nebula & galaxies

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  1. 1. Nebulae &GalaxiesB y : J a s m i n e Ta m , J e n n if e r L e e , &
  2. 2. What is a nebula?A nebula is an interstellar cloud of dust, hydrogen, helium andother ionized gases
  3. 3. How do nebulae form stars?Gas, dust, and other materials clump together to form massesGravity pulls other matter to the clumpEventually, clump will become massive enough to form stars
  4. 4. How are nebulae formed?Collapse of interstellar gas in space Ultraviolet rays from surrounding stars ionizes the surrounding gas making the nebula visibleSupernova explosions from stars of over 100 solar massesWhen stars lose their outer layers of gases at the end of their lives
  5. 5. Types of Nebula:Diffuse Nebula Supernova RemnantEmission ReflectionDark Nebula NebulaNebula PlanetaryH II RegionsNebula
  6. 6. Diffuse Nebula:Nebulae which are extended and do not contain (visible) well-defined boundariesSome diffuse nebula contain enough gas and dust to form about 100,000 stars the size of the sunMay be positioned near a bright star
  7. 7. Diffuse Nebula Emission NebulaLight from a nearby star energizes the gasatoms of the nebula causing this nebula to beable to emit lightThere are 2 types of emission nebulaePlanetary NebulaH II Regions
  8. 8. Diffuse Nebula Emission NebulaPlanetary Nebula H II RegionsOccurs during red giantNewly formed stars emit phase of a star when ultraviolet light which outer layers of star isionize the surrounding shed gasesUltraviolet radiation fromexposed core ionizesshed layers Ring Nebula Pillars of CreationEagle Nebula
  9. 9. Diffuse Nebula Reflection NebulaDo NOT emit lightDust particles reflect light from starsUsually blue in colour because dust grains Witch Head Trifid Nebula reflect more blue light than red light Nebula
  10. 10. Supernova RemnantCaused by the explosion of a starConsists of the ejected matter from the explosionCrab Nebula
  11. 11. Dark Nebula
  12. 12. Dark Nebula What is it?Interstellar cloud that is extremely dense withinterstellar dust grains located in thecoldest, darkest places of the nebula.It is dark enough to block out ALL light! Even the neighbouring stars around the nebula!
  13. 13. Coal Sack NebulaBrilliant example of a dark nebula, as it can easily be seen by human eyes.On bright, starry nights, its seen as a dark patch on the night sky, clearly apparent from the background of Milky WayBelongs to the constellation Crux, and can only be seen in the Southern Hemisphere
  14. 14. Snake NebulaDark Nebulae have no definite shape and boundariesMany twist and turn into convulsing shapes. A good example is the Snake NebulaAlso known as Barnard 72, it isS-shaped and found in theconstellation OphiuchusPart of the Great Dark Horse Nebula
  15. 15. Horse Head NebulaPerhaps the most famous of theDark Nebulae, also known asBarnard 33, is the Horse HeadNebula.Found in constellation Orion,and it lies behind the starAlnitak.Categorized and found byEdward EmersonAbout 1600 light years awayMore apparent because the bright nebula, IC 434 is behind it, casting a larger shadow.
  16. 16. Bok Globules and New StarsSmall dark nebulae are often referred to as Bok Globules.Cool clouds of gas and dust that are more spherical in shape, resembling drops of waterNamed after Bart J. Bok (American astronomer)Believed to create lower mass stars.Dark Nebulae also site for creating new stars, as mentioned by Jen.
  17. 17. So What Happens When a Star Explodes?As mentioned before, if the star was less than 8 solar masses, it will turn into a planetary nebulaeIf more than 8 solar masses, it will turn into a supernova remnant!Supernova remnant is the structure left behind after a supernova explosion (star goes BOOM)Heats up interstellar medium and sends out important metals throughout universe
  18. 18. Types of Supernova Remnants (I)2 main types: First type is the shell-typeremnant (heats up interstellar mediumduring explosion) Interstellar medium: dust and gasbetween stars and galaxies (aftersupernova explosion becomeshot)Cygnus Loop: example of a shell typeremnant (show picture) Found in constellation Cygnus (extremely large for a supernova remnant) Scientists have found 4 smaller nebulae inside the Loop!
  19. 19. Types of Supernova Remnants (II)Crab NebulaSecond type is crab-type remnant. Famous Crab Nebula found in (also called pulsar wind nebulae) constellation Taurus (show picture)Contains neutron star that sends outregular pulses ofstar called CrabCentral neutron radiationPulsarThese supernova remnants filled withhigh energytimes per second neutronSpins 30.2 electrons from thestarwhile emitting radiation
  20. 20. Galaxies
  21. 21. What are Spiral Galaxies?Thin structures similar to a diskHave arms of stars spiralled around the galaxys center.Tightly wound spiral called Sa ; loose spiral iscalled Sc.Consist of mainly young, new starsHave interstellar matter in galaxy disk approximately 10,000 to almost 100,000 light years in diameter
  22. 22. What are Spiral Galaxies?Center of the spiral galaxy bulge (a dense concentration of stars)Diameter of a few thousand light yearsExtends above and below the disk.Spiral arms & blue waves in the galaxy disks density hold high proportion of huge, hot starsStars shine longer & have brighter light than smaller, more common stars, eg. Sun
  23. 23. What are Barred-Spiral (SB) Galaxies? Very similar to spiral galaxies Have a bar of stars running through the middle Tightly wound barred-spiral galaxy is called SBa; loosely wound barred-spiral galaxy Called SBc.
  24. 24. What are Barred-Spiral (SB) Galaxies?Theories of bar fueling stars during its evolution.Theories of bar created by density wave from the galaxys centerCaused the inner stars to reshape its orbit.Those stars orbit further out T the structure of bar
  25. 25. Milky Way (aka Earths Galaxy)Part of the Local Group which contains over 24 othergalaxiesContains many beautiful and important features Nebula in Orions sword. Birthing ground where powerful stars produced.Created from swallowing other galaxiesStars from the Sagittarius Dwarf GalaxyAs old as the universeMilky Way: 13.6 billion yrs ; universe 13. 7 billion yrs.Galaxys disk and the bulge not created until 10-12 billion yrs ago
  26. 26. Milky Way (aka Earths Galaxy)Has halo of approximately 150 globular clusters scattered around galactic centerGlobular clusters = thousands of millions of old stars tightlygrouped together Only 20-30 light years across = concentrated in a swarm Stars so old most less than two solar masses & glow yellow- red.Dusty and gassyOnly allow to see 6000 light years in visible spectrumDeflects visible lightInfrared light can still pass through Use infrared telescope (Spitzer Space Telescope) and clearly seegalaxys center and regions where stars form
  27. 27. Milky Way (aka Earths Galaxy)Have super massive black hole = Sagittarius A*Diameter 15x SunsSource of X-rays and radio waves from galaxys center200 + billion starsOnly 2500 seen from EarthLow # of stars because too far from center 6000 light years closer, night sky = brighter!Theory of having halo of dark matterInvisible but existence believed through simulations
  28. 28. The End (: