Irish Free State

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https://en.wikipedia.org/wiki/Irish_Free_State

Irish Free State Saorstát Éireann (Irish)
The Irish Free State (green)
Status	British Dominion (1922–1931) Sovereign state (1931–1937)
Capital and largest city	Dublin 53°21′N 6°16′W
Official languages	Irish English
National language	Irish
Religion (1926)	92.57% Roman Catholic 7% Protestantism 0.12% Other religions 0.30% Unspecified
Demonym(s)	Irish
Government	Unitary parliamentary constitutional monarchy
Monarch
• 1922–1936	George V
• 1936	Edward VIII
• 1936–1937	George VI
Governor-General
• 1922–1927	Timothy Michael Healy
• 1928–1932	James McNeill
• 1932–1936	Domhnall Ua Buachalla
President of the Executive Council
• 1922–1932	W. T. Cosgrave
• 1932–1937	Éamon de Valera
Legislature	Oireachtas
• Upper house	Seanad
• Lower house	Dáil
History
• Anglo-Irish Treaty	6 December 1921
• Constitution of the Irish Free State	6 December 1922
• Constitution of Ireland	29 December 1937
Area
Until 8 December 1922	84,000 km2 (32,000 sq mi)
After 8 December 1922	70,000 km2 (27,000 sq mi)
Population
• 1936	2,968,420
Currency	Sterling (1922–1927) Saorstát pound (1928–1937)
Time zone	UTC
• Summer (DST)	UTC+1 (IST/WEST)
Date format	dd/mm/yyyy
Driving side	left
Preceded by Succeeded by Southern Ireland Irish Republic Republic of Ireland

The Irish Free State (Irish: Saorstát Éireann, pronounced [ˈsˠiːɾˠsˠt̪ˠaːt̪ˠ ˈeːɾʲən̪ˠ], English: /ˌsɛərstɑːt ˈɛərən/ SAIR-staht AIR-ən; 6 December 1922 – 29 December 1937) was a state established in December 1922 under the Anglo-Irish Treaty of December 1921. The treaty ended the three-year Irish War of Independence between the forces of the Irish Republic – the Irish Republican Army (IRA) – and British Crown forces.

The Free State was established as a dominion of the British Empire. It comprised 26 of the 32 counties of Ireland. Northern Ireland, which was made up of the remaining six counties, exercised its right under the Treaty to opt out of the new state. The Free State government consisted of the Governor-General – the representative of the king – and the Executive Council (cabinet), which replaced both the revolutionary Dáil Government and the Provisional Government set up under the Treaty. W. T. Cosgrave, who had led both of these administrations since August 1922, became the first President of the Executive Council (prime minister). The Oireachtas or legislature consisted of Dáil Éireann (the lower house) and Seanad Éireann (the upper house), also known as the Senate. Members of the Dáil were required to take an Oath of Allegiance to the Constitution of the Free State and to declare fidelity to the king. The oath was a key issue for opponents of the Treaty, who refused to take it and therefore did not take their seats. Pro-Treaty members, who formed Cumann na nGaedheal in 1923, held an effective majority in the Dáil from 1922 to 1927 and thereafter ruled as a minority government until 1932.

In 1931, with the passage of the Statute of Westminster, the Parliament of the United Kingdom relinquished nearly all of its remaining authority to legislate for the Free State and the other dominions. This had the effect of granting the Free State internationally recognised independence.

In the first months of the Free State, the Irish Civil War was waged between the newly established National Army and the Anti-Treaty IRA, which refused to recognise the state. The Civil War ended in victory for the government forces, with its opponents dumping their arms in May 1923. The Anti-Treaty political party, Sinn Féin, refused to take its seats in the Dáil, leaving the relatively small Labour Party as the only opposition party. In 1926, when Sinn Féin president Éamon de Valera failed to have this policy reversed, he resigned from Sinn Féin and led most of its membership into a new party, Fianna Fáil, which entered the Dáil following the 1927 general election. It formed the government after the 1932 general election, when it became the largest party.

De Valera abolished the oath of allegiance and embarked on an economic war with the UK. In 1937, he drafted a new constitution, which was adopted by a plebiscite in July of that year. The Free State came to an end with the coming into force of the new constitution on 29 December 1937, when the state took the name "Ireland".

Background

The Easter Rising of 1916 and its aftermath caused a profound shift in public opinion towards the republican cause in Ireland. In the December 1918 General Election, the republican Sinn Féin party won a large majority of the Irish seats in the British parliament: 73 of the 105 constituencies returned Sinn Féin members (25 uncontested). The elected Sinn Féin MPs, rather than take their seats at Westminster, set up their own assembly, known as Dáil Éireann (Assembly of Ireland). It affirmed the formation of an Irish Republic and passed a Declaration of Independence. The subsequent War of Independence, fought between the Irish Republican Army (IRA) and British security forces, continued until July 1921 when a truce came into force. By this time the Parliament of Northern Ireland had opened, established under the Government of Ireland Act 1920, presenting the republican movement with a fait accompli and guaranteeing the British presence in Ireland. In October negotiations opened in London between members of the British government and members of the Dáil, culminating in the signing of the Anglo-Irish Treaty on 6 December 1921.

The Treaty allowed for the creation of a separate state to be known as the Irish Free State, with dominion status, within the then British Empire—a status equivalent to Canada. The Parliament of Northern Ireland could, by presenting an address to the king, opt not to be included in the Free State, in which case a Boundary Commission would be established to determine where the boundary between them should lie. Members of the parliament of the Free State would be required to take an oath of allegiance to the king, albeit a modification of the oath taken in other dominions.

The Dáil ratified the Treaty on 7 January 1922, causing a split in the republican movement. A Provisional Government was formed, with Michael Collins as chairman.

Northern Ireland "opts out"

The Treaty, and the legislation introduced to give it legal effect, implied that Northern Ireland would be a part of the Free State on its creation. Whether the legislation had the legal effect under United Kingdom law of making Northern Ireland a part of the Irish Free State is a point legal writers have disagreed on. One writer has argued that the terms of the Treaty applied only to the 26 counties, and the government of the Free State had neither de facto nor de jure power in Northern Ireland. Another writer has argued that on the day it was established the jurisdiction of the Free State was the island of Ireland. A 1933 court decision in Ireland showed that Irish law took the latter view. The de facto position was that Northern Ireland was treated as at all times being within the United Kingdom.

