the age old question of How can we test the role of parasites in the fitness of cliff swallows?

What contributions did Vesto Slipher and Edwin Hubble make to our understanding of the  distribution and motion of galaxies in the universe?  

Hubble, building on Slipher's work of recording the redshifts associated with many galaxies, determined  that all galaxies are moving away from us.

How are absorption lines used to understand the radial motion of galaxies toward or away  from us?

Absorption lines, when juxtaposed with a standard candle or "resting" spectrum, either move toward  the red side of the spectrum (700 nm) or to the blue side of the spectrum (400 nm). If it's closer to red  than the standard candle, then it is moving away from us. Closer to blue means it's moving toward us. We also discuss several other topics like Anthropology is a study of what?

Study Guide © Alyeska Dronsfield 2019. For personal use only, not for redistribution.

How can we use them to calculate a galaxy’s redshift?  

Compare them to a standard candle.  

How can we use the redshift to calculate a galaxy’s recession velocity?  The farther the galaxy's shift is from the "resting" spectrum, the faster it is moving away from us.

How does Hubble’s Law relate distance and recession velocity of galaxies?  The farther a galaxy is from us, the faster it is moving.  

How can we use it to calculate distance or velocity?  

V = Ho D

H is about 70, the Bubble constant.

What is a redshift survey and what can one tell us about the distribution of galaxies in the  universe?  

A redshift survey is a survey of a section of the sky to measure objects' redshift. By using Hubble's law,  we can estimate the distance of objects from Earth. It can help us further "map out" galaxies.  

What does the Cosmological Principle state about the structure and properties of the  universe?  

The principle states that the universe appears the same in all directions and is made of the same  materials throughout. Isotropic & homogenous.

How is the universe changing?  

The universe is expanding.

What observations tell us it is expanding?  

Galaxies that are farther away from us are

What does the expansion of the universe imply for the distances between galaxy clusters?  The distances between galaxy clusters are growing larger.

What effect does this expansion have on stars within a galaxy or galaxies within groups?  Very little effect, as stars & galaxies have gravities that outweigh the pull of the expanding universe,  USUALLY.

What effect does this expansion have on the light reaching us from distant galaxies?  Distant galaxies will appear redder as they are moving faster away from us than closer galaxies.

How does the speed of light impact the way in which we observe distant objects?  The speed of light is constant relative to any object moving at a constant velocity. It appears they are  moving "around us" and that we are central, but we are moving relative to them as well.

What does the expansion of the universe imply for the state of the very early universe?  The early universe was much smaller.

Was it hotter or cooler?  

Hotter, as everything was concentrated tightly.

More dense or less dense?  

More dense, as everything was all jumbled closely together.  

How has the distribution of objects in the universe changed over time as the universe has  aged and expanded?

The space between objects has grown in size.  

Study Guide © Alyeska Dronsfield 2019. For personal use only, not for redistribution.

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