Our Universe: Creation, Galaxies, Stars and

Celestial Objects

BIG BANG THEORY

• universe began with one huge exploding atom that relapsed all the energy and matter that exists today

• 13.8-15 Billion years ago• Hydrogen and Helium, the make-up of stars, were the

first two elements formed in less than a quarter of a second!

• explosion was so enormous, that all objects in the universe are still moving outward today from the initial blast!

• radiation from this explosion is also still traveling across our universe in the form of microwaves (a specific type of energy)

Big Bang Timeline

Evidence of Big Bang

• Background radiation is the aftermath of gas, dust and energy from the initial explosion that is found in every part of our universe.

• It proves that there definitely was some explosion beyond enormous, billions of years ago!

RED SHIFT• shift towards the red end of the spectrum of

colors given off by objects in space• demonstrates that an object is moving away

from us and everything else• is evidence of the “push” from the initial Big

Bang• BLUE shift would demonstrate that an object

is moving TOWARDS us!

Absorption Lines from a supercluster of galaxies

Common Questions about BIG BANG

• Where is the center of the Universe?– There no center of the universe because there is no

edge of the universe– In a finite universe, space is curved so that if you

could travel billions of light years in a straight line you would finish back where you started.

– It is also possible that our universe is infinite. In both examples, groups of galaxies completely fill the universe and are moving apart at all points making the universe expand

Where did the Big Bang occur in the Universe?

• Space and time were created in the Big Bang. At the beginning of the universe, the space was completely filled with matter.

• The matter was originally very hot and very dense and then expanded and cooled to eventually produce the stars and galaxies we see in the universe today.

Is the Earth expanding with the universe?

• The Earth is not expanding and neither is the Milky Way galaxy.

• These objects formed under the influence of gravity and stopped moving apart.

• Gravity also holds galaxies together into groups and clusters. It is mainly the groups and clusters of galaxies that are moving apart in the universe.

What exists outside the universe?

• Space was created in the Big Bang. Our universe has no edge or boundary - there is no outside of our universe.

What existed before the Big Bang?

• Time was created in the Big Bang - we do not know if it existed before the Big Bang.

• Some theories suggest that our universe is part of an infinity of universes (called a multiverse) which are being continuously created. This is possible but very hard to prove.

Future of the Universe

Open Universe• theory states that everything in the

universe will continue to move outward and away with continual expansion infinitely

• Eventually, all stars would burn out leaving our universe with empty darkness.

Closed Universe• This theory supports the idea that

eventually that outward expansion from the initial Big Bang will wear.

• At this point, the force of gravity will begin to pull everything back together again.

• Then, another Big Bang will occur!

FLAT UNIVERSE

• A flat universe results if the expansion slows to a halt in an infinite amount of time but never contracts.

• Expansion occurs so slow that it appears to have stopped.

3 Types of Galaxies

Galaxy- a cluster of billions and trillions of stars bound

together by gravity

Elliptical Galaxy

• round and flattened ovals

• (This is the most common type of galaxy)

• Messier 32 (2.65 million light-years away in the constellation Andromeda)

Irregular Galaxy

• smaller galaxies with no distinct shape

• Ex: Magellanic Clouds (160,000 light years away)

Spiral Galaxy• Galaxies with

spiraling arms that rotate around a central bulge of massive substance in the center.

THE MILKY WAY

• spiral galaxy• center is full

of extremely massive, Red Super-Giant Stars

• center is over 28,000 light years away

• 1 light year (which is measure of distance, NOT time) is the distance light travels in a year. Light travels at a speed of 9.5x1015

m/s!!!• Which means it takes ________years for the

light of the stars in the center to travel through space and be seen by our planet!!!

• The direction towards the center is toward the constellation Sagittarius

• Our galaxy contains over 200 billion stars!

STATISTICS AND FACTS• Sun orbital speed around the center is 220km/s, orbital

period is 240 million years.• The sun will complete 20 revolutions around center in its

lifetime.• It is believed that there may be a massive black hole at the

center of our galaxy pulling the massive supergiants in!!• Most stars in MW are 207,000 AU (AU= distance between

sun and earth) apart, but in the center they are only 1000Au apart

• AU = 149,597,871 km (92,955,807 miles)

Life Cycle of a Star

Medium Star

Gravity condenses the star to shrink

Giant Star(Where protostars are

formed)

White dwarf will eventually stop nuclear fusion and become a

black dwarf-”Dead

Star”

Nebula- the birth of a star

Orion Nebula

A Nebula is a cloud of cosmic gas and dust where stars are formed.•gases of these nebulas are mostly hydrogen and helium (the two gases that make up all stars!)•Gravity begins to pull the gases inward during the birth of a star.•Then, with gravity, the density of the gases increases which causes the pressure and temperature to increase, until the star finally stabilizes.

Lagoon Nebula

Horsehead Nebula

• A star can exist anywhere from 1 Million to 30 Billion years! (depending on size)

• Our Sun has around 5 Billion years remaining. It is predicted to only exist for 10 Billion total years.

YOUNG STARS• Protostar:• A baby star - formed in the nebulas after the gases have

condensed enough to begin nuclear fusion• In Nuclear fusion, hydrogen atoms are converted into helium,

releasing the ENORMOUS amount of energy that causes stars to become very hot!

• The amount of energy released per gram of mass is equal to the amount of energy released by 22,000 tons of TNT. (The nuclear explosion at Hiroshima only released an amount equal to 13,000 tons of TNT)

Medium Stars• Temperature= 6000°C• Color = yellow/orange• Example= Our Sun

(closest star is proxima centauri)

• Size= over 90 million miles in diameter! (actually measured in solar radii)

GIANT STARS• Color= Red or

Blue• Temperature=

4500°C• Size= 10 x time

the size of the Sun

RED SUPERGIANT STARS

• Color= Red• Temperature= 3000°C• Size= 1000 x the size of

the Sun!! • As size increases, temp.

decreases because the heat of nuclear fusion is spread out over such an enormous volume!

