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  • Writer's pictureSven Piper

Chandra X-Ray Observatory

Updated: 7 days ago

Chandra X-Ray Observatory
Chandra X-Ray Observatory (Credit: NASA)

The Chandra X-ray Observatory, formerly known as the Advanced X-ray Astronomical Facility (AXAF), was launched by Space Shuttle Columbia on July 23, 1999, and is part of NASA's Great Observatory program. This program also includes the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Spitzer Space Telescope.

It was named in honor of Indian-American astronomer Subrahmanyan Chandrasekhar, who is known for determining the mass limit for white dwarf stars to become neutron stars.

Chandra's images are twenty-five times sharper than those of the best previous X-ray telescope, allowing it to detect and image X-ray sources billions of light years away. Thus, Chandra has greatly enhanced our understanding of the origin, evolution, and destiny of the universe.

X-ray telescopes are the only way we can observe extremely hot matter with temperatures of millions of degrees Celsius. However, X-rays do not reflect off mirrors the same way visible light does. Due to their high energy, X-ray photons penetrate into the mirror much like bullets slamming into a wall. Similarly, just as bullets ricochet when they hit a wall at a grazing angle, X-rays also ricochet off mirrors. This means that X-ray telescopes must be very different from optical telescopes, requiring mirrors that are precisely shaped and aligned nearly parallel to incoming X-rays, giving them more of a barrel-like appearance than the familiar dish shape of optical telescopes.

X-ray observatories must be placed high above Earth's atmosphere because it absorbs the vast majority of X-rays, making them undetectable from Earth-based telescopes.

Structure of the Chandra X-Ray Observatory
Structure of the Chandra X-Ray Observatory

The Telescope

The Chandra telescope system features four pairs of mirrors, along with a support structure designed to facilitate both the telescope and its scientific instruments’ operation as an observatory. The system includes solar panels that provide power to the instruments, a thermal control system to regulate the telescope’s temperature, and a communications system that transmits data back to astronomers on Earth.


In 2003, New Scientist announced that the space telescope was losing its sight because Chandra was suffering from a mysterious build-up of grease on an optical filter in front of one of its cameras, blocking almost half the light at some frequencies. The scientists were not sure what was causing the build-up. Analysis of the contamination showed that it contained carbon and fluorine.

Mission Results:

  • Twenty-five times sharper: The Chandra X-ray Observatory can make images 25 times sharper than the best previous X-ray telescope.

  • X-ray sources: Chandra can detect and image X-ray sources billions of light years away.

  • Understanding the universe: Chandra has greatly enhanced our understanding of the origin, evolution, and destiny of the universe.

  • Launched in 1999: The Chandra X-ray Observatory was launched by the Space Shuttle on July 23, 1999.

  • High-resolution camera: Chandra has a high-resolution camera that records X-ray images and a spectrometer that determines the energy level of the X-rays.

  • X-ray telescope: The mirrors on Chandra are the largest, most precisely shaped and aligned, and smoothest mirrors ever constructed.

Major Discoveries:


  • Chandra Discovery Solves Solar Paradox: The problem was the vexing question as to how much neon the Sun contains, because neon plays an important role in regulating the rate at which energy flows from nuclear reactions in the Sun's core to its surface.

  • Chandra Finds Long-Sought Link to Origin of Millisecond Pulsars: New Chandra observations provide the best information yet on why such neutron stars, called millisecond pulsars, are rotating so fast.

  • Orbiting Stars Flooding Space with Gravitational Waves: Chandra data from observations of RX J0806.3+1527 show that its X-ray intensity varies. This implies that J0806 is a binary star system where two white dwarf stars are orbiting each other. Energy loss by gravitational waves will cause the stars to move closer together. X-ray and optical observations indicate that the orbital period of this system is decreasing by 1.2 milliseconds every year, which means that the stars are moving closer together at a rate of about 2 feet per day.

  • Chandra Supplies Data on the Growth of Black Holes: By combining data from the Chandra Deep Field-North (CDFN) with observations at submillimeter and optical wavelengths, an international team of scientists has found evidence that many extremely luminous adolescent galaxies and their central black holes underwent a phenomenal spurt of growth 10 billion to 12 billion years ago. This growth spurt may have set the stage for the appearance of quasars, distant galaxies that contain the largest and most active black holes in the Universe.


  • Chandra Opens New Line of Investigation on Dark Energy: New Chandra results suggest that the dark energy density may be constant.


  • X-rays Found From a Lightweight Brown Dwarf: A Chandra observation revealed X-rays produced by TWA 5B, a brown dwarf orbiting a young binary star system known as TWA 5A.


  • Young Star Cluster Found Aglow With Mysterious X-Ray Cloud: The X-ray spectrum of the cloud shows an excess of high-energy X-rays, which indicates that the X-rays come from trillion-volt electrons moving in a magnetic field. Such particles are typically produced by exploding stars, or in the strong magnetic fields around neutron stars or black holes, none of which is evident in RCW 38. One possible origin for the high-energy electrons is an undetected supernova that occurred in the cluster.

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