Today is the 15th anniversary of the launch of the Chandra X-ray Observatory. Chandra is one of NASA's "Great Observatories," along with the Hubble Space Telescope and Spitzer Space Telescope. Since its launch, its x-ray vision and high sensitivity have helped us to better understand the universe.

Chandra orbits at 139,000 km (86,500 miles) above the Earth, which is more than a third of the way to the moon. This helps it to avoid being affected by the Earth's shadow when making observations. It is used to detect x-rays from very hot areas of the universe, such as supernova stars and clusters of galaxies. In order to do so, it uses a nested group of four highly sensitive mirrors. When x-rays strike the mirrors, they are focused onto electronic detectors. In this way, Chandra is able to produce extremely detailed images.

NASA likens Chandra's resolving power (the ability to read two points that are close together) to being able to read a stop sign from 12 miles (19 km) away. It can observe x-rays from particles up until to the last second before they fall into a black hole. Despite these capabilities, the power required to run Chandra is just 2 kW, which is about the same as a hair dryer.

"Chandra changed the way we do astronomy," explains Paul Hertz, NASA's Astrophysics Division director in Washington. "It showed that precision observation of the x-rays from cosmic sources is critical to understanding what is going on. 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."

Amongst the applications of Chandra that Gizmag has recently covered have been its study of dark matter in the Milky Way and imaging the gas ejections and high-energy particles of the NGC 4258 galaxy. It has also been used to observe black holes elsewhere across the universe.

The concept for Chandra was initially proposed in 1976. The satellite was named after Indian-American Nobel laureate and astrophysicist Subrahmanyan Chandrasekhar. It was launched into space aboard the Space Shuttle Columbia in 1999 and remains the largest satellite ever launched by the shuttle.

"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," says Chandra Project scientist Martin Weisskopf.

To celebrate Chandra's anniversary, four new images taken by the satellite have been released. They each show remnants of supernova stars and demonstrate its unique imaging ability. The images release show Tycho, G292.0+1.8, the Crab Nebula and 3C58.

The Tycho and G292.0+1.8 images are examples of how Chandra can trace the expanding debris of an exploded star and the associated shock waves. The Crab Nebula and 3C58 images demonstrate its ability to capture clouds of high-energy particles, light years across, following the explosions of of massive stars.

It is hoped that Chandra will continue to provide observations for another decade or more.

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