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By Michael Klesius
Photograph by NASA/Daniel Wang, University of Massachusetts

The orbiting Chandra X-ray Observatory lifts the veil on exploding stars, pulsars, quasars, and black holes.

Get a taste of what awaits you in print from this compelling excerpt.

Hidden from the view of a stargazer on Earth, the x-rays that reveal the most violent events in the cosmos find sharp focus with Chandra. The Chandra X-ray Observatory, named for renowned astrophysicist Subrahmanyan Chandrasekhar, is the third of NASA's four Great Observatories (with the Hubble Space Telescope, the now defunct Compton Gamma Ray Observatory, and the soon-to-launch Space Infrared Telescope Facility). Sent into orbit in July 1999, Chandra has electrified astronomy with discoveries about the nature of black holes, the formation of galaxies, and the life cycles of stars.

* * * * * *

Unlike satellites such as Hubble that circle the planet every 90 minutes, Chandra orbits Earth every 2.6 days. It travels a third of the way to the moon to allow longer observation time and to slip beyond Earth's Van Allen radiation belts, which can disrupt imaging.

* * * * * *

What could be emitting x-rays way out there? To find out, astronomers pointed Chandra into the southern hemisphere at a tiny patch of sky that appeared blank. For a total of 11 days over the course of more than a year, Chandra soaked up the faintest x-rays from this remote spot. Like a bore hole into deep space and the distant past, the resulting image, called Deep Field South, clearly showed a great variety of x-ray sources, including luminous quasars and active galactic nuclei powered by supermassive black holes. Chandra is giving scientists a peek at galaxies at a much earlier stage of formation. "That's the excitement," says Harvey Tananbaum, director of the Chandra X-ray Center at the Smithsonian Astrophysical Observatory. "Chandra shows us how spectacular the universe is."

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In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.

Did You Know?
Chandra's million-second exposure of deep space, which revealed some of the most remote celestial objects imaginable, must bring thrilling satisfaction to the scientists who struggled to convince the astronomical community that the x-ray sky would yield wonderful secrets. Alternately dismissed as a futile endeavor and grudgingly endorsed for simple experiments, x-ray astronomy has come to maturity in a surprisingly short time.

By the 1950s we had been observing the sky with optical telescopes for 350 years, but the x-ray universe was still an enigma. Earth's atmosphere absorbs x-rays, thus no observations of the high-energy objects that emit them can be done with ground-based telescopes. Young physicists stretched their intellects and imaginations to build detectors that could transcend the obstacles—human or earthly—and observe the elusive particles theorized to zip through space and bombard the upper atmosphere. The post World War II era gave these physicists an opportunity to place their nascent detectors on leftover sounding rockets and launch them a hundred miles (160 kilometers) above Earth.

The first celestial x-ray source was discovered in 1962. It was an unusual bright blue star located in the direction of the constellation Scorpius. The observation lasted all of 350 seconds. Scientists persevered, sending their instruments up on rockets and balloons whenever they could. In 1970 the first Earth-orbiting satellite dedicated to x-ray astronomy—named Uhuru—was launched and operated for three years. A couple dozen missions have flown since, and right now two other orbiting x-ray observatories—NASA's Rossi X-ray Timing Explorer and the European Space Agency's XMM-Newton Observatory—complement the discoveries Chandra is making. X-ray astronomy is giving us spectacular vision of an explosive and turbulent universe. Ultimate recognition of the significance of revealing the x-ray sky came in October 2002 when Riccardo Giacconi, a stalwart x-ray astronomer, was awarded the Nobel Prize in physics.

— Barbara W. McConnell

Did You Know?

Related Links
Chandra X-ray Observatory Center
Visit the main site for images made by the Chandra observatory, with links to historical information, spacecraft data, and other resources.

NASA Space Science
Go to this page for links to images and news about all areas of space science.

Space Missions
Find information on past, present, and future space missions at this site.

Hubble Space Telescope
One of NASA's Great Observatories, the Hubble Space Telescope complements observations made by Chandra.


Maran, Stephen P., ed. The Astronomy and Astrophysics Encyclopedia. Van Nostrand, 1992.

Mitton, Jacqueline. Cambridge Dictionary of Astronomy. Cambridge University Press, 2001.

Tucker, Wallace, and Karen Tucker. Revealing the Universe, The Making of the Chandra X-ray Observatory. Harvard University Press, 2001.


NGS Resources
DeVorkin, David. "Beyond Earth: Mapping the Universe:" National Geographic Books, 2002.

Nyquist, Kate. "Exploring Space," National Geographic Books, 2002.

Trefil, James. "Other Worlds: Images of the Cosmos From Earth and Space," National Geographic Books, 1999.

Sawyer, Kathy. "Unveiling the Universe," National Geographic (October 1999), 8-41.

Newcott, William R. "Time Exposures: The Hubble Telescope Views the Universe From Space," National Geographic (April 1997), 2-17.

Smith, Bradford. "New Eyes on the Universe," National Geographic (January 1994), 2-41.


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