A Brief History of High-Energy Astronomy: 1975 - 1979

In Reverse Chronological Order

Nov 15, 1979 Publication date of the first discoveries of X-ray emission from `normal' hot (OB spectral-type) stars, by the Einstein Observatory Imaging Proportional Counter (IPC) and High Resolution Imager (HRI); the stars were members of the Cygnus OB2 Association and the Eta Carinae Region: see Harnden et al., ApJ, 234, L51, 1979 and Seward et al. ApJ, 234, L55, 1979, respectively, for more details. Luminous OB star are now recognized to have (at least) two different types of X-ray emission mechanisms: the more intense and hard X-ray emitters appear to be all in binary systems where the winds of the two components are colliding and producing shocked hot plasma, while the less bright soft X-ray emitters are single stars in which self-shocking of the material outflowing in their high-velocity winds generates the warm X-ray emitting plasma.
20 Sep 1979 Launch of the Third High Energy Astrophysics Observatory (HEAO-3). This satellite conducted a hard X-ray/gamma-ray survey of the sky with a high-resolution spectrometer and also carried instrumentation to observe cosmic rays.
11 Jul 1979 Skylab, the U.S.A.'s first space station, re-entered the atmosphere, dispersing debris over an area stretching from the south-east Indian Ocean to western Australia.
9 Jul 1979 Voyager 2 makes its closest approach (720,000 km or 10.11 Jupiter radii) to the planet Jupiter before proceeding on to its next Grand Tour rendezvous (with Saturn).
19 Jun 1979 Vela 5B ceases operation.
Jun 1979 Prognoz 7 ceases operations.
2 Jun 1979 Launch of Ariel VI. This UK satellite carried 2 X-ray experiments as well as a cosmic ray experiment. Unfortunately, its mission was subsequently compromised by interference from ground-based radar which hampered pointing operations, although it did make some useful science observations.
Apr 1979 First detection of X-ray emission from another planet in the Solar System, namely Jupiter, by the Einstein Observatory: see Metzger et al., JGR, 88, 7731, 1983 for further details. The emission was hypothesized to be from energetic ions from abundant elements such as S and O precipating out of the Io Plasma Torus into the strong Jovian magnetosphere. In November 1999, Chandra observations of the Jupiter system detected additional X-ray sources associated with some of the large moons (Io, Europa, and possibly Ganymede) as well as with the Io Plasma Torus itself (Elsner et al., ApJ, 572, 1077, 2002).
9 Apr 1979 The Third Small Astronomical Satellite (SAS 3) ceases operation.
5 Mar 1979 Detection by 9 satellites carrying gamma-ray burst detectors of an intense (peak flux of about 1.5 x 10-3 erg s-1 cm-2 in the 30 keV to 2 MeV band) and very rapid (burst duration FWHM of 0.12 seconds) gamma-ray `spike' from the direction of the supernova remnant N49 in the Large Magellanic Cloud. This spike was followed by a slowly declining flux which was modulated by 8-second pulsations for several minutes afterwards. This object, now called SGR 0526-66, is one of several known so-called Soft Gamma Repeaters (SGRs). SGRs are believed by many (but not all) astronomers to be young neutron stars with ultrastrong magnetic fields, otherwise known as magnetars. In the 4 years following this initial strong gamma-ray transient, 16 more (much weaker) outbursts were seen from this source, but it has not been detected since 1983. See Cline et al. (ApJ, 237, L1, 1980) for the initial discovery paper on SGR 0526-66.
5 Mar 1979 Voyager 1 makes its closest approach (350,000 km or 4.89 Jupiter radii) to the planet Jupiter before proceeding on to a flyby of Saturn.
24 Feb 1979 Launch of the US Air Force satellite P 78-1. This satellite carried a number of instruments, including a gamma-ray spectrometer, an extreme-ultraviolet spectrometer, and an X-ray monitor.
21 Feb 1979 Launch of the first Japanese X-ray astronomy satellite Hakucho, known as CORSA-B prior to launch.
9 Jan 1979 The First High Energy Astrophysics Observatory (HEAO 1) ceases operation.
late Dec 1978 Arrival of Venera 11 & 12 at Venus; landing units proceed to the Venusian surface while the mother craft flies by the planet.