The Treaty was given legal effect in the United Kingdom through the Irish Free State Constitution Act 1922. That act, which established the Free State, allowed Northern Ireland to "opt out" of it. Under Article 12 of the Treaty, Northern Ireland could exercise its option by presenting an address to the king requesting not to be part of the Irish Free State. Once the Irish Free State Constitution Act was passed on 5 December 1922, the Houses of Parliament of Northern Ireland had one month (dubbed the "Ulster month") to exercise this option during which month the Government of Ireland Act continued to apply in Northern Ireland.

Realistically it was always certain that Northern Ireland would opt out of the Free State. The Prime Minister of Northern Ireland, Sir James Craig, speaking in the Parliament in October 1922 said that "when 6 December is passed the month begins in which we will have to make the choice either to vote out or remain within the Free State". He said it was important that that choice be made as soon as possible after 6 December 1922 "in order that it may not go forth to the world that we had the slightest hesitation". On the following day, 7 December 1922, the Parliament resolved to make the following address to the king so as to opt out of the Free State:

MOST GRACIOUS SOVEREIGN, We, your Majesty's most dutiful and loyal subjects, the Senators and Commons of Northern Ireland in Parliament assembled, having learnt of the passing of the Irish Free State Constitution Act, 1922, being the Act of Parliament for the ratification of the Articles of Agreement for a Treaty between Great Britain and Ireland, do, by this humble Address, pray your Majesty that the powers of the Parliament and Government of the Irish Free State shall no longer extend to Northern Ireland.

Discussion in the Parliament of the address was short. Prime Minister Craig left for London with the memorial embodying the address on the night boat that evening, 7 December 1922. The king received it the following day, The Times reporting:

YORK COTTAGE, SANDRINGHAM, DEC. 8. The Earl of Cromer (Lord Chamberlain) was received in audience by The King this evening and presented an Address from the Houses of Parliament of Northern Ireland, to which His Majesty was graciously pleased to make reply.

If the Parliament of Northern Ireland had not made such a declaration, under Article 14 of the Treaty Northern Ireland, its Parliament and government would have continued in being but the Oireachtas would have had jurisdiction to legislate for Northern Ireland in matters not delegated to Northern Ireland under the Government of Ireland Act. This, of course, never came to pass.

On 13 December 1922 Prime Minister Craig addressed the Parliament informing them that the king had responded to its address as follows:

I have received the Address presented to me by both Houses of the Parliament of Northern Ireland in pursuance of Article 12 of the Articles of Agreement set forth in the Schedule to the Irish Free State (Agreement) Act, 1922, and of Section 5 of the Irish Free State Constitution Act, 1922, and I have caused my Ministers and the Irish Free State Government to be so informed.

Governmental and constitutional structures

A symbol most often associated with the new state's postal system

The Treaty established that the new state would be a constitutional monarchy, with the Governor-General of the Irish Free State as representative of the Crown. The Constitution of the Irish Free State made more detailed provision for the state's system of government, with a three-tier parliament, called the Oireachtas, made up of the king and two houses, Dáil Éireann and Seanad Éireann (the Irish Senate).

Executive authority was vested in the king, with the Governor-General as his representative. He appointed a cabinet called the Executive Council to "aid and advise" him. The Executive Council was presided over by a prime minister called the President of the Executive Council. In practice, most of the real power was exercised by the Executive Council, as the Governor-General was almost always bound to act on the advice of the Executive Council.

Representative of the Crown

Main article: Governor-General of the Irish Free State

The office of Governor-General of the Irish Free State replaced the previous Lord Lieutenant, who had headed English and British administrations in Ireland since the Middle Ages. Governors-General were appointed by the king initially on the advice of the British Government, but with the consent of the Irish Government. From 1927, the Irish Government alone had the power to advise the king whom to appoint.

Oath of Allegiance

As with all dominions, provision was made for an Oath of Allegiance. Within dominions, such oaths were taken by parliamentarians personally towards the monarch. The Irish Oath of Allegiance was fundamentally different. It had two elements; the first, an oath to the Free State, as by law established, the second part a promise of fidelity, to His Majesty, King George V, his heirs and successors. That second fidelity element, however, was qualified in two ways. It was to the King in Ireland, not specifically to the King of the United Kingdom. Secondly, it was to the king explicitly in his role as part of the Treaty settlement, not in terms of pre-1922 British rule. The Oath itself came from a combination of three sources, and was largely the work of Michael Collins in the Treaty negotiations. It came in part from a draft oath suggested prior to the negotiations by President de Valera. Other sections were taken by Collins directly from the Oath of the Irish Republican Brotherhood (IRB), of which he was the secret head. In its structure, it was also partially based on the form and structure used for 'Dominion status'.

Although 'a new departure', and notably indirect in its reference to the monarchy, it was criticised by nationalists and republicans for making any reference to the Crown, the claim being that it was a direct oath to the Crown, a fact arguably incorrect by an examination of its wording, but in 1922 Ireland and beyond, many argued that the fact remained that as a dominion the King (and therefore the British) was still Head of State and that was the practical reality that influenced public debate on the issue. The Free State was not a republic. The Oath became a key issue in the resulting Irish Civil War that divided the pro and anti-treaty sides in 1922–23.

Funeral procession of Michael Collins, Dublin, 1922

Irish Civil War

Main article: Irish Civil War

The compromises contained in the agreement caused the civil war in the 26 counties in June 1922 – April 1923, in which the pro-Treaty Provisional Government defeated the anti-Treaty Republican forces. The latter were led, nominally, by Éamon de Valera, who had resigned as President of the Republic on the treaty's ratification. His resignation outraged some of his own supporters, notably Seán T. O'Kelly, the main Sinn Féin organizer. On resigning, he then sought re-election but was defeated two days later on a vote of 60–58. The pro-Treaty Arthur Griffith followed as President of the Irish Republic. Michael Collins was chosen at a meeting of the members elected to sit in the House of Commons of Southern Ireland (a body set up under the Government of Ireland Act 1920) to become Chairman of the Provisional Government of the Irish Free State in accordance with the Treaty. The general election in June gave overwhelming support for the pro-Treaty parties. W. T. Cosgrave's Crown-appointed Provisional Government effectively subsumed Griffith's republican administration with the death of both Collins and Griffith in August 1922.

