SCIENCE IN THE MEDIABRINGING CUTTING EDGE ASTRONOMY FROM SCIENTISTS TO STUDENTSPUBLIC OUTREACH PROGRAM FOR THE SUZAKU SATELLITEStudents: Alfaro Estefany, Alfaro Mónica, Landeros Jaqueline, Morales Mauricio,Morales Andrea, Samayoa Diana.AGN:Active Galactic NucleiAPRIL 2013
CONTENT1. What are active galactic nuclei (AGN)?2. What is an accretion disk?3. How do astronomers study accretion disks in AGN?4. What does the «doughnut shaped ring» refer to?5. Sketch of an AGN with accretion disk, black hole,torus and jets.6. Types of AGN7. What is a shrouded AGN or quasar? Why can´t weobserve the shrouded AGN in the infrared?Questions assigned under NASA´s Education and Public OutreachProgram for the Suzaku Satellite. Materials for Session 1.
1. What are Active Galactic Nuclei (AGN)?http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.htmlAn artists conception of an AGNhttp://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.htmlAre galaxies whose nucleus (or central core) produces moreradiation than the entire rest of the galaxy.Can have a supermassive black hole(millions of times the mass of the Sun) atthe center or be as small as our solar system!
Definition:Its the ring of gas and dust which may include material drawn from nearbystars or even captured galaxies.http://herschel.jpl.nasa.gov/galaxies.shtml2. What is an accretion disk?http://www.astro.virginia.eduThe yellowish ring of this animatedAGN represents the accretion diskhttp://www.gemini.edu/gallery/v/Posters-and-Prints/album10/GemMSF_FNL_jan22-2.jpg.htmlIf we make a perpendicular cut in an AGNwe will find the accretion disk extending froma thick red ring to a bright blue flattening one
Accretion disks arise when material (usually gas)is being transferred fromone celestial object to another.An artists concept of the accretion disk around the binary star system WZ Sge.http://www.noao.edu/outreach/press/pr08/pr0802.html«Accretion» means collecting ofadditional material.http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/001106a.html
Accretion disks in AGN are hard to imagine because theyare very small and far away.http://www.mssl.ucl.ac.uk/www_astro/research.html
3. How do Astronomers studyaccretion disks in AGN?An accretion disk forms, emitting huge amounts of light across the electromagnetic spectrum(infrared to gamma rays). The black hole plus the accretion disk produce the phenomena thatmake AGN visible. http://imagine.gsfc.nasa.gov/docs/science/know_l2/active_galaxies.htmlIt is supermassive black holes what makes AGNso powerful!As the material spirals into the black hole, it heats up to enormoustemperatures and emits radiation. http://herschel.jpl.nasa.gov/galaxies.shtmlhttp://spiff.rit.edu/classes/phys240/lectures/blackholes/blackholes.html
4. What does the “doughnutshaped ring” refer to?The 2 enormous powerful jets ofthe AGN are fueled by theemition and reflection of energyat the torus, a donut-shaped gascloud that absorbs and reflectsenergy from the accretion disk.JETJETACCRETION DISKTORUShttp://phys.org/news/2012-03-torus-galactic-nucleus.html
JetsJetsAccretion disks arise whenmaterial (usually gas) isbeing transferred from onecelestial object to another."accretion" means collectingof additional material.Not even light can escapetheir gravity, and since nothingcan travel faster than light,nothing can escape frominside a black hole.http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html5. Sketch of an AGN: Let´s review
The strong rotating magneticfield of a black hole createsthe jets ofaccelerated matter that isemitted from the polar regions.JetsJetsThis torus is not asdense, but it is muchwarmer (up to thousandsof degrees) and loadedwith many more calories.http://heasarc.gsfc.nasa.gov/docs/objects/agn/agntext.html
6. Types of AGNThey are the most luminous, powerful, andenergetic objects known of at this time. Theyseem to inhabit the centers of active younggalaxies and can emit up to a thousand timesthe energy output of our entire galaxy.According to Hubble’s law the redshift showsthat quasars are very distant and, because oftheir distance, much older than our universe.http://www.universetoday.com/73222/what-is-a-quasar/#ixzz2RxKCwgNwA) QUASARS
They are point-likes in the sky.Their visible light is often partiallypolarized.Their output in all wavelength bands variesmore rapidly and by a larger amount than aquasar.B) BLAZARShttp://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980116b.htmlBlazars and quasars areintrinsically the same object— a supermassive black hole witha surroundingaccretion disk, producing a jet —but seen at different orientationangleswith respect to the jet’s axis.http://www.astronomy.com/en/News-Observing/Ask%20Astro/2011/01/Blazar%20vs,-d-,%20quasar.aspx
Japanese and NASA Satellites Unveil New Type of Active Galaxy 07.30.2007http://web.hallym.ac.kr/~physics/course/a2u/agn/agn.htm
They are quasars, positioned in such a way that their dusty rings hide their light,while others are buried in dust-drenched galaxies.Spitzer appears to have found both types of missing quasars by looking ininfrared light. Unlike X-rays and visible light, infrared light can travel through gasand dust.http://www.nasa.gov/vision/universe/starsgalaxies/spitzer-080305.html7. What is a “shrouded” AGN?
Who are we? We find that we live on an insignificant planet of a humdrum star lost in a galaxytucked away in some forgotten corner of a universe in which there are far more galaxies thanpeople.Carl SaganSCIENCE IN THE MEDIABRINGING CUTTING EDGE ASTRONOMY FROM SCIENTISTS TO STUDENTSPUBLIC OUTREACH PROGRAM FOR THE SUZAKU SATELLITE