SUMMARY / RELATED TOPICS

Giant star

A giant star is a star with larger radius and luminosity than a main-sequence star of the same surface temperature. They lie above the main sequence on the Hertzsprung–Russell diagram and correspond to luminosity classes II and III; the terms giant and dwarf were coined for stars of quite different luminosity despite similar temperature or spectral type by Ejnar Hertzsprung about 1905. Giant stars have radii up to a few hundred times the Sun and luminosities between 10 and a few thousand times that of the Sun. Stars still more luminous than giants are referred to as hypergiants. A hot, luminous main-sequence star may be referred to as a giant, but any main-sequence star is properly called a dwarf no matter how large and luminous it is. A star becomes a giant after all the hydrogen available for fusion at its core has been depleted and, as a result, leaves the main sequence; the behaviour of a post-main-sequence star depends on its mass. For a star with a mass above about 0.25 solar masses, once the core is depleted of hydrogen it contracts and heats up so that hydrogen starts to fuse in a shell around the core.

The portion of the star outside the shell expands and cools, but with only a small increase in luminosity, the star becomes a subgiant. The inert helium core continues to grow and increase in temperature as it accretes helium from the shell, but in stars up to about 10-12 M☉ it does not become hot enough to start helium burning. Instead, after just a few million years the core reaches the Schönberg–Chandrasekhar limit collapses, may become degenerate; this causes the outer layers to expand further and generates a strong convective zone that brings heavy elements to the surface in a process called the first dredge-up. This strong convection increases the transport of energy to the surface, the luminosity increases and the star moves onto the red-giant branch where it will stably burn hydrogen in a shell for a substantial fraction of its entire life; the core continues to gain mass and increase in temperature, whereas there is some mass loss in the outer layers. § 5.9. If the star's mass, when on the main sequence, was below 0.4 M☉, it will never reach the central temperatures necessary to fuse helium.

P. 169. It will therefore remain a hydrogen-fusing red giant until it runs out of hydrogen, at which point it will become a helium white dwarf. § 4.1, 6.1. According to stellar evolution theory, no star of such low mass can have evolved to that stage within the age of the Universe. In stars above about 0.4 M☉ the core temperature reaches 108 K and helium will begin to fuse to carbon and oxygen in the core by the triple-alpha process.§ 5.9, chapter 6. When the core is degenerate helium fusion begins explosively, but most of the energy goes into lifting the degeneracy and the core becomes convective; the energy generated by helium fusion reduces the pressure in the surrounding hydrogen-burning shell, which reduces its energy-generation rate. The overall luminosity of the star decreases, its outer envelope contracts again, the star moves from the red-giant branch to the horizontal branch. Chapter 6; when the core helium is exhausted, a star with up to about 8 M☉ has a carbon–oxygen core that becomes degenerate and starts helium burning in a shell.

As with the earlier collapse of the helium core, this starts convection in the outer layers, triggers a second dredge-up, causes a dramatic increase in size and luminosity. This is the asymptotic giant branch analogous to the red-giant branch but more luminous, with a hydrogen-burning shell contributing most of the energy. Stars only remain on the AGB for around a million years, becoming unstable until they exhaust their fuel, go through a planetary nebula phase, become a carbon–oxygen white dwarf. § 7.1–7.4. Main-sequence stars with masses above about 12 M☉ are very luminous and they move horizontally across the HR diagram when they leave the main sequence becoming blue giants before they expand further into blue supergiants, they start core-helium burning before the core becomes degenerate and develop smoothly into red supergiants without a strong increase in luminosity. At this stage they have comparable luminosities to bright AGB stars although they have much higher masses, but will further increase in luminosity as they burn heavier elements and become a supernova.

Stars in the 8-12 M☉ range have somewhat intermediate properties and have been called super-AGB stars. They follow the tracks of lighter stars through RGB, HB, AGB phases, but are massive enough to initiate core carbon burning and some neon burning, they form oxygen–magnesium–neon cores, which may collapse in an electron-capture supernova, or they may leave behind an oxygen–neon white dwarf. O class main sequence stars are highly luminous; the giant phase for such stars is a brief phase of increased size and luminosity before developing a supergiant spectral luminosity class. Type O giants may be more than a hundred thousand times as luminous as the sun, brighter than many supergiants. Classification is complex and difficult with small differences between luminosity classes and a continuous range of intermediate forms; the most massive stars develop giant or supergiant spectral features while still burning hydrogen in their cores, due to mixing of heavy elements to the surface and high luminosity which produces a powerful stellar wind and causes the star's atmosphere to expand.