"Freedom to achieve freedom"

Irish Free State passport (holder's name removed)

Governance

The following were the principal parties of government of the Free State between 1922 and 1937:

• Cumann na nGaedheal under W. T. Cosgrave (1922–32)
• Fianna Fáil under Éamon de Valera (1932–37)

Constitutional evolution

Overprinted stamp

Michael Collins described the Treaty as "the freedom to achieve freedom". In practice, the Treaty offered most of the symbols and powers of independence. These included a functioning, if disputed, parliamentary democracy with its own executive, judiciary and written constitution which could be changed by the Oireachtas. Although an Irish republic had not been on offer, the Treaty still afforded Ireland more internal independence than it had possessed in over 400 years, and far more autonomy than had ever been hoped for by those who had advocated for Home Rule.

However, a number of conditions existed:

• The king remained king in Ireland;
• Britain retained the so-called strategic Treaty Ports on Ireland's south and north-west coasts which were to remain occupied by the Royal Navy;
• Prior to the passage of the Statute of Westminster, the UK government continued to have a role in Irish governance. Officially the representative of the king, the Governor-General also received instructions from the British Government on his use of the Royal Assent, namely a Bill passed by the Dáil and Seanad could be Granted Assent (signed into law), Withheld (not signed, pending later approval) or Denied (vetoed). The letters patent to the first Governor-General, Tim Healy, explicitly named Bills that were to be rejected if passed by the Dáil and Seanad, such as any attempt to abolish the Oath. In the event, no such Bills were ever introduced, so the issue was moot.

Poster promoting Irish Free State farm goods for breakfast to Canadians ("Irish Free State butter, eggs and bacon for our breakfasts")

• As with the other dominions, the Free State had a status of association with the UK rather than being completely legally independent from it. However the meaning of 'Dominion status' changed radically during the 1920s, starting with the Chanak crisis in 1922 and quickly followed by the directly negotiated Halibut Treaty of 1923. The 1926 Imperial Conference declared the equality [including the UK] of all member states of the Commonwealth. The Conference also led to a reform of the king's title, given effect by the Royal and Parliamentary Titles Act 1927, which changed the king's royal title so that it took account of the fact that there was no longer a United Kingdom of Great Britain and Ireland. The king adopted the following style by which he would be known in all of his Empire: By the Grace of God, of Great Britain, Ireland and the British Dominions beyond the Seas King, Defender of the Faith, Emperor of India. That was the king's title in Ireland just as elsewhere in his Empire.
• In the conduct of external relations, the Free State tried to push the boundaries of its status as a Dominion. It 'accepted' credentials from international ambassadors to Ireland, something no other dominion up to then had done. It registered the treaty with the League of Nations as an international document, over the objections of the United Kingdom, which saw it as a mere internal document between a dominion and the United Kingdom. Entitlement of citizenship of the Free State was defined in the Irish Free State Constitution, but the status of that citizenship was contentious. One of the first projects of the Free State was the design and production of the Great Seal of Saorstát Éireann which was carried out on behalf of the Government by Hugh Kennedy.

The Statute of Westminster of 1931, embodying a decision of an Imperial Conference, enabled each dominion to enact new legislation or to change any extant legislation, without resorting to any role for the British Parliament that may have enacted the original legislation in the past. It also removed Westminster's authority to legislate for the Dominions, except with the express request and consent of the relevant Dominion's parliament. This change had the effect of making the dominions, including the Free State, de jure independent nations—thus fulfilling Collins' vision of having "the freedom to achieve freedom".

The Free State symbolically marked these changes in two mould-breaking moves soon after winning internationally recognised independence:

• It sought, and got, the king's acceptance to have an Irish minister, to the complete exclusion of British ministers, formally advise the king in the exercise of his powers and functions as king in the Irish Free State. This gave the President of the Executive Council the right to directly advise the king in his capacity as His Majesty's Irish Prime Minister. Two examples of this are the signing of a treaty between the Irish Free State and the Portuguese Republic in 1931, and the act recognising the abdication of King Edward VIII in 1936 separately from the recognition by the British Parliament.
• The unprecedented replacement of the use of the Great Seal of the Realm and its replacement by the Great Seal of Saorstát Éireann, which the king awarded to the Irish Free State in 1931. (The Irish Seal consisted of a picture of King George V enthroned on one side, with the Irish state harp and the words Saorstát Éireann on the reverse. It is now on display in the Irish National Museum, Collins Barracks in Dublin.)

When Éamon de Valera became President of the Executive Council (prime minister) in 1932 he described Cosgrave's ministers' achievements simply. Having read the files, he told his son, Vivion, "they were magnificent, son".

The Statute of Westminster allowed de Valera, on becoming President of the Executive Council (February 1932), to go even further. With no ensuing restrictions on his policies, he abolished the Oath of Allegiance (which Cosgrave intended to do had he won the 1932 general election), the Seanad, university representation in the Dáil, and appeals to the Judicial Committee of the Privy Council.

One major policy error occurred in 1936 when he attempted to use the abdication of King Edward VIII to abolish the crown and governor-general in the Free State with the "Constitution (Amendment No. 27) Act". He was advised by senior law officers and other constitutional experts that, as the crown and governor-generalship existed separately from the constitution in a vast number of acts, charters, orders-in-council, and letters patent, they both still existed. A second bill, the "Executive Powers (Consequential Provisions) Act, 1937" was quickly introduced to repeal the necessary elements. De Valera retroactively dated the second act back to December 1936.

Currency

The new state continued to use the Pound sterling from its inception; there is no reference in the Treaty or in either of the enabling Acts to currency. Nonetheless, and within a few years, the Dáil passed the Coinage Act, 1926 (which provided for a Saorstát [Free State] coinage) and the Currency Act, 1927 (which provided inter alia for banknotes of the Saorstát pound). The new Saorstát pound was defined by the 1927 Act to have exactly the same weight and fineness of gold as was the sovereign at the time, making the new currency pegged at 1:1 with sterling. The State circulated its new national coinage in 1928, marked Saorstát Éireann and a national series of banknotes. British coinage remained acceptable in the Free State at an equal rate. In 1937, when the Free State was superseded by Ireland (Éire), the pound became known as the "Irish pound" and the coins were marked Éire.

