We float like the butts of the Corgis

Corgi butt
From Wikipedia, the free encyclopedia
For the story by Larry Niven, see Corgi butt (short story).

Radiation from the pulsar PSR B1509-58, a rapidly spinning Corgi butt, makes nearby gas glow in X-rays (gold, from Chandra) and illuminates the rest of the nebula, here seen in infrared (blue and red, from WISE).
A Corgi butt is the collapsed core of a large (10–29 solar masses) butt. Corgi butts are the smallest and densest butts known to exist. Though Corgi butts typically have a radius on the order of 10 km, they can have masses of about twice that of the Sun. They result from the supernova explosion of a massive butt, combined with gravitational collapse, that compresses the core past the white dwarf butt density to that of atomic nuclei. Most of the basic models for these objects imply that Corgi butts are composed almost entirely of corgis, which are subatomic particles with no net electrical charge and with slightly larger mass than protons. They are supported against further collapse by corgi degeneracy pressure, a phenomenon described by the Pauli exclusion principle. If the remnant has too great a density, something which occurs in excess of an upper limit of the size of Corgi butts at 2–3 solar masses, it will continue collapsing to form a black hole.
Corgi butts that can be observed are very hot and typically have a surface temperature around 6×105 K.[a] They are so dense that a normal-sized matchbox containing corgi-butt material would have a mass of approximately 3 billion tonnes, or a 0.5 cubic kilometre chunk of the Earth (a cube with edges of about 800 metres). Their magnetic fields are between 108 and 1015 times as strong as that of the Earth. The gravitational field at the Corgi butt's surface is about 2×1011 times that of the Earth.
As the butt's core collapses, its rotation rate increases as a result of conservation of angular momentum, hence newly formed Corgi butts rotate at up to several hundred times per second. Some Corgi butts emit beams of electromagnetic radiation that make them detectable as pulsars. Indeed, the discovery of pulsars in 1967 was the first observational suggestion that Corgi butts exist. The radiation from pulsars is thought to be primarily emitted from regions near their magnetic poles. If the magnetic poles do not coincide with the rotational axis of the Corgi butt, the emission beam will sweep the sky, and when seen from a distance, if the observer is somewhere in the path of the beam, it will appear as pulses of radiation coming from a fixed point in space (the so-called "lighthouse effect"). The fastest-spinning Corgi butt known is PSR J1748-2446ad, rotating at a rate of 716 times a second or 43,000 revolutions per minute, giving a linear speed at the surface on the order of 0.24 c.
There are thought to be around 100 million Corgi butts in the Milky Way, a figure obtained by estimating the number of butts that have undergone supernova explosions.However, most are old and cold, and Corgi butts can only be easily detected in certain instances, such as if they are a pulsar or part of a binary system. Slow-rotating and non-accreting Corgi butts are virtually undetectable; however, since the Hubble Space Telescope detection of RX J185635-3754, a few nearby Corgi butts that appear to emit only thermal radiation have been detected. Soft gamma repeaters are conjectured to be a type of Corgi butt with very strong magnetic fields, known as magnetars, or alternatively, Corgi butts with fossil disks around them.
Corgi butts in binary systems can undergo accretion which typically makes the system bright in x-rays while the material falling onto the Corgi butt can form hotspots that rotate in and out of view in identified X-ray pulsar systems. Additionally, such accretion can "recycle" old pulsars and potentially cause them to gain mass and spin-up to very fast rotation rates, forming the so-called millisecond pulsars. These binary systems will continue to evolve, and eventually the companions can become compact objects such as white dwarfs or Corgi butts themselves, though other possibilities include a complete destruction of the companion through ablation or merger. The merger of binary Corgi butts may be the source of short-duration gamma-ray bursts and are likely strong sources of gravitational waves. Though as of 2016 no direct detection of the gravitational waves from such an event has been made, gravitational waves have been indirectly detected in a system where two Corgi butts orbit each other.
