Social identity theory

From Wikipedia, the free encyclopedia

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

Social identity is the portion of an individual's self-concept derived from perceived membership in a relevant social group.

As originally formulated by social psychologists Henri Tajfel and John Turner in the 1970s and the 1980s, social identity theory introduced the concept of a social identity as a way in which to explain intergroup behaviour. "Social identity theory explores the phenomenon of the 'ingroup' and 'outgroup', and is based on the view that identities are constituted through a process of difference defined in a relative or flexible way depends on the activities in which one engages" This theory is described as a theory that predicts certain intergroup behaviours on the basis of perceived group status differences, the perceived legitimacy and stability of those status differences, and the perceived ability to move from one group to another. This contrasts with occasions where the term "social identity theory" is used to refer to general theorizing about human social selves. Moreover, and although some researchers have treated it as such, social identity theory was never intended to be a general theory of social categorization. It was awareness of the limited scope of social identity theory that led John Turner and colleagues to develop a cousin theory in the form of self-categorization theory, which built on the insights of social identity theory to produce a more general account of self and group processes.

The term social identity approach, or social identity perspective, is suggested for describing the joint contributions of both social identity theory and self-categorization theory. Social identity theory suggests that an organization can change individual behaviours if it can modify their self-identity or part of their self-concept that derives from the knowledge of, and emotional attachment to the group.

Development

Social scientist William Graham Sumner

 

Social psychologist Henri Tajfel

Historical background

The term 'social identity theory' achieved academic currency only in the late 1970s, but the basic underlying concepts associated with it had emerged by the early twentieth century. William G. Sumner, writing in 1906, captures the primary dynamics in this excerpt from his influential work Folkways: A Study of the Sociological Importance of Usages, Manners, Customs, Mores, and Morals:

"Loyalty to the group, sacrifice for it, hatred and contempt for outsiders, brotherhood within, warlikeness without,—all grow together, common products of the same situation. ... Men of an others-group are outsiders with whose ancestors the ancestors of the we-group waged war. ... Each group nourishes its own pride and vanity, boasts itself superior, exalts its own divinities, and looks with contempt on outsiders. Each group thinks its own folkways the only right ones, and if it observes that other groups have other folkways, these excite its scorn."

By the late 1920s the collectivist perspective had all but disappeared from mainstream social psychology. Over fifty years later, around the time of the first formal use of the term 'social identity theory', Tajfel wrote this on the state of social psychology:

"Thus, social categorization is still conceived as a haphazardly floating 'independent variable' which strikes at random as the spirit moves it. No links are made or attempted, between the conditions determining its presence and mode of operation, and its outcomes in widely diffused commonalities of social behaviour. Why, when and how is social categorisation salient or not salient? What kind of shared constructions of social reality, mediated through social categorization, lead to a social climate in which large masses of people feel they are in long-term conflict with other masses? What, for example, are the psychological transitions from a stable to an unstable social system?" (Original emphasis, p. 188)

Thus, social identity theory in part reflects a desire to reestablish a more collectivist approach to social psychology of the self and social groups.

Aspects

Henri Tajfel suggests that soldiers of opposing armies, fighting outside of view, is an illustrative example of behaviour at the extreme intergroup end of the intergroup-interpersonal continuum (shown: U.S. Marines in Fallujah, 2004).

The interpersonal-intergroup continuum

Social identity theory states that social behaviour will want a person to change their behaviour while in a group. It varies along a continuum between interpersonal behaviour and intergroup behaviour. Completely interpersonal behaviour would be behaviour determined solely by the individual characteristics and interpersonal relationships that exists between only two people. Completely intergroup behaviour would be behaviour determined solely by the social category memberships that apply to more than two people. The authors of social identity theory state that purely interpersonal or purely intergroup behaviour is unlikely to be found in realistic social situations. Rather, behaviour is expected to be driven by a compromise between the two extremes. The cognitive nature of personal vs. social identities, and the relationship between them, is more fully developed in self-categorization theory. Social identity theory instead focuses on the social structural factors that will predict which end of the spectrum will most influence an individual's behaviour, along with the forms that the behaviour may take.

Positive distinctiveness

A key assumption in social identity theory is that individuals are intrinsically motivated to achieve positive distinctiveness. That is, individuals "strive for a positive self-concept". As individuals to varying degrees may be defined and informed by their respective social identities (as per the interpersonal-intergroup continuum) it is further derived in social identity theory that "individuals strive to achieve or to maintain positive social identity". The precise nature of this striving for positive self-concept is a matter of debate (see the self-esteem hypothesis). Both the interpersonal-intergroup continuum and the assumption of positive distinctiveness motivation arose as outcomes of the findings of minimal group studies. In particular, it was found that under certain conditions individuals would endorse resource distributions that would maximize the positive distinctiveness of an in-group in contrast to an out-group at the expense of personal self-interest.

The "black is beautiful" movement and the associated African American embrace of African hairdos (like afros), culture, traditions, and music was provided by Tajfel and colleagues as an example of the cognitive creativity of low-status groups in the face of stable intergroup relations (shown: Lauryn Hill, 2005).

Positive distinctiveness strategies

Building on the above components, social identity theory details a variety of strategies that may be invoked in order to achieve positive distinctiveness. The individual's choice of behaviour is posited to be dictated largely by the perceived intergroup relationship. In particular the choice of strategy is an outcome of the perceived permeability of group boundaries (e.g., whether a group member may pass from a low status group into a high status group), as well as the perceived stability and legitimacy of the intergroup status hierarchy. The self-enhancing strategies detailed in social identity theory are detailed below. Importantly, although these are viewed from the perspective of a low status group member, comparable behaviours may also be adopted by high status group members.

Individual mobility

It is predicted that under conditions where the group boundaries are considered permeable individuals are more likely to engage in individual mobility strategies. That is, individuals "disassociate from the group and pursue individual goals designed to improve their personal lot rather than that of their ingroup".

Social creativity

Where group boundaries are considered impermeable, and where status relations are considered reasonably stable, individuals are predicted to engage in social creativity behaviours. Here, low-status ingroup members are still able to increase their positive distinctiveness without necessarily changing the objective resources of the ingroup or the outgroup. This may be achieved by comparing the ingroup to the outgroup on some new dimension, changing the values assigned to the attributes of the group, and choosing an alternative outgroup by which to compare the ingroup.