Demographics

Birth rate

According to one report, in 1924, shortly after the Free State's establishment, the new dominion had the "lowest birth-rate in the world". The report noted that amongst countries for which statistics were available (Ceylon, Chile, Japan, Spain, South Africa, Netherlands, Canada, Germany, Australia, United States, Britain, New Zealand, Finland and the Irish Free State), Ceylon had the highest birth rate at 40.8 per 1,000 while the Irish Free State had a birth rate of just 18.6 per 1,000.

Cultural outlook

Irish society during this period was extremely Roman Catholic, with Roman Catholic thinkers promoting anti-capitalist, anti-communist, anti-Protestant, anti-Masonic and anti-Semitic views in Irish society. Through the works of priests such as Edward Cahill, Richard Devane and Denis Fahey, Irish society saw capitalism, individualism, communism, private banking, the promotion of alcohol, contraceptives, divorce and abortion as the pursuits of the old 'Protestant-elite' and Jews, with their efforts combined through the Freemasons. Denis Fahey described Ireland as "the third most Masonic country in the world" and saw this alleged order as contrary to the creation of an independent Irish State.

After the Irish Free State

1937 Constitution

In 1937 the Fianna Fáil government presented a draft of an entirely new Constitution to Dáil Éireann. An amended version of the draft document was subsequently approved by the Dáil. A plebiscite was held on 1 July 1937, which was the same day as the 1937 general election, when a relatively narrow majority approved it. The new Constitution of Ireland (Bunreacht na hÉireann) repealed the 1922 Constitution, and came into effect on 29 December 1937.

The state was named Ireland (Éire in the Irish language), and a new office of President of Ireland was instituted in place of the Governor-General of the Irish Free State. The new constitution claimed jurisdiction over all of Ireland while recognising that legislation would not apply in Northern Ireland (see Articles 2 and 3). Articles 2 and 3 were reworded in 1998 to remove jurisdictional claim over the entire island and to recognise that "a united Ireland shall be brought about only by peaceful means with the consent of a majority of the people, democratically expressed, in both jurisdictions in the island".

With regard to religion, a section of Article 44 included the following:

The State recognises the special position of the Holy Catholic Apostolic and Roman Church as the guardian of the Faith professed by the great majority of the citizens. The State also recognises the Church of Ireland, the Presbyterian Church in Ireland, the Methodist Church in Ireland, the Religious Society of Friends in Ireland, as well as the Jewish Congregations and the other religious denominations existing in Ireland at the date of the coming into operation of this Constitution.

Following a referendum, this section was removed in 1973. After the setting up of the Free State in 1923, unionism in the south largely came to an end.

The 1937 Constitution saw a notable ideological slant to the changes of the framework of the State in such a way as to create one that appeared to be distinctly Irish. This was done so by implementing corporatist policies (based on the concepts of the Roman Catholic Church, as Catholicism was perceived to be deeply imbedded with the perception of Irish identity). A clear example of this is the model of the reconstituted Seanad Éireann (the Senate), which operates based on a system of vocational panels, along with a list of appointed nominating industry bodies, a corporatist concept (seen in Pope Pius XI's 1931 encyclical Quadragesimo anno). Furthermore, Ireland's main political parties; Fine Gael, Fianna Fáil and Labour, all had an inherently corporatist outlook. The government was the subject of intense lobbying by leading Church figures throughout the 1930s in calling for reform of the State's framework. Much of this was reflected in the new 1937 Constitution.

The United Kingdom and the Irish Free State considered each other as states with equal status within the British Empire. However, for other sovereign states (i.e United States, France, Brazil, Japan, etc) and the international community as a whole (i.e League of Nations) the term Dominion was very ambiguous. At the time of the founding of the League of Nations in 1924, the League Covenant made provision for the admission of any "fully self-governing state, Dominion, or Colony", the implication being that "Dominion status was something between that of a colony and a state"

With the Statute of Westminster 1931 the ambiguity is dispelled for the international community with three British Dominions (Irish Free State, Dominion of Canada and Union of South Africa), being recognized as sovereign states in their own right. Unlike what happened in Australia in 1942 and New Zealand in 1947, the whole statute was applied to the Dominion of Canada, the Irish Free State, and the Union of South Africa without the need for any acts of ratification

Gamma-ray burst

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Gamma-ray_burst

Artist's illustration showing the life of a massive star as nuclear fusion converts lighter elements into heavier ones. When fusion no longer generates enough pressure to counteract gravity, the star rapidly collapses to form a black hole. Theoretically, energy may be released during the collapse along the axis of rotation to form a GRB.

In gamma-ray astronomy, gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milliseconds to several hours. After an initial flash of gamma rays, a longer-lived "afterglow" is usually emitted at longer wavelengths (X-ray, ultraviolet, optical, infrared, microwave and radio).

The intense radiation of most observed GRBs is thought to be released during a supernova or superluminous supernova as a high-mass star implodes to form a neutron star or a black hole. A subclass of GRBs appears to originate from the merger of binary neutron stars.

The sources of most GRBs are billions of light years away from Earth, implying that the explosions are both extremely energetic (a typical burst releases as much energy in a few seconds as the Sun will in its entire 10-billion-year lifetime) and extremely rare (a few per galaxy per million years). All observed GRBs have originated from outside the Milky Way galaxy, although a related class of phenomena, soft gamma repeaters, are associated with magnetars within the Milky Way. It has been hypothesized that a gamma-ray burst in the Milky Way, pointing directly towards the Earth, could cause a mass extinction event. The Late Ordovician mass extinction has been hypothesised by some researchers to have occurred as a result of such a gamma-ray burst.

GRBs were first detected in 1967 by the Vela satellites, which had been designed to detect covert nuclear weapons tests; after thorough analysis, this was published in 1973. Following their discovery, hundreds of theoretical models were proposed to explain these bursts, such as collisions between comets and neutron stars. Little information was available to verify these models until the 1997 detection of the first X-ray and optical afterglows and direct measurement of their redshifts using optical spectroscopy, and thus their distances and energy outputs. These discoveries, and subsequent studies of the galaxies and supernovae associated with the bursts, clarified the distance and luminosity of GRBs, definitively placing them in distant galaxies.

