A Brief History of High-Energy Astronomy: 1995 - 1999

In Reverse Chronological Order

Dec 10 1999 Launch of the X-Ray Multi-Mirror Mission (XMM), renamed after launch to XMM-Newton . XMM-Newton is an ESA facility-class X-ray observatory, the second cornerstone of ESA's Horizon 2000 program, and has an anticipated lifetime of ten years. XMM-Newton works in the energy range from 0.1 to 15 keV, and its large effective area of 4650 square cm will enable it to observe cosmic X-ray sources down to a limiting flux of order 10-16 erg/sec/cm2. To broaden the scope of XMM-Newton's investigations, it also carries an Optical Monitor that can simultaneously study the optical/UV properties of the observed sources (still operational).
Aug 27 1999 Departure of the last regular crew from the Mir Space Station.
Jul 23 1999 Launch of the Chandra X-Ray Observatory (CXO; formerly known as the Advanced X-ray Astrophysics Facility or AXAF), the last of NASA's `Great Observatories'. Chandra has an unprecedented ability to make high spatial-resolution X-ray observations, and additional capabilities using gratings to make high spectral-resolution observations, of celestial X-ray sources (still operational).
Jun 24 1999 Launch of the Far Ultraviolet Spectroscopic Explorer (FUSE): the first in a series of NASA Medium-Class Explorer missions, with a primary objective to cover the wavelength range between 900 and 1250 Angstroms (90 -125 nanometers) and primary science goals that include measuring the deuterium to hydrogen ratio in interstellar and intergalactic media and studying the chemical evolution of galaxies.
Apr 28 1999 Launch of A Broad-band Imaging X-Ray All-Sky Survey (ABRIXAS), a small satellite mission which was designed to observe the X-ray sky in the energy band from 0.5 to 10 keV. This mission was the product of a consortium of German institutions: the Astrophysikalisches Institut Potsdam (AIP), the Max-Planck-Institut fur extraterrestrische Physik (MPE), and the Institut fur Astronomie und Astrophysik, Tubingen (IAAT). ABRIXAS experienced problems with its battery shortly after launch, and contact with it was lost on May 1 1999. The scientific part of the mission was declared a loss on July 1 1999.
Mar 28 1999 at 09:00 UT Launch of a Black Brant V sounding rocket from White Sands, New Mexico carrying an X-ray astronomy payload designed to observe the diffuse X-ray background in the 60 - 1000 eV energy range (12.4 - 200 Angstrom wavelength range). This experiment was the first to carry a new type of thermal X-ray detector called a quantum calorimeter, or a microcalorimeter. This instrument attained spectral resolution values (~ 9 eV) similar to that of previous Bragg Crystal Spectrometer experiments, but with much higher throughput. Several lines of C VI, O VII and O VIII were clearly detected in just ~100 seconds of live time on the main target region, and the fluxes of these lines imply that at least 42% of the observed diffuse background in the ROSAT R4 band centered at 0.65 keV comes from thermal emission located at redshift < 0.01. See McCammon et al. (ApJ, 576, 188, 2002) for a complete report.
Feb 23 1999 Launch of the Advanced Research and Global Observation Satellite (ARGOS): one of the experiments on this USAF satellite is the Unconventional Stellar Aspect (USA) Experiment which is designed to do X-ray timing and time-resolved spectroscopy of relatively bright X-ray sources, such as X-ray binaries.
Feb 12 1999 End of operations of the Roentgen Satellite (ROSAT), an X-ray (0.1 - 2 keV) and EUV (0.02 - 0.3 keV) astronomy mission due to an international collaboration between Germany, the UK, and the US. This mission had two phases, an All-Sky Survey phase in which the spinning satellite mapped the entire sky in both X-rays and the EUV (and detected more than 100,000 discrete X-ray sources), and a pointed observation phase in which the satellite could make deep observations of selected positions in the sky. The results obtained from more than 8 years of ROSAT observations revolutionized the field of X-ray astronomy, e.g., by increasing the number of known X-ray sources by a factor of 30 over the number known prior to ROSAT.
Jan 23 1999 First detection of optical prompt emission associated with a gamma-ray burst, GRB 990123, by the Robotic Optical Transient Search Experiment (ROTSE). This optical emission reached a peak visual magnitude of about 9 about 40 seconds after the start of the GRB (Akerlof et al. (1999), Nature, 398, 400). Within hours of the GRB, it was discovered that the optical object had absorption lines in its spectrum at a redshift of 1.60, implying that the GRB was at a cosmological distance such that the energy release, if isotropic, was in excess of 1054 erg (for comparison, if the Sun were to shine at its present luminosity for 10 billion years, it would emit only 1051 erg of light over that period).
Nov 27 1998 End of operations of Granat, a Russian-led mission dedicated to X-ray and gamma-ray astronomy. Its instruments included WATCH, an all-sky monitor in the 6 to 120 keV energy band, SIGMA, a coded-mask X-ray telescope, PHEBUS, a gamma-ray burst experiment, and 4 other experiments.
Nov 20 1998 Launch of the first element (the Zarya Control Module or the Functional Cargo Block) of the International Space Station (ISS).
Aug 27 1998 Detection by 5 satellites carrying gamma-ray burst detectors (GGS-Wind, Ulysses, RXTE, BeppoSAX, and NEAR) of an intense (peak flux of about >= 3.4 x 10-3 erg s-1 cm-2 in the energy range above 25 keV) and rapid (burst duration FWHM of ~ 1 second) gamma-ray `spike' from SGR 1900+14, a previously known Soft Gamma Repeater or SGR. This main peak was followed by a slowly declining flux which was modulated by 5.16 second pulsations for several minutes afterwards. 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 months preceding this strong gamma-ray transient, SGR 1900+14 had come out of a long dormant phase and had emitted frequent strong bursts. See Cline et al. (IAU Circular 7002 1998) and Hurley et al. (Nature, 397, 41 199) for the initial discovery papers on this energetic `flare' or transient. See also the entry for 4 B.C.E. for a suggestion about an event which may have been responsible for the origin of SGR 1900+14.