Social competition

Here an ingroup seeks positive distinctiveness and requires positive differentiation via direct competition with the outgroup in the form of ingroup favoritism. It is considered competitive in that in this case favoritism for the ingroup occurs on a value dimension that is shared by all relevant social groups (in contrast to social creativity scenarios). Social competition is predicted to occur when group boundaries are considered impermeable, and when status relations are considered to be reasonably unstable. Although not privileged in the theory, it is this positive distinctiveness strategy that has received the greatest amount of attention.

Political psychology

In political science, social identity theory has been incorporated as the subconsitituency politics theory of representation. This theory holds that political elites are individually rational, and they use identity instrumentally to cultivate minimum winning constituencies (e.g., via the "microtargeting" of ads). An example of microtargeting is Russian use of social media advertising alleged to have influenced the 2016 presidential election. Separately, a recent Science Advances article validates a computational model of in-group favoritism and political economy developed by Princeton political scientist Nolan McCarty using public opinion polling data.

Implications

Ingroup favoritism

Main article: In-group favoritism

In-group favoritism (also known as "ingroup bias", despite Turner's objections to the term) is an effect where people give preferential treatment to others when they are perceived to be in the same ingroup. Social identity attributes the cause of ingroup favoritism to a psychological need for positive distinctiveness and describes the situations where ingroup favoritism is likely to occur (as a function of perceived group status, legitimacy, stability, and permeability). It has been shown via the minimal group studies that ingroup favoritism may occur for both arbitrary ingroups (e.g. a coin toss may split participants into a 'heads' group and a 'tails' group) as well as non-arbitrary ingroups (e.g. ingroups based on cultures, genders, sexual orientation, and first languages).

Continued study into the relationship between social categorization and ingroup favoritism has explored the relative prevalences of the ingroup favoritism vs. outgroup discrimination, explored different manifestations of ingroup favoritism, and has explored the relationship between ingroup favoritism and other psychological constraints (e.g., existential threat).

System justification theory was originally proposed by John Jost and Mahzarin Banaji in 1994 to build on social identity theory and to understand important deviations from ingroup favoritism, such as outgroup favoritism on the part of members of disadvantaged groups (Jost & Banaji, 1994; Jost, 2020).

Prosocial behaviors

Social identification can lead individuals to engage in prosocial behaviours towards others. Examples include contexts such as food drives  or even shared purchasing patterns, as might occur for motorcycle riders. Interestingly, consumers may have sub-identities that are nested into a larger identity. As a result, "[w]hen consumers identify with the overall community, they assist other consumers. However, consumers are less likely to help consumers in the overall community when identifying with a subgroup".

Reluctance to bet against identity-relevant outcomes

Social identities are a valued aspect of the self, and people will sacrifice their pecuniary self-interest to maintain the self-perception that they belong to a given social group. Political partisans and fans of sports teams (e.g., Republicans and Democrats, or MLB, NFL, NCAA fans) are reluctant to bet against the success of their party or team because of the diagnostic cost such a bet would incur to their identification with it. As a result, partisans and fans will reject even very favorable bets against identity-relevant desired outcomes. More than 45% of N.C.A.A. basketball and hockey fans, for example, turned down a free, real chance to earn $5 if their team lost its upcoming game.

Controversies

Self-esteem hypothesis

Social identity theory proposes that people are motivated to achieve and maintain positive concepts of themselves. Some researchers, including Michael Hogg and Dominic Abrams, thus propose a fairly direct relationship between positive social identity and self-esteem. In what has become known as the "self-esteem hypothesis", self-esteem is predicted to relate to in-group bias in two ways. Firstly, successful intergroup discrimination elevates self-esteem. Secondly, depressed or threatened self-esteem promotes intergroup discrimination. Empirical support for these predictions has been mixed.

Some social identity theorists, including John Turner, consider the self-esteem hypothesis as not canonical to social identity theory. In fact, the self-esteem hypothesis is argued to be conflictual with the tenets of the theory. It is argued that the self-esteem hypothesis misunderstands the distinction between a social identity and a personal identity. Along those lines, John Turner and Penny Oakes argue against an interpretation of positive distinctiveness as a straightforward need for self-esteem or "quasi-biological drive toward prejudice". They instead favour a somewhat more complex conception of positive self-concept as a reflection of the ideologies and social values of the perceiver. Additionally, it is argued that the self-esteem hypothesis neglects the alternative strategies to maintaining a positive self-concept that are articulated in social identity theory (i.e., individual mobility and social creativity).

Positive-negative asymmetry

In what has been dubbed the Positive-Negative Asymmetry Phenomenon, researchers have shown that punishing the out-group benefits self-esteem less than rewarding the in-group. From this finding it has been extrapolated that social identity theory is therefore unable to deal with bias on negative dimensions. Social identity theorists, however, point out that for ingroup favouritism to occur a social identity "must be psychologically salient", and that negative dimensions may be experienced as a "less fitting basis for self-definition". This important qualification is subtly present in social identity theory, but is further developed in self-categorization theory. Empirical support for this perspective exist. It has been shown that when experiment participants can self-select negative dimensions that define the ingroup no positive–negative asymmetry is found.

Intergroup similarity

It has been posited that social identity theory suggests that similar groups should have an increased motivation to differentiate themselves from each other. Subsequently, empirical findings where similar groups are shown to possess increased levels of intergroup attraction and decreased levels of in-group bias have been interpreted as problematic for the theory. Elsewhere it has been suggested that this apparent inconsistency may be resolved by attending to social identity theory's emphasis on the importance of the perceived stability and legitimacy of the intergroup status hierarchy.

Predictive power

Social identity theory has been criticised for having far greater explanatory power than predictive power. That is, while the relationship between independent variables and the resulting intergroup behaviour may be consistent with the theory in retrospect, that particular outcome is often not that which was predicted at the outset. A rebuttal to this charge is that the theory was never advertised as the definitive answer to understanding intergroup relationships. Instead it is stated that social identity theory must go hand in hand with sufficient understanding of the specific social context under consideration. The latter argument is consistent with the explicit importance that the authors of social identity theory placed on the role of "objective" factors, stating that in any particular situation "the effects of [social identity theory] variables are powerfully determined by the previous social, economic, and political processes".

