Thursday, 27 April 2017

The Chandra X-Ray Telescope

As part of a presentation on "Astronomy in the News", I collated some information on The Chandra X-Ray Telescope, from various sources, which I am also posting here for the benefit of my readers.

The Chandra X-Ray Telescope

In 1976 the Chandra X-ray Observatory (called AXAF at the time) was proposed to NASA by Riccardo Giacconi and Harvey Tananbaum.

Since cosmic X-ray radiation is absorbed by the Earth's atmosphere, space-based telescopes are needed for X-ray astronomy. Applying himself to this problem, Giacconi worked on the instrumentation for X-ray astronomy; from rocket-borne detectors in the late 1950s and early 1960s, to Uhuru, the first orbiting X-ray astronomy satellite, in the 1970s – pictured here.

Giacconi's pioneering research continued in 1978 with the Einstein Observatory, the first fully imaging X-ray telescope put into space, and later with the Chandra X-ray Observatory, which was launched in 1999 and is still in operation. 

X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects.

X-rays are a form of light, but much more energetic than the light detected by our eyes. The energy of an X-ray photon (light particle) is ~1000 times that of a photon of visible light. They are part of the electromagnetic spectrum which includes visible light, radio waves, microwaves and infra red radiation.

What the picture shows is that X-rays are emitted from things that are really hot - millions of degrees. K stands for Kelvin - a temperature scale which has the same units as Celsius, but starts at absolute zero (-273o C). The shorter the wavelength (higher frequency) the higher the energy of the light.

X-ray missions produce a wide range data in many forms. The main three are discussed here; they all result from the type of detector used in X-ray telescopes and also from the fact that X-rays are very high energy. This means that they act as particles rather than waves and so it is easy to measure the energy of each individual photon. They can also record the time a photon hit the detector and also where it came from, to a very high accuracy in the case of CHANDRA.

Above we see Ttree different clusters as imaged by the CHANDRA satellite.

Images are the most easily accessible result from X-ray missions. The raw output of an X-ray detector is the "events" file - which shows how many photons hit each pixel of the detector. However the extra information, for example the energies of the photons, give a greater insight into what is going on in the object under study.

The CHANDRA X-ray Observatory was launched on the 23rd July 1999 by the Space Shuttle Columbia. It was designed to provide high resolution imaging of X-ray sources; as opposed to XMM-NEWTON which has better spectral resolution but worse imaging capabilities. It was the follow up to the EINSTEIN observatory which flew from November 1978 to April 1981and was far superior in all ways. CHANDRA was placed into an elliptical orbit so that it spent little time in the Earths radiation belts, and so allows up to 48hrs (172.8 ksec) of uninterrupted observing time.

In January 2017, the Chandra X-ray Observatory revealed the as yet deepest X-ray image of the outer space which could contain more than a couple of thousands of black holes.

Most of the supermassive black holes revealed by Chandra are believed to be billions of years old. More exactly, they could be as old as the Big Bang. Their formation period was traced back as far as this cosmic event.

Astronomers from the University of Durham’s Centre for Extragalactic Astronomy have confirmed the discovery of two supermassive black holes located close to the Milky Way. Working in conjunction with the Chandra observatory, the scientists were delighted to reveal the discovery to the scientific world.

They couldn’t directly observe the black holes as they are shielded by huge clouds of dust and gas, but deep X-ray imaging has allowed the scientists to confirm the discovery.

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