Chapter 17 Flashcards
What is a galaxy
It is an immense isolated cloud of hundreds of millions to hundreds of billions of stars and vast clouds of interstellar gas
What galaxies can be seen without the aid of a telescope
Andromeda and the large and small Magellanic Clouds
Who identified the large and small magellanic
Abd Al-rahman Al-Sufi
Who observed “fuzzy” objects in the 18th century
Charles messier
Who systematically mapped the heavens in the 19th century
William Herschel, they created the new general catalog
Who determined that galaxies can be divided based of their shape into three types and two sub types
Edwin Hubble
What are spiral galaxies
They have two or more arms winding out the center that look like they’re spinning, classified with the letter S and then followed by a letter from a-d to determine how large the nucleus is or how wound up the arms are
What are elliptical galaxies
They are smooth and featureless, classified with the letter E and followed by 0-7 to express flatness
What are irregular galaxies
They neither have arms or uniform appearance, the stars seem to be scattered randomly, classified as Irr
What are barred spirals
These are spiral galaxies whos arms emerge from the ends of elongated central region rather than the core of the galaxy, classified with the letters SB and followed by the letters a-d. the Milky Way is probably a SB galaxy
What are S0 galaxies
They are disk systems with no evidence of arms, they are thought to be an in between of S and E. S0 lacks gas to produce O and B
What type of star types are in spiral galaxies and what is it’s interstellar content
Pop 1 and pop 2, it’s interstellar content is 15% by mass in disk
What types of stars are in elliptical galaxies and what is it’s interstellar content
Only pop 2 and it’s interstellar content us very low density
What types of stars are in irregular galaxies and what is it’s interstellar content
Blue stars, it’s interstellar content is as much as 50% by mass
What method is used to measure the distance of galaxies
The standard candles method
What are the standard candles
They are usually cepheid variables, supergiant stars, planetary nebulas, supernovas etc.
What do all galaxies do relative to the Milky Way
They move away from it
What is the reason radial speeds increase
They increased with a galaxy’s distance, this is called recession velocity
What are galaxy clusters
Galaxies held close together by their mutual gravity
How close are galaxy clusters together
Several million light years across
What group does the Milky Way belong to
The local group
How many members does the local group contain
Around 30 members, with the largest 3 being M31, M33, and the Milky Way. Most of the local group galaxies are feint/small “dwarf” galaxies
What are superclusters
A group of galaxy clusters that attract more clusters
How many galaxies does a supercluster contain
It contains half a dozen to several dozen galaxy clusters that spread over tens to hundreds of millions of light years
What shape do superclusters have
Irregular shape