SIT-lite

Some researchers interpret social identity theory as drawing a direct link between identification with a social group and ingroup favoritism. This is because social identity theory was proposed as a way of explaining the ubiquity of ingroup favoritism in the minimal group paradigm. For example, Charles Stangor and John Jost state that "a main premise of social identity theory is that ingroup members will favour their own group over other groups". This interpretation is rejected by other researchers. For example, Alex Haslam states that "although vulgarized versions of social identity theory argue that 'social identification leads automatically to discrimination and bias', in fact…discrimination and conflict are anticipated only in a limited set of circumstances". The likening of social identity theory with social competition and ingroup favouritism is partly attributable to the fact that early statements of the theory included empirical examples of ingroup favouritism, while alternative positive distinctiveness strategies (e.g., social creativity) were at that stage theoretical assertions. Regardless, in some circles the prediction of a straightforward identification-bias correlation has earned the pejorative title "social identity theory-lite". This raises the problem of whether social identity theory really does explain the ubiquity of ingroup favoritism in the minimal group paradigm without making recourse to "the generic norm hypothesis" originally proposed by Tajfel but later abandoned.

Trans-Neptunian object

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Trans-Neptunian_object

This article is about solar system objects beyond Neptune. For hypothetical planets, see Planets beyond Neptune.

Artistic comparison of Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar, Sedna, Orcus, Salacia, 2002 MS₄, and Earth along with the Moon

A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au).

Typically, TNOs are further divided into the classical and resonant objects of the Kuiper belt, the scattered disc and detached objects with the sednoids being the most distant ones. As of October 2020, the catalog of minor planets contains 678 numbered and more than 2,000 unnumbered TNOs. The first trans-Neptunian object to be discovered was Pluto in 1930. It took until 1992 to discover a second trans-Neptunian object orbiting the Sun directly, 15760 Albion. The most massive TNO known is Eris, followed by Pluto, Haumea, Makemake, and Gonggong. More than 80 satellites have been discovered in orbit of trans-Neptunian objects. TNOs vary in color and are either grey-blue (BB) or very red (RR). They are thought to be composed of mixtures of rock, amorphous carbon and volatile ices such as water and methane, coated with tholins and other organic compounds.

Twelve minor planets with a semi-major axis greater than 150 au and perihelion greater than 30 au are known, which are called extreme trans-Neptunian objects (ETNOs).

History

Discovery of Pluto

Pluto imaged by New Horizons

The orbit of each of the planets is slightly affected by the gravitational influences of the other planets. Discrepancies in the early 1900s between the observed and expected orbits of Uranus and Neptune suggested that there were one or more additional planets beyond Neptune. The search for these led to the discovery of Pluto in February 1930, which was too small to explain the discrepancies. Revised estimates of Neptune's mass from the Voyager 2 flyby in 1989 showed that the problem was spurious. Pluto was easiest to find because it has the highest apparent magnitude of all known trans-Neptunian objects. It also has a lower inclination to the ecliptic than most other large TNOs.

Subsequent discoveries

After Pluto's discovery, American astronomer Clyde Tombaugh continued searching for some years for similar objects, but found none. For a long time, no one searched for other TNOs as it was generally believed that Pluto, which up to August 2006 was classified a planet, was the only major object beyond Neptune. Only after the 1992 discovery of a second TNO, 15760 Albion, did systematic searches for further such objects begin. A broad strip of the sky around the ecliptic was photographed and digitally evaluated for slowly moving objects. Hundreds of TNOs were found, with diameters in the range of 50 to 2,500 kilometers. Eris, the most massive TNO, was discovered in 2005, revisiting a long-running dispute within the scientific community over the classification of large TNOs, and whether objects like Pluto can be considered planets. Pluto and Eris were eventually classified as dwarf planets by the International Astronomical Union. In December 2018, the discovery of 2018 VG18, nicknamed "Farout", was announced. Farout is the most distant solar system object so-far observed and is about 120 au away from the sun. It takes 738 years to complete one orbit.

Classification

Distribution of trans-Neptunian objects

Euler diagram showing the types of bodies in the Solar System.

According to their distance from the Sun and their orbital parameters, TNOs are classified in two large groups: the Kuiper belt objects (KBOs) and the scattered disc objects (SDOs). The diagram to the right illustrates the distribution of known trans-Neptunian objects (up to 70 au) in relation to the orbits of the planets and the centaurs for reference. Different classes are represented in different colours. Resonant objects (including Neptune trojans) are plotted in red, classical Kuiper belt objects in blue. The scattered disc extends to the right, far beyond the diagram, with known objects at mean distances beyond 500 au (Sedna) and aphelia beyond 1,000  ((87269) 2000 OO67).

KBOs

The Edgeworth-Kuiper belt contains objects with an average distance to the Sun of 30 to about 55 au, usually having close-to-circular orbits with a small inclination from the ecliptic. Edgeworth-Kuiper belt objects are further classified into the resonant trans-Neptunian object, that are locked in an orbital resonance with Neptune, and the classical Kuiper belt objects, also called "cubewanos", that have no such resonance, moving on almost circular orbits, unperturbed by Neptune. There are a large number of resonant subgroups, the largest being the twotinos (1:2 resonance) and the plutinos (2:3 resonance), named after their most prominent member, Pluto. Members of the classical Edgeworth-Kuiper belt include 15760 Albion, 50000 Quaoar and Makemake.

Another subclass of Kuiper belt objects is the so-called scattering objects (SO). These are non-resonant objects that come near enough to Neptune to have their orbits changed from time to time (such as causing changes in semi-major axis of at least 1.5 AU in 10 million years), and are thus undergoing gravitational scattering. Scattering objects are easier to detect than other trans-Neptunian objects of the same size because they come nearer to Earth, some having perihelia around 20 AU. Several are known with g-band absolute magnitude below 9, meaning that the estimated diameter is more than 100 km. It is estimated that there are between 240,000 and 830,000 scattering objects bigger than r-band absolute magnitude 12, corresponding to diameters greater than about 18 km. Scattering objects are hypothesized to be the source of the so-called Jupiter-family comets (JFCs), which have periods of less than 20 years.

SDOs

The scattered disc contains objects farther from the Sun, with very eccentric and inclined orbits. These orbits are non-resonant and non-planetary-orbit-crossing. A typical example is the most-massive-known TNO, Eris. Based on the Tisserand parameter relative to Neptune (T_N), the objects in the scattered disc can be further divided into the "typical" scattered disc objects (SDOs, Scattered-near) with a T_N of less than 3, and into the detached objects (ESDOs, Scattered-extended) with a T_N greater than 3. In addition, detached objects have a time-averaged eccentricity greater than 0.2 The Sednoids are a further extreme sub-grouping of the detached objects with perihelia so distant that it is confirmed that their orbits cannot be explained by perturbations from the giant planets, nor by interaction with the galactic tides.

Physical characteristics

Looking back at Pluto, the largest visited KBO so far

Given the apparent magnitude (>20) of all but the biggest trans-Neptunian objects, the physical studies are limited to the following:

• thermal emissions for the largest objects (see size determination)
• colour indices, i.e. comparisons of the apparent magnitudes using different filters
• analysis of spectra, visual and infrared

Studying colours and spectra provides insight into the objects' origin and a potential correlation with other classes of objects, namely centaurs and some satellites of giant planets (Triton, Phoebe), suspected to originate in the Kuiper belt. However, the interpretations are typically ambiguous as the spectra can fit more than one model of the surface composition and depend on the unknown particle size. More significantly, the optical surfaces of small bodies are subject to modification by intense radiation, solar wind and micrometeorites. Consequently, the thin optical surface layer could be quite different from the regolith underneath, and not representative of the bulk composition of the body.

Small TNOs are thought to be low-density mixtures of rock and ice with some organic (carbon-containing) surface material such as tholin, detected in their spectra. On the other hand, the high density of Haumea, 2.6–3.3 g/cm³, suggests a very high non-ice content (compare with Pluto's density: 1.86 g/cm³). The composition of some small TNOs could be similar to that of comets. Indeed, some centaurs undergo seasonal changes when they approach the Sun, making the boundary blurred (see 2060 Chiron and 7968 Elst–Pizarro). However, population comparisons between centaurs and TNOs are still controversial.

Color indices

See also: Asteroid color indices

Colors of trans-Neptunian objects. Mars and Triton are not to scale. Phoebe and Pholus are not trans-Neptunian.

Illustration of the relative sizes, albedos and colours of some large TNOs

Colour indices are simple measures of the differences in the apparent magnitude of an object seen through blue (B), visible (V), i.e. green-yellow, and red (R) filters. The diagram illustrates known colour indices for all but the biggest objects (in slightly enhanced colour). For reference, two moons: Triton and Phoebe, the centaur Pholus and the planet Mars are plotted (yellow labels, size not to scale). Correlations between the colours and the orbital characteristics have been studied, to confirm theories of different origin of the different dynamic classes:

• Classical Kuiper belt object (cubewano) seem to be composed of two different colour populations: the so-called cold (inclination <5°) population, displaying only red colours, and the so-called hot (higher inclination) population displaying the whole range of colours from blue to very red. A recent analysis based on the data from Deep Ecliptic Survey confirms this difference in colour between low-inclination (named Core) and high-inclination (named Halo) objects. Red colours of the Core objects together with their unperturbed orbits suggest that these objects could be a relic of the original population of the belt.
• Scattered disc objects show colour resemblances with hot classical objects pointing to a common origin.

While the relatively dimmer bodies, as well as the population as the whole, are reddish (V−I = 0.3–0.6), the bigger objects are often more neutral in colour (infrared index V−I < 0.2). This distinction leads to suggestion that the surface of the largest bodies is covered with ices, hiding the redder, darker areas underneath.

Mean-color indices of dynamical groups in the outer Solar System 

Color	Plutinos	Cubewanos	Centaurs	SDOs	Comets	Jupiter trojans
B–V	0.895±0.190	0.973±0.174	0.886±0.213	0.875±0.159	0.795±0.035	0.777±0.091
V–R	0.568±0.106	0.622±0.126	0.573±0.127	0.553±0.132	0.441±0.122	0.445±0.048
V–I	1.095±0.201	1.181±0.237	1.104±0.245	1.070±0.220	0.935±0.141	0.861±0.090
R–I	0.536±0.135	0.586±0.148	0.548±0.150	0.517±0.102	0.451±0.059	0.416±0.057

Spectral type

See also: Asteroid spectral types

Among TNOs, as among centaurs, there is a wide range of colors from blue-grey (neutral) to very red, but unlike the centaurs, bimodally grouped into grey and red centaurs, the distribution for TNOs appears to be uniform. The wide range of spectra differ in reflectivity in visible red and near infrared. Neutral objects present a flat spectrum, reflecting as much red and infrared as visible spectrum. Very red objects present a steep slope, reflecting much more in red and infrared. A recent attempt at classification (common with centaurs) uses the total of four classes from BB (blue, or neutral color, average B−V = 0.70, V−R = 0.39, e.g. Orcus) to RR (very red, B−V = 1.08, V−R = 0.71, e.g. Sedna) with BR and IR as intermediate classes. BR (intermediate blue-red) and IR (moderately red) differ mostly in the infrared bands I, J and H.

Typical models of the surface include water ice, amorphous carbon, silicates and organic macromolecules, named tholins, created by intense radiation. Four major tholins are used to fit the reddening slope:

• Titan tholin, believed to be produced from a mixture of 90% N₂ (nitrogen) and 10% CH₄ (methane)
• Triton tholin, as above but with very low (0.1%) methane content
• (ethane) Ice tholin I, believed to be produced from a mixture of 86% H₂O and 14% C₂H₆ (ethane)
• (methanol) Ice tholin II, 80% H₂O, 16% CH₃OH (methanol) and 3% CO₂

As an illustration of the two extreme classes BB and RR, the following compositions have been suggested

• for Sedna (RR very red): 24% Triton tholin, 7% carbon, 10% N₂, 26% methanol, and 33% methane
• for Orcus (BB, grey/blue): 85% amorphous carbon, +4% Titan tholin, and 11% H₂O ice

Size determination and distribution

Size comparison between the Moon, Neptune's moon Triton, Pluto, several large TNOs, and the asteroid Ceres. Their respective shapes are not represented.

