Orion HST

Cloudy workshop

Nearly all of the quantitative information we have about the cosmos is the result of spectroscopy, the science of using spectra to make physical measurements. We can directly measure the temperature, density, pressure, or composition of a cloud of gas or a star, using a telescope and a spectrometer.

The spectrum forms in highly non-equilibrium gas and dust. Analytical theory cannot be used to understand the conditions so numerical simulations are required. Cloudy is a code that does this - it calculates the ionization, chemistry, radiation transport, and dynamics simultaneously and self consistently, building from a foundation of atomic and molecular processes. The result is a prediction of the conditions in the material and its observed spectrum. These predictions depend on detailed atomic and molecular processes, a complication, but is also why the spectrum reveals so much about its source.

Perhaps the best way to check if Cloudy is something that might be helpful in your research is to see how others have used it. The NASA ADS web site provides links to papers that cite our documentation. Have a look at what the papers that cited the 2017, 2013, or original PASP review did.

Workshop format

We will cover observation, theory, and apply Cloudy to a wide variety of astronomical environments, including the interstellar medium, AGB stars, Active Galactic Nuclei, Starburst galaxies, and the intergalactic medium. The sessions will consist of a mix of textbook study, using Osterbrock & Ferland, Astrophysics of Gaseous Nebulae and Active Galactic Nuclei, and application of Cloudy to research problems chosen by participants. No prior experience with Cloudy is assumed, although participants should have a reasonable knowledge of undergraduate-level spectroscopy and atomic physics.

Participants will break up into small teams and organize research projects of mutual interest. Previous projects are summarized on the participants pages.

Christophe Morriset made videos of presentations at the 2017 Tonantzintla workshop. You can view them here. These give a sense of what the workshops are like and what we do.

How to register

Go to the registration tab for instructions for future workshops.


The workshop schedule is on the agenda page. Participants should arrive the evening before the first day, and plan on staying for the full duration of the workshop. The workshop ends with the presentation and discussion of project results late Friday afternoon.

More information

The homework page describes what must be done to prepare for the workshop. The transportation and lodging page gives more information on the workshop location.

Next workshop

None planned at this time.

Where: TBA

Previous workshops

Where: University of Kentucky, Room B108a of the Young Library
When: Tuesday May 29 through the end of Friday June 1. Participants

Where: Queen's University Belfast, Computer Suite (Room F024), Second Floor, Main Physics Building, School of Mathematics and Physics.
When: August 18-22 Participants

Where: Leiden University, Observatory computer room, Huygens building
: Oct 10 Participants

: Queen's University Belfast, Computer Suite (Room F024), Second Floor, Main Physics Building, School of Mathematics and Physics.
When: January 12-16 Participants

Where: Durham University Ogden Center, room OC218.
When: March 26 Participants

Where: Nicolaus Copernicus Astronomical Center, Warsaw
When: May 4-8 Participants

Where: Inter-University Centre for Astronomy and Astrophysics, Pune, India. Workshop Website
When: Sept 21-26 Participants

:Shangdong University at Weihai, China
When: 2016 June 20-24 Information and registration, Participants

Where: Guillermo Haro advanced school at INAOE (Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla, Mexico)
When: 2017 July 3rd to 14th  Information, Participants

Where: Queen's University Belfast
When: 2017 July 31 - August 4. More information, participants

Where: NARIT, Chiang Mai, Thailand
2018 May 14-25, information, participants

Where: University of Kentucky, Lexington
When: 2019 May 20 - 24, information, participants

Where: Cambridge University, DAMTP
When: 2019 July 1, agenda