The Universe, the Big Bang , Stars, and Galaxies

“The universe is a pretty big place, it’s bigger than anything anyone has ever dreamed of before. So if it just us, seems like an

awful waste of space, right?”

Universe

The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope data accumulated over a period from September 3, 2003 through January 16, 2004. It is the deepest image of the universe ever taken in visible light, looking back in time more than 13 billion years. The HUDF contains an estimated 10,000 galaxies. The total field of view represents only 1 ten millionth of the total sky.

• consists of all matter, empty space, and energy that exists

• objects are so far away, we are seeing what they looked like millions of years ago

• the visible universe is a region some 28 billion light years in diameter.– it takes one year for light to travel 5+ trillion

miles (a light year)

• around 14-20 billion years old

The Big Bang Theory

• Origins– began with a large explosion called the

big bang theory– only energy before this, no matter– first hydrogen and helium were formed– larger elements were formed later by stars

• Evidence1. is expanding, therefore must have been

smaller at one point• evident by galaxies’ red shift

– most look red because they are moving away from us

• if they were moving towards us, they would look bluer (blue shift)

2. cosmic background radiation– scientists found “noise” in our galaxy that was

the cosmic microwave background radiation predicted by the Big Bang theory

3. most elements in universe are H and He– when stars reach the end of their life cycle,

they distribute C, O, and Fe into the universe• if the universe was older, there would be more C,

O, and Fe

StarsShow Planet and Stars Scale video

• Closest star to Sun is Proxima Centauri– 4.2 light years away

• life cycle varies depending on the size• all begin life inside a huge cloud of gas (mostly

hydrogen) and dust called a nebula

• then turns into a protostar – H is converted to He

– gravity squeezes the atoms of a star so tight that the electrons are stripped away and the bare nuclei of atoms almost touch each other

• The Hertsprun-Russell (H-R) Diagram– graphs the brightness and

temperature of stars

– helps astronomers understand how stars change over time

• for average, Sun-sized stars– eventually runs out of H– gets hotter making C and O atoms– expands outwards making a red giant

– hydrogen fusion stops• no more energy exploding outward• gravity pulls matter inwards• VERY high density, bright, and is called a white dwarf• outer layers often expand and drift away creating a planetary nebula

• for larger stars– larger elements (up to iron) are fused together– eventually may turn into a supernova

• quickly collapses because run out of energy and gravity is now the strongest force

– core collapses and then rebounds outward with a shock wave that makes a bright explosion (supernova)

– at this point, heavier elements are created

• if the leftover core is very, very dense, it may form a very small neutron star or a black hole with VERY powerful gravity

Galaxies• a collection of millions or billions of stars• we are in a spiral galaxy called the Milky

Way (Monte Python Galaxy song - 2:43)

• nearest to us is the Andromeda galaxy– 2.2 million light years from earth

• galaxies can also be elliptical and irregular shaped.