Clouds Orbiting a Supermassive Black Hole

Link to NASA Feature page is HERE


We have completed observational work (A. Markowitz, M. Krumpe, & R. Nikutta, 2014, MNRAS, in press) to test new theoretical models that describe the configuration of gaseous material in the vicinity of accreting supermassive black holes. These models (M. Elitzur & I. Shlosman, 2006, ApJ, 648, L101; M. Elitzur 2007, ASPC, 373, 415) quantify the material surrounding supermassive black holes as "clumpy" or "cloudy," as opposed to be distributed in a homogeneous "donut" as per the classical standard picture (e.g., C.M. Urry & P. Padovani, 1995, PASP, 107, 803).

As per the model, what we observe on Earth for any one given black hole system depends on the orientation of the black hole system relative to us: from some angles, there are many clouds blocking our line of sight to the central black hole/light engine; from other angles, we have a relatively clean, cloud-free line of sight.

Using NASA's Rossi X-ray Timing Explorer, we monitored the X-ray activity of 55 supermassive black hole systems to search for eclipse events where clouds drifted in front of, and temporarily dimmed, their central light source. We found 12 such eclipse events (including four previously discovered with RXTE) in eight black hole systems, which is consistent with what the new model predicts. Most of our clouds reside light-weeks to light-months from their respective black holes, in or beyond the dust sublimation region. Our work is thus complementary to other recent studies of X-ray-absorbing clouds that reside much closer to the black hole, in the non-dusty Broad Line Region (e.g., G. Risaliti et al. 2011, MNRAS, 410, 1027, R. Maiolino et al., 2010, A&A, 517A, 47, using Chandra, XMM-Newton, or Suzaku).

Link to paper:

"First X-ray-Based Statistical Tests for Clumpy-Torus Models: Eclipse Events from 230 Years of Monitoring of Seyfert AGN," A. Markowitz, M. Krumpe, & R. Nikutta, accepted 2013 Dec. for publication in Monthly Notices of the Royal Astronomical Society, available on the Oxford Univ. Press website, at (1402.2779), or available here. (Note: to be updated when journal volume/page numbers are assigned).


Conceptual animation was generated by Dr. Wolfgang Steffen, UNAM, Mexico. The aim of the video is to visually describe the distribution and movement of gas clouds orbiting a supermassive black hole, and the possible range of observations we see from Earth.

Clouds are preferentially distributed towards the "equatorial plane." The camera starts at an angle well below this plane, giving relatively unobscured views of the "central engine" (cloud eclipse events along this line of sight are rare). The camera then moves to points near the equatorial plane, illustrating that here, the likelihood of having sightlines blocked by multiple clouds is extremely high. The camera then moves away from the equatorial plane towards regions of relatively fewer clouds. The double-cloud eclipse event that transits near the end represents the eclipse event we observed in the black hole system NGC 3783: possibly a cloud getting ripped in half by the tidal forces of the black hole.

Animation combined with intro/outro produced by NASA/GSFC/SVS is HERE.

Technical version: Here, we include icons depicting varying model X-ray spectra to illustrate the effects of variable absorption on the observed X-ray spectrum.
.flv version (31 MB)
.mpg version (167 MB)
On W. Steffen's YouTube page

Non-technical version: Here, we use an analogy to the local weather one might experience on Earth. Weather forecasters use models to predict the likelihood that you will have a "sunny" or "partly cloudy" or "mostly cloudy" sky: depending on how many clouds are present that day, one's line of sight to the Sun may be blocked by clouds or stay relatively cloud-free. In the video, we include weather forecasting symbols ranging from mostly sunny to extremely cloudy, corresponding to the amount of observed "cloudiness" in the black hole system depending on position.
.flv version (31 MB)
.mpg version (167 MB)
On W. Steffen's YouTube page

"Plain" version with no icons:
.flv version (31 MB)
.mpg version (167 MB)
On W. Steffen's YouTube page


Selected Still-Frames:

These pictures are based on the above video; you may use them freely, but only if you give appropriate credit: "Credit: Conceptual illustration by Wolfgang Steffen, Inst. de Astronomía, UNAM, based on Markowitz, Krumpe, & Nikutta (2014) and Elitzur & Shlosman (2006)"

Relatively-unobscured (low probability of eclipse) view:
Frame 1910 Frame 1730
Partially-obscured (moderately-high probability of eclipse) view:
Frame 1250 Frame 1340 Frame 0560
Transit of the double-cloud event in NGC 3783:
Frame 1520 Frame 1550

Selected Article Links (so far...):


Royal Astronomical Society (
RoyalAstroSoc on Twitter


Universidad Andrés Bello, Santiago: (SPANISH)

Universität Erlangen-Nürnberg: (GERMAN)

Alphagalileo (via Robert Massey, RAS)
Eurekalert: Susan Brown's (UCSD) text
Eurekalert: Frank Reddy's (GSFC) text

Astronomy Magazine (
Science Daily
Astronomy Picture of the Day
AAS Press on Twitter (link to RAS site)
Universe Today (multiple videos)
Science World Report (they wrote some expanded text) (RUSSIAN)
Csillagászati Hírportál (Astronomical News Portal) (HUNGARIAN)
BioBioChile (SPANISH)
Europa Press (Spain) (SPANISH)
Der Standard (Austria) (GERMAN)
El Mercurio (Chile) (SPANISH)
I.F.L. Science
Science Newsline
Daily Kos (link to Science Daily)
F.A.U. Blog (English)
Extrem News (GERMAN)
Granz Wissenschaft-Aktuell (GERMAN; link to FAU) (SPANISH)
La Isla de la Astronomia (SPANISH) (SPANISH)
El Sofista's Blog (SPANISH)
World News (
FAI news (Italy; links to RAS)
Financial Express (India)
ZeeNews (India)
Authint Mail (Kashmir) (India)
ANI News (India)
Jharkhand News (Jharkhand, India)
News Voice (Sweden; link to blog (For some reason, they added a picture of NGC 4258 and appended a random paragraph of text on NGC 4258 to Susan's text.)
Nanowerk News (link to
American 4+
Airing News (link to Universe Today)
Science, Space, & Robots (links to (multiple videos) (link to RAS site)
Groupe Astronomie Spa (FRENCH; links to RAS & NASA) (Croatia)
SciTech Daily
Aerospace & Defense News
Dark Matter Hunters ( Space News
Big Think (Chinese)
Free Republic
State of Delmarva (links to
e! Science News (links to
Physics Inventions
Nets247 (links to
In A Gist (links to NASA page)
AstroNews U.S.
MyScienceAcademy (contains trivia about the 1960s Scottish rock band "Clouds")
Science 2.0
365 Days of Astronomy

Last updated: 2014 Mar 23