This page was edited by Tom Henry LMC Spring 2011

AGN or Active Galactic Nuclei are Supermassive black holes in the centers of almost every galaxy. Here are some links I found to sources that describe AGN very well.

The First page I found was Active Galatic Nuclei

This page briefly explains how AGN are able to be seen through the use of x-ray sensors and infrared cameras, and how not all of them are not absorbing the galixy that they are in. I found the language used to be very understandable and easy to read

Author: Califorina Institute of Technology
Date accessed: 5/23/2011
Audience: Middle school and up


The second page that I found was AGN

This page goes into great detail about how black holes are formed and how supermassive black holes become so massive. Unfortunatly there is a lot of reading on this page and it is definatly based on a college audience. I had to read it a couple of times to understand it.

Author: Unknown
Date accessed: 5/23/2011
Audience: College Plus


The third page I found was AGN & Supermassive Black Holes

This page goes great lengths to describe how x-rays emitted from AGN allow astronomers to determine the size of it and to see its shape and wither or not it is consuming the galaxy. The language in this page was very easy to understand.

Aurthor: Institute of Astronomy X-Ray Group
Date Accessed: 5/23/2011
Audience: High school and up

The fourth page that I found was Galactic Mergers Fail to Feed Black Holes

This page explains a theory many astronomers had about how AGN feed on galaxies and what could trigger them from being dormant to being active again. This link explains a cleaver study that was preformed and how they followed all the right procedures and how they were even able to make it a blind study. The writing and word choice used for this link is very easy to read and understand if you have the knowledge of the scientific process.

Author: Nicholos Wethington
Date Accessed: 5/23/2011
Audience: High school plus


The fifth page that I found was Active Galaxies and Quesars

This page explains how you can tell the difference between an AGN and a Non-Active Galactic Nuclei. The difference is in the about of energy that is released. This site also explains how
Seyferts, Quasaurs, and Blazars (The names for active galaxies) are really all the same just from different views. The language used on this page is easy to read unfortunatly there is a lot of highlighting and that make the reading a little tedious.

Author: Dr. Barbara Mattson, Meredith Gibb, and Phil Newman
Date Accessed:5/23/2011
Audience: High school plus

This page was edited by Katie Silva LMC Spring 2011

Accretion Disks


Accretion disks form when material such as gas is being transfered from one object to another. "Accretion" means the collecting of additional material and a "disk" is something with a flat and round surface. To find out more, I posted the following links that are very good sources of information regarding accretion disks.

external image blackhole3.jpg























Image location: http://maxim.gsfc.nasa.gov/images/blackhole3.jpg


The first page I visited was http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/001106a.html This page was great in the fact that it answered the questions regarding the basics of accretion disks. I found the context of the explanation easy to understand. What was also helpful is the fact that at the end of the explanation, the author offered another two websites which could further back up his explanation.
Author: Hanns Krimm for "Ask an Astrophysicist"
Date Accessed: 5/14/11
Audience: High School students and above.

external image protostar.jpg
Image location: http://www.physics.hku.hk/~nature/CD/regular_e/lectures/images/chap14/protostar.jpg


The second page I found was http://imagine.gsfc.nasa.gov/docs/features/exhibit/asca_agndisk.html This page explained relativistic accretion disks in AGN (active galactic nuclei: A class of galaxies which spew massive amounts of energy from their centers, more than ordinary galaxies). A chart was also given in order to explain accretion disks in a binary system. The explanation was a pretty straight forward and it provides readers with further information about where accretion disks can be found.
Date Accessed: 5/14/11
Audience: High school students and above.

external image accretiondisk_hst.jpg
Image location: http://antwrp.gsfc.nasa.gov/apod/ap991219.html


The third page that I visited was http://www.daviddarling.info/encyclopedia/A/accretiond.html It gave me a pretty simple and easy to understand definition of accretion disks and it offers many links to different terms of objects related to the disks. Other things covered in this page are areas in the universe where accretion disks tend to form.
Date Accessed: 5/14/11
Audience: Middle school students and above.

external image dust_disk_080205.jpg
Image location: http://www.daviddarling.info/images/dust_disk_080205.jpg


The next website I visited was http://www.astrophysicsspectator.com/topics/disks/Accretion.html This page on accretion disks is very thorough in its explanation. I really liked the way it went into depth about how these disks are formed and where they can be found. On top of offering a more technical explanation, the website I found this page on is very easy to navigate, and has a lot of links to different terms found in astronomy (planets, stars, galaxies, etc.).
Date Accessed: 5/14/11
Audience: Middle school students and above.
Author: Issue 2.20, May 25, 2005. The Astrophysics Spectator.


external image A_disk.gif
Image location: http://ircamera.as.arizona.edu/astr_250/images/A_disk.gif


The fifth webpage I visited was http://www.astronomy.com/asy/default.aspx?c=a&id=6464 This was an article about dark matter being found in accretion disks. This was really interesting, as it says that the current models of accretion disks are actually wrong, since the disks themselves are actually larger than they appear to be. It made for an interesting read, however, I felt that it was too short and that the author should of explained more about dark matter.
Date Accessed: 5/14/11
Audience: Middle School students and above.
Author: Article provided by NOAO.

external image accretion-old.ashx?bc=ffffff&mw=200
Image location: http://www.astronomy.com/~/media/import/images/c/5/5/accretion-old.ashx?bc=ffffff&mw=200

I found the above websites to be very useful in helping me understand what accretion disks do. I had no prior knowledge of them before doing this project, but I feel that with the information obtained through each of these links individually as well as all of them together, I have a better understanding of the subject and hope that you do too!