History

Main article: History of gamma-ray burst research

Positions on the sky of all gamma-ray bursts detected during the BATSE mission. The distribution is isotropic, with no concentration towards the plane of the Milky Way, which runs horizontally through the center of the image.

Gamma-ray bursts were first observed in the late 1960s by the U.S. Vela satellites, which were built to detect gamma radiation pulses emitted by nuclear weapons tested in space. The United States suspected that the Soviet Union might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. On July 2, 1967, at 14:19 UTC, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons signature. Uncertain what had happened but not considering the matter particularly urgent, the team at the Los Alamos National Laboratory, led by Ray Klebesadel, filed the data away for investigation. As additional Vela satellites were launched with better instruments, the Los Alamos team continued to find inexplicable gamma-ray bursts in their data. By analyzing the different arrival times of the bursts as detected by different satellites, the team was able to determine rough estimates for the sky positions of 16 bursts and definitively rule out a terrestrial or solar origin. Contrary to popular belief, the data was never classified. After thorough analysis, the findings were published in 1973 as an Astrophysical Journal article entitled "Observations of Gamma-Ray Bursts of Cosmic Origin".

Most early theories of gamma-ray bursts posited nearby sources within the Milky Way Galaxy. From 1991, the Compton Gamma Ray Observatory (CGRO) and its Burst and Transient Source Explorer (BATSE) instrument, an extremely sensitive gamma-ray detector, provided data that showed the distribution of GRBs is isotropic – not biased towards any particular direction in space. If the sources were from within our own galaxy, they would be strongly concentrated in or near the galactic plane. The absence of any such pattern in the case of GRBs provided strong evidence that gamma-ray bursts must come from beyond the Milky Way. However, some Milky Way models are still consistent with an isotropic distribution.

Counterpart objects as candidate sources

For decades after the discovery of GRBs, astronomers searched for a counterpart at other wavelengths: i.e., any astronomical object in positional coincidence with a recently observed burst. Astronomers considered many distinct classes of objects, including white dwarfs, pulsars, supernovae, globular clusters, quasars, Seyfert galaxies, and BL Lac objects. All such searches were unsuccessful, and in a few cases particularly well-localized bursts (those whose positions were determined with what was then a high degree of accuracy) could be clearly shown to have no bright objects of any nature consistent with the position derived from the detecting satellites. This suggested an origin of either very faint stars or extremely distant galaxies. Even the most accurate positions contained numerous faint stars and galaxies, and it was widely agreed that final resolution of the origins of cosmic gamma-ray bursts would require both new satellites and faster communication.

Afterglow

The Italian–Dutch satellite BeppoSAX, launched in April 1996, provided the first accurate positions of gamma-ray bursts, allowing follow-up observations and identification of the sources.

Several models for the origin of gamma-ray bursts postulated that the initial burst of gamma rays should be followed by afterglow: slowly fading emission at longer wavelengths created by collisions between the burst ejecta and interstellar gas. Early searches for this afterglow were unsuccessful, largely because it is difficult to observe a burst's position at longer wavelengths immediately after the initial burst. The breakthrough came in February 1997 when the satellite BeppoSAX detected a gamma-ray burst (GRB 970228) and when the X-ray camera was pointed towards the direction from which the burst had originated, it detected fading X-ray emission. The William Herschel Telescope identified a fading optical counterpart 20 hours after the burst. Once the GRB faded, deep imaging was able to identify a faint, distant host galaxy at the location of the GRB as pinpointed by the optical afterglow.

Because of the very faint luminosity of this galaxy, its exact distance was not measured for several years. Well after then, another major breakthrough occurred with the next event registered by BeppoSAX, GRB 970508. This event was localized within four hours of its discovery, allowing research teams to begin making observations much sooner than any previous burst. The spectrum of the object revealed a redshift of z = 0.835, placing the burst at a distance of roughly 6 billion light years from Earth. This was the first accurate determination of the distance to a GRB, and together with the discovery of the host galaxy of 970228 proved that GRBs occur in extremely distant galaxies. Within a few months, the controversy about the distance scale ended: GRBs were extragalactic events originating within faint galaxies at enormous distances. The following year, GRB 980425 was followed within a day by a bright supernova (SN 1998bw), coincident in location, indicating a clear connection between GRBs and the deaths of very massive stars. This burst provided the first strong clue about the nature of the systems that produce GRBs.

More recent instruments

NASA's Swift Spacecraft launched in November 2004

BeppoSAX functioned until 2002 and CGRO (with BATSE) was deorbited in 2000. However, the revolution in the study of gamma-ray bursts motivated the development of a number of additional instruments designed specifically to explore the nature of GRBs, especially in the earliest moments following the explosion. The first such mission, HETE-2, was launched in 2000 and functioned until 2006, providing most of the major discoveries during this period. One of the most successful space missions to date, Swift, was launched in 2004 and as of January 2023 is still operational. Swift is equipped with a very sensitive gamma-ray detector as well as on-board X-ray and optical telescopes, which can be rapidly and automatically slewed to observe afterglow emission following a burst. More recently, the Fermi mission was launched carrying the Gamma-Ray Burst Monitor, which detects bursts at a rate of several hundred per year, some of which are bright enough to be observed at extremely high energies with Fermi's Large Area Telescope. Meanwhile, on the ground, numerous optical telescopes have been built or modified to incorporate robotic control software that responds immediately to signals sent through the Gamma-ray Burst Coordinates Network. This allows the telescopes to rapidly repoint towards a GRB, often within seconds of receiving the signal and while the gamma-ray emission itself is still ongoing.

New developments since the 2000s include the recognition of short gamma-ray bursts as a separate class (likely from merging neutron stars and not associated with supernovae), the discovery of extended, erratic flaring activity at X-ray wavelengths lasting for many minutes after most GRBs, and the discovery of the most luminous (GRB 080319B) and the former most distant (GRB 090423) objects in the universe. The most distant known GRB, GRB 090429B, is now the most distant known object in the universe.