Characteristically, big (bright) objects are typically on inclined orbits, whereas the invariable plane regroups mostly small and dim objects.

It is difficult to estimate the diameter of TNOs. For very large objects, with very well known orbital elements (like Pluto), diameters can be precisely measured by occultation of stars. For other large TNOs, diameters can be estimated by thermal measurements. The intensity of light illuminating the object is known (from its distance to the Sun), and one assumes that most of its surface is in thermal equilibrium (usually not a bad assumption for an airless body). For a known albedo, it is possible to estimate the surface temperature, and correspondingly the intensity of heat radiation. Further, if the size of the object is known, it is possible to predict both the amount of visible light and emitted heat radiation reaching Earth. A simplifying factor is that the Sun emits almost all of its energy in visible light and at nearby frequencies, while at the cold temperatures of TNOs, the heat radiation is emitted at completely different wavelengths (the far infrared).

Thus there are two unknowns (albedo and size), which can be determined by two independent measurements (of the amount of reflected light and emitted infrared heat radiation). Unfortunately, TNOs are so far from the Sun that they are very cold, hence producing black-body radiation around 60 micrometres in wavelength. This wavelength of light is impossible to observe on the Earth's surface, but only from space using, e.g. the Spitzer Space Telescope. For ground-based observations, astronomers observe the tail of the black-body radiation in the far infrared. This far infrared radiation is so dim that the thermal method is only applicable to the largest KBOs. For the majority of (small) objects, the diameter is estimated by assuming an albedo. However, the albedos found range from 0.50 down to 0.05, resulting in a size range of 1,200–3,700 km for an object of magnitude of 1.0.

Notable objects

For a more comprehensive list, see List of trans-Neptunian objects and List of unnumbered trans-Neptunian objects.

 

Object	Description
134340 Pluto	a dwarf planet and the first TNO discovered
15760 Albion	the prototype cubewano, the first Kuiper belt object discovered after Pluto
(385185) 1993 RO	the next plutino discovered after Pluto
(15874) 1996 TL66	the first object to be identified as a scattered disc object
1998 WW31	the first binary Kuiper belt object discovered after Pluto
47171 Lempo	a plutino and triple system consisting of a central binary pair of similar size, and a third outer circumbinary satellite
20000 Varuna	a large cubewano, known for its rapid rotation (6.3 h) and elongated shape
28978 Ixion	large plutino, was considered to be among the largest Kuiper belt objects upon discovery
50000 Quaoar	large cubewano with a satellite; sixth-largest-known Kuiper belt object and was considered to be among the largest Kuiper belt objects upon discovery
90377 Sedna	a distant object, proposed for a new category named extended scattered disc (E-SDO), detached objects, distant detached objects (DDO) or scattered-extended in the formal classification by DES.
90482 Orcus	The largest known plutino, after Pluto. Has a relatively large satellite.
136108 Haumea	a dwarf planet, the third-largest-known trans-Neptunian object. Notable for its two known satellites, rings, and unusually short rotation period (3.9 h). It is the most massive known member of the Haumea collisional family.
136472 Makemake	a dwarf planet, a cubewano, and the fourth-largest known trans-Neptunian object
136199 Eris	a dwarf planet, a scattered disc object, and currently the most massive known trans-Neptunian object. It has one known satellite, Dysnomia
(612911) 2004 XR190	a scattered disc object following a highly inclined but nearly circular orbit
225088 Gonggong	second-largest scattered-disc object with a satellite
(528219) 2008 KV42 "Drac"	the first retrograde TNO, having an orbital inclination of i = 104°
(471325) 2011 KT19 "Niku"	a TNO having an unusually high orbital inclination of 110°
2012 VP113	a sednoid with a large perihelion of 80 au from the Sun (50 au beyond Neptune)
486958 Arrokoth	contact binary cubewano encountered by the New Horizons spacecraft in 2019
2018 VG18 "Farout"	the first trans-Neptunian object discovered while beyond 100 au (15 billion km) from the Sun
2018 AG37 "FarFarOut"	most distant observable trans-Neptunian object at 132 au (19.7 billion km) from the Sun

Exploration

Kuiper belt object 486958 Arrokoth, in images taken by the New Horizons spacecraft

The only mission to date that primarily targeted a trans-Neptunian object was NASA's New Horizons, which was launched in January 2006 and flew by the Pluto system in July 2015 and 486958 Arrokoth in January 2019.

In 2011, a design study explored a spacecraft survey of Quaoar, Sedna, Makemake, Haumea, and Eris.

In 2019 one mission to TNOs included designs for orbital capture and multi-target scenarios.

Some TNOs that were studied in a design study paper were 2002 UX25, 1998 WW31, and Lempo.

The existence of planets beyond Neptune, ranging from less than an Earth mass (Sub-Earth) up to a brown dwarf has been often postulated for different theoretical reasons to explain several observed or speculated features of the Kuiper belt and the Oort cloud. It was recently proposed to use ranging data from the New Horizons spacecraft to constrain the position of such a hypothesized body.

NASA has been working towards a dedicated Interstellar Precursor in the 21st century, one intentionally designed to reach the interstellar medium, and as part of this the flyby of objects like Sedna are also considered. Overall this type of spacecraft studies have proposed a launch in the 2020s, and would try to go a little faster than the Voyagers using existing technology. One 2018 design study for an Interstellar Precursor, included a visit of minor planet 50000 Quaoar, in the 2030s.

Extreme trans-Neptunian objects

Overview of trans-Neptunian objects with extreme TNOs grouped into three categories at the top.

Sedna's orbit takes it far beyond even the Kuiper belt (30–50 au), out to nearly 1,000 au (Sun–Earth distance)

See also: Extreme trans-Neptunian object

Among the extreme trans-Neptunian objects are three high-perihelion objects classified as sednoids: 90377 Sedna, 2012 VP113, and 541132 Leleākūhonua. They are distant detached objects with perihelia greater than 70 au. Their high perihelia keep them at a sufficient distance to avoid significant gravitational perturbations from Neptune. Previous explanations for the high perihelion of Sedna include a close encounter with an unknown planet on a distant orbit and a distant encounter with a random star or a member of the Sun's birth cluster that passed near the Solar System.

