Solving the mystery of black holes

Editor's note: Meg Urry is the Israel Munson professor of physics and astronomy and chairwoman of the department of physics at Yale University, where she is the director of the Yale Center for Astronomy and Astrophysics. This article was written in association with the Op-Ed Project.

Anchorage, Alaska (CNN) -- In Ballroom E of the Den'aina conference center here Wednesday, a small group of astronomers and journalists listened to the NASA feed from Kwajalein island, between Hawaii and Australia, where a Pegasus rocket aboard an L1011 plane was about to launch the NuSTAR space telescope. I was there as a member of the science team for NuSTAR, which is part of NASA's Small Explorer program

Many years in the making, NuSTAR carries an important scientific instrument designed to look for energetic X-rays from cosmic sources like black holes and exploded stars.

Most of us know about X-rays used for diagnostic imaging of broken limbs or for security scans at the airport. They are a high-energy form of light, energetic enough to penetrate clothing or flesh.

Meg Urry

But X-rays are also a form of light emitted from the hottest, most energetic matter in the universe. They tell us about enormous clusters of galaxies held together by gravity, for example, or about the chemical elements produced by exploding stars called supernovae.

X-rays also come from matter falling onto black holes, both the "small" black holes in our Milky Way galaxy, which are about 10 times the mass of our sun, and the "supermassive" black holes, which are millions to billions times larger than the sun and lie in the center of nearly every galaxy.

The launch of NuSTAR means there will be an important new observatory for studying the cosmos.

More on the launch of NuSTAR from CNN Light Years

Black holes exert a strong gravitational pull on the stars and galactic matter around them. As material falls toward the black hole, it gains energy, just as any object gains energy when you drop it. The pull of a black hole is so strong that infalling matter heats up to millions of degrees, as hot as or hotter than the interior of the sun. All hot matter emits light, and the higher the temperature, the more energetic the light -- hence the X-rays emitted by growing black holes.

NuSTAR is very well-matched to the temperature of material surrounding black holes. Moreover, it is the first space telescope capable of taking pictures in high-energy X-rays that penetrate even dense clouds of surrounding matter.

This means NuSTAR can see growing black holes regardless of their surroundings. Thanks to earlier observations with the Chandra X-ray telescope, along with the Hubble Space Telescope and the Spitzer Infrared Space Telescope, we know that most black hole growth occurs behind a thick cloud of gas and dust. It's basically hidden from view, as if behind an opaque curtain. As a result, current estimates of the overall growth of black holes over cosmic time still involvs some guesswork. NuSTAR will change those guesses into firm measurements: the amount of black hole.

Fiona Harrison, a Caltech professor and leader of the NuSTAR project, worked with her team for more than a decade to develop the technology and design for NuSTAR. Wednesday morning, her hard work paid off.

Omar Baez, the NASA launch director, polled the launch team for readiness to launch. "Go," they said, one after the other. "Ready for launch," Baez said.

One final checklist, then, at last, the countdown: three, two, one -- and the L1011 released the Pegasus rocket. It fired.

NuSTAR is launched.

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The opinions expressed in this commentary are solely those of Meg Urry.