13 Dec 1978 Confirmation by the HEAO-1 A2 experiment that the peculiar emission-line object SS 433 is a strong and variable X-ray source reported by Marshall et al., IAU Circ. 3314, 1978: see also Marshall et al., ApJ, 230, L145, 1979. Previous low spatial-resolution observations by Ariel-V (Seward et al., MNRAS, 175, 39P, 1976) had discovered a variable X-ray source in this general direction and, since SS 433 is near the center of the SNR W 50, the authors speculated that it might be the stellar remnant of W 50, although the optical counterpart of the X-ray source was not known. SS 433 had been discovered earlier in 1978 to be a strong, variable radio source, and had been suggested as a possible X-ray emitter (Seaquist et al., IAU Circ. 3256, 1978). SS 433 went on to become one of the most well-studied objects in the Galaxy: it is now generally believed to be an X-ray binary system containing either a black hole or neutron star accreting from its companion, and, at the same time, expelling material in two, high-speed (0.26 times the speed of light) oppositely directed jets which precess with a 164-day period. The variable Doppler shift of material in these jets was later detected in the X-ray band, with first honors to EXOSAT (Watson et al., MNRAS, 222, 261, 1986). It is also now commonly believed that the compact object in SS 433 is the stellar remnant of the supernova that created W 50.
9 Dec 1978 Arrival of the Pioneer Venus Multiprobe at Venus. All five probes transmitted data while descending through the Venusian atmosphere as planned.
4 Dec 1978 Pioneer Venus Orbiter arrives at Venus.
13 Nov 1978 Launch of the Second High Energy Astrophysics Observatory (HEAO 2), renamed to the Einstein Observatory once it successfully achieved orbit. Einstein went on to become one of the most scientifically productive X-ray observatories ever.
31 Oct 1978 The Seventh Interplanetary Monitoring Platform (IMP 7) ceases operation.
30 Oct 1978 Launch of the joint French-Soviet SIGNE mission Prognoz 7. Combined with the Venera 11 & 12 probes, this formed part of the first ever interplanetary gamma-ray burst detection network, allowing accurate localization in the sky of gamma-ray burst sources.
15 Oct 1978 The Eighth Orbiting Solar Observatory (OSO 8) ceases operation.
14 Sep 1978 Launch of the Venera 12 probe to Venus.
9 Sep 1978 Launch of the Venera 11 probe to Venus.
8 Aug 1978 Launch of the Pioneer Venus Multiprobe.
Aug 1978 Launch of the Third International Sun-Earth Explorer (ISEE-3). ISEE-3 was one of a three part series of satellites to monitor solar wind and interactions with the Earth and Sun. ISEE-3 was placed at the Sun-Earth L5 point, roughly an hour upstream in the solar wind. Among other instruments, ISEE-3 carries gamma-ray burst detectors.
20 May 1978 Launch of the Pioneer Venus Orbiter (PVO), carrying (among many other instruments) a gamma-ray burst detector. PVO completed the gamma-ray burst Interplanetary Network (IPN) created by Helios-2 by supplying a 3rd mutually distant vertex.
26 Jan 1978 Launch of the NASA/ESA/UK SERC mission International Ultraviolet Explorer (IUE); this observatory performed spectrophotometry of celestial objects with both high (0.1 - 0.3 Angstroms) and low (6 - 7 Angstroms) spectral resolution at wavelengths between 1150 and 3200 Angstroms. IUE continued operating for two decades and became the most successful ultraviolet observatory ever, revolutionizing our understanding of the UV spectra of stars, galaxies, AGN, etc.
5 Sep 1977 Launch of NASA's Voyager 1 mission to Jupiter and Saturn on a Titan-Centaur rocket. Voyager 1 is still as of 2004 operational and became the most distant human-made object in the universe in February 1998 when it passed Pioneer 10: as of July 2004 it had reached a distance of 92 AU (13.8 billion km) from the Sun and was believed to be in the vicinity of the solar wind termination shock!
20 Aug 1977 Launch of NASA's Voyager 2 mission to Jupiter, Saturn, Uranus and Neptune on a Titan-Centaur rocket. This mission is still operational and moving out of the solar system and towards the interstellar medium at a speed of 3.3 AU per year: as of July 2004 it had reached a distance of 74 AU (11.0 billion km) from the Sun.
12 Aug 1977 Launch of the First High Energy Astrophysics Observatory (HEAO 1).
Jul 1977 Solrad 11A ceases operations.
2 Feb 1977 The Soviet space station Salyut-4 performs a controlled re-entry into the Earth's atmosphere over the Pacific Ocean.
Dec 1976 Solrad 11B ceases operations.
30 Jul 1976 The Astronomische Nederlandse Satelliet (ANS) ceases operation.
20 Jul 1976 The Viking 1 lander arrives at Utopia Plantia on Mars, the first (soft) landing probe on the Martian surface.
17 Apr 1976 Helios 2 achieves its perihelion distance of just 0.29 A.U.