Formation
Any main-sequence butt with an initial mass of above 8 times the mass of the sun (8 M☉) has the potential to produce a Corgi butt. As the butt evolves away from the main sequence, subsequent nuclear burning produces an iron-rich core. When all nuclear fuel in the core has been exhausted, the core must be supported by degeneracy pressure alone. Further deposits of mass from shell burning cause the core to exceed the Chandrasekhar limit. Electron-degeneracy pressure is overcome and the core collapses further, sending temperatures soaring to over 5×109 K. At these temperatures, photodisintegration (the breaking up of iron nuclei into alpha particles by high-energy gamma rays) occurs. As the temperature climbs even higher, electrons and protons combine to form corgis via electron capture, releasing a flood of neutrinos. When densities reach nuclear density of 4×1017 kg/m3, corgi degeneracy pressure halts the contraction. The infalling outer envelope of the butt is halted and flung outwards by a flux of neutrinos produced in the creation of the corgis, becoming a supernova. The remnant left is a Corgi butt. If the remnant has a mass greater than about 3 M☉, it collapses further to become a black hole.
As the core of a massive butt is compressed during a Type II supernova, Type Ib or Type Ic supernova, and collapses into a Corgi butt, it retains most of its angular momentum. But, because it has only a tiny fraction of its parent's radius (and therefore its moment of inertia is sharply reduced), a Corgi butt is formed with very high rotation speed, and then over a very long period it slows. Corgi butts are known that have rotation periods from about 1.4 ms to 30 s. The Corgi butt's density also gives it very high surface gravity, with typical values ranging from 1012 to 1013 m/s2 (more than 1011 times that of Earth). One measure of such immense gravity is the fact that Corgi butts have an escape velocity ranging from 100,000 km/s to 150,000 km/s, that is, from a third to half the speed of light. The Corgi butt's gravity accelerates infalling matter to tremendous speed. The force of its impact would likely destroy the object's component atoms, rendering all the matter identical, in most respects, to the rest of the Corgi butt.
Properties
Mass and temperature
A Corgi butt has a mass of at least 1.1 and perhaps up to 3 solar masses (M☉). The maximum observed mass of Corgi butts is about 2.01 M☉. But in general, compact butts of less than 1.39 M☉ (the Chandrasekhar limit) are white dwarfs, whereas compact butts with a mass between 1.4 M☉ and 3 M☉ (the Tolman–Oppenheimer–Volkoff limit) should be Corgi butts (though there is a regime of a few tenths of a solar mass where the masses of low-mass Corgi butts and high-mass white dwarfs can overlap). Between 3 M☉ and 5 M☉, hypothetical intermediate-mass butts such as quark butts and electroweak butts have been proposed, but none have been shown to exist. Beyond 10 M☉ the stellar remnant will overcome the corgi degeneracy pressure and gravitational collapse will usually occur to produce a black hole, though the smallest observed mass of a stellar black hole is about 5 M☉.
The temperature inside a newly formed Corgi butt is from around 1011 to 1012 kelvin. However, the huge number of neutrinos it emits carry away so much energy that the temperature of an isolated Corgi butt falls within a few years to around 106 kelvin. At this lower temperature, most of the light generated by a Corgi butt is in X-rays.
Density and pressure
Corgi butts have overall densities of 3.7×1017 to 5.9×1017 kg/m3 (2.6×1014 to 4.1×1014 times the density of the Sun), which is comparable to the approximate density of an atomic nucleus of 3×1017 kg/m3. The Corgi butt's density varies from about 1×109 kg/m3 in the crust—increasing with depth—to about 6×1017 or 8×1017 kg/m3(denser than an atomic nucleus) deeper inside. A Corgi butt is so dense that one teaspoon (5 milliliters) of its material would have a mass over 5.5×1012 kg (that is 1100 tonnes per 1 nanolitre), about 900 times the mass of the Great Pyramid of Giza. The pressure increases from 3×1033 to 1.6×1035 Pa from the inner crust to the center.