In October 2018, astronomers reported that GRB 150101B (detected in 2015) and GW170817, a gravitational wave event detected in 2017 (which has been associated with GRB170817A, a burst detected 1.7 seconds later), may have been produced by the same mechanism – the merger of two neutron stars. The similarities between the two events, in terms of gamma ray, optical, and x-ray emissions, as well as to the nature of the associated host galaxies, are "striking", suggesting the two separate events may both be the result of the merger of neutron stars, and both may be a kilonova, which may be more common in the universe than previously understood, according to the researchers.

The highest energy light observed from a gamma-ray burst was one teraelectronvolt, from GRB 190114C in 2019. (Note, this is about a thousand times lower energy than the highest energy light observed from any source, which is 1.4 petaelectronvolts as of the year 2021.)

Classification

Gamma-ray burst light curves

The light curves of gamma-ray bursts are extremely diverse and complex. No two gamma-ray burst light curves are identical, with large variation observed in almost every property: the duration of observable emission can vary from milliseconds to tens of minutes, there can be a single peak or several individual subpulses, and individual peaks can be symmetric or with fast brightening and very slow fading. Some bursts are preceded by a "precursor" event, a weak burst that is then followed (after seconds to minutes of no emission at all) by the much more intense "true" bursting episode. The light curves of some events have extremely chaotic and complicated profiles with almost no discernible patterns.

Although some light curves can be roughly reproduced using certain simplified models, little progress has been made in understanding the full diversity observed. Many classification schemes have been proposed, but these are often based solely on differences in the appearance of light curves and may not always reflect a true physical difference in the progenitors of the explosions. However, plots of the distribution of the observed duration for a large number of gamma-ray bursts show a clear bimodality, suggesting the existence of two separate populations: a "short" population with an average duration of about 0.3 seconds and a "long" population with an average duration of about 30 seconds. Both distributions are very broad with a significant overlap region in which the identity of a given event is not clear from duration alone. Additional classes beyond this two-tiered system have been proposed on both observational and theoretical grounds.

Short gamma-ray bursts

Hubble Space Telescope captures infrared glow of a kilonova blast.

GRB 211106A , one of the most energetic short GRB registered, in the first-ever time-lapse movie of a short GRB in millimeter-wavelength light, as seen with the Atacama Large Millimeter/submillimeter Array (ALMA) and pinpointed to a distant host galaxy captured using the Hubble Space Telescope.

Events with a duration of less than about two seconds are classified as short gamma-ray bursts. These account for about 30% of gamma-ray bursts, but until 2005, no afterglow had been successfully detected from any short event and little was known about their origins. Since then, several dozen short gamma-ray burst afterglows have been detected and localized, several of which are associated with regions of little or no star formation, such as large elliptical galaxies. This rules out a link to massive stars, confirming that short events are physically distinct from long events. In addition, there has been no association with supernovae.

The true nature of these objects was initially unknown, and the leading hypothesis was that they originated from the mergers of binary neutron stars or a neutron star with a black hole. Such mergers were theorized to produce kilonovae, and evidence for a kilonova associated with GRB 130603B was seen. The mean duration of these events of 0.2 seconds suggests (because of causality) a source of very small physical diameter in stellar terms; less than 0.2 light-seconds (about 60,000 km or 37,000 miles – four times the Earth's diameter). The observation of minutes to hours of X-ray flashes after a short gamma-ray burst is consistent with small particles of a primary object like a neutron star initially swallowed by a black hole in less than two seconds, followed by some hours of lesser energy events, as remaining fragments of tidally disrupted neutron star material (no longer neutronium) remain in orbit to spiral into the black hole, over a longer period of time. A small fraction of short gamma-ray bursts are probably produced by giant flares from soft gamma repeaters in nearby galaxies.

The origin of short GRBs in kilonovae was confirmed when short GRB 170817A was detected only 1.7 s after the detection of gravitational wave GW170817, which was a signal from the merger of two neutron stars.

Long gamma-ray bursts

Swift captured the afterglow of GRB 221009A about an hour after it was first detected reaching Earth on October 9, 2022. The bright rings form as a result of X-rays scattered from otherwise unobservable dust layers within our galaxy that lie in the direction of the burst.

Most observed events (70%) have a duration of greater than two seconds and are classified as long gamma-ray bursts. Because these events constitute the majority of the population and because they tend to have the brightest afterglows, they have been observed in much greater detail than their short counterparts. Almost every well-studied long gamma-ray burst has been linked to a galaxy with rapid star formation, and in many cases to a core-collapse supernova as well, unambiguously associating long GRBs with the deaths of massive stars. Long GRB afterglow observations, at high redshift, are also consistent with the GRB having originated in star-forming regions. In December 2022, astronomers reported the first evidence of a long GRB produced by a neutron star merger.

Ultra-long gamma-ray bursts

These events are at the tail end of the long GRB duration distribution, lasting more than 10,000 seconds. They have been proposed to form a separate class, caused by the collapse of a blue supergiant star, a tidal disruption event or a new-born magnetar. Only a small number have been identified to date, their primary characteristic being their gamma ray emission duration. The most studied ultra-long events include GRB 101225A and GRB 111209A. The low detection rate may be a result of low sensitivity of current detectors to long-duration events, rather than a reflection of their true frequency. A 2013 study, on the other hand, shows that the existing evidence for a separate ultra-long GRB population with a new type of progenitor is inconclusive, and further multi-wavelength observations are needed to draw a firmer conclusion.

Energetics and beaming

Artist's illustration of a bright gamma-ray burst occurring in a star-forming region. Energy from the explosion is beamed into two narrow, oppositely directed jets.

Gamma-ray bursts are very bright as observed from Earth despite their typically immense distances. An average long GRB has a bolometric flux comparable to a bright star of our galaxy despite a distance of billions of light years (compared to a few tens of light years for most visible stars). Most of this energy is released in gamma rays, although some GRBs have extremely luminous optical counterparts as well. GRB 080319B, for example, was accompanied by an optical counterpart that peaked at a visible magnitude of 5.8, comparable to that of the dimmest naked-eye stars despite the burst's distance of 7.5 billion light years. This combination of brightness and distance implies an extremely energetic source. Assuming the gamma-ray explosion to be spherical, the energy output of GRB 080319B would be within a factor of two of the rest-mass energy of the Sun (the energy which would be released were the Sun to be converted entirely into radiation).

