National Aeronautics and Space Administration

A Brief History of High-Energy Astronomy: Before Common Era (BCE)

In Reverse Chronological Order

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Apr, 4 BCE (or BC)	Chinese astronomers observe and record for about a month a `po star' towards the direction of the modern constellation of Aquila. Wang et al. (ApJ, 569, L43, 2002) argue that this `po star', unlike most others which are now believed to be comets, was actually a hypernova (an exceptional supernova like SN 1998bw which has much more kinetic energy release than the typical value), and that the soft gamma repeater SGR 1900+14 is the neutron star created in this event.
48 BCE (or BC)	Chinese astronomers observe and record a `guest star' which is now suspected to be a supernova explosion, possibly the one which produced the supernova remnant SNR 021.5-00.9 (Wang et al. 1986, Highlights of Astronomy, 7, 583).
134 BCE (or BC)	Chinese (and Greek) astronomers observe and record a `guest star' which is now suspected to be a supernova explosion, possibly the one which produced the supernova remnant RCW 103 = SNR 332.4-00.4 (Wang et al. 1986, Highlights of Astronomy, 7, 583).
240 BCE (or BC)	The first reliably recorded appearance of Halley's Comet (P1/Halley), by Chinese astronomers.
523 BCE (or BC)	Chinese astronomers observe and record a `guest star' which is now suspected to be a supernova explosion, possibly the one which produced the supernova remnant CTB 87 = SNR 074.9+01.2 (Wang et al. 1986, Highlights of Astronomy, 7, 583).
~1180 BCE (or BC)	The collapse of the 9 largest Mediterranean kingdoms, including Babylon, Egypt, Troy, Minos & Mycenea, marking the end of the Late Bronze age. Dr. Eric Cline has argued that this was due to a complex web of factors, likely triggered by natural phenomena, such as large earthquakes, droughts and famines, which caused mass migrations out of the affected regions and resulting conflicts with the neighboring peoples.
14th Century BCE (or BC)	A great new star is observed by Chinese astronomers during the Shang Dynasty and recorded on an "oracle bone of tortoise". Xu et al. (1992, A&A, 256, 483) suggest that this event "may be the first [supernova] explosion recorded by mankind" and was caused by the explosion of a massive star in the nearby Rho Oph molecular cloud, and that the effects are still visible as the gamma-ray source 2CG 353+16.
5,000 years ago	The beginning of construction of the first phase of Stonehenge (near the modern-day town of Amesbury in England). This complex of stones, pits and ditches has many alignments which, it has been argued, suggest that it was designed to be an astronomical observatory.
7,000 years ago	Construction of a circular walled compound near the modern-day town of Goseck in Germany which has been claimed to be Europe's oldest astronomical observatory, predating Stonehenge by more than 2000 years, based on features that align with winter solstice sunrise and sunset.
12,000 years ago	Beginning of the current interglacial period (the Holocene era) on the Earth, following the end of the Earth's Last Glacial Period.
12,900 years ago	Sudden onset of the Younger Dryas Cooling, followed by a return to Ice Age conditions for a thousand years or so. Napier (2010) argues that this Younger Dryad Boundary, which is marked by catastrophic wildfires over North America, the extinctions of 35 genera of mammals, and widespread soot, magnetic grains and nanodiamonds, was caused by the impact of a dense swarm of debris from a disintegrating large (50-100 km) short-period comet with the Earth, and that the remaining debris of this comet is still visible every late Fall as the Taurid Meteor Shower.
22,000 years ago	The supernova that created the Vela remnant occurred about 250 pc from the Earth according to Firestone 2014, ApJ, 789, 29, based on an analysis of of the terrestrial radiocarbon (14C) and beryllium (10Be) records and on the increase in nitrate accumulation in the East Antarctic icesheet, believed to be caused by the gamma rays and cosmic rays produced in the supernova explosion. This supernova was the most recent, nearby (<~ 300 pc) one that has occurred, and its association withe the Vela SNR is plausible, although there is no direct evidence for this hypothesis. Based on this event and 3 other likely near-Earth supernovae in the last 50,000 years, the author infers an average frequency of nearby supernova of one every 12,500 years, so it looks like we are overdue for another one! Watch the skies!
26,500 years ago	The Oranui Supereruption, the most recent volcanic supereruption in the Earth's history, where a supereruption is an eruption with a Volcanic Explosivity Index (VEI) >= 8, in which a volcano situated at what is now Lake Taupo on the North Island of New Zealand ejected a volume of 1,170 km3 of material and deposited an ash layer 7 inches thick as far away as the Chatham Islands (1,000 km distant). This supereruption is the last known to have occurred. The VEI is a logarithmic scale, notice, so that the Oranui eruption was a thousand times more potent than the 1908 eruption of Mount St Helens which had a VEI of 5!
