X-Ray Vision in Outer Space! Chandra Sees Previously Invisible Phenomena

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October 07, 1999

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By Cassie Ferguson
Gazette Staff

Chinese astronomers first spotted the Crab Nebula in 1054 A.D., when the star's explosive demise was so bright they could see it by daylight. Ever since, stargazers have investigated the still-pulsating core of the explosion with tools from simple telescopes to gamma-ray telescopes. The most recent Chandra images, released in late September, allow researchers to trace the path of energy through the swirling nebula, providing clues to why the explosion could still be glowing so brightly 1,000 years later. According to Murray, who likens the Crab to a cosmic spinning top, the newly discovered clouds surrounding the core may be material orbiting the neutron star. Image courtesy CXC/NASA/SAO

Aiming Chandra's eye at the remains of supernova Cassiopeia A revealed tantalizing hints of the hidden heart of the stellar explosion, either a neutron star or black hole. The new images, among the first captured by the telescope, show the former star as a bright point with two waves streaming from it, an outer one rushing at millions of miles per hour like a giant sonic boom, trailed by a slower wave of explosion debris superheated to 50 million degrees. Of the images, Harvey Tananbaum, director of the Smithsonian Astrophysical Observatory's Chandra X-ray Center, said, "We were astounded." Image courtesy CXC/NASA/SAO

Couched in a cloud of gas and high-energy particles, collapsed star PSR 0540-69 spins 20 times per second, broadcasting radio beams in a manner similar to a lighthouse signal. Using Chandra, Stephen Murray, an associate of the Harvard College Observatory, spotted the supernova remnant, which was first discovered by Harvard College Observatory Associate Frederick Seward and his colleagues with the Einstein Observatory over a decade ago. The new image helps to explain the complex physics of how energy is transferred from the star to its surroundings. "The X-ray images allow us to look into the interior and to get a sense of dynamics," said Murray. Image courtesy CXC/NASA/SAO

An artist's rendition of the Chandra X-ray observatory. Image courtesy CXC/TRW

It takes something beyond the scale of spectacular to capture the imagination of astrophysicists or astronomers, people for whom matters such as the speed of light and billions of miles are routine. Images from the new Chandra X-ray observatory have impressed space researchers enough that they describe them with a giddy glint in their eyes and use terms such as "beautiful," "awesome," and a "dream come true."

Hundreds of people affiliated with the Harvard-Smithsonian Center for Astrophysics (CfA) helped to build and operate Chandra. The space telescope is designed to observe X-rays, revealing phenomena such as the blatant violence of a stellar explosion and the more subtle workings of energy transfer among its remains – events that are invisible to the human eye. Shuttle astronauts launched the $1.5 billion satellite containing the observatory late in July. Weeks later, researchers had a taste of the data to come.

At a September NASA press conference held to release Chandra's first images, Robert Kirshner, professor of astronomy, said, "To do this on Day One to me is like an infant somehow opening its eyes for the first time and discovering a new planet."

Taken during the initial checkout and calibration of the observatory, the first images included snapshots of the remains of 320-year-old supernova Cassiopeia A. Researchers could even pick out the previously indistinguishable collapsed star at the center of Cassiopeia A. Harvey Tananbaum, director of the Smithsonian Astrophysical Observatory's Chandra X-ray Center, said "Those of us who have worked on it are absolutely enthralled with it."

Since then, Chandra has revealed a steady stream of images of quasars and supernovas – pictures of X-rays, which are then painted with "false" color to represent different energy intensities. Researchers at the CfA and other institutions have planned hundreds of projects using the observatory.

Stephen Murray, associate director of the high e nergy astrophysics division at the CfA and an associate of the Harvard College Observatory, one of the telescope's principal research investigators, will use Chandra to survey vast stretches of "empty" space. Using the high-resolution camera, one of two cameras on the Chandra Observatory, he plans to "pick a part of space and stare at it."

"It turns out that when we see visible light, we only see a fraction of what's there. Some material is so hot that it only emits X-rays. We want to see everything," Murray said. "I expect to see some things I haven't seen before, new X-ray animals in the zoo."

In the future, Chandra may reveal more about black holes, colliding galaxies, quasars, and other yet-to-be-discovered stellar exotics. As it records information about the life cycle of energy in the universe, the observatory may also uncover how stellar materials such as calcium and carbon could become part of a planet or the life that inhabits it.

Murray said, "It's wondrous to think that everything inside you was in a star or even two generations of stars."