History of X-ray astronomy

By 1927, interest in the detection of X-ray and ultraviolet (UV) radiation at high altitudes inspired researchers to launch Goddard's rockets into the upper atmosphere to support theoretical studies and data gathering.

Other systems displayed a characteristic X-ray pulse, just as pulsars had been found to do in the radio regime, which allowed a determination of the spin rate of the neutron star.

[3] The study of X-ray astronomy continued to be carried out using data from a host of satellites that were active from the 1980s to the early 2000s: the HEAO Program, EXOSAT, Ginga, RXTE, ROSAT, ASCA, as well as BeppoSAX, which detected the first afterglow of a gamma-ray burst (GRB).

By looking at the sky with X-ray and gamma-ray instruments, we collect important information in our attempt to address questions such as how the universe began and how it evolves, and gain some insight into its eventual fate.

From 1965 to 1972 there were over a dozen balloon-borne experiments (mostly from New Mexico), including the first such to take place from Australia (1966), one in which hard X-ray emission was discovered (albeit with crude angular resolution) from a region towards the Galactic Center whose centroid is located among subsequently identified sources GX1+4, GX3+1, and GX5-1.

A balloon-borne experiment in 1968 was based on the multi-anode multi-layer xenon gas proportional chamber that had recently been developed in our lab and represented the first use of such a high performance instrument for X-ray astronomy.

Observations down to lower energies were begun with a series of high altitude sounding rocket experiments; by this stage Steve Holt had already joined the program.

A 1972 rocket-borne observation of Cas A, the youngest supernova remnant in our galaxy, yielded the first detection of an X-ray spectral line, iron K-line emission at ~7 keV.

The 1.24 second pulsar period associated with Her X-1 is immediately evident from the data, while the rate profile for Cyg X-3 is completely consistent with the statistical fluctuations in counts expected for a source that is constant, at least for the 15s duration of the exposure shown.

The Cyg X-1 data, on the other hand, clearly exhibit the chaotic "shot noise" behavior characteristic of this black-hole candidate and also provided preliminary evidence for the additional feature of millisecond "burst" sub-structure, noted for the first time in this observation.

The sharp cut-off at ~24 keV in the flat spectrum observed for Her X-1 in this exposure provided the first reported evidence for radiative transfer effects to be associated with a highly magnetized plasma near the surface of a neutron star.

The black-body spectral component observed for Cyg X-3 during this experiment gave strong evidence that this emission is from the immediate vicinity of a compact object the size of a neutron star.

An observation of Cyg X-3 a year later with the same instrument yielded an optically thin thermal spectrum for this source and provided the first evidence for strong spectral iron K-line emission from an X-ray binary.

[2] Our large area PCA (Proportional Counter Array) on the current RXTE (Rossi X-ray Timing Explorer) mission genuinely reflects the heritage of our sounding rocket program.

Jean Swank joined the program in time for the beginning of our OSO-8 experiment (1975-1978), the first broadband (2-40 keV) orbiting observatory based on multi-anode multi-layer proportional chambers, one that showed the power of X-ray spectroscopy; for example, it established that iron K-line emission is a ubiquitous feature of clusters of galaxies.

[2] The HEAO-1 A2 full-sky cosmic X-ray experiment (1977-1979) provided the most comprehensive data (still the most definitive) on the cosmic X-ray background broadband spectrum and large-scale structure, and a much used complete sample of the brightest extragalactic sources; it posed the challenging "spectral paradox" just now being unraveled with new results on evolution (from deep surveys) and on individual source spectra extending into the gamma-ray band.

By the use of conical foil optics, developed in our lab, the response of a grazing incidence X-ray telescope was extended to 12 keV, amply covering the crucial iron K-band of emission.

Substantial improvement in the capability of solid-state non-dispersive spectrometers has been achieved in our lab (in collaboration with the University of Wisconsin) by the successful development of quantum calorimeters with resolution better than 10 eV (FWHM).

