National Aeronautics and Space Administration

A Brief History of High-Energy Astronomy: 1970 - 1974

In Reverse Chronological Order

26 Dec 1974	Launch of the Soviet space station Salyut-4. Salyut-4 carried an X-ray instrument, the Filin telescope, which observed a variety of X-ray binaries over the 2-year mission duration.
19 Oct 1974 at 20:05 UT	First detection of an X-ray flare from an M dwarf star, namely the flare star YZ CMi (Ross 882), by the Utrecht soft-energy (0.2 - 0.28 keV) and medium-energy (1 - 7 keV) detectors on the Astronomical Netherlands Satellite (ANS): see Heise et al. (ApJ, 202, L73, 1975) for more details.
15 Oct 1974	Launch of the Ariel V X-ray observatory. Ariel V operated for 5.5 years and detected 250 X-ray sources, which are listed in two papers, McHardy, I.M., et al. (1981, MNRAS, 197, 893) and Warwick, R.S., et al. (1981, MNRAS, 197, 865), comprising the 3rd Ariel-V Sky Survey Instrument Catalog.
30 Aug 1974	Launch of the Astronomische Nederlandse Satelliet (Astronomical Netherland Satellite or ANS). This satellite was a collaborative effort between the Netherlands and the USA. The University of Groningen and Utrecht (Netherlands) provided the ultraviolet and soft X-ray experiments, while the American Science and Engineering company provided the hard X-ray experiment. ANS operated for almost 3 years and made a number of important discoveries, including detecting the first X-ray bursts and making the first observations of stellar flares in the X-ray band.
15 Jun 1974 at 05:15 UT	Launch of a Black Brant VC sounding rocket from White Sands, New Mexico carrying an X-ray astronomy payload. While scanning across the Coma cluster of galaxies, this detected an intense soft and steep-spectrum X-ray source that was later (12 Jun 1975) redetected by the low-energy X-ray telescope on SAS-3. The source was soon identified with the hot white dwarf HZ 43, and, after competing theories for the X-ray emission mechanism were considered and rejected, this is now recognized as being the first detection of photospheric X-ray emission from a (single) white dwarf. See Margon et al. (ApJ, 203, L25, 1976) and Hearn et al. (ApJ, 203, L21, 1976) for more details concerning these observations. In the interval between these two observations, the white dwarf in the Sirius system (Sirius B) was observed and detected by the soft X-ray detector on the ANS satellite, thereby becoming the second white dwarf detected as a photospheric X-ray source: see Mewe et al. (Nature, 256, 711, 1975) for the discovery report.
5 Apr 1974	First X-ray detection of Alpha Aurigae or Capella, a nearby pair of cool giant stars in a binary system with a 104-day orbital period, by a proportional counter onboard a sounding rocket. See Catura et al. 1975, ApJ, 196, L47 for more details about this discovery, which was the first detection of X-rays from the coronae of normal stars (apart from the Sun, of course, which was first detected in 1948 as an X-ray emitter): until this date, all discrete extrasolar X-ray sources had either been identified with unusual objects such as (i) binary systems containing accreting black holes, neutron stars or white dwarfs, (ii) supernova remants, and (iii) external galaxies and quasars, or had not had reliable counterpart identifications at other wavelengths.
8 Jun 1973	A power failure on the Second Small Astronomical Satellite (SAS 2) terminates its collection of data. The gamma-ray (20 MeV to 1 GeV) instrument on this satellite detected the diffuse gamma-ray background as well as a handful of spatially compact discrete gamma-ray sources.
14 May 1973	Launch of Skylab, the USA's first space station.
6 Apr 1973	Launch of the space probe Pioneer 11 to Jupiter and Saturn. After completing its planned mission, Pioneer 11 flies on into the outer reaches of the Solar System to attempt to detect the heliopause.
Mar 1973	Uhuru (SAS 1) ceases operation.
1973	Formation of the European Space Agency (ESA), `Europes's gateway to space'. This multinational entity superceded the European Launcher Development Organization (ELDO) and the European Space Research Organization (ESRO). Its mission is `to shape the development of Europe's space capability and ensure that investment in space continues to deliver benefits to the people of Europe'.
15 Nov 1972	Launch of NASA's Second Small Astronomical Satellite (SAS 2), the first satellite dedicated to celestial gamma-ray observations.
23 Sep 1972	Launch of the Seventh Interplanetary Monitory Platform (IMP 7).
Sep 1972	The Sixth Interplanetary Monitoring Platform (IMP 6) ceases operations.
21 Aug 1972	Launch of the Copernicus satellite, also known as the Third Orbiting Astronomical Observatory 3 (OAO 3).
14 May 1972 at 03:46 UT	First detection of a gamma-ray burst (GRB) at X-ray energies in the 7-100 keV energy range, simultaneously with its detection in hard X-rays and gamma-rays, by the UCSD Cosmic X-ray Telescope on the OSO-7 satellite. The fluence or time-integrated flux of this strong GRB was ~ 5 x 10-4 erg cm-2.
16 Apr 1972	Launch of Apollo 16, a lunar mission which carried a similar orbital science payload to Apollo 15, namely an Apollo sub-satellite, an X-ray fluorescence spectrometer and a gamma-ray spectrometer, both of which were used to study the composition of the lunar surface.
1972	First secure identification of the compact object in an X-ray binary system as an infinitely collapsed star or black hole. The optical companion (HDE 226868) to the X-ray source Cyg X-1 had been identified in 1971, and subsequent radial-velocity studies of this star, together with an assumption for its likely mass, implied a mass for the compact object which excluded other possibilities such as a neutron star. (See Webster & Murdin 1972, Nature, 235, 37 and Bolton 1972, Nature, 235, 271 for more details). As an interesting aside, the term "black hole" for an infinitely collapsed object had been coined only one year previous to this by John Wheeler.
