Galaxies and Universe

1. Galaxies and Universe

2. What are Galaxies? • A galaxy is an immense structure of stars, planets, gases and debris that all revolves around one centre of mass. • gravity is derived from the Greek word “galaxias” which means milky most likely named because the way it looked. • Most scientists believe that in the visible universe there are approximately 50 – 100 billion galaxies.

3. Our Galaxy Our Galaxy • Our galaxy is called the Milky Way, a spiral galaxy; it has a diameter of approximately 100,000 light-years. • The thickest point is 10,000 light-years from top to bottom, from the centre of the Milky Way the sun is about 26,000 light-years.

4. Active Galaxies • An active galaxy is; a galaxy where a major portion of the energy created is not given off by the standard mechanisms of a galaxy. • Certain active galaxies give off vast amounts of radiation (radio, infrared, ultraviolet, X-ray and gamma-ray waves) • Others are continually changing over short periods of time in brightness. • The current idea of how an active galaxy is powered is by a colossal black hole in the centre, where hot jets of gas get poured in contrary directions at a momentum close to light.

5. Active Galaxies continued • The black hole is encircled by gas, which spirals into it and gives off vast amounts of radiation before vanishing into the hole.

6. QUASARS • A quasi-stellar radio source or quasar is a distant galaxy that is full of energy, they are the most incandescent, powerful, and active objects recognized in the universe. • They can release up to a thousand times the amount of power of our whole Milky Way. • Most quasars are known to be farther than three billion light-years away.

7. QUASARS • Because of the great distances to the furthest quasars and the finite velocity of light, we see them and their surrounding space as they existed in the very early universe.

8. BLAZARS • A blazing quasi-stellar object AKA a blazar is basically a compact quasar. • powered by material falling onto a supermassive black hole at the center of the host galaxy. • Perpendicular to the accretion disk, a pair of relativistic jets carry a highly energetic plasma away from the AGN.

10. Types of Galaxies There are 4 types of galaxies, these are appropriately named, Spiral galaxies, Lenticular galaxies, Elliptical galaxies, Irregular galaxies. These types of galaxies are spread across space.

11. Spiral galaxies • Spiral Galaxies consist of interstellar material and star clusters. • This galaxy itself is shaped like larges disc which extends from the center in a spiral pattern. • The star clusters in spiral galaxies are arranged in eye catching formations. • When viewed these clusters can been seen as bulges of interstellar material and stars. • The pattern structures in the disk are most, caused by gravitational interaction with neighboring galaxies • Spiral galaxies have both population I and population II stars.

12. Lenticular galaxies • These galaxies like spiral galaxies are shaped like discs. • Lenticular galaxies do not spiral because they have used up much of its interstellar material. • Because there is so little interstellar material star formation usually does not occur therefore Lenticular galaxies only posses population II stars.

13. Elliptical galaxies • Elliptical galaxies are circular shaped and can be described as looking like large bright spheres. • This type of galaxy is mainly made up of population II stars, with low amounts of interstellar medium. • Elliptical galaxies have limited star formation. • Elliptical galaxies are filled with globular clusters. • Make up 10-25 percent of local galaxies

14. Irregular galaxies • Irregular galaxies like the name suggest have no common shape. • All Irregular galaxies were all once either spiral or elliptical galaxies but deformed due to gradational activities • Irregular galaxies have large amounts of interstellar material therefore there is star production.

15. Origin of Universe (Big Bang) • 14 million years ago all matter in space was in a dense and hot state • Over time this matter cooled and expanded • This caused the production of Galaxies and stars.

16. What is the Big Bang Theory? • Universe first existed as tiny region of space-time • Energy was transformed into high speed particles • Expansion slowed down but is continuously occurring • As the universe expanded it cooled, but was still not cool enough for atoms of matter to survive • When electrons and protons did combine they would be ripped appart by collision with high energy particles.

17. What is the Big Bang Theory? Continued • Over hundred thousand years it became cool enough for atoms to survive. • The atoms began to clump together into clouds of gas. • As more stars formed and died heavier atoms were created which later fused in planets.

19. Evidence of the Big Bang Theory • There is scientific evidence that the Big Bang (theory) actually occurred. • The universe is continuously expanding, how we know this is that galaxies are constantly moving farther apart. • This means that galaxies were closer together in the past. • The name of the scientist who discovered this is Edwin Hubble.

20. Evidence continued • The second piece of evidence is cosmic background radiation. • This is radiation that was left behind from the beginning of the universe. • This was discovered by Arno Penzias and Robert Wilson • http://www.videojug.com/expertanswer/studying-the-universe-2/is-the-static-on-your-tv-something-to-do-with-the-big-bang