Cosmos - A Sketch of Physical Description of the Universe - Alexander Von Humboldt - Volume 3
Organizing the cosmos Galaxies & our Universe There is still uncertainty on exactly how the universe...
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Transcript of Organizing the cosmos Galaxies & our Universe There is still uncertainty on exactly how the universe...
Organizing the cosmosOrganizing the cosmosGalaxies Galaxies
& our & our Universe Universe
There is still uncertainty on exactly how the universe and our solar system formed. There are many theories but no one knows for sure. By studying distant galaxies astronomers may
one day determine how the universe was formed
What is a Galaxy?What is a Galaxy?
A large group of A large group of stars, dust, and stars, dust, and gases held gases held together by gravitytogether by gravity
Interstellar Interstellar Matter- Matter- dust and dust and gases found gases found between starsbetween stars
Our Milky WayOur Milky Way
SizeSize: large spiral disk : large spiral disk 100,000 light year wide & 100,000 light year wide & 10,000 thick10,000 thick
StructureStructure: Spiral disk-like : Spiral disk-like shape like our solar shape like our solar systemsystem
Galaxy is Greek for milkGalaxy is Greek for milk
**Our Sun is 1 of 100 Billion **Our Sun is 1 of 100 Billion stars in the stars in the Milky Way Milky Way GalaxyGalaxy
The sun rotates around the The sun rotates around the galaxy once about every 240 galaxy once about every 240 million yearsmillion years
Pinwheel GalaxyPinwheel GalaxyLargest galaxy known to Largest galaxy known to
datedate
The giant spiral disk of The giant spiral disk of stars, dust and gas is stars, dust and gas is 170,000 light-years 170,000 light-years across or across or nearly twice nearly twice the diameter of our Milky the diameter of our Milky WayWay. The galaxy is . The galaxy is estimated to contain at estimated to contain at least one trillion stars. least one trillion stars. Approximately 100 billion Approximately 100 billion of these stars alone of these stars alone might be like our Sun in might be like our Sun in terms of temperature terms of temperature and lifetime. and lifetime.
Andromeda GalaxyAndromeda Galaxy Our closest neighborOur closest neighbor
It is visible as a It is visible as a faint smudge on a faint smudge on a moonless night, it is moonless night, it is one of the farthest one of the farthest objects visible to objects visible to the naked eye, and the naked eye, and can be seen even can be seen even from urban areas from urban areas with binocularswith binoculars
2.3 million ly away2.3 million ly away
Did You Know ?Did You Know ?
The Milky Way galaxy, and its closest The Milky Way galaxy, and its closest neighbor, the Andromeda galaxy, are neighbor, the Andromeda galaxy, are on a collision course with each other! on a collision course with each other! This collision between these two spiral This collision between these two spiral galaxies will likely occur in about 3 galaxies will likely occur in about 3 billion years, and the resulting galaxy is billion years, and the resulting galaxy is expected to be an elliptical. expected to be an elliptical.
Galaxy Classification
In 1924, Edwin Hubble divided galaxies into
different “classes” based on their appearance.
Galaxies differ in size, shape, and ages of their stars
•Hubble classification serves as the basic language of the field.
Types of GalaxiesTypes of Galaxies
Spirals & Ellipticals & Spirals & Ellipticals & IrregularsIrregulars(oh my!) (oh my!)
1. 1. Spiral GalaxySpiral Galaxy
Disk shapedDisk shaped (looks like a pinwheel) (looks like a pinwheel) Contain mixture of young/old stars Contain mixture of young/old stars
Greater concentration of stars near the Greater concentration of stars near the middle (older stars)middle (older stars)
Arms (younger stars)Arms (younger stars) are seen are seen extending from central nucleusextending from central nucleus
Orderly rotational motionOrderly rotational motion Our own Galaxy is a spiralOur own Galaxy is a spiral..
Types of Spiral GalaxiesTypes of Spiral Galaxies
Normal Spiral Normal Spiral Galaxies- Galaxies- a flattened, a flattened, rotating galaxy with rotating galaxy with pinwheel-like armspinwheel-like arms of of interstellar material interstellar material and young stars and young stars winding out from its winding out from its centercenter or nucleus or nucleus
Barred Spiral Barred Spiral Galaxies-Galaxies- a galaxy a galaxy having having straight arms straight arms extending from its extending from its centercenter Spiral arms Spiral arms attach to attach to
the bar instead of the the bar instead of the center diskcenter disk
2. 2. Elliptical GalaxiesElliptical Galaxies
(not a disk) and (not a disk) and often football shapedoften football shaped
Smooth round shapeSmooth round shape No armsNo arms Very little interstellar Very little interstellar
matter leads to matter leads to minimal star minimal star formationsformations
Composed of old Composed of old starsstars
Random star motionRandom star motion 60% of all galaxies60% of all galaxies
“Space footballs”
3. 3. Irregular GalaxiesIrregular Galaxies
No exact size or shapeNo exact size or shape Composed of mostly young starsComposed of mostly young stars Lacks symmetryLacks symmetry Small and faintSmall and faint
Final Galaxy Final Galaxy vocabulary….vocabulary….1. Most Galaxies are 1. Most Galaxies are
located in groups located in groups called a called a clustercluster..
2. 2. Local GroupLocal Group – the – the name for the name for the cluster of galaxies cluster of galaxies the Milky Way is the Milky Way is inin
3.3. Super cluster Super cluster – – Gigantic Cluster Gigantic Cluster of galaxiesof galaxies
Skip QuasarsSkip Quasars
Hubble’s Tuning ForkHubble’s Tuning Forkdiagram classifying diagram classifying
different galaxies by shapedifferent galaxies by shape
Use your Hubble’s Tuning Fork Diagram to help you identify these Galaxies: