It’s not always possible to observe the night sky from the surface of the Earth. The blocking effects of the atmosphere mean we sometimes need to put telescopes out into space. The Chandra X-Ray Observatory is one such telescopes and it has just completed its 25th year of observations. To celebrate, NASA have just released 25 never-before-seen images of various celestial objects in x-rays. The collection includes images showing the region around black holes, giant clouds of hot gas and extreme magnetic fields. Sadly though, NASA is planning on shutting down the mission to save budget so best to enjoy the images while you can.
Back in the 1970’s NASA received a proposal from Riccardo Giacconi and Harvey Tananbaum to launch an x-ray telescope into space. An orbiting observatory was necessary because the Earth’s atmosphere blocks x-rays from reaching the surface. The x-rays Giacconi and Tananbaum were hoping to capture come from some of the hottest and most energetic places in the universe. The proposal eventually became the Chandra X-Ray Telescope and it was chosen to be part of NASA’s Great Observatories along with the Hubble Space Telescope with each instrument exploring different wavelengths.
Chandra was launched in July 1999 from the space shuttle Columbia and is undoubtedly one of the most successful and powerful x-ray telescopes ever built. It was named after Subrahmanyan Chandrasekhar the nobel prize winning astrophysicist. It orbits the Earth in a highly elliptical orbit varying between 16,000 kilometres and 133,000 kilometres (almost a third of the distance to the Moon) altitude so it can operate for most of its time above the radiation belts around Earth.
The strange shape of the telescope is necessary due to the high energy of x-rays. In a conventional telescope, the mirror is placed perpendicular to the incoming light so it strikes it head on before being reflected back up the tube. If the same approach was tried with high energy x-rays they would just fly straight through the mirror. Instead, incoming x-rays catch a mirror at an angle, deflecting them a little to their focus. The first reflection surface is a paraboloid and the second a hyperboloid. The arrangement is known as the Wolter 1 configuration.
It is important to study x-rays because it gives us an opportunity to study high energy events. Supernova remnants, galaxy clusters and neutron star mergers are just some of the events we can study. Before Chandra, high altitude balloons had been used to try and get above much of the atmosphere for x-ray astronomy but Chandra was a real game changer in helping to understand the high energy physics in the cosmos.
With 25 years of successful operation, Chandra continues to be used in conjunction with other observatories such as James Webb Space Telescope, the Imaging X-Ray Polarimetry Explorer and of course Hubble. 25 years on though and to celebrate, NASA has released a new image set from nearly 25,000 observations and they reveal objects in stunning new detail.
It’s difficult to pick a favourite among the images but I think the Crab Nebula is one of my favourites. Visually it looks pretty unimpressive but switch the view to x-rays and it suddenly looks stunning. As a star that has exploded at the end of its life the true majestic nature of this supernova remnant is unveiled.
Despite 25 years of superb operation, a letter written by Patrick Slane, the director of Chandra explain budget challenges may mean Chandra will be shutting down. Such a shame for such a successful observatory that really has changed our view of the universe.
The full image can be seen at : 25 Images to Celebrate NASA’s Chandra 25th Anniversary