Cosmology, Galaxies, and Stars OUR VISIBLE UNIVERSE

Cosmology, Galaxies, and Stars OUR VISIBLE UNIVERSE

Cosmology Cosmology is the study of the universe; its nature, origin and evolution. General Relativity is the mathematical basis of cosmology from which equations were derived that described both the energy and matter content of the universe. Outward Expansion: The Universe struggles with the force of its outward expansion (most likely dark energy) and the inward force of gravity; ultimately the strongest force will win and determine the future of our universe. The rate of expansion can and is calculated and this can in turn date the age of the universe.

Mathematical equations and models support the Big Bang Theory. Before the Big Bang, there was an emptiness called singularity. The expansion is theorized to have begun with a single primordial ( beginning) atom. Expansion shows that the universe must have had a beginning. The beginning was a rapid expansion rather than an explosion and there was no sound or bang. The young universe was extremely hot but cooled with expansion. About 750,000 after initial expansion, the first radiation appeared. The Big Bang-13.7 billion years ago

Electromagnetic Spectrum The larger the radiation, the least dangerous but travels further is space- Radio The smaller the more intense and dangerous- gamma

Evidence to Support the Big Bang Theory Hubble s Law It is the observation that the further away the object, usually a galaxy, the faster is moving away. The observation supports the Big Bang Theory. However, the increased speed of further objects it not yet understood, could be dark energy. Cosmic Background radiation Shortly after the initial expansion, the universe filled with electromagnetic energy. With the expansion, the energy gained longer wavelengths. The cosmic background radiation was first observed in Holmdel NJ with a radio telescope. This energy was observed being emitted from every object in space.

Spectral Lines are created by the different chemicals burned within the star. Each element has a specific fingerprint or alignment of spectral lines. The spectra can help us determine what the stars are made of, as well as the motion of the stars. Redshift- it is the shift of spectral lines toward the red (longer wavelength) end of the spectrum The longer wavelength demonstrates that the object is moving away. Redshift supports the Big Bang Theory Redshift is being demonstrated in the above spectral lines. The Supercluster is moving further and faster away than the sun. Star Spectra

Possible outcomes for the future: Open Universe This 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. 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. Closed Universe: The Big Crunch 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!

Dark Matter and Dark Energy Cosmologists estimate that the universe is 21% matter (stars, planets ) and 78% dark energy and luminous energy. This is a force that is believed to be like an anti-gravitational force that could be the cause of the dramatic expansion of the Universe. Dark matter and dark energy are still undefined today. We believe dark matter 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.

Types of Galaxies: Galaxy- a cluster of billions and trillions of stars bound together by gravity Elliptical Galaxyround and flattened ovals (This is the most common type of galaxy) Irregular Galaxysmaller galaxies with no distinct shape. Spiral Galaxy- Galaxies with spiraling arms that rotate around a central bulge of massive substance in the center. Barred Galaxy- A flattened disk with two distinct rotating arms

The Hubble Telescope Finding: The Hubble Telescope found the oldest thing in the Universe. The galaxy is 13.2-billion years old, we are technically seeing this galaxy when it was very young, but its light is only reaching Earth now.

Groups and Clusters of Galaxies Most galaxies are located in groups rather than spread out. Local Group: The Milky Way belongs to a small group of galaxies called the Local Group. It is 2 million ly in diameter Has 40 members The Milky Way and Andromeda are the largest. Large Clusters: There are clusters are larger than the local group, anywhere from 5-30 million ly. Superclusters: These gigantic formations are hundreds of millions of light-years in size. Our Local Group A distant Supercluster

The Milky Way Formation The Milky Way began forming around 13 billion years ago, give or take 800 million years. The that the halo, central disk, contains such old stars, suggests the halo formed first. The galaxy began as a spherical cloud. The cloud eventually collapsed under its own gravity. The halo also contains the super giant stars which burn heavier elements. There is also a galactic black hole that is larger than our solar system. Galactic Black holes- weighing a few billion times the mass of the sun, most galaxies have a supermassive Black holes in their center. (ours is slightly smaller than our solar system!)

