Release = 8.0.1
Beta = 9.0.b5
Aurora = 10.0a2
Nightly = 11.a1

Aurora is the name of one of the channels and is not tied to any one version. Currently the versions on each channel is Release = 8.0.1 Beta = 9.0.b5 Aurora = 10.0a2 Nightly = 11.a1 When Firefox 9.0 is on Release channel the 10.a2 will move/merge to Beta channel as 10.0b1 and the 11.0a1 will start move/merge process to the Aurora channel as 11.0a1 within a few days. Then the version 12.0a1 will start on the Nightly channel. This process will start as early as December 20. Aurora gets update patches every 1 to 3 or so days whenever there are checkins while the Nightly gets checkins everyday and sometimes has a respin. The Aurora and more so the Nightly channels are meant more for testers and devs and not regular Firefox users. https://wiki.mozilla.org/Releases

Beta is already 9.0b5: *http://www.mozilla.com/en-US/firefox/all-beta.html *https://www.mozilla.com/en-US/firefox/9.0/releasenotes/