Recent Discoveries with the Chandra X-Ray Telescope - Essay Example

Astronomy final essay project: Recent discoveries using the Chandra X-ray telescope The Big Bang created the universe nearly 14 billion (1010) years ago, the earth was formed 4.6 x 1010 years ago, and the modern man (Homo sapiens sapiens) appeared around 0.2 x 106 million years ago. But the universe remained a dark, deep and mysterious entity until the emergence of the telescope, Lippersheys ‘Looker’, 400 years ago. Today, the availability of very sophisticated and powerful visible-light telescopes as well as telescopes capable of detecting invisible forms of radiation such as infrared, ultraviolet, radio, X-, and gamma rays has revolutionized the study of the universe. The telescope is an instrument which focuses and detects different types of electromagnetic radiation from distant objects and produces their images, even images of objects not seen by the human eye. Add-on technologies including the camera, computer interfacing, spectrography, and space related devices such as rockets and satellite have improved the usefulness of the telescope several-fold. Following the advances made since the 1960s in the field of space science, telescopes housed in satellites orbiting the earth have enabled astronomers to view a wider segment of the electromagnetic spectrum and discover and learn more about stars, black holes, pulsars, quasars, galaxies et al. NASAs Great Observatories for Space Astrophysics consist of a series of four orbiting satellites carrying telescopes designed to study the Universe in both visible light (the Hubble Space Telescope) and non-visible forms of radiation e.g., gamma rays (the Compton Gamma Ray Observatory), X-rays (the Chandra X-ray Observatory), and infrared rays (Spitzer Space Telescope). Chandra X-ray Observatory Known as the Advanced X-Ray Astrophysics Facility (AXAF) during its design and construction, Chandra was given the present name in 1998 in honor of the late Indian-American Nobel laureate astrophysicist Subrahmanyan Chandrasekhar. Optical telescopes reveal only a portion of the universe whereas telescopes which are sensitive to electromagnetic radiation other than visible wavelengths have detected X-rays from explosions produced by black holes, besides infrared radiation from stars (http://chandra.harvard.edu/ten/). The first imaging X-ray telescope used in space was the brain-child of Riccardo Giacconi and his collaborators who succeeded in obtaining the first solar X-ray picture in 1963 with the rocket-borne X-ray telescope designed and fabricated by them. The Chandra X-ray Observatory is equipped with X-ray telescopes that are 100 million times more sensitive than Giacconi’s 1963 instrument (Space Today Online, 2008). In July 1999, Chandra was put in a low Earth orbit by the NASA space shuttle Columbia, flight STS-93, from where, using its own thrusters, plus an Inertial Upper Stage (IUS) two-stage solid-fuel rocket, Chandra travelled to a higher unusual orbit, elliptical in shape, and 6200 to 86800 miles above the Earths radiation belts (Space Today Online, 2002; Chandra X-ray Observatory, 2009). It takes 64 hours and 18 minutes for Chandra to complete an orbit during which an uninterrupted observation period of 55 hours is possible. Just after a month in orbit, Chandra collected its first light on August 19, 1999. The X-ray image showed the supernova remnant Cassiopeia A, ten-lightyears-wide, and about 10,000 lightyears away from Earth (See Fig. 1). In the eleven years since it has been operational, Chandra X-ray Observatory has been exploring the hot turbulent regions in space. The Observatory has produced innumerable high-quality X-ray images of star clusters, supernova remnants, galactic eruptions, and collisions between clusters of galaxies, supergiant black holes in the centers of galaxies, has helped confirm the domination of galaxies and the universe by dark matter and dark energy whose gravitational force repels rather than attracts, although the nature of the dark energy still remains a huge mystery. The vastly improved sensitivity of Chandra’s instruments will increase our understanding of the origin, evolution, and destiny of the universe. Chandra X-ray Telescope The X-ray telescope is one of the three major parts of the Observatory, the other two being the science instruments (e.g., high-resolution camera, advanced CCD imaging spectrometer and high resolution spectrometers) that produce and analyze X-ray images, and the spacecraft that carries the telescope and the other instruments. In brief, an X-ray telescope collects and detects X-rays emitted from a source outside the Earths atmosphere and resolves the X-rays into an image. X-rays impinging on any material, perpendicular to it, are mostly absorbed and not reflected. Therefore, normal incidence mirrors such as those used in optical telescopes do not work in an X-ray telescope. X-ray telescopes are designed such that the X-ray photons impinge on a mirror made of a suitable material (such as single-layer gold or iridium) at a small, glancing angle of incidence such that the X-rays are reflected onto a CCD, the type of detector found in common video detectors. Soft X-rays (energy range 0.12 to 12 keV; wavelength 0.1–10 nm) are less penetrating than hard X-rays (12 to 120 keV; wavelength 0.1 nm or less) and, therefore, easier to focus (NASA, 2004). At a low incident angle e.g., 0.6°, which is close to the critical angle for total external reflection of iridium, the X-ray penetrates just a few nanometers deep and are mostly reflected. As the incident angle increases, X-rays penetrate deeper. Paraxial rays that is, rays hitting the mirror