A star whose initial mass is less than 0.25 M☉ will not become a giant star at all. For most of

Four Pieces for Mirai (Overture)

Four Pieces for Mirai is an extended play by American musician James Ferraro. It was self-released on May 18, 2018 on his Bandcamp page and to other music platforms. Ferraro released the album on cassette; the EP is the overture to Ferraro's Four Pieces For Mirai series. Four Pieces for Mirai is an overture to Ferraro's own post-apocalyptic narrative, Four Pieces For Mirai,'a large body of work that spans across multiple releases', involving Mirai, a malware that turns networked devices running Linux into remotely controlled "bots" that can be used as part of a botnet in large-scale network attacks. Mirai's presence in the narrative is that of a savior, rather than a destructive force. In the Bandcamp description for the release, Ferraro describes Four Pieces For Mirai as'integrating medieval chorals to baroque to ambient noise to MIDI generated music, other musical anthropology'. In this introductory prologue Ferraro reveals a dystopian present, a society in servitude to its digital network and its savior Mirai a computer virus with a "denial of service" malware system that attacks "Internet of Things" devices.

In essence disrupting the hold of the internet on humanity. It is from this aspect that Ferraro builds his philosophical allegory of technological plague, hyper connectivity, social famine and virtual exodus. All tracks are written by James Ferraro

Glen O'Hara

Glen O'Hara is an academic historian at Oxford Brookes University in the United Kingdom. He gained a Double First at Oxford University as an undergraduate between 1993 and 1996, a Distinction as an M. Sc. Student in Economic and Social History in the 1996-97 academic year. While at Oxford, he won the Eubule Thelwall Prize for History and the Gladstone Prize for History and Politics. After a period as a schoolteacher, as a journalist at The Independent, he moved back into academia at University College London, he took his PhD there in 2002 under the supervision of Professor Kathleen Burk, UCL's Professor of Modern History. In 2001 he was appointed Lecturer in Economic History at the University of Bristol, where he spent a year before moving to New College, Oxford, as lecturer in Modern History, he took up his present post as a lecturer at Oxford Brookes in January 2005 and was promoted to Senior Lecturer in January 2006, before becoming Reader in the History of Public Policy during October 2010 and Professor of Modern and Contemporary History in October 2013.

During November 2006 he was a Visiting Fellow of the University of Oslo. His work chiefly looks at British governments' decision-making and ideas in the twentieth century, drawing on insights from disciplines as far apart a geography, literary theory, telecommunications, diplomatic history, management studies and economics, he has released a book about British social planning in the 1960s. His work has begun to emphasise long-term elements in the making of British'national identity' the country's status as an island and oceanic nation as reflected in his 2010 book Britain and the Sea. More he argued—both in print and online—that the British Conservatives' electoral strength is weaker than is apparent, that the 2010-2015 Coalition government's spending reductions were too rapid and economically unsound. At the same time, he serves on the International Advisory Board of Reinvention: A Journal of Undergraduate Research, which aims to encourage students to pursue their own research interests by publishing articles based on original undergraduate work.'The Politics of Water in Post-War Britain'.

Governing Post-War Britain: The Paradoxes of Progress. Britain and the Sea since 1600. Numbers and the People: Statistics and the British Public Sphere since 1750. From Dreams to Disillusionment: Economic and Social Planning in 1960s Britain; the Modernisation of Britain? Harold Wilson and the British Labour Governments of 1964-1970.'Time and Planning in British Government, c.1959-c.1979', Journal of Modern European History.'Professor Kathleen Burk and the History of Diplomacy', Diplomacy and Statecraft 24, 1, pp. 1–20.'Parties and Parliament: Britain's "Ombudsman" and the Politics of the 1960s', Journal of British Studies 50, 3, pp. 690–714.'New Histories of British Imperial Communications and the "Networked World" of the Nineteenth and Early Twentieth Centuries', History Compass 8, 7, pp. 609–25.'The Parliamentary Commissioner for Administration, the Foreign Office and the Sachsenhausen Case', Historical Journal 53, 3, pp. 771–81.'"This is What Growth Does": British Views of the European Economies in the Prosperous "Golden Age" of 1951-1973', Journal of Contemporary History 44, 4, pp. 697–717.'"The Sea is Swinging into View": Modern British Maritime History in a Globalised World', English Historical Review CXXIV, 510, pp. 1109–34.'"What the Electorate Can Be Expected to Swallow": Nationalisation and the Shifting Boundaries of the State in Post-War Britain', Business History 51, 4, pp. 1–28.

‘Towards a New Bradshaw: Economic Statistics and the British State in the 1950s and 1960s’, Economic History Review 60, 1, pp. 1–34. ‘“Dynamic, Thrilling Change”: The Wilson Government's Economic Policy 1964-1970’, Contemporary British History 20, 3, pp. 383–402. ‘“We Are Faced Everywhere With a Growing Population”: Demographic Change and the British State, 1955-64’, Twentieth Century British History 15, 3, pp. 243–66. ‘“Intractable and Baffling”: The Incomes Policy of the Conservative Government, 1957-64’, Contemporary British History 18, 1, pp. 25–53