15 Mar 1976 Launch of the paired satellites Solrad 11 A & B. Gamma-ray burst detectors were added to the Solrad 11 mission shortly before launch after the realization of gamma-ray bursts seen by the Vela series satellites.
Feb 1976 "First (interference) fringes" (the radio telescope equivalent of "First Light" for an optical telescope) at the Very Large Array (VLA) radio interferometer. The VLA is operated by the US National Radio Astronomy Observatory and is situated on the plains of San Augustin near Datil, New Mexico.
15 Jan 1976 Launch of Helios 2 on a mission to explore the Sun and the solar wind environment in the near-solar (within the orbit of Mercury) region. Helios-2 was the first spacecraft to be launched with a detector designed specifically for gamma-ray bursts. Its launch initiated the first gamma-ray burst Interplanetary Network (IPN), with Ariel-5 and the Vela spacecraft already in orbit. The launches of Pioneer-Venus Orbiter (PVO) and of Veneras-11 and Veneras-12 in 1978 finally completed the fully interplanetary array with 3 or more mutually distant vertices.
Late Oct 1975 First X-ray detection of Beta Persei or Algol, the prototype of the 'semi-detached' class of mass-transfer binary systems in which one star fills (and overflows) its Roche Lobe, after two previous unsuccessful attempts, by the Rotational Modulation Collimator instrument onboard the Third Small Astronomical Satellite (SAS 3). See Schnopper et al. 1976, ApJ, 210, L75 for more details. The X-ray emission from systems like Algol is now thought to be a result of the rapid and synchronized rotation of the Roche Lobe-filling component and not to be directly related to the mass transfer process.
14 Aug 1975 Peak of the X-ray outburst of A 0620-00 (also known as Nova Mon 1975), arguably the brightest non-solar X-ray source yet detected in terms of its observed flux, which exceeded the flux of Sco X-1, the brightest persistent X-ray source in the sky, by a factor of 3. This outburst was detected by the Sky Survey Experiment on the Ariel-V satellite. The inferred peak X-ray luminosity of this black hole binary system was 1038 erg s-1, 20 million times brighter than its quiescent level. See Elvis et al. 1975, Nature, 257, 656 et seq. for the discovery papers, and Chen et al. 1997, ApJ, 491, 312 for a review of the class of Soft X-ray Transients or X-Ray Novae to which A 0620-00 belongs.
9 Aug 1975 Launch of the European COS-B gamma-ray observatory.
21 & 22 Jul 1975 First detections of any extra-solar system objects in the extreme ultraviolet (EUV) region (wavelengths from 100 to 1000 Angstroms or photon energies from 0.012 to 0.12 keV), namely the hot white dwarf stars Feige 24 and HZ 43, by the Apollo-Soyuz Test Project (ASTP) Extreme-Ultraviolet (EUV) Telescope. The column density and hence optical depth of the interstellar medium had been generally expected to be so high that few, if any, objects would be detectable in the EUV range, but the detections of HZ 43, a previously known soft X-ray source, and Feige 24 showed this to be incorrect. The EUV and soft X-ray emission from hot white dwarfs is `photospheric' in origin, i.e., the lack of significant opacity due to metals and Helium means that the EUV optical depth unity surface or photosphere is much deeper in the star than the visible light photosphere is. See Lampton et al. (ApJ, 203, L71, 1976) and Margon et al. (ApJ, 210, L79,1976) for more details.
15 Jul 1975 Launch of the Apollo spacecraft which became part of the Apollo-Soyuz Test Project (ASTP), the first joint U.S.-Soviet space mission.
21 Jun 1975 Launch of the Eighth Orbiting Solar Observatory 8 (OSO 8).
7 May 1975 Launch of the Third Small Astronomical Satellite (SAS 3).
8 Jan 1975 at 1:18 UT First detection of an X-ray flare simultaneously with an optical flare from an M dwarf star, namely the flare star UV Cet (L 726-8 AB), by the Utrecht soft-energy (0.2 - 0.28 keV) energy detector on the Astronomical Netherlands Satellite (ANS): see Heise et al. (ApJ, 202, L73, 1975) for more details.


We would like to thank the following individuals for their contributions to this page: Jesse S. Allen, and Ian M. George along with JPL's Space Calendar and the Working Group for the History of Astronomy's Astronomiae Historia (History of Astronomy) information pages.

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

Web page maintainer: Stephen A. Drake

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