Dr. Pramod Pawar (Chair) & Dr. Nilkanth Vagshette (Co-Chair)

X-ray telescopes are a key tool in the study of high-energy astrophysical phenomena, such as black holes, neutron stars, and supernova remnants. X-rays are emitted by these objects due to their high temperatures and intense magnetic fields, but they are absorbed by the Earth’s atmosphere, making it necessary to use telescopes that can observe in space. In this article, we will discuss the instrumentation of X-ray telescopes and the various technologies used to detect X-rays.

X-ray telescopes work by collecting X-rays with a mirror that reflects them onto a detector. Unlike visible light, which can be focused with a simple curved mirror or lens, X-rays require more sophisticated optics due to their short wavelengths. The mirror must be made of materials that are highly reflective to X-rays, such as nickel or gold, and it must be shaped to a very precise curvature to focus the X-rays onto the detector. In addition, X-ray telescopes typically have multiple nested mirrors, arranged in a series of concentric shells, to increase the collecting area and improve the resolution.

The detectors used in X-ray telescopes are typically based on solid-state devices, such as charge-coupled devices (CCDs) or complementary metal-oxide-semiconductor (CMOS) detectors. These devices work by converting the X-rays into electrical signals, which can be read out and processed to create an image. However, X-rays have too much energy to be absorbed directly by the detector material, so they must be first converted into visible light. This is typically done using a scintillator, a material that emits visible light when struck by an X-ray. The visible light is then detected by the CCD or CMOS sensor.

In addition to mirrors and detectors, X-ray telescopes also require sophisticated cooling systems to keep the detector and other components at very low temperatures. This is because the detectors generate heat when they are exposed to X-rays, and this can cause them to malfunction if not properly cooled. Some X-ray telescopes use mechanical coolers, such as Stirling engines, to cool the detector, while others use passive cooling techniques, such as radiative cooling to space.

One of the key challenges in X-ray astronomy is dealing with the background radiation that is present in the X-ray band. This background radiation is due to the X-rays emitted by the hot gas in our own galaxy and by other X-ray sources throughout the universe. To reduce the background radiation, X-ray telescopes are often placed in space, above the Earth’s atmosphere. However, even in space, there is still some residual background radiation that must be carefully measured and subtracted from the data.

In summary, X-ray telescopes are complex instruments that require sophisticated optics, detectors, and cooling systems to operate. X-ray telescopes typically use nested mirrors and solid-state detectors, and they require careful background subtraction to extract the signal from the sources being studied. Despite these challenges, X-ray telescopes have been used to make many important discoveries in astrophysics, and they continue to be a key tool for studying the high-energy universe.

Last Updated on March 7, 2023 by Sonkamble Satish