Fifteen years ago, NASA's Chandra X-ray Observatory was launched into space aboard the Space Shuttle Columbia. Since its deployment on July 23, 1999, Chandra has helped revolutionize our understanding of the universe through its unrivaled X-ray vision.
Chandra, one of NASA's current "Great Observatories," along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.
With its superb sensitivity and resolution, Chandra has observed objects ranging from the closest planets and comets to the most distant known quasars. It has imaged the remains of exploded stars, or supernova remnants, observed the region around the supermassive black hole at the center of the Milky Way, and discovered black holes across the universe. Chandra also has made a major advance in the study of dark matter by tracing the separation of dark matter from normal matter in collisions between galaxy clusters. It is also contributing to research on the nature of dark energy.
To celebrate Chandra's 15th anniversary, four new images of supernova remnants — the Crab Nebula, Tycho, G292.0+1.8, and 3C58 — are being released. These supernova remnants are very hot and energetic and glow brightly in X-ray light, which allows Chandra to capture them in exquisite detail.
The images of the Tycho and G292.0+1.8 supernova remnants show how Chandra can trace the expanding debris of an exploded star and the associated shock waves that rumble through interstellar space at speeds of millions of miles per hour. The images of the Crab Nebula and 3C 58 show how extremely dense, rapidly rotating neutron stars produced when a massive star explodes can create clouds of high-energy particles light years across that glow brightly in X-rays.
- Tycho: More than four centuries after Danish astronomer Tycho Brahe first observed the supernova that bears his name, the supernova remnant it created is now a bright source of X-rays. The supersonic expansion of the exploded star produced a shock wave moving outward into the surrounding interstellar gas, and another, reverse shock wave moving back into the expanding stellar debris. This Chandra image of Tycho reveals the dynamics of the explosion in exquisite detail. The outer shock has produced a rapidly moving shell of extremely high-energy electrons (blue), and the reverse shock has heated the expanding debris to millions of degrees (red and green). There is evidence from the Chandra data that these shock waves may be responsible for some of the cosmic rays — ultra-energetic particles — that pervade the Galaxy and constantly bombard the Earth.
- G292.0+1.8: At a distance of about 20,000 light years, G292.0+1.8 is one of only three supernova remnants in the Milky Way known to contain large amounts of oxygen. These oxygen-rich supernovas are of great interest to astronomers because they are one of the primary sources of the heavy elements (that is, everything other than hydrogen and helium) necessary to form planets and people. The X-ray image from Chandra shows a rapidly expanding, intricately structured, debris field that contains, along with oxygen (yellow and orange), other elements such as magnesium (green) and silicon and sulfur (blue) that were forged in the star before it exploded.
- The Crab Nebula: In 1054 AD, Chinese astronomers and others around the world noticed a new bright object in the sky. This “new star” was, in fact, the supernova explosion that created what is now called the Crab Nebula. At the center of the Crab Nebula is an extremely dense, rapidly rotating neutron star left behind by the explosion. The neutron star, also known as a pulsar, is spewing out a blizzard of high-energy particles, producing the expanding X-ray nebula seen by Chandra. In this new image, lower-energy X-rays from Chandra are red, medium energy X-rays are green, and the highest-energy X-rays are blue.
- 3C58: 3C58 is the remnant of a supernova observed in the year 1181 AD by Chinese and Japanese astronomers. This new Chandra image shows the center of 3C58, which contains a rapidly spinning neutron star surrounded by a thick ring, or torus, of X-ray emission. The pulsar also has produced jets of X-rays blasting away from it to both the left and right, and extending trillions of miles. These jets are responsible for creating the elaborate web of loops and swirls revealed in the X-ray data. These features, similar to those found in the Crab, are evidence that 3C58 and others like it are capable of generating both swarms of high-energy particles and powerful magnetic fields. In this image, low, medium, and high-energy X-rays detected by Chandra are red, green, and blue respectively.
"Chandra changed the way we do astronomy. It showed that precision observation of the X-rays from cosmic sources is critical to understanding what is going on," said Paul Hertz, NASA's Astrophysics Division director in Washington. "We're fortunate we've had 15 years — so far — to use Chandra to advance our understanding of stars, galaxies, black holes, dark energy, and the origin of the elements necessary for life."
Chandra orbits far above Earth's X-ray absorbing atmosphere at an altitude up to 139,000 km (86,500 mi), allowing for long observations unobscured by Earth's shadow. When it was carried into space in 1999, it was the largest satellite ever launched by the shuttle.
"We are thrilled at how well Chandra continues to perform," said Belinda Wilkes, director of the Chandra X-ray Center (CXC) in Cambridge, Massachusetts. "The science and operations teams work very hard to ensure that Chandra delivers its astounding results, just as it has for the past decade and a half. We are looking forward to more ground-breaking science over the next decade and beyond."
Originally called the Advanced X-ray Astrophysics Facility (AXAF), the telescope was first proposed to NASA in 1976. Prior to its launch aboard the shuttle, the observatory was renamed in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar. Known to the world as Chandra (which means "moon" or "luminous" in Sanskrit), he was widely regarded as one of the foremost astrophysicists of the 20th century.
"Chandra continues to be one of the most successful missions that NASA has ever flown as measured against any metric — cost, schedule, technical success and, most of all, scientific discoveries," said Martin Weisskopf, Chandra Project Scientist at the Marshall Space Flight Center in Huntsville, Ala. "It has been a privilege to work on developing and maintaining this scientific powerhouse, and we look forward to many years to come."
NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, MA, controls Chandra's science and flight operations.
Additional information on Chandra and the 15th anniversary can be found at: http://chandra.si.edu/15th