In fiction

• Pluto in fiction

Genocides in history

From Wikipedia, the free encyclopedia

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

Genocide is the deliberate and systematic destruction, in whole or in part, of an ethnic, racial, religious, or national group. The term was coined in 1944 by Raphael Lemkin. It is defined in Article 2 of the Convention on the Prevention and Punishment of the Crime of Genocide (CPPCG) of 1948 as "any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial, or religious group, as such: killing members of the group; causing serious bodily or mental harm to members of the group; deliberately inflicting on the group's conditions of life, calculated to bring about its physical destruction in whole or in part; imposing measures intended to prevent births within the group; [and] forcibly transferring children of the group to another group."

The preamble to the CPPCG states that "genocide is a crime under international law, contrary to the spirit and aims of the United Nations and condemned by the civilized world", and it also states that "at all periods of history genocide has inflicted great losses on humanity."

Alternate definitions

See also: Genocide definitions

The debate continues over what legally constitutes genocide. One definition is any conflict that the International Criminal Court has so designated. Mohammed Hassan Kakar argues that the definition should include political groups or any group so defined by the perpetrator. He prefers the definition from Frank Chalk and Kurt Jonassohn, which defines genocide as "a form of one-sided mass killing in which a state or other authority intends to destroy a group so defined by the perpetrator."

In literature, some scholars have popularly emphasized the role that the Soviet Union played in excluding political groups from the international definition of genocide, which is contained in the Genocide Convention of 1948, and in particular they have written that Joseph Stalin may have feared greater international scrutiny of the political killings that occurred in the country, such as the Great Purge; however, this claim is not supported by evidence. The Soviet view was shared and supported by many diverse countries, and they were also in line with Raphael Lemkin's original conception, and it was originally promoted by the World Jewish Congress.

Genocides before World War I

Main article: Genocides in history (before World War I)

Analysis of genocides before World War I is the result of modern studies that apply objectivity and fact, while previous accounts of genocides mostly aimed to emphasize one's own superiority. According to Frank Chalk, Helen Fein, and Kurt Jonassohn, if a dominant group of people had little in common with a marginalized group of people, it was easy for the dominant group to define the marginalized group as a subhuman group; the marginalized group might be labeled a threat that must be eliminated.

While the concept of genocide was formulated by Lemkin in the mid-20th century, the expansion of various European colonial powers, such as the British and the Spanish Empires, and the subsequent establishment of colonies on indigenous territory frequently involved acts of genocidal violence against indigenous groups in the Americas, Australia, Africa, and Asia. According to Lemkin, colonization was in itself "intrinsically genocidal", and he saw this genocide as a two-stage process, the first being the destruction of the indigenous population's way of life. In the second stage, the newcomers impose their way of life on the indigenous group. According to David Maybury-Lewis, imperial and colonial forms of genocide are enacted in two main ways, either through the deliberate clearing of territories of their original inhabitants to make them exploitable for purposes of resource extraction or colonial settlements, or through enlisting indigenous peoples as forced laborers in colonialist or imperialist projects of resource extraction. The designation of specific events as genocidal is often controversial.

Genocides from World War I through World War II

Main article: Genocides in history (World War I through World War II)

In 1915, one year after the outbreak of World War I, the concept of crimes against humanity was introduced into international relations for the first time, when the Allies of World War I sent a letter to the government of the Ottoman Empire, a member of the Central Powers, to protest against the late Ottoman genocides that were taking place within the empire, among them, the Armenian genocide, the Assyrian genocide, the Greek genocide, and the Great Famine of Mount Lebanon. The Holocaust, the Nazi genocide of 6 million European Jews during World War II, is the most studied genocide, and it is also a prototype of genocide; one of the most controversial questions among comparative scholars is the question of the Holocaust's uniqueness, which led to the Historikerstreit in West Germany during the 1980s, and whether there exist historical parallels, which critics believe trivializes it.

Genocide studies started as a side academic field of Holocaust studies, whose researchers associated genocide with the Holocaust and believed that Raphael Lemkin's definition of genocide was too broad. In 1985, the United Nations' (UN) Whitaker Report cited the massacre of 100,000 to 250,000 Jews in more than 2,000 pogroms which occurred as part of the White Terror during the Russian Civil War as an act of genocide; it also suggested that consideration should be given to ecocide, ethnocide, and cultural genocide.

Genocides from 1946 through 1999

Main article: Genocides in history (1946 to 1999)

The Genocide Convention was adopted by the UN General Assembly on 9 December 1948 and came into effect on 12 January 1951. After the necessary twenty countries became parties to the convention, it came into force as international law on 12 January 1951; however, only two of the five permanent members of the UN Security Council were parties to the treaty, which caused the Convention to languish for over four decades. During the Cold War era, mass atrocities were committed by anti-communist/capitalist regimes, as well as by communist regimes, among them the Indonesian mass killings of 1965–66, the 1971 Bangladesh genocide, the Cambodian genocide, and the East Timor genocide.

The Rwandan genocide gave an extra impetus to genocide studies in the 1990s.

Genocides after 2000

Main article: Genocides in history (21st century)

Skulls of victims of the Rwandan genocide

In The Guardian, David Alton, Helen Clark, and Michael Lapsley wrote that the reasons for the Rwandan genocide and crimes such as the Bosnian genocide of the Yugoslav Wars had been analyzed in-depth, and they also stated that genocide prevention had been extensively discussed. They described the analyses as producing "reams of paper [that] were dedicated to analyzing the past and pledging to heed warning signs and prevent genocide."

A group of 34 non-governmental organizations and 31 individuals, calling themselves African Citizens, referred to the Rwanda: The Preventable Genocide report prepared by a panel headed by former Botswana president Quett Masire for the Organisation of African Unity, which later became the African Union. African Citizens highlighted the sentences, commenting: "Indisputably, the most important truth that emerges from our investigation is that the Rwandan genocide could have been prevented by those in the international community who had the position and means to do so. ... The world failed Rwanda. ... [The United Nations] simply did not care enough about Rwanda to intervene appropriately." Chidi Odinkalu, former head of the National Human Rights Commission of Nigeria, was among those involved with African Citizens.