32,000 years ago	A supernova occurred about 160 pc from the Earth according to Firestone 2014, ApJ, 789, 29, based on an analysis of of the terrestrial radiocarbon (14C) and beryllium (10Be) records, and the increase in nitrate accumulation in the East Antarctic icesheet, caused by supernova-related gamma rays and cosmic rays. This supernova was the second most recent, nearby (<~ 300 pc) one that has occurred.
37,000 years ago	A supernova occurred about 180 pc from the Earth according to Firestone 2014, ApJ, 789, 29, based on an analysis of of the terrestrial radiocarbon (14C) and beryllium (10Be) records, and the increase in nitrate accumulation in the East Antarctic icesheet, caused by supernova-related gamma rays and cosmic rays. This supernova was the third most recent, nearby (<~ 300 pc) one that has occurred.
44,000 years ago	A supernova occurred about 110 pc from the Earth according to Firestone 2014, ApJ, 789, 29, based on an analysis of of the terrestrial radiocarbon (14C) and beryllium (10Be) records, and the increase in nitrate accumulation in the East Antarctic icesheet, caused by supernova-related gamma rays and cosmic rays. This supernova was the closest supernova to the Earth in the last 50,000 years. The author identifies 19 more enhancements in the 10Be/9Be ratio in marine sediments most of which are likely caused by even earlier (between 57,000 and 295,000 years ago), nearby (<~ 300 pc) supernovae. The Galaxy is a dangerous place!
74,000 years ago	The Toba Supereruption, one of the Earth's largest known eruptions (called a volcanic supereruption, being an eruption with a Volcanic Explosivity Index (VEI of 8). This eruption of a volcano situated at what is now Lake Toba in Sumatra, Indonesia ejected a volume of 2,800 km3 of material and deposited an ash layer 6 inches thick over a large part of South Asia. This supereruption is the largest known to have occurred in the last two million years. It is hypothesized that afterwards there first followed a decade-long 'volcanic winter', and then a thousand year-long global cooling episode during which the populations of humans and a number of other large mammals declined precipitously.
110,000 years ago	Beginning of the Earth's Last Glacial Period, which lasted for one hundred thousand years. During this colder than average glacial period in the Pleistocene Epoch, massive ice sheets covered Canada, the northern USA, and much of northern Europe.
2.588 million years ago	Beginning of the current 'Quaternary Ice Age' or the Pleistocene Epoch on the Earth, a period of time containing 10 or more 100,000 years or longer glacial periods, separated by shorter (about 10,000 years) inter-glacial periods. Fascinatingly, the causes of the Ice ages and glacial periods are still being actively studied, although periodic changes in the eccentricity of the Earth's orbit around the Sun, the precession of the equinoxes and/or changes in the tilt of the Earth's polar axis to the plane of its orbit are leading contenders. The changes in the fraction of carbon dioxide in the Earth's atmosphere, ocean currents, atmospheric climate patterns such as El Nino, and plate tectonics are all thought to contribute to these long-timescale fluctuations in the Earth's surface temperature.
2 - 3 million years ago	A core-collapse supernova explosion may have occurred nearby (10-100 parsecs), as inferred from the discovery in deep-ocean layers of the unstable isotope 60Fe which is created in significant amounts only in such supernovae. Other evidence for a nearby supernova several million years go is the existence of the `Local Hot Bubble' in the interstellar medium in which the Solar System is embedded. See Fields et al. 2005 (ApJ, 621, 901) and Ludwig et al. 2016, PNAS, 113, 9232) for more details on the 60Fe measurements, but also see Fitoussi et al. (2007, astro-ph preprint) whose study failed to find 60Fe in the layers of a marine sediment deposited at this era. The possibility of a connection between this supernova and the global cooling event called the Quaternary Ice Age (see above) is tantalising but highly speculative.
35 million years ago	A 6-km diameter object strikes the eastern shore of the US in the location of the present-day Chesapeake Bay, the last large impact known to have struck the Earth, causing significant local destruction and a tsunami which may have crested high enough to have engulfed as far inland as the Blue Ridge Mountains. This impact left a crater 85 km in diameter and a layer of ejecta surrounding it rich in tektites (spherules) indicative of melted and fused rock.
56 million years ago	A large object strikes near the eastern shore of the US. No impact crater has been identified for this event which occurred at the Paleocene-Eocene (P-E) boundary and coincided with (triggered?) a rapid carbon-cycle perturbation, a global warming event, rapid expansion of mammal and terrestrial plant populations, and extinctions of deep-sea benthic organisms. The evidence of this impact, principally the discovery of silicate glass spherules identified as microtektites and microkrystites in a discrete stratigraphic layer found in 3 sections along the Atlantic margin, is presented in Schaller et al. (2016, Science, 354, 225).
