7.2 Galaxies Flashcards
Galaxy
A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. A galaxy is held together by gravity. Our galaxy, the Milky Way, also has a supermassive black hole in the middle. Are cosmic engines that turn gas into stars and vice versa.
Galaxies can be categorized into four groups by morphology(shape and size) Spiral galaxy Barred spiral galaxy Elliptical galaxy Irregular galaxy
Black holes
A region of space where gravity is so strong that not even light can escape. They are formed by a supernova. And can be big or small
Small
Formed when the universe started
Stellar
Mass is 29x more than mass of the sun formed through supernovas
Supermassive
Mass of more than 1million star made at same time as its galaxy
Dark matter
Matter in the universe that is invisible because it does not interact with light or any other type of radiation . It had a gravitational force and makes up 90% of the universe
Star clusters
A concentration of a group stars bound together by gravity in a small region of space. Divided into:
Open clusters
Youngest star group
Had a few hundred to a few thousand stars
Globular cluster
Hundreds to thousands of stars
Drawn together by gravity to form a spherical form
Oldest star groups in the galaxy
Spiral galaxies
S galaxies
They have bulge and disk components(arms)
Range from mostly bulge and barely detectable disk to totally dominated by disk
Arms rotate about the centet,with arms continually forming as old ones disappear and change shape
Gravity keeps the spiral from falling apart
Have hundreds of thousands of star clusters
Central bulge
A widening near the core of a spiral or barred spiral galaxy
New stars rarely form there due to lack of gas and dust between stars
It is surrounded by a galactic halo that also surrounds most of the disks and is made up of individual stars
Barred spiral
Same as a spiral galaxy but has a bar through the middle
Elliptical
Pure bulge and no disk component
Extremely large and massive
Shape varies from sphere to long and cylindrical
Contains little dust hence more old stars less young stars
Made when other galaxies merge
Small ones are called dwarf elliptical
Dwarf galaxies
Are dwarf elliptical and dwarf irregular
Smaller versions
Not very luminous or massive
There are more of these types of galaxies than any other types
Classified by the garbage can of galaxy classification
Irregular galaxies
Neither elliptical nor spiral odd shoes
Formed when one galaxy collided with another or one galaxy got close enough to another than gravity pulled some stars away
Galaxy clusters
A group of galaxies in an area Local group More than 2000 billion stars inside Local group local cluster Local supercluster
Disk
Flattened systems that rotate
Orbits of stars and gases are circular rotating about the disk axis
Star formation is on going it can be fairly consistent over the age of the galaxy
10-50% of the mass is of gas and dust
Age of stars ranges from old as galaxy to new
Spiral arms form as sustained density waves where majority of star formation occurs
Bulges
SpheriidL systems with little or no rotation
Orbits of stars are randomly oriented and height eccentric sometimes even radial
Gas consumed efficiently long ago hence star formation completed long ago
Ages of stars are mostly old near the age of the galaxy
Very little to no gas all converted into stars
Overall structure is smooth
SMC small Magellanic Clouds
Irregular galaxy that issmall
Sattelite of the Milky Way
Not forming any new stars
L6c large Magellanic Clouds
Irregular galaxy that is small
Is still formin stars
Sattelite if the milky way
