Cover Stories: Cygnus X-1—The Bigger Picture

Science  03 Aug 2012:
Vol. 337, Issue 6094, pp. 497
DOI: 10.1126/science.337.6094.497

Cover stories offer a look at the story behind the art on the cover: who made it, how it got made, and why.

Melissa Weiss

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See the special section in this issue

The Science cover is a great canvas but also a restrictive one: 8.25 inches wide, 10.5 inches tall, portrait orientation, no exceptions. At times that has forced us to make some tough choices. Case in point: The visualization of Cygnus X-1 used for this week’s special issue on black holes. Arresting as the image is, it’s only part of a larger, even more dynamic visualization (shown below), created by Melissa Weiss, who since 2001 has served full time as illustrator and graphic designer for the Education and Public Outreach program of NASA's Chandra X-Ray Observatory project.

Cygnus X-1, an object with a long pedigree in black-hole science, plays a prominent role in the special issue Review by Rob Fender and Tomaso Belloni and was a natural choice for this cover. Originally discovered in 1964, this binary system was the first x-ray source that dynamical observations suggested might contain a black hole. The object has spawned many papers since its discovery, including the three 2011 studies, based on Chandra data and other observations, that formed the raw material for Weiss's visualization.

[Cygnus X-1 was also, incidentally, the subject of a celebrated wager between two astrophysical titans, Stephen Hawking and Kip Thorne (the author of a Perspective in this issue). In 1974, Hawking bet Thorne that the Cygnus X-1 system did not contain a black hole. By 1990, however, enough data had been accumulated that the object’s black-hole origins were beyond reasonable doubt, and Hawking conceded the bet. As previously agreed-upon payment, he sent Thorne a year’s subscription to a well-known men’s magazine—“to the outrage,” as Hawking later wrote, “of Kip’s liberated wife” (1).]

Melissa Weiss's complete visualization of the Cygnus X-1 system.

CREDIT: NASA/CXC/M.Weiss

Weiss’s visualization shows the spinning black hole—15 times the mass of the Sun but less than 60 kilometers across—next to its companion star, the blue supergiant HDE 226868. The black hole’s powerful gravity is capturing material from the star’s stellar wind, which sweeps into an accretion disk surrounding the black hole and some of which is spewed out in two perpendicular high-energy jets. At its event horizon, Chandra data suggest, the Cygnus X-1 black hole is spinning at a rate of more than 800 times per second.

How does one visualize something so remote from ordinary human experience? Weiss says it’s very much a team effort, involving the scientists who obtain, interpret, and model the data; a talented communications team that distills the science’s significance into plain language and working sketches; and Weiss, who turns those ideas into art.

There are also, of course, multiple iterations until everyone is satisfied. Often choices that she has made for visual reasons (say, the texture, shading, and color contrasts on the surface of the star) don’t make the cut when reviewed by the scientific team. “I never ignore their critiques,” notes Weiss, even though they might diminish some of the visual impact. Ultimately, she says, “there are two things that are important in the outcome. One, is the science right—are we getting all the details that we do know about in there? And, two, is it an image that will be striking for people that might not necessarily understand the whole concept?” These criteria apply not just to this particular visualization but to imagery for all Science covers.

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Chandra X-ray image of Cygnus X-1

CREDIT: NASA/CXC

Making things even more challenging, Weiss says, is the nature of the data from Chandra itself – in the x-ray rather than the visible part of the spectrum and often picturing very remote objects, such as the 6000-light-years–distant Cygnus X-1. “If you’re looking at the Chandra image of Cygnus,” she notes, “it’s just a blue glowing orb. It doesn’t explain at all, really, what you’re seeing.” Her work, she hopes, can go beyond that: “While not a photograph by any means,” it represents one way of “making us understand the possibilities of what we’re seeing.”

For us at Science, the challenge was fitting Weiss’s beautiful, but strongly horizontal, visualization into the strictly vertical showcase of our cover. In general I don’t like to crop artwork as fine as this, and we did indeed try to avoid it, experimenting with rotating the image 90 degrees or so (since there is, after all, no “up” or “down” in space). But we found that those other orientations, although still scientifically accurate, skewed enough away from what readers might expect as to be distractingly jarring. So in the end, we presented only part of the image on the cover, and are pleased to provide the rest of the story here.

—Yael Fitzpatrick, Art Director, Science

References and Notes

  1. More images can be found on on the Chandra site.
  2. Black hole special issue introduction.

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