65 million years ago	The K-T (Cretaceous-Tertiary: more correctly known as the K-Pg or Cretaceous-Paleogene) extinction event causes the extinction of about 50 - 70% of the species of life on the Earth, most notoriously the dinosaurs. This extinction event is widely believed to be due to the impact of a large object such as a comet or asteroid, and the 180 kilometer-diameter Chicxulub crater in Mexico's Yucatan Peninsula is generally regarded to be the impact site. For more on the origins and travails of terrestrial life (and on the search for extraterrestrial life), see NASA's Astrobiology site.
205 million years ago	The Triassic-Jurassic extinction event causes the extinction of a good fraction of the species of life on the Earth, e.g., up to 50% of marine species, and many types of archosaurs, therapsids, and large amphibians, either due to the impact of one or more large comets or asteroids (Spray et al. (1998, Nature, 392, 171 note the possible association with "impact-generated shocked-quartz-bearing shale beds in Italy"), or alternatively to a surge in volcanic activity triggered by the first stage of the breakup of the supercontinent dubbed Pangaea which injected more than 1013 tons of carbon in the form of methane into the atmosphere and caused a strong global warming event.
214 million years ago	According to Spray et al. (1998, Nature, 392, 171), 5 or more km-size objects impact the Earth and leave a chain of craters over 4000 km long. The largest crater (~ 100 km diameter) is at Manicouagan in eastern Canada. The authors suggest that these apparently simultaneous impacts were due to the fragmentation of a larger object, and that the aftereffects of this event may have caused a previously reported mass extinction event in the Late Triassic era at the Carnian-Norian boundary.
250 million years ago	The Permian-Triassic extinction event, also known as the "Great Dying" causes the extinction of many species of life on the Earth, e.g., 95% of marine species and 70% of land species, perhaps due to the impact of a large object such as a comet or asteroid. This is the largest such extinction event known in the history of life on earth. Recently, a 125-mile diameter feature has been discovered off the coast of Australia, the Bedout High, which has been suggested is an impact crater of the correct age and size for such a large event (see Becker et al. 2004, Science, 304, 1469 for more details), although this is still not the consensus among impact cratering scientists. Alternatively, a massive volcanic eruption which covered an area of several million square km with basaltic lava, the so-called Siberian Traps, the cause of which is an active area of scientific debate, has been fingered as the cause of the 'Great Dying".
360 million years ago	The transition from the Devonian to the Carboniferous periods causes the elimination of many species (about 70%) of life on the Earth. This was not a sudden occurrence but occurred over a few million years, and thus it is unlikely to have been caused by a single large impact event.
440 million years ago	Two Ordovician-Silurian extinction events cause the extinction of many species of life on the Earth, perhaps due to the onset and decline of a major glaciation episode.
500 million years ago	The Cambrian-Ordovician series of extinction events cause the extinction of many species of life on the Earth, such as brachiopods, conodonts, and trilobites. Melott et al. (2004, International Journal of Astrobiology, 3, 55) have presented arguments that this extinction may have been triggered by a gamma-ray burst associated with a nearby (within 3 kiloparsecs) galactic supernova.
1.7 - 1.4 billion years ago	The intermittent operation of the first-known 'natural' nuclear fission reactors on the Earth as water inundated uranium deposits in Oklo, Gabon (West Africa). Such natural nuclear reactors cannot function today because the fraction of fissile 235U in rocks is too low for (normal) water to act as a neutron moderator.
2.4 billion years ago	The Great Oxygenation Event, in which significant amounts of biologically-produced molecular oxygen first appeared in the Earth's atmosphere, mostly replacing some of the previous primary constituents such as carbon dioxide and ammonia.
2.7 billion years ago	The appearance on the Earth of eukaryotes, lifeforms with complex cells in which the genetic material is contained in distinct nuclei.
3.26 billion years ago	The impact of an asteroid of ~50 km diameter on the Earth, causing widespread devastation, due both to the initial collision, the resultant crustal fracturing, and to subsequent giant tsunamis and seismic activity, according to Sleep and Lowe (2014, Geochemistry, Geophysics, Geosystems). The molten rock rained back down to the surface in drops which became spherules, leaving a debris layer with the Iridium enhancement typical of the impact of a carbonaceous chondrite body. The evidence for this event can be found in the Barberton Greenstone Belt, South Africa. The exact site of the impact itself is not known, and, indeed, there may have been other similarly large impacts during the Archean era (2.5 to 3.8 billion years ago) the evidence for which remains to be found. See this Universe Today article for a popular-level discussion.