SUPERNOVA (PLANETARY NEBULA)• If a star is extremely massive, the

extreme density of the core collapses under the gravity causing a stellar explosion known as a supernova.

• The catastrophic explosion releases elements and cosmic dust for millions of the years.

• These explosions are more intense than 1 million nuclear bombs!

Actual Supernova-70 mill light years

away and occurred millions of years ago!

Why are supernovae important to us?

• These explosions create the heavier elements that are used and make up humans!!!

• If a star has a lower mass, it will eventually shrink to a planetary nebula.

• The planetary nebula then condenses to a white dwarf and eventually a black dwarf.

BLACK DWARF or DEAD STARS

• These are stars that have burned out and nuclear fusion is no longer occurring, therefore these stars are creating no energy.

• Pressure causes these stars to become extremely dense, similar to squeezing an aircraft carrier into a glass jar!

Both images are computer animations. Black Dwarfs do not give

off any light to be seen.

WHITE DWARF STARS

• Color = White• Temperature

= 15,000°C• Size= Average

around the size of Texas

Neutron StarColor: BlueTemperature: 35,000°CSize: A little larger than New York City (5-10 Miles)

•is extremely dense and small.•As the star decreases in size, the pressure increases so immensely that the temperature increases dramatically.•As temperature increases, so does brightness.•A Neutron Star is almost 1.5 million times brighter than our Sun!

Color of Stars• Stars are different

colors depending on their distance, energy, age and temperature

• Blue stars are the HOTTEST

• Red stars are COOLER than blue stars

Brightness

• The distance of a star affects its brightness• APPARENT Magnitude is how bright a star

is depending on how far away it is from us on Earth

• ABSOLUTE Magnitude is how bright a star is, assuming that ALL stars are the SAME distance away!

For Example:

• The sun’s absolute magnitude is + 5, in comparison to other stars it’s not that bright

• The sun’s apparent magnitude is -26.8 because to us, the sun is close and very bright

H-R Diagram

• Hertz sprung-Russell diagram–Shows relationship between a star’s

surface temperature and it’s absolute magnitude (actual brightness)

–Usually a star will follow a diagonal line down the H-R diagram during it’s life time, this is called the MAIN SEQUENCE

BLACK HOLES

• a theoretical space where the gravitational pull is so incredibly strong that no radiation, including heat and light, can exist

• These black holes are a million to a billion times more massive than our sun!

• Is there a black hole in the center of our Milky Way- YES!

These are computer animations- true black holes cannot be seen because light cannot reflect off

them to create a shape.

• descriptions of black holes are based on equations in the theory of general relativity developed by Albert Einstein in 1916.

• The surface of a black hole is known as the event horizon.

• This is not a normal surface that you could see or touch. At the event horizon, the pull of gravity becomes infinitely strong. Thus, an object can exist there for only an instant as it plunges inward at the speed of light.

GALACTIC BLACKHOLES

• weighing a few billion times the mass of the sun, most galaxies have a supermassive blackhole in their center.

• (ours is slightly smaller than our solar system!)

This is an actual black hole in the center of our galaxy. The black hole cannot be seen but we can see its gravitational pull “eating”

everything around it

Variable Stars•Variable Stars- stars that pulsate in brightness because of the expansion and contraction of their outer layers, or the blocking of their light by another object.

•are brightest at their largest diameter and dimmest at their smallest diameter.

Dark Matter and Dark Energy• a “force” that is believed to

be like an anti-gravitational force.

• 78% of universe is dark matter

• Dark matter and dark energy are still undefined today.

• We believe it consists of subatomic particles, smaller than protons and neutrons

• Scientists recognize the effects of dark energy, but they still do not know exactly what it is.

ASTEROIDS

• large pieces of rocky debris, some larger than our moon.

• Most are located in the asteroid belt between Mars and Jupiter

• do not have a specific orbit, they cluster in the belt and are continuously knocked out or pulled in my Jupiter.

Computer animated asteroid impact

Images of asteroids in space

Meteors and Meteorites• Meteors- pieces of rock that

burn up in our atmosphere. (shooting star)

• A meteor is the visible streak of light that occurs when a meteoroid enters the Earth's atmosphere

• Meteorite- pieces of rock that survive burning up in our atmosphere and land on the surface of the Earth.

Meteor Shower

Meteorite

COMETS• balls of ice and dust in

a specific orbit in space.

• Kuiper Belt and Orrt Clouds-these are two areas at the edge of our solar system where comets are located until knocked into a new, closer orbit

Halley’s Comet (Every 76 years - 2062)

Kuiper belt

What if one hits us???Asteroids and other objects come close to our planet EVERY DAY! Most of the time we never notice them, but with improving technologies we are detecting more of them, and detecting them earlier.

In fact, on Wednesday Sept. 8th, 2010 NASA telescopes spotted 2 asteroids (both around 30 feet in diameter) that came very close to Earth. One actually passed between the orbit of Earth and the Moon.

Neither would have been large enough to cause large scale damage. The majority of these asteroids would burn up while entering our atmosphere.

-This blue ring is the Oort cloud,

nearly a light year away (to put it in

perspective)

-Sedna is the furthest known

object to orbit our sun. The IAU (International

Astronomy Union) has yet to define it as a planet/dwarf planet/asteroid.

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ONE LIGHT YEAR• 10 trillion kilometres (1016 meters) • 6 trillion miles• about 63,241.1 astronomical units • (One astronomical unit is the distance

from the Sun to the Earth. It takes approximately 499 seconds (8.32 minutes) for light to travel this distance)