parallel to the optical axis, will be focused on a point, but images of objects that are off-axis will be severely blurred. Wolter (1952) circumvented this problem by combining two elements, a paraboloid, followed by a confocal and coaxial hyperboloid (Fig. 2). Recent discoveries made by Chandra There are more than 100,000 X-ray sources across the Universe that have been detected. The farthest object seen in X-rays is 13 billion lightyears from Earth. (www.spacetoday.org). A few of the interesting discoveries made in recent times by the Chandra X-ray Observatory are: 1. Sagittarius A* (or Sgr A*, for short), the supermassive black hole at the center of the Milky Way whose image was obtained on 5 Jan 2010 (Fig. 3). It is known for a long time that Sgr A* is relatively quiet compared to other black holes of similar size. The Chandra image revealed other interesting features of this region including supernova remnants and mysterious filaments; 2. Image (M31) of Earth’s nearest neighbor spiral galaxy outside of the Milky Way, nearly 50,000 light years across in size, and about 2.9 million light years away from Earth released on 17 Feb 2010 (Fig. 4). Analysis of the data indicated that the merger of two white dwarfs (that is, stars of enormously collapsed sizes, whose nuclear fuel is nearly exhausted and who are about to die) is the main trigger for Type Ia supernovas (white dwarfs blown apart by a sudden thermonuclear explosion) for the area observed by Chandra; 3. Image released on 3 March 2010 shows NGC 1068, an extremely bright spiral galaxy located about 50 million light years from Earth, and containing a rapidly growing “supermassive” black hole at its center which is twice as massive as the one in the Milky Way. The X-ray images show a strong wind being driven away from the center of NGC 1068 at a rate of about a million miles per hour (Fig. 5). It is suspected that the wind is produced because of the acceleration and heating of the surrounding gas as it swirls towards the black hole. 4. Quasars are among the most luminous objects that look like distant stars in the Universe. They are produced by gas falling into a supermassive black hole in the center of a galaxy. Chandra Observatory showed, for the first time, a spatially resolved binary quasar (i.e., a double quasar) inhabiting an ongoing galaxy merger. These bright sources, collectively called SDSS J1254+0846 (Fig. 6), are located about 4.6 billion light years away from Earth. The distance between them is about 70 thousand light years. According to Green (2010), "Quasars are the most luminous compact objects in the Universe, and though about a million of them are now known, its incredibly hard work to find two quasars side by side." The result provides strong evidence to show that a pair of quasars would be triggered during a merger of the galaxies. References Green, P.J., Myers, A.D., Barkhouse, W.A., et al., 2010. SDSS J1254+0846: A binary quasar caught in the act of merging. The Astrophysical Journal, 710: 1578-1588. Retrieved on 17 May 2010 from http://hea-www.harvard.edu/~pgreen/Papers/SDSS1254.pdf NASA, 2004. New NASA-Japanese Telescope Images Uncharted Wavelengths. Retrieved on 17 May 2010 from http://www.nasa.gov/vision/universe/starsgalaxies/infocus_firstlight.html Space Today Online, 2002. Chandra X-ray Observatory. Retrieved 16 May 2010 from http://www.spacetoday.org/DeepSpace/Telescopes/GreatObservatories/ Chandra/Chandra.html Space Today Online, 2008. The 400th anniversary of the telescope. Retrieved on 16 May 2010 from http://www.spacetoday.org/DeepSpace/ Telescopes/400thAnniversary/TelescopeAnniv400.html Wolter, H. (1952). "Glancing Incidence Mirror Systems as Imaging Optics for X-rays". Ann. Physik 10: 94 Fig. 1.Chandra X-ray Observatory collected its first light on August 19, 1999. The X-ray image was the ten-lightyears-wide supernova remnant Cassiopeia A, which is 10,000 lightyears from Earth. [Source: http://www.spacetoday.org/DeepSpace/Telescopes/GreatObservatories/ Chandra/Chandra.html] Fig. 2. Two element reflection image system of a Wolter type X-ray telescope. The two surfaces (a paraboloid and a hyperboloid) reflect the incident X-rays to a common focus. (Modified from: http://imagine.gsfc.nasa.gov/docs/science/how_l2/xtelescopes_systems.html) Fig. 3. X-ray image of Sagittarius A*, the supermassive black hole at the center of the Milky Way galaxy (5 January 2010) Color code: The X-rays are shown in 3-colors: red (2-3.3 keV), green (3.3-4.7 keV), blue (4.7-8 keV) (Source: http://chandra.harvard.edu/photo/2010/sgra/) Fig. 4. An X-ray/optical/infrared composite image showing M31, Earth’s nearest neighbor spiral galaxy outside of the Milky Way in the constellation Andromeda (17 February 2010). Color code:X-rays are gold, the optical data are light blue, and the infrared data are red. (Source: http://chandra.harvard.edu/photo/2010/type1a/) Fig. 5. A composite image showing NGC 1068, one of Earth’s nearest and brightest galaxies, located about 50 million light years from Earth, and containing a rapidly growing supermassive black hole (3 March 2010). Color code: red, X-rays; green, optical data; blue, radio data (Source: http://chandra.harvard.edu/photo/2010/ngc1068/) Fig. 6. Image SDSS J1254+0846 (3 February 2010) showing a Quasar pair captured in galaxy collision about 4.6 billion light years from Earth. Located in the Zodiac constellation Virgo (the maiden), visible in both Hemispheres. X-rays from Chandra have been overlaid on an optical image from the Baade-Magellan telescope in Chile for viewing. Color code explained: X-rays are blue; the optical data are yellow (Source: http://chandra.harvard.edu/photo/2010/sdss/) Read More