1998 Publication of reports from two separate research groups that indicate with a moderately high level of confidence that, based on the magnitude versus redshift relation of distant Type Ia supernova explosions, the Universe is accelerating; e.g., Riess at al. 1998, AJ, 116, 1009). This unexpected result was the first clue for the existence of the `dark energy' which represents the bulk (about 73%) of the mass-energy in the Universe (the rest of the Universe is: 23% `dark matter', 3.6% non-luminous intergalactic matter, and only 0.4% stars and luminous gas: a very bizarre recipe!). The nature of dark energy has not yet been established, although many theoretical speculations on this topic have been published, e.g., quintessence, vacuum energy, etc.
Oct 15 1997 at 04:43 am EDT Launch on a Titan IV/Centaur launch vehicle from Cape Canaveral, Florida of the Cassini-Huygens spacecraft. This joint NASA-ESA-Italian Space Agency mission will systematically explore Saturn, Titan, the rings, and the other satellites upon its arrival there in 2004.
Apr 21 1997 Launch of the Spanish Minisat 1 carrying Low Energy Gamma Ray Imager (LEGRI) experiment on the INTA (Spanish space agency) MINISAT-01 platform. This instrument was used to study gamma-ray bursts.
Feb 28 1997 First detection of an optical afterglow associated with a gamma-ray burst, GRB 970228. At 2:58 UT a gamma-ray burst was detected by the BeppoSAX satellite, and an optical follow-up made 21 hours later discovered a transient fading source which appeared to be associated with a faint galaxy: van Paradijs et al. (1997) Nature, 386, 686 for more details. This and subsequent observations of optical afterglows of GRBs appeared to be consistent with GRBs in general lieing at cosmological distances.
Nov 04 1996 Unsuccessful launch of the High-Energy Transient Experiment (HETE-01) satellite and the Satelite de Aplicaciones Cientificas B (SAC-B) satellite carrying the Cosmic Unresolved Background Instrument using CCDs (CUBIC) (an X-ray spectrometer). Unfortunately, the Pegasus XL third stage failed to separate properly and both spacecraft remained attached. As a result, no scientific data were obtained from this mission, which was declared a loss: however, a HETE-02 mission was approved and was launched on Oct 9, 2000.
Sep 30 1996 Shut-down of IUE operations. After almost 19 years of mission operations, the International Ultraviolet Explorer spacecraft was shut down at 18:42 UT (due to budget constraints). During its lifetime, IUE collected over 100,000 spectra from approximately 9300 objects. An archive of its data is available at the Multimission Archive at the Space Telescope Science Institute (MAST).
Apr 30 1996 Launch of Satellite per Astronomia a raggi X (Italian for X-ray Astronomy Satellite), renamed "BeppoSAX" after it reached its orbit).
Mar 26 - 28 1996 Discovery of X-ray and EUV emission from Comet C/1996 B2 (Hyakutake). This was the first-ever report of either X-rays (Lisse et al. (1996) or EUV emission ( Pye et al. (1996) from a comet, and was based on observations using the ROSAT High-Resolution Imager (X-ray) and Wide-Field Camera (EUV) instruments. It was soon realized, however, by Dennerl et al. (1996), that the ROSAT Position-Sensitive Proportional Counter had in fact detected the X-ray emission from several comets during the All-Sky Survey carried out in 1990 - 1991, but this had not been recognized at that time.
Jan 18 1996 Publication date of the discovery of the first, generally credited isolated (non-binary) neutron star by Walter et al. (Nature, 379, 233, 1996), based on ROSAT observations. This object, named RX J185635-3754, is a bright X-ray source (1.5 x 10-11 erg cm-2 s-1 in the 0.1 - 2.4 keV band), but had no identified optical counterpart brighter than 23rd magnitude, according to this paper. Later studies discovered a 26th magnitude counterpart, and derived a close distance of 60 - 120 pc, but there is still debate as to its exact nature: most astronomers believe that it is likely a young, hot X-ray bright neutron star which is the stellar remnant of a massive star in the nearby Upper Sco Association that exploded as a supernova about a million years ago, although other suggestions include it being an old neutron star which is emitting X-rays due to accretion of material from the interstellar medium, or even not a neutron star at all, but a quark or strange star (e.g., Drake et al., ApJ, 572, 996, 2002). Since 1996, a handful of other isolated neutron stars have been proposed, e.g., RBS 1223, RBS 1774, RX J0720.4-3125: see the review by Treves et al. (PASP, 112, 297, 2000) for more details.
Dec 30 1995 Launch of the Rossi X-ray Timing Explorer (RXTE) (still operational).
Dec 7 1995 Descent of the Galileo atmospheric probe into Jupiter's cloud deck. The atmospheric probe detached from the main Galileo platform in July 1995.
Sep 30 1995 Termination of the Pioneer 11 mission due to failing power supply.
Jun 29 1995
9:00 EDT
Space shuttle Atlantis (STS-71) docks with the Russian space station Mir. It is the second joint U.S. - Russian mission, and the 100th U.S. manned mission.


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.

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

Web page maintainer: Stephen A. Drake

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