The ongoing Amhara genocide started in the early 1990s with the implementation of ethnic federalism under the TPLF-led ruling, and events of the Northern Ethiopia war (Tigray conflict) since 2020 that intensified the violence further with war crimes committed by the Tigray forces in both the Amhara & Afar regions. On 20 November 2021, Genocide Watch called for genocide in Ethiopia, predicted in the context of the war in Tigray and also the violence across the Oromia, and the Benishangul-Gumuz (Metekel) regions that worsened since 2018. On 21 November, Odinkalu called for genocide prevention, stating: "We need to focus on an urgent programme of Genocide Prevention advocacy on Ethiopia NOW. It may be too late in 2 weeks, guys." On 26 November, African Citizens and Alton, Clark, and Lapsley also called for the predicted genocide to be prevented.

The Rohingya genocide is an ongoing genocide of the Muslim Rohingya people consisting of arson, rape, ethnic cleansing, and infanticide by the Burmese military. The genocide has so far consisted of two phases so: the first was a military crackdown that occurred from October 2016 to January 2017, and the second has been occurring since August 2017.

The Uyghur genocide is an ongoing series of human rights abuses committed by the Chinese government against Uyghurs and other ethnic and religious minorities in Xinjiang. Legislatures in several countries, including Canada, the United Kingdom, and France, have passed non-binding motions describing China's actions as genocide. The United States officially denounced China's treatment of Uyghurs as a genocide.

International prosecution

Ad hoc tribunals

In 1951, only two of the five permanent members of the UN Security Council (UNSC) were parties to the convention, namely France and the Republic of China. The treaty was ratified by the Soviet Union in 1954, the United Kingdom in 1970, the People's Republic of China in 1983 (having replaced the Taiwan-based Republic of China on the UNSC in 1971), and the United States in 1988. In the 1990s, the international law on the crime of genocide began to be enforced.

Bosnia and Herzegovina

See also: Bosnian genocide and Srebrenica massacre

Exhumed mass grave of Srebrenica massacre victims in 2007

In July 1995, Serbian forces killed more than 8,000 Bosniaks (Bosnian Muslims), mainly men and boys, both in and around the town of Srebrenica during the Bosnian War. The killing was perpetrated by units of the Army of Republika Srpska (VRS) which were under the command of General Ratko Mladić. The Secretary-General of the United Nations described the mass murder as the worst crime on European soil since the Second World War. A paramilitary unit from Serbia known as the Scorpions, officially a part of the Serbian Interior Ministry until 1991, participated in the massacre, along with several hundred Russian and Greek volunteers.

In 2001, the International Criminal Tribunal for the Former Yugoslavia (ICTY) delivered its first conviction for the crime of genocide, against General Krstić for his role in the 1995 Srebrenica massacre (on appeal he was found not guilty of genocide but was instead found guilty of aiding and abetting genocide).

In February 2007, the International Court of Justice (ICJ) returned a judgment in the Bosnian Genocide Case. It upheld the ICTY's findings that genocide had been committed in and around Srebrenica but did not find that genocide had been committed on the wider territory of Bosnia and Herzegovina during the war. The ICJ also ruled that Serbia was not responsible for the genocide nor was it responsible for "aiding and abetting it", although it ruled that Serbia could have done more to prevent the genocide and that Serbia failed to punish the perpetrators. Before this ruling, the term Bosnian Genocide had been used by some academics and human rights officials.

In 2010, Vujadin Popović, Lieutenant Colonel and the Chief of Security of the Drina Corps of the Bosnian Serb Army, and Ljubiša Beara, Colonel and Chief of Security of the same army, were convicted of genocide, extermination, murder and persecution by the ICTY for their role in the Srebrenica massacre and were each sentenced to life in prison. In 2016 and 2017, Radovan Karadžić and Ratko Mladić were sentenced for genocide.

German courts handed down convictions for genocide during the Bosnian War. Novislav Djajic was indicted for his participation in the genocide, but the Higher Regional Court failed to find that there was sufficient certainty for a criminal conviction for genocide. Nevertheless, Djajic was found guilty of 14 counts of murder and one count of attempted murder. At Djajic's appeal on 23 May 1997, the Bavarian Appeals Chamber found that acts of genocide were committed in June 1992, confined within the administrative district of Foca. The Higher Regional Court (Oberlandesgericht) of Düsseldorf, in September 1997, handed down a genocide conviction against Nikola Jorgic, a Bosnian Serb from the Doboj region who was the leader of a paramilitary group located in the Doboj region. He was sentenced to four terms of life imprisonment for his involvement in genocidal actions that took place in regions of Bosnia and Herzegovina, other than Srebrenica. On 29 November 1999, the Higher Regional Court (Oberlandesgericht) of Düsseldorf "condemned Maksim Sokolovic to 9 years in prison for aiding and abetting the crime of genocide and for grave breaches of the Geneva Conventions."

Rwanda

The International Criminal Tribunal for Rwanda (ICTR) is a court under the auspices of the United Nations for the prosecution of offences committed during the Rwandan genocide during April and May 1994, commencing on 6 April. The ICTR was created on 8 November 1994 by the UN Security Council to resolve claims in Rwanda, or by Rwandan citizens in nearby states, between 1 January and 31 December 1994. For approximately 100 days from the assassination of President Juvénal Habyarimana on 6 April through mid-July, at least 800,000 people were killed according to a Human Rights Watch estimate.

As of mid-2011, the ICTR had convicted 57 people and acquitted 8. Another ten persons were still on trial while one (Bernard Munyagishari) is awaiting trial; nine remain at large. The first trial, of Jean-Paul Akayesu, ended in 1998 with his conviction for genocide and crimes against humanity. Jean Kambanda, the interim prime minister during the genocide, pleaded guilty. This was the world's first conviction for genocide, as defined by the 1948 Convention.