Chandra X-ray Telescope The X-ray telescope is one of the three major parts of the Observatory, the other two being the science instruments (e.g., high-resolution camera, advanced CCD imaging spectrometer and high resolution spectrometers) that produce and analyze X-ray images, and the spacecraft that carries the telescope and the other instruments. In brief, an X-ray telescope collects and detects X-rays emitted from a source outside the Earths atmosphere and resolves the X-rays into an image.

X-rays impinging on any material, perpendicular to it, are mostly absorbed and not reflected. Therefore, normal incidence mirrors such as those used in optical telescopes do not work in an X-ray telescope. X-ray telescopes are designed such that the X-ray photons impinge on a mirror made of a suitable material (such as single-layer gold or iridium) at a small, glancing angle of incidence such that the X-rays are reflected onto a CCD, the type of detector found in common video detectors. Soft X-rays (energy range 0.

12 to 12 keV; wavelength 0.1–10 nm) are less penetrating than hard X-rays (12 to 120 keV; wavelength 0.1 nm or less) and, therefore, easier to focus (NASA, 2004). At a low incident angle e.g., 0.6°, which is close to the critical angle for total external reflection of iridium, the X-ray penetrates just a few nanometers deep and are mostly reflected. As the incident angle increases, X-rays penetrate deeper. Paraxial rays that is, rays hitting the mirror parallel to the optical axis, will be focused on a point, but images of objects that are off-axis will be severely blurred.

Wolter (1952) circumvented this problem by combining two elements, a paraboloid, followed by a confocal and coaxial hyperboloid (Fig. 2). Recent discoveries made by Chandra There are more than 100,000 X-ray sources across the Universe that have been detected. The farthest object seen in X-rays is 13 billion lightyears from Earth. (www.spacetoday.org). A few of the interesting discoveries made in recent times by the Chandra X-ray Observatory are: 1. Sagittarius A* (or Sgr A*, for short), the supermassive black hole at the center of the Milky Way whose image was obtained on 5 Jan 2010 (Fig. 3). It is known for a long time that Sgr A* is relatively quiet compared to other black holes of similar size.

The Chandra image revealed other interesting features of this region including supernova remnants and mysterious filaments; 2. Image (M31) of Earth’s nearest neighbor spiral galaxy outside of the Milky Way, nearly 50,000 light years across in size, and about 2.9 million light years away from Earth released on 17 Feb 2010 (Fig. 4). Analysis of the data indicated that the merger of two white dwarfs (that is, stars of enormously collapsed sizes, whose nuclear fuel is nearly exhausted and who are about to die) is the main trigger for Type Ia supernovas (white dwarfs blown apart by a sudden thermonuclear explosion) for the area observed by Chandra; 3.

Image released on 3 March 2010 shows NGC 1068, an extremely bright spiral galaxy located about 50 million light years from Earth, and containing a rapidly growing “supermassive” black hole at its center which is twice as massive as the one in the Milky Way. The X-ray images show a strong wind being driven away from the center of NGC 1068 at a rate of about a million miles per hour (Fig. 5). It is suspected that the wind is produced because of the acceleration and heating of the surrounding gas as it swirls towards the black hole. 4. Quasars are among the most luminous objects that look like distant stars in the Universe.

They are produced by gas falling into a supermassive black hole in the center of a galaxy. Chandra Observatory showed, for the first time, a spatially resolved binary quasar (i.e., a double quasar) inhabiting an ongoing galaxy merger. These bright sources, collectively called SDSS J1254+0846 (Fig. 6), are located about 4.6 billion light years away from Earth. The distance between them is about 70 thousand light years.

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