Our Galaxy: The Milky Way The center is over 28,000 light years away. Which means it takes 28,000 years for the light of the stars in the center to travel through space and be seen by our planet!!! 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. A light year is the distance light travels in one year, moving at 186,000 miles/second. The direction towards the center is toward the constellation Sagittarius. Our galaxy contains over 100 billion stars! The Sun is located on the Orion Arm Most stars in the Milky Way are 207,000 AU (AU= distance between sun and earth, 90 million miles) apart, but in the center they are only 1000Au apart!!! Sun

Hertzsprung-Russel Diagram The H-R Diagram, is a diagram that shows the relationship between temperature and brightness. As a star becomes hotter, it becomes brighter. Main sequence is the pattern of the average star. The sun is located within the Main Sequence. The stranger exceptions to this pattern are located outside of the main sequence.

Life Cycle of a Star White dwarf will eventually stop nuclear fusion and become a black dwarf- Dead Star Medium Star Gravity condenses the star to shrink (Where protostars are formed) Giant Star

Nebula- the birth of a star Orion Nebula Lagoon Nebula Horsehead Nebula A Nebula is a cloud of cosmic gas and dust where stars are formed. The gases of these nebulas are mostly hydrogen and helium. These are 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. 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: After the nebula, the cloud collapses own its own gravity. As the cloud contacts, it rotation forces form it into a disk with a hot, condensed object called a protostar. Once the protostar becomes hot enough, nuclear fusion will begin. Nuclear fusion converts hydrogen to helium in the core of a star. Once this begins, the star becomes more stable between the outward force of gravity and the inward force of gravity. Medium Star: Temperature= 6000 C Color = yellow/orange Example= Our Sun (closest star is proxima centauri) Exist for up to 10 billion years

Giant and Supergiant Stars Giant Stars When a star runs hydrogen in the core causing the star to expand. The core now has the ability to make carbon in the core. Color= Red or Blue Temperature= 4500 C Size= 10 x time the size of the Sun Red Super Giant Stars Under goes more reaction phases and thus produces many different elements in its core. Color= Red Temperature= 3000 C Size= 1000 x the size of the Sun!! As size increases, the temperature decreases because the heat of nuclear fusion is spread out over such an enormous volume!

Supernova to a Planetary Nebula A star that begins with mass between 8-20 times the Sun s mass will end up with a core that is too massive to be stable. The star s core then produces iron and no energy which causes the core to violently collapse. Then entire outer portion of the star is blown off in a massive explosion, supernova. This explosion leaves behind heavier elements which can condense to planetary nebulas, such as our own solar system. A distant supernova explosion might be brighter than the galaxy in which it is found. Computer Animation Actual Supernova- 70 mill light years away and occurred millions of years ago!

White and Black Dwarf Stars White Dwarf Stars: Color = White Temperature= 15,000 C Size= Average around the size of Texas 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.

Neutron Star Pulsar Some neutron stars are unique in the have a pulsating pattern of light. This causing them to emit their magnetic fields into cones or spinning beams of lights. Color: Blue Temperature: 35,000 C Size: A little larger than New York City (5-10 Miles) The Neutron Star is extremely dense and small. The neutron star forms when are a supergiant star s protons and electrons combine to form neutrons. The creates pressure that halts the collapse of the core. These neutrons stars can have 1.5 to 3 times more mass that the sun. 10,000,000,000,000,000 g/cm 3

Black holes Some stars are too massive to form neutron stars. The pressure can not support the star s core. Usually happens to stars that are at least 20 time our sun. The star than collapses compacting the matter into a smaller volume. The remaining, extremely, small and dense object becomes a black hole. These are computer animations- true black holes cannot be seen because light cannot reflect off them to create a shape. The gravity of these objects is so greater that not even light can escape. The fundamental descriptions of black holes are based on equations in the theory of general relativity developed by the German-born physicist Albert Einstein. The theory was published in 1916. The EVENT HORIZON is the area of no return, where an object is within the gravitational pull of a black hole and there is no escape. This is an actual black hole in the center of our galaxy. The black hole cannot be seen but can be observed by what it is eating as the stars simply disappear under its enormous gravity.

Nebular Theory: Creation of Our Solar System A massive nebula remained for a large supernova. Cloud began to rotate quickly and flatten The Nebular Theory states that gaseous clouds nebulae(most likely the remnants of a massive supernova), slowly rotate, gradually collapse and flatten due to gravity and eventually form stars and planets. Our solar system was formed 4.568 billion years ago when a small part of a giant cloud collapsed inward on its own gravity. Very hot proto-sun began to form Our sun and Planetisimals formed. First the protostar, our young sun, cloud (a nebular cloud) contracted and cooled, flattening and shedding rings of material in the process which later collapsed to form the Planetisimals. Matter Accretion or snow-balled into today s planets.