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A glowing supernova remnant, a cat’s paw-shaped nebula and the iconic “Pillars of Creation” are featured in 25 never-before-seen images taken to celebrate the 25th anniversary of NASA’s Chandra X-ray Observatory.
Named in honor of the late Indian-American astrophysicist Subrahmanyan Chandrasekhar, Chandra was launched into space aboard the space shuttle Columbia on July 23, 1999. The crew, including STS-93 Commander Eileen Collins, placed the telescope into its oval-shaped orbit, which takes Chandra to a distance around Earth that is almost one-third the distance to the Moon.
“On behalf of the STS-93 crew, we are extremely proud of the Chandra X-ray Observatory and its brilliant team who built and launched this astronomical treasure,” Collins said in a statement shared in a NASA announcement on Monday. “Chandra’s discoveries have consistently amazed and impressed us for the past 25 years.”
Chandra has made about 25,000 observations of the universe so far.
The telescope observes the universe in X-ray light, which is invisible to the human eye. X-rays are emitted by some of the most energetic events and hottest objects in the universe, including exploding stars, matter orbiting black holes, galactic collisions, and even exoplanets.
“For a quarter of a century, Chandra has made one incredible discovery after another,” Pat Slane, director of the Chandra X-ray Center at the Center for Astrophysics in Cambridge, Massachusetts, said in a statement. “Astronomers have used Chandra to probe mysteries we didn’t yet know about when we built the telescope, including exoplanets and dark energy.”
But the telescope’s future could be in jeopardy due to NASA budget cuts that threaten to end the mission early by the end of this decade. And without another world-class X-ray observatory to immediately replace it, astronomy research could suffer.
Revealing the hidden universe
The idea for the Chandra mission was first put forward in 1976 by astrophysicists Riccardo Giacconi and Harvey Tananbaum, who realized the importance of having a large X-ray telescope and began its design. Along with the Hubble Space Telescope and the now retired Spitzer Space Telescope and the Compton Gamma-ray Observatory, Chandra is one of NASA’s “Great Observatories” designed in the early 20th century to study the universe at different wavelengths of light.
Slane said the telescope has the highest-quality X-ray mirrors ever built, providing not only spectacular images but also the ability to identify detailed structures that reveal the underlying physics of energetic cosmic objects.
During its mission, Chandra studied the remains of exploded stars to see how matter and energy behave in space under the most extreme conditions.
Shortly after its launch, the observatory focused on Cassiopeia A, a supernova remnant that became an iconic target. Chandra returned to the feature again and again, revealing new information each time.
A remnant is an expanding cloud of matter and energy released when a star explodes. Over time, Chandra’s X-ray data of the remnant allowed astronomers to identify a dense neutron star at the center of the remnant left over from the explosion, and a “superfluid” inside the neutron star. The fluid suggests that the originally massive star may have been inverted as it exploded, helping astronomers better understand the violent evolution of stars.
The observatory has also observed the birth of stars in the Cat’s Paw Nebula and the famous “Pillars of Creation,” and peered into the heart of our own Milky Way galaxy to help astronomers study the supermassive black hole at its center. And Chandra has observed giant galaxy clusters containing hundreds of thousands of glowing galaxies, as well as the soup of superheated gas around galaxies that can only be seen in X-ray light.
“Before Chandra, it was known that there was a kind of haze of diffuse X-ray emission coming from all directions in the sky. With Chandra, we now know that it’s not a haze at all; it’s a large collection of distant black holes whose emissions coalesce in dimmer telescopes,” Slane said.
“There are hundreds of examples like this where Chandra’s sensitivity has led to new discoveries or provided confirmation for existing theories,” he added. “The legacy is not a specific discovery, but unique contributions to the study of things as close as the planets in our Solar System to supermassive black holes near the edge of time.”
With more than 10,000 scientific papers written based on Chandra data, the telescope is one of NASA’s most productive astrophysics missions.
An uncertain future
Slane said NASA’s budget cannot cover all of its current programs and new projects planned for the future may be started, so some older missions like Chandra will face cuts.
“Speaking for Chandra, the cuts will fall somewhere between significantly reducing the observatory’s scientific productivity and support for its user community, or closing the observatory,” he said. “NASA sincerely does not want to do the latter, and the community — and Congress — have been vocal about not reducing funding for a NASA Great Observatory that is still healthy, producing great science, and has no replacement in sight. NASA is currently working to address the overall budget situation and provide final guidance for Chandra.”
Members of the astronomy community have launched a grassroots campaign called Save Chandra to raise awareness and support for the telescope’s future.
NASA’s budget allocation for Chandra will gradually decrease over the coming years, according to a budget request the agency released in March. While the telescope will receive $68.3 million in 2023, Chandra will receive only $41.1 million for operations starting in fiscal 2025. The budget allocation for Chandra will then drop to $26.6 million per year starting in fiscal 2026 and continuing through fiscal 2028, and then to just $5.2 million in fiscal 2029, effectively ending the mission.
Despite 25 years in space, Chandra remains healthy, and nearly all of the spacecraft’s systems are in good working order, Slane said. If any issues arise, such as trying to keep the telescope cool and at its optimum operating temperature, he said the Chandra team has found creative solutions that don’t reduce the telescope’s efficiency. There’s also no concern about the telescope running out of fuel.
Although successor telescope concepts have been considered to replace Chandra, such as the Lynx X-ray Observatory with better imaging capabilities, their development has not been selected as a top priority, so there is no immediate X-ray observatory to deploy if the Chandra mission ends at the end of the decade.
Chandra plays an important role not only as an X-ray telescope, but also in providing data that matches observations from other telescopes. Combined, all of these wavelengths of light provide a more complete picture that allows astronomers to unravel the ongoing mysteries of the universe. The loss of the telescope will also impact the next generation of X-ray astronomers whose research is supported by Chandra.
“The loss of Chandra at this time would be devastating not just for X-ray astronomy, but for much of astronomy,” Slane said. “Operation into the next decade would provide a framework within which — in addition to continuing to produce top-level science — NASA can plan for the natural continuation and growth of the U.S. X-ray astronomy program.”
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