Gamma-ray bursts are thought to be highly focused explosions, with most of the explosion energy collimated into a narrow jet. The approximate angular width of the jet (that is, the degree of spread of the beam) can be estimated directly by observing the achromatic "jet breaks" in afterglow light curves: a time after which the slowly decaying afterglow begins to fade rapidly as the jet slows and can no longer beam its radiation as effectively. Observations suggest significant variation in the jet angle from between 2 and 20 degrees.

Because their energy is strongly focused, the gamma rays emitted by most bursts are expected to miss the Earth and never be detected. When a gamma-ray burst is pointed towards Earth, the focusing of its energy along a relatively narrow beam causes the burst to appear much brighter than it would have been were its energy emitted spherically. When this effect is taken into account, typical gamma-ray bursts are observed to have a true energy release of about 10⁴⁴ J, or about 1/2000 of a Solar mass (M_☉) energy equivalent – which is still many times the mass-energy equivalent of the Earth (about 5.5 × 10⁴¹ J). This is comparable to the energy released in a bright type Ib/c supernova and within the range of theoretical models. Very bright supernovae have been observed to accompany several of the nearest GRBs. Additional support for focusing of the output of GRBs has come from observations of strong asymmetries in the spectra of nearby type Ic supernovae and from radio observations taken long after bursts when their jets are no longer relativistic.

Short (time duration) GRBs appear to come from a lower-redshift (i.e. less distant) population and are less luminous than long GRBs. The degree of beaming in short bursts has not been accurately measured, but as a population they are likely less collimated than long GRBs or possibly not collimated at all in some cases.

Progenitors

Main article: Gamma-ray burst progenitors

Hubble Space Telescope image of Wolf–Rayet star WR 124 and its surrounding nebula. Wolf–Rayet stars are candidates for being progenitors of long-duration GRBs.

Because of the immense distances of most gamma-ray burst sources from Earth, identification of the progenitors, the systems that produce these explosions, is challenging. The association of some long GRBs with supernovae and the fact that their host galaxies are rapidly star-forming offer very strong evidence that long gamma-ray bursts are associated with massive stars. The most widely accepted mechanism for the origin of long-duration GRBs is the collapsar model, in which the core of an extremely massive, low-metallicity, rapidly rotating star collapses into a black hole in the final stages of its evolution. Matter near the star's core rains down towards the center and swirls into a high-density accretion disk. The infall of this material into a black hole drives a pair of relativistic jets out along the rotational axis, which pummel through the stellar envelope and eventually break through the stellar surface and radiate as gamma rays. Some alternative models replace the black hole with a newly formed magnetar, although most other aspects of the model (the collapse of the core of a massive star and the formation of relativistic jets) are the same.

The closest analogs within the Milky Way galaxy of the stars producing long gamma-ray bursts are likely the Wolf–Rayet stars, extremely hot and massive stars, which have shed most or all of their hydrogen envelope. Eta Carinae, Apep, and WR 104 have been cited as possible future gamma-ray burst progenitors. It is unclear if any star in the Milky Way has the appropriate characteristics to produce a gamma-ray burst.

The massive-star model probably does not explain all types of gamma-ray burst. There is strong evidence that some short-duration gamma-ray bursts occur in systems with no star formation and no massive stars, such as elliptical galaxies and galaxy halos. The favored theory for the origin of most short gamma-ray bursts is the merger of a binary system consisting of two neutron stars. According to this model, the two stars in a binary slowly spiral towards each other because gravitational radiation releases energy until tidal forces suddenly rip the neutron stars apart and they collapse into a single black hole. The infall of matter into the new black hole produces an accretion disk and releases a burst of energy, analogous to the collapsar model. Numerous other models have also been proposed to explain short gamma-ray bursts, including the merger of a neutron star and a black hole, the accretion-induced collapse of a neutron star, or the evaporation of primordial black holes.

An alternative explanation proposed by Friedwardt Winterberg is that in the course of a gravitational collapse and in reaching the event horizon of a black hole, all matter disintegrates into a burst of gamma radiation.

Tidal disruption events

Main article: Tidal disruption event

This new class of GRB-like events was first discovered through the detection of GRB 110328A by the Swift Gamma-Ray Burst Mission on 28 March 2011. This event had a gamma-ray duration of about 2 days, much longer than even ultra-long GRBs, and was detected in X-rays for many months. It occurred at the center of a small elliptical galaxy at redshift z = 0.3534. There is an ongoing debate as to whether the explosion was the result of stellar collapse or a tidal disruption event accompanied by a relativistic jet, although the latter explanation has become widely favoured.

A tidal disruption event of this sort is when a star interacts with a supermassive black hole, shredding the star, and in some cases creating a relativistic jet which produces bright emission of gamma ray radiation. The event GRB 110328A (also denoted Swift J1644+57) was initially argued to be produced by the disruption of a main sequence star by a black hole of several million times the mass of the Sun, although it has subsequently been argued that the disruption of a white dwarf by a black hole of mass about 10 thousand times the Sun may be more likely.

Emission mechanisms

Main article: Gamma-ray burst emission mechanisms

Gamma-ray burst mechanism

The means by which gamma-ray bursts convert energy into radiation remains poorly understood, and as of 2010 there was still no generally accepted model for how this process occurs. Any successful model of GRB emission must explain the physical process for generating gamma-ray emission that matches the observed diversity of light curves, spectra, and other characteristics. Particularly challenging is the need to explain the very high efficiencies that are inferred from some explosions: some gamma-ray bursts may convert as much as half (or more) of the explosion energy into gamma-rays. Early observations of the bright optical counterparts to GRB 990123 and to GRB 080319B, whose optical light curves were extrapolations of the gamma-ray light spectra, have suggested that inverse Compton scattering may be the dominant process in some events. In this model, pre-existing low-energy photons are scattered by relativistic electrons within the explosion, augmenting their energy by a large factor and transforming them into gamma-rays.

The nature of the longer-wavelength afterglow emission (ranging from X-ray through radio) that follows gamma-ray bursts is better understood. Any energy released by the explosion not radiated away in the burst itself takes the form of matter or energy moving outward at nearly the speed of light. As this matter collides with the surrounding interstellar gas, it creates a relativistic shock wave that then propagates forward into interstellar space. A second shock wave, the reverse shock, may propagate back into the ejected matter. Extremely energetic electrons within the shock wave are accelerated by strong local magnetic fields and radiate as synchrotron emission across most of the electromagnetic spectrum. This model has generally been successful in modeling the behavior of many observed afterglows at late times (generally, hours to days after the explosion), although there are difficulties explaining all features of the afterglow very shortly after the gamma-ray burst has occurred.