>= 3.5 billion years ago	The beginning of life on the Earth, based on the age of the oldest known terrestrial lifeforms. These were prokaryotes, single-celled lifeforms that lack nuclei, mitochondria or organelles. This age has often been obtained from the geological dating of their fossilized remains, but a new study (Tashiro et al. 2017, Nature, 549, 516) identifying the presence of biological activity from the total organic carbon contents and carbon isotope values of graphite and carbonate in the oldest metasedimentary rocks from northern Labrador "indicates the oldest evidence of organisms greater than 3.95 [billion years]". For more on the origins of terrestrial life and on the search for extraterrestrial life, see NASA's Astrobiology site.
3.9 billion years ago	The Late Heavy Bombardment (LHB) of the larger objects in the inner Solar System (like the Earth and its Moon) by a large number of asteroids and comets, possibly caused by the orbital migration of the giant planets from wider initial orbits to their present orbits. Many scientists in this field believe that, until the LHB ended, the Earth's surface could not be a viable site for the sustained development of life. Recently however, re-examinations of the large impacts that produced cratering on the Moon, e.g., by Boehnke and Harrison (2016, PNAS, 113, 10802), have cast doubt as to whether there was an LHB "spike" at this time and argue that the LHB actually extended over a much longer period from 3.4 to 4.2 billion years ago, e.g., Zellner (2017, OLEB, 47, 261).
4.47 billion years ago	Formation of the Earth, strictly speaking, the era by which the Earth had finished accumulating most of its present mass, i.e., the era when the Earth was impacted by a Mars-sized object (which has been dubbed by some researchers Theia), and the Moon formed out of the ejecta (Jacobson et al. 2014, Nature, 508, 84).
4.567 billion years ago	Formation of the Solar System (strictly speaking, the era in which the oldest known accreted objects formed in the solar `nebula'): see Jacobsen (2003, Science, 300, 1513) for a brief discussion of the era of the formation of the Solar System and the Earth.
8 billion years ago	Formation of the first stars in the thin disk of our Galaxy, the Milky Way, as inferred from measurements of the coolest and dimmest white dwarf stars in the solar neighborhood, see e.g., Leggett et al., 1998, ApJ, 497, 294.
11.1 billion years ago	The age of the oldest known X-ray detected cluster of galaxies, CL J0001+0220. This cluster has a spectroscopic redshift of 2.506 and contains 11 massive (> 1011 solar masses) galaxies in the central 80-kpc region; see Wang et al., 2016, ApJ, in press who note that "the large integrated stellar mass at such high redshift challenges our understanding of massive cluster formation".
12.6 billion years ago	Formation of the first (oldest) stellar aggregates in our Galaxy, the Milky Way, as determined from the ages of its oldest globular clusters, and thus the lower limit to the age of the Milky Way itself, see e.g., Krauss and Chaboyer (2003, Science, 299, 65). Some individual stars in the halo component of our Galaxy may be even older, e.g., the star HE 1523-0901 has been estimated to be 13.2 billion years old, and the F-type Pop II star HD 140283 has been estimated by Creevey et al. (2015, A&A, 575, A26) has been estimated to be 13.7 ± 0.7 Gyr (billion years) old, i.e., to have formed within a few hundred millions of years after the Big Bang, making it the oldest known star in the Universe.
~13.1 billion years ago	Formation of the first galaxies and the start of the re-ionization of the Universe: the oldest known 'galaxies' to date are UDFj-39546284 and UDFy-38135539 , visible as faint red 'blobs' in the Hubble Ultra-Deep Field, and with estimated ages of 13.2 and 13.1 billion years, respectively (based on UDFj's photometric redshift of 10.3 and UDFy's spectroscopic redshift of 8.6).
12.9 - 13.55 billion years ago	The Dark Ages of the Universe, after the hydrogen and helium ions that constitute most of its baryonic mass combined with free electrons to form neutral atoms (and the universe became transparent), and before significant numbers of stars and galaxies were formed and began to emit 'light', so that, apart from the slowly cooling CMB, there were no intrinsic sources of emission in the Universe (apart from the 21-cm hydrogen emission line, and some other weak spectral lines such as the Li I resonance line). The duration of this period of darkness has been confirmed by measurements made by NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite.
13.82 billion years ago	Formation of the Universe, also known as the `Big Bang', according to measurements made by ESA's Planck satellite. This age agrees within the error bars with the age of 13.77 billion years derived from measurements made by NASA's Wilkinson Microwave Anisotropy Probe (WMAP). After 380,000 years of expansion, the universe cools enough (to ~3,000 K) so that the hydrogen and helium ions that constitute most of its baryonic mass combine with free electrons to form neutral atoms, and the universe becomes transparent: this is called the era of recombination. The photons from this era are still observable today (after being redshifted by a factor of ~1,100 due the the expansion of the Universe) as the 2.7255K black-body cosmic microwave background (CMB) radiation.

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Acknowledgements

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

Web page maintainer: Stephen A. Drake