Such spectrometers have been used in a sounding-rocket-borne experiment to study spectral lines from the hot interstellar medium of our galaxy and will soon play a major role in the joint Japanese/American Suzaku orbiting X-ray observatory launched in July 2005.

On January 28, 1949, an NRL X-ray detector (Blossom) was placed in the nose cone of a V-2 rocket and launched at White Sands Missile Range in New Mexico.

It was intended primarily to observe the Sun, which it did very well during its 2-year lifetime, but it also detected a flaring episode from the source Sco X-1 and measured the diffuse cosmic X-ray background.

OSO 7 was primarily a solar observatory designed to point a battery of UV and X-ray telescopes at the Sun from a platform mounted on a cylindrical wheel.

The entire SIV-B stage underwent a series of preprogrammed maneuvers, scanning about 1° every 15 seconds, to allow the instrument to sweep across selected regions of the sky.

The pointing direction was determined during data processing, using the inertial guidance system of the SIV-B stage combined with information from two visible star sensors which formed part of the experiment.

It consisted of a single large (~1500 cm2) proportional counter, electrically divided by fine wire ground planes into separate signal-collecting areas and looking through collimator vanes.

Analysis of the data from the S150 experiment provided strong evidence that the soft X-ray background cannot be explained as the cumulative effect of many unresolved point sources.

Five fields of inquiry were particularly well suited for investigation with P78-1 data: Launched on February 21, 1981, the Hinotori satellite observations of the 1980s pioneered hard X-ray imaging of solar flares.

Tenma carried GSFC detectors which had an improved energy resolution (by a factor of 2) compared to proportional counters and performed the first sensitive measurements of the iron spectral region for many astronomical objects.

With respect to the asymmetric iron line broadening, Edward Cackett of the University of Michigan commented, "We're seeing the gas whipping around just outside the neutron star's surface,".

It shows that the way neutron stars accrete matter is not very different from that of black holes, and it gives us a new tool to probe Einstein's theory", says Tod Strohmayer of NASA's Goddard Space Flight Center.

Chandra 's image of Saturn (left) and Hubble optical image of Saturn (right). Saturn's X-ray spectrum is similar to that of X-rays from the Sun . 14 April 2003
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The Rossi X-ray Timing Explorer ( RXTE ) is a satellite that observes the time structure of astronomical X-ray sources. The RXTE has three instruments—the Proportional Counter Array, the High-Energy X-ray Timing Experiment (HEXTE), and one instrument called the All Sky Monitor. The RXTE observes X-rays from black holes , neutron stars , X-ray pulsars and x-ray bursts .
NRL scientists J. D. Purcell, C. Y. Johnson, and Dr. F. S. Johnson among those recovering instruments from a V-2 used for upper atmospheric research above the New Mexico desert. This is V-2 number 54, launched January 18, 1951 (photo by Dr. Richard Tousey, NRL).
Aerobee Hi Missile, White Sands Missile Range Museum.
This is a display model of a GRAB satellite at the National Cryptologic Museum . The satellites carried two sets of instruments: an unclassified experiment (called Solrad ) and a then-classified payload to collect electronic intelligence ( ELINT ) (called Tattletale).
The satellites launched with the Thor-Delta rocket system became known as the TD satellites. TD-1A was successfully launched on March 11, 1972 from Vandenberg Air Force Base (March 12 in Europe).
The P78-1 or Solwind satellite
Images released to celebrate the International Year of Light 2015 (IYL 2015)
( Chandra X-Ray Observatory ).
XMM-Newton spectrum from superheated iron atoms at the inner edge of the accretion disk orbiting the neutron star in Serpens X-1. The line is usually a symmetrical peak, but it exhibits the classic features of distortion due to relativistic effects. The extremely fast motion of the iron-rich gas causes the line to spread out. The entire line has been shifted to longer wavelengths (left, red) because of the neutron star's powerful gravity. The line is brighter toward shorter wavelengths (right, blue) because Einstein's special theory of relativity predicts that a high-speed source beamed toward Earth will appear brighter than the same source moving away from Earth. Credit: Sudip Bhattacharyya and Tod Strohmayer.