1 / 39

Types of Galaxies

Spiral. Barred Spiral. Lenticular. Elliptical. Irregular. Types of Galaxies. Deep Sky Catalogs. Messier Catalog Charles Messier, 1781 110 objects (40 galaxies) New General Catalog (NGC) JLE Dreyer, 1888 7840 objects. Messier Objects. Spiral Galaxies (face on). Sa. Sb. Sc.

freya
Download Presentation

Types of Galaxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spiral Barred Spiral Lenticular Elliptical Irregular Types of Galaxies

  2. Deep Sky Catalogs • Messier Catalog • Charles Messier, 1781 • 110 objects (40 galaxies) • New General Catalog (NGC) • JLE Dreyer, 1888 • 7840 objects

  3. Messier Objects

  4. Spiral Galaxies(face on) Sa Sb Sc NGC 1357 M81 Bode’s Galaxy NGC 4321

  5. Spiral Galaxies(edge on) Sa Sb Sc M104 Sombrero Galaxy NGC 891 NGC 4631 Herring Galaxy

  6. Spiral Galaxiesvariety of spiral arms Poorly defined spiral arms Well defined spiral arms M33 Triangulum Galaxy M74

  7. The Winding Dilemma

  8. Density Waves

  9. Barred Spiral Galaxies SBa SBb SBc NGC 4650 M83 Southern Pinwheel Galaxy NGC 1365

  10. Lenticular Galaxieslack spiral arms S0 M102

  11. Elliptical Galaxies E1 E4 E5 M105 M49 M59

  12. Elliptical Galaxies Giant Elliptical Galaxies Dwarf Elliptical Galaxy Virgo cluster M84 (right) and M86 (left) over 2 million ly diameter Leo I (type E4) 3000 ly diameter

  13. Hubble’s Classification Scheme

  14. Irregular Galaxies Large Magellanic Cloud (LMC) NGC 4485 (top) NGC 4490 (bottom)

  15. Structure in the Universe

  16. Galaxy Clusters Virgo cluster Fornax cluster

  17. Galaxy Clusters Hercules cluster

  18. The Local Group

  19. Galactic Collisions NGC 4676 “The Mice” BGC 2207 and IC 2163

  20. Galactic Collisions M81 M82 NGC 3077 visible radio

  21. Simulated collisions animation

  22. The redshifts of remote superclusters indicate that the universe is expanding • During the 1920s, Edwin Hubble and Milton Humanson were studying galaxy spectra • They found that galaxy spectral lines were redshifted • They measured the distance to galaxies by finding Cepheid variables and using the period-luminosity relationship • They found that the most distant galaxies had the largest redshifts • This is called the HUBBLE FLOW.

  23. Hubble’s Law slope = 75 km/s/Mpc called Hubble’s Constant

  24. Astronomers measure distances to distant galaxies using supernovae and the Tully-Fisher relation • Standard candle method • If you know how bright something really is and compare that to how bright it looks, then the distance can be determined • Supernovae • All Type Ia supernovae have the same luminosity (M=-19) • Tully-Fischer Relation • The broader the spectral line, the faster it is rotating and the more luminous the galaxy.

  25. Methods of estimating distance • Parallax (up to 150 pc) • Spectroscopic Parallax (40pc-10kpc) • RR Lyrae variable stars (5-100 kpc) • Cepheid variables (1kpc-30Mpc) • Tully-Fisher relation (700kpc-150Mpc) • Type Ia supernovae (1 to 1000 Mpc)

  26. Quasars look like stars but have huge redshifts • object with a spectrum much like a dim star • highly red shifted • enormous recessional velocity • huge distance (ala Hubble’s Law) • must be enormously bright to be visible at such a great distance • Quasi-stellar object • QSO or Quasar

  27. Active Galaxies bridge the energy gap between ordinary galaxies and quasars • peculiar galaxies (pec) • appear to be blowing themselves apart • Seyfert galaxies • luminous, star-like nuclei with strong emission lines • BL Lacertae objects (BL Lacs) • featureless spectrum with a brightness that can vary by a factor of 15 times in a few months.

  28. Radio image of Cygnus A showing a small but very bright radio galaxy in the middle of the 320,000 ly wide lobes

  29. Active galaxies lie at the center of double radio sources

  30. Supermassive black holes lurk at the centers of some galaxies • High resolution spectroscopy allows astronomers to peak at the motion of gas near centers of galaxies • Some galaxies exhibit high-velocity jets of material leaving the center • Observations suggest that the centers of some galaxies are incredibly massive • All of this suggests the existence of supermassive black holes

  31. Giant Gas Clouds (surrounding the galaxy) Intergalactic gas jet Galaxy (which is actually quite large)

  32. Jets of matter ejected from around a black hole may explain quasars and active galaxies

  33. Jets of matter ejected from around a black hole may explain quasars and active galaxies

  34. From where you observe it might make all the difference ...

  35. TONIGHT:Telescope observations • 8:45 pm Tuesday, May 20, after night class (telescopes on the roof) • Weather permitting (looks good!) • Attendance not required, but strongly recommended and will be for credit • If you can’t make it, see me for an alternate assignment

  36. Class Website http://www.hartnell.edu/faculty/kjordahl All lectures from the semester will be available by next week (as HTML and PowerPoint) Catch up on your reading in the textbook!

More Related