1972	First identification of a cataclysmic variable(a close binary system with a white dwarf star accreting matter from its cool dwarf star companion), EX Hydrae, with an X-ray source that had been previously detected by the Uhuru satellite: see Warner 1972, MNRAS, 158, 425, for more details. (It was subsequently realized that the Uhuru X-ray source, due to the detector's low spatial resolution, actually was probably a composite source, with similar amounts of X-ray emission from EX Hya and a cluster of galaxies which lies only 20 arcminutes away).
26 Jul 1971	Launch of Apollo 15, a lunar mission which carried an Apollo sub-satellite, an X-ray fluorescence spectrometer and a gamma-ray spectrometer, both of which were used to study the composition of the lunar surface.
29 Jun 1971	At 18:28 GMT, Soyuz 11 undocks from the Salyut 1 space station. At 23:17, Soyuz 11 landed. When the capsule was opened, all three cosmonauts (Georgi Dobrovolsky, Vladislav Volkov, and Viktor Patsayev) were found dead. Further investigation revealed that a valve had been jerked open by the separation of the orbital and landing modules, bleeding out the atmosphere of the capsule into space.
14 Mar 1971	Launch of the Sixth Interplanetary Monitoring Platform (IMP 6). IMP 6, along with the Vela series satellites and IMP 7, is among the first satellites to detect gamma-ray burst sources.
22 Feb 1971	Launch of an Aerobee-350 sounding rocket from Wallops Island, Virginia carrying X-ray polarimeters, which obtained the first significant detection of linear polarization in the X-ray band of any extrasolar object, namely the Crab supernova remnant. The amount and position angle of this polarized emission agreed well with that found in optical emission from the SNR, and `provides conclusive evidence for [it being produced by] the synchrotron emission mechanism'. See Novick et al. (ApJ, 174, L1, 1972) for more details.
21 Dec 1970 - 20 Jan 1971	A series of observations of the Magellanic Clouds by the Uhuru X-ray observatory detected diffuse emission as well as three discrete sources in the Large Magellanic Cloud (extending previous rocket observations which had found two sources), dubbed LMC X-1, LMC X-2, and LMC X-3, and one highly variable source in the Small Magellanic Cloud, dubbed SMC X-1. The latter source varied on a time scale of hours, implying a size no bigger than the solar system; this was the first detection of `an X-ray source of stellar dimensions in an external galaxy': see Leong et al., ApJ, 170, L67, 1971 for more details.
15 Dec 1970	The Soviet spacecraft Venera 7 lands on Venus and begins transmitting data, making it the first lander to successfully function after a soft landing on another planet.
12 Dec 1970	Launch of Uhuru (SAS 1), the first earth-orbiting mission entirely dedicated to X-ray astronomy. The satellite's name means "Freedom" in Swahili.
24 Sep 1970 at 12:54 UT	Launch of a Thor missile from Johnston Atoll that carried three proportional counters and 13 scintillation counterssensitive to 1.5 to 12 (?) keV and 5 to 75 keV X-rays, respectively. This experiment detected a very hard and extended towards the Small Magellanic Cloud, the first X-ray detection of the SMC, re-detected the Large Magellanic Cloud (detected for the first time in a similar flight on 29 Oct 1968) with a strong suggestion that its X-ray emission was due to two separate spatial sources: see Price et al., ApJ, 168, L7, 1971 for more details.
13 May 1970 at 08:03 UT	Launch of a Terrier-Sandhawk rocket from Kauai, Hawaii that carried a 640 square cm proportional counter sensitive to 0.2 to 12 keV X-rays. This experiment detected a score or so of discrete sources, including the Puppis and Vela SNRs, and the peculiar star Eta Carinae. Eta Carinae, arguably the most massive star in the Milky Way Galaxy, has been extensively studied for over 150 years since it prolonged outburst in the 1830's and 1840's when it was the second brightest star in the sky, but much still remains to be understood about it. Its bright and hard X-ray emission has likewise been extensively studied for the more than 30 years since this rocket flight, and modern studies suggest that it is mostly due to the winds from the observed star and a fainter secondary star colliding and being shock-heated to high temperatures (>= 50 million K).
24 Apr 1970	First detection of Quasi-Periodic Oscillations (QPOs) in the X-ray emission from an X-ray binary system, in an observation of Sco X-1 by proportional counters flown on an Aerobee rocket: see Angel et al. (ApJ, 169, L57, 1971) for more details. This, and a subsequent Hakucho observation of QPOs in the Rapid Burster (Tawara et al. (Nature, 299, 38, 1982), ushered in a `Golden Age' of QPOs brought about by the superior timing capabilities in this regard of the EXOSAT Observatory: see Lewin at al. (Space Sci Revs, 46, 273, 1988) for an EXOSAT-era review of the QPO phenomenon.
8 Apr 1970	Co-launch of the Vela 6A and 6B satellites, the final pair of Vela satellites that were launched in order to monitor compliance with the Limited Test Ban Treaty of 1963. Together with the Vela 5A and Vela 5B satellites, these satellites are often credited with the first discovery of the events called gamma-ray bursts (GRBs) although it was later realized that the Vela 4A and Vela 4B satellites had actually earlier detected at least one GRB in 1967.

Acknowledgements

Web page author: Stephen A. Drake (based on an original by Jesse S. Allen)

Web page maintainer: Stephen A. Drake