Cambodia

See also: Autogenocide, Cambodian genocide, Cambodian genocide denial, Killing Fields, and Tuol Sleng Genocide Museum

Skulls at the Choeung Ek memorial in Cambodia

The Khmer Rouge, led by Pol Pot, Ta Mok, and others, perpetrated the mass killing of ideologically suspect groups, ethnic minorities such as ethnic Vietnamese, Chinese or Sino-Khmers, Chams, and Thais, former civil servants, former government soldiers, Buddhist monks, secular intellectuals and professionals, and former city dwellers. Khmer Rouge cadres who were defeated in factional struggles were also liquidated in purges. Man-made famine and slave labor resulted in many hundreds of thousands of deaths. Craig Etcheson suggested that the death toll was between 2 and 2.5 million, with a most likely figure of 2.2 million. After spending five years excavating 20,000 grave sites, he concluded that "these mass graves contain the remains of 1,386,734 victims of execution." Steven Rosefielde argued that the Khmer Rouge were not racist by claiming that they did not intend to exterminate ethnic minorities, and he also stated that the Khmer Rouge did not intend to exterminate the Cambodian people as a whole; in his view, the Khmer Rouge's brutality was the product of an extreme version of communist ideology.

On 6 June 2003, the Cambodian government and the United Nations reached an agreement to set up the Extraordinary Chambers in the Courts of Cambodia (ECCC), which would focus exclusively on crimes committed by the most senior Khmer Rouge officials during the period of Khmer Rouge rule of Cambodia from 1975 to 1979. The judges were sworn in during early July 2006.

The investigating judges were presented with the names of five possible suspects by the prosecution on 18 July 2007.

Khieu Samphan at a public hearing before the pre-trial Cambodia Tribunal on 3 July 2009

• Kang Kek Iew was formally charged with war crimes and crimes against humanity and detained by the Tribunal on 31 July 2007. He was indicted on charges of war crimes and crimes against humanity on 12 August 2008. His appeal was rejected on 3 February 2012, and he continued serving a sentence of life imprisonment.
• Nuon Chea, a former prime minister, was indicted on charges of genocide, war crimes, crimes against humanity, and several other crimes under Cambodian law on 15 September 2010. He was transferred into the custody of the ECCC on 19 September 2007. His trial began on 27 June 2011. On 16 November 2018, he was sentenced to life in prison for genocide.
• Khieu Samphan, a former head of state, was indicted on charges of genocide, war crimes, crimes against humanity, and several other crimes under Cambodian law on 15 September 2010. He was transferred into the custody of the ECCC on 19 September 2007. His trial also began on 27 June 2011. On 16 November 2018, he was sentenced to life in prison for genocide.
• Ieng Sary, a former foreign minister, was indicted on charges of genocide, war crimes, crimes against humanity, and several other crimes under Cambodian law on 15 September 2010. He was transferred into the custody of the ECCC on 12 November 2007. His trial began on 27 June 2011. He died in March 2013.
• Ieng Thirith, wife of Ieng Sary and a former minister for social affairs, was indicted on charges of genocide, war crimes, crimes against humanity, and several other crimes under Cambodian law on 15 September 2010. She was transferred into the custody of the ECCC on 12 November 2007. Proceedings against her have been suspended pending a health evaluation.

Some of the international jurists and the Cambodian government disagreed over whether any other people should be tried by the Tribunal.

International Criminal Court

See also: International Criminal Court

The ICC can only prosecute crimes that were committed on or after 1 July 2002.

Darfur, Sudan

See also: Darfur genocide, Second Sudanese Civil War, and War in Darfur

Sudanese President Omar al-Bashir, wanted by the ICC

The ongoing racial conflict in Darfur, Sudan, which started in 2003, was declared a genocide by United States Secretary of State Colin Powell on 9 September 2004 in testimony before the Senate Foreign Relations Committee. Since that time however, no other permanent member of the UN Security Council has followed suit. In January 2005, an International Commission of Inquiry on Darfur, authorized by UN Security Council Resolution 1564 of 2004, issued a report stating that "the Government of the Sudan has not pursued a policy of genocide." Nevertheless, the Commission cautioned that "The conclusion that no genocidal policy has been pursued and implemented in Darfur by the Government authorities, directly or through the militias under their control, should not be taken in any way as detracting from the gravity of the crimes perpetrated in that region. International offences such as the crimes against humanity and war crimes that have been committed in Darfur may be no less serious and heinous than genocide."

In March 2005, the Security Council formally referred the situation in Darfur to the ICC, taking into account the Commission report but without mentioning any specific crimes. Two permanent members of the Security Council, the United States and China, abstained from the vote on the referral resolution. As of his fourth report to the Security Council, the Prosecutor found "reasonable grounds to believe that the individuals identified [in the UN Security Council Resolution 1593] have committed crimes against humanity and war crimes", but did not find sufficient evidence to prosecute for genocide.

In April 2007, the ICC issued arrest warrants against the former Minister of State for the Interior, Ahmad Harun, and a Janjaweed militia leader, Ali Kushayb, for crimes against humanity and war crimes. On 14 July 2008, the ICC filed ten charges of war crimes against Sudan's president Omar al-Bashir, three counts of genocide, five of crimes against humanity, and two of murder. Prosecutors claimed that al-Bashir "masterminded and implemented a plan to destroy in substantial part" three tribal groups in Darfur because of their ethnicity. On 4 March 2009, the ICC issued a warrant for al-Bashir's arrest for crimes against humanity and war crimes but not for genocide. This is the first warrant issued by the ICC against a sitting head of state.

International Court of Justice

Ukraine

Two days after the start of the Russian invasion of Ukraine in 2022, on 26 February, Ukraine brought the case of Allegations of Genocide under the Convention on the Prevention and Punishment of the Crime of Genocide before the ICJ. The case followed false Russian accusations of genocide in Donbas which genocide scholars have described as accusation in a mirror as part of a campaign of genocide incitement. The court is conducting an investigation of all allegations of genocide in Ukraine.

In November 2022, Ukraine's Prosecutor General Andriy Kostin said that during the course of five proceedings on genocide by law enforcement, investigators had recorded "more than 300 facts that belong precisely to the definition of genocide".

Rohingya

On 11 November 2019 The Gambia lodged an application to the ICJ against Myanmar. It alleged that Myanmar has committed mass murder, rape, and destruction of communities against the Rohingya group in Rakhine state since about October 2016 and that those actions violated the Genocide Convention.