Systems containing millions, or even billions, of stars Observable universe contains as many as 50...
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Transcript of Systems containing millions, or even billions, of stars Observable universe contains as many as 50...
•Systems containing millions, or even billions, of stars
•Observable universe contains as many as 50 billion to 100 billion galaxies; millions of light years apart
•No two galaxies are alike, but they can be grouped
Galaxies
•Sun is one star of hundreds of billions; we are 26,000 light years from the center
•Spiral galaxy; thin disk with a central bulge
•diameter is about 100,000 light years
Our Galaxy: The Milky Way
•Part of Local Group: more than 30 galaxies
•Neighbors: 2 large Magellanic clouds (seen in southern hemisphere only) and Andromeda (seen in northern hemisphere)
Our Galaxy: The Milky Way
Spiral Galaxy
Elliptical Galaxy
Irregular Galaxy
• Galaxies that emit more energy than given off by their stars—lots of light
• Milky Way is not an active galaxy
• Powered by a supermassive black hole at its center
• Quasars: very distant objects that are highly luminous
Active Galaxies
Active Galaxy
http://www.spacetelescope.org/images/opo9814d/
Big Bang (artist view)http://nothingoutofnothing.files.wordpress.com/2010/05/bigbang.jpg
http://www.youtube.com/watch?v=gs-yWMuBNr4
• explains the history from a tiny fraction of a second after it came into being up to the present time
• 13.7 billion years ago the universe began: superhot & superdense
• expanded from a single point very rapidly and continues to expand today
The Big Bang Model
• became cooler as it expanded, allowing atoms to form
• atoms clumped together, mostly hydrogen
• hydrogen gathered into clouds, clouds gathered into stars, stars into galaxies over billions of years
The Big Bang Model
Big Banghttp://3.bp.blogspot.com/-PFXq_QZOZbE/T5GokOaONTI/AAAAAAAADMY/Kl32j-Jpcqs/s1600/Big+bang+expansion+diagram+2.PNG
• distance is increasing between galaxies (redshift)
• presence of cosmic background radiation (big bang leftovers)
Big Bang Evidence