Chandra
FIREBALL. Chandra's debut was this spectacular image of a supernova remnant, designated Cassiopeia A. The X-ray image shows an expanding shell of hot gas produced by the supernova explosion. This gaseous shell is about 10 light years in diameter and has a temperature of about 50 million degrees. Visible to astronomers for the first time is the bright spot at the center of the image, which may be a neutron star or a black hole.

Following its flawless launch from the space shuttle Columbia on July 25, the Chandra X-Ray Observatory climbed smoothly toward its final orbit. Before it got there, though, eager astronomers began checking the viewing systems on the huge X-ray telescope, which promise to shed new light on hot, violent events in the universe and provide clues to the origin of life. Less than a month later, the atronomers were ready. With Chandra pointed at a distant galaxy, the the sunshade door protecting its sensitive optics opened and the telescope received its "first light."


Rosat image Optical image
COMPARISON. The Chandra image (upper left) vastly exceeds the resolution of the same view of Cassiopeia A recorded by ROSAT(top). Meanwhile, an image of the same scene in visible light (bottom) reveals little of the violent activity of this supernova remnant.

Observers at the Harvard-Smithsonian Astrophysical Observatory's Chandra X-ray Center in Cambridge, Mass. cheered and applauded as the first images were transmitted back to Earth from Chandra's High Resolution Camera. One records the aftermath of a gigantic stellar explosion in such stunning detail that scientists can see evidence of what may be a neutron star or black hole near the center. Another shows a powerful X-ray jet blasting 200,000 light years into intergalactic space from a distant quasar.

The pictures, which were released on August 26, erased fears that Chandra might be plagued with flaws such as those that crippled the Hubble Space Telescope in its early years. And they seem to indicate that Chandra--the latest of NASA's Great Observatories--will meet or exceed astronomers' wildest expectations as a new tool for probing the origins of the cosmos. Because X-rays are absorbed by the atmosphere, images in that wavelength can only be obtained from space-based instruments. Chandra has a resolving power some 20 to 50 times greater than that of ROSAT--until now, the most sensitive X-ray telescope in orbit. As such, Chandra will provide astronomers with a much clearer window on stellar explosions, black holes, quasars and neutron stars.

Chandra's most spectacular image so far is of a supernova remnant, first seen from Earth 320 years ago, called Cassiopeia A (top). Astronomers believe Cas A was produced by the explosion of a massive star. Material blasted into space from the explosion crashed into surrounding material at 10 million miles per hour, creating a vast 50-million degree bubble of X-ray emitting gas. The image may help solve the mystery of whether the explosion left behind a neutron star, black hole or nothing at all. The image shows a bright object near the center of the remnant. Longer observations with Chandra can determine if this is the long sought after neutron star or black hole.

"We were astounded by these images," says Harvey Tananbaum, director of the Chandra X-ray Center. "We see the collision of the debris from the exploded star with the matter around it; we see shock waves rushing into interstellar space at millions of miles per hour; and as a real bonus, we see for the first time a tantalizing bright point near the center of the remnant that could possibly be a collapsed star associated with the outburst."

Quasar
QUASAR JET. A powerful X-ray jet blasts out from quasar PKS 0637-752 into intergalactic space for a distance of at least 200,000 light years. It's presence means that electromagnetic forces are accelerating electrons to extremely high energies over enormous distances.

The young telescope also sent back a picture of a distant and very luminous quasar, known as PKS 0637-752. It is so far away that we see it as it was 6 billion years ago, and it radiates with the power of 10 trillion suns from a region smaller than our solar system. Astronomers believe the source of this prodigious energy is a supermassive black hole. Radio observations of PKS 0637-752 show that it has an extended radio jet that stretches across several hundred thousand light years. Chandra's X-ray image reveals a powerful X-ray jet of similar size that is probably due to a beam of extremely high-energy particles.

But as impressive as they are, the images made by Chandra's High Resolution Camera are not the whole story. Other equally important instruments onboard Chandra are its spectromers. One of these devices, the High Energy Transmission Grating Spectrometer (HETGS), was activated on August 28.

Astronomers
YEAH! Elated astronomers at the Harvard-Smithsonian Astrophysical Observatory celebrate as Chandra beams back its first images.

The spectrometers spread the X-rays from the telescope's mirrors into a spectrum, much as a prism spreads light into separate colors. The spectrum can then be read by Chandra's imaging detectors, like a cosmic bar code from which scientists can deduce the chemical composition and temperature of stellar objects. The HETGS, which was developed at MIT, will allow a one-thousand-fold improvement in the capability to measure X-ray spectra from space.

The HETGS's first target was Capella, a star some 40 light-years away in the constellation Auriga. Capella is actually two stars orbiting one another and possibly interacting in ways that pump extra heat into the corona, which appears more active than that of our sun. How a star manages to heat its corona to temperatures a thousand times hotter than its own surface is still a puzzle, and astronomers hope that observations with the HETGS can solve it.

Chandra should help resolve other outstanding mysteries. Heavy elements in hot gas produce X-rays of specific energies. Chandra's ability to precisely measure these X-rays tells how much of each element is present. And with this information, astronomers can investigate how the elements necessary for life, such as oxygen and carbon, are created and spread throughout the galaxy by exploding stars. "Chandra will help to confirm one of the most fascinating theories of modern science," says Professor Robert Kirshner of Harvard University, "that we came from the stars."