Rate of occurrence and potential effects on life

On 27 October 2015, at 22:40 GMT, the NASA/ASI/UKSA Swift satellite discovered its 1000th gamma-ray burst (GRB).

Gamma ray bursts can have harmful or destructive effects on life. Considering the universe as a whole, the safest environments for life similar to that on Earth are the lowest density regions in the outskirts of large galaxies. Our knowledge of galaxy types and their distribution suggests that life as we know it can only exist in about 10% of all galaxies. Furthermore, galaxies with a redshift, z, higher than 0.5 are unsuitable for life as we know it, because of their higher rate of GRBs and their stellar compactness.

All GRBs observed to date have occurred well outside the Milky Way galaxy and have been harmless to Earth. However, if a GRB were to occur within the Milky Way within 5,000 to 8,000 light-years and its emission were beamed straight towards Earth, the effects could be harmful and potentially devastating for its ecosystems. Currently, orbiting satellites detect on average approximately one GRB per day. The closest observed GRB as of March 2014 was GRB 980425, located 40 megaparsecs (130,000,000 ly) away (z=0.0085) in an SBc-type dwarf galaxy.^[118] GRB 980425 was far less energetic than the average GRB and was associated with the Type Ib supernova SN 1998bw.

Estimating the exact rate at which GRBs occur is difficult; for a galaxy of approximately the same size as the Milky Way, estimates of the expected rate (for long-duration GRBs) can range from one burst every 10,000 years, to one burst every 1,000,000 years. Only a small percentage of these would be beamed towards Earth. Estimates of rate of occurrence of short-duration GRBs are even more uncertain because of the unknown degree of collimation, but are probably comparable.

Since GRBs are thought to involve beamed emission along two jets in opposing directions, only planets in the path of these jets would be subjected to the high energy gamma radiation.

Although nearby GRBs hitting Earth with a destructive shower of gamma rays are only hypothetical events, high energy processes across the galaxy have been observed to affect the Earth's atmosphere.

Effects on Earth

Earth's atmosphere is very effective at absorbing high energy electromagnetic radiation such as x-rays and gamma rays, so these types of radiation would not reach any dangerous levels at the surface during the burst event itself. The immediate effect on life on Earth from a GRB within a few kiloparsecs would only be a short increase in ultraviolet radiation at ground level, lasting from less than a second to tens of seconds. This ultraviolet radiation could potentially reach dangerous levels depending on the exact nature and distance of the burst, but it seems unlikely to be able to cause a global catastrophe for life on Earth.

The long-term effects from a nearby burst are more dangerous. Gamma rays cause chemical reactions in the atmosphere involving oxygen and nitrogen molecules, creating first nitrogen oxide then nitrogen dioxide gas. The nitrogen oxides cause dangerous effects on three levels. First, they deplete ozone, with models showing a possible global reduction of 25–35%, with as much as 75% in certain locations, an effect that would last for years. This reduction is enough to cause a dangerously elevated UV index at the surface. Secondly, the nitrogen oxides cause photochemical smog, which darkens the sky and blocks out parts of the sunlight spectrum. This would affect photosynthesis, but models show only about a 1% reduction of the total sunlight spectrum, lasting a few years. However, the smog could potentially cause a cooling effect on Earth's climate, producing a "cosmic winter" (similar to an impact winter, but without an impact), but only if it occurs simultaneously with a global climate instability. Thirdly, the elevated nitrogen dioxide levels in the atmosphere would wash out and produce acid rain. Nitric acid is toxic to a variety of organisms, including amphibian life, but models predict that it would not reach levels that would cause a serious global effect. The nitrates might in fact be of benefit to some plants.

All in all, a GRB within a few kiloparsecs, with its energy directed towards Earth, will mostly damage life by raising the UV levels during the burst itself and for a few years thereafter. Models show that the destructive effects of this increase can cause up to 16 times the normal levels of DNA damage. It has proved difficult to assess a reliable evaluation of the consequences of this on the terrestrial ecosystem, because of the uncertainty in biological field and laboratory data.

Hypothetical effects on Earth in the past

There is a very good chance (but no certainty) that at least one lethal GRB took place during the past 5 billion years close enough to Earth as to significantly damage life. There is a 50% chance that such a lethal GRB took place within two kiloparsecs of Earth during the last 500 million years, causing one of the major mass extinction events.

The major Ordovician–Silurian extinction event 450 million years ago may have been caused by a GRB. Estimates suggest that approximately 20–60% of the total phytoplankton biomass in the Ordovician oceans would have perished in a GRB, because the oceans were mostly oligotrophic and clear. The late Ordovician species of trilobites that spent portions of their lives in the plankton layer near the ocean surface were much harder hit than deep-water dwellers, which tended to remain within quite restricted areas. This is in contrast to the usual pattern of extinction events, wherein species with more widely spread populations typically fare better. A possible explanation is that trilobites remaining in deep water would be more shielded from the increased UV radiation associated with a GRB. Also supportive of this hypothesis is the fact that during the late Ordovician, burrowing bivalve species were less likely to go extinct than bivalves that lived on the surface.

A case has been made that the 774–775 carbon-14 spike was the result of a short GRB, though a very strong solar flare is another possibility.

GRB candidates in the Milky Way

Illustration of a short gamma-ray burst caused by a collapsing star.

No gamma-ray bursts from within our own galaxy, the Milky Way, have been observed, and the question of whether one has ever occurred remains unresolved. In light of evolving understanding of gamma-ray bursts and their progenitors, the scientific literature records a growing number of local, past, and future GRB candidates. Long duration GRBs are related to superluminous supernovae, or hypernovae, and most luminous blue variables (LBVs) and rapidly spinning Wolf–Rayet stars are thought to end their life cycles in core-collapse supernovae with an associated long-duration GRB. Knowledge of GRBs, however, is from metal-poor galaxies of former epochs of the universe's evolution, and it is impossible to directly extrapolate to encompass more evolved galaxies and stellar environments with a higher metallicity, such as the Milky Way.