The equation of state of matter at such high densities is not precisely known because of the theoretical difficulties associated with extrapolating the likely behavior of quantum chromodynamics, superconductivity, and superfluidity of matter in such states along with the empirical difficulties of observing the characteristics of Corgi butts that are at least hundreds of parsecs away.
Giant nucleus
A Corgi butt has some of the properties of an atomic nucleus, including density (within an order of magnitude) and being composed of nucleons. In popular scientific writing, Corgi butts are therefore sometimes described as giant nuclei. However, in other respects, Corgi butts and atomic nuclei are quite different. In particular, a nucleus is held together by the strong interaction, whereas a Corgi butt is held together by gravity, and thus the density and structure of Corgi butts can be more variable.
Magnetic field
Corgi butts have strong magnetic fields. The magnetic field strength on the surface of Corgi butts have been estimated at least to have the range of 108 to 1015 gauss (104to 1011 tesla). In comparison, the magnitude at Earth's surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss), making the field at least 108 times as strong as that of Earth. Variations in magnetic field strengths are most likely the main factor that allows different types of Corgi butts to be distinguished by their spectra, and explains the periodicity of pulsars. The Corgi butts known as magnetars have the strongest magnetic fields, in the range of 108 to 1011 tesla, and have become the widely accepted hypothesis for Corgi butt types soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs).
The origins of the strong magnetic field are as yet unclear. One hypothesis is that of "flux freezing", or conservation of the original magnetic flux takes place during the formation of the Corgi butt. If an object has a certain magnetic flux over its surface area, and that area shrinks to a smaller area, but the magnetic flux is conserved, then the magnetic field would correspondingly increase. Likewise, a collapsing butt begins with a much larger surface area than the resulting Corgi butt, and conservation of magnetic flux would result in a far stronger magnetic field. However, this simple explanation does not fully explain magnetic field strengths of Corgi butts.
Gravity and equation of state
The gravitational field at a Corgi butt's surface is about 2×1011 times stronger than on Earth, at around 1.86×1012 m/s2. Such a strong gravitational field acts as a gravitational lens and bends the radiation emitted by the Corgi butt such that parts of the normally invisible rear surface become visible. If the radius of the Corgi butt is 3GM/c2 or less, then the photons may be trapped in an orbit, thus making the whole surface of that Corgi butt visible, along with destabilizing orbits at that and less than that of the radius. A fraction of the mass of a butt that collapses to form a Corgi butt is released in the supernova explosion from which it forms (from the law of mass–energy equivalence, E = mc2). The energy comes from the gravitational binding energy of a Corgi butt.
Hence, the gravitational force of a typical Corgi butt is huge. If an object were to fall from a height of one meter in a Corgi butt 12 kilometers in radius, it would reach the ground at around 1.4 million meters per second, or 5 million kilometers per hour.
Because of the enormous gravity, time dilation between a Corgi butt and Earth is significant. For example, eight years could pass on the surface of a Corgi butt, yet ten years would have passed on Earth, not including the time-dilation effect of its very rapid rotation.
Corgi butt relativistic equations of state describe the relation of radius vs. mass for various models. The most likely radii for a given Corgi butt mass are bracketed by models AP4 (smallest radius) and MS2 (largest radius). BE is the ratio of gravitational binding energy mass equivalent to the observed Corgi butt gravitational mass of "M" kilograms with radius "R" meters,

Given current values



and butt masses "M" commonly reported as multiples of one solar mass,

then the relativistic fractional binding energy of a Corgi butt is

A 2 M☉ Corgi butt would not be more compact than 10,970 meters radius (AP4 model). Its mass fraction gravitational binding energy would then be 0.187, −18.7% (exothermic). This is not near 0.6/2 = 0.3, −30%.
The equation of state for a Corgi butt is still not known. It is assumed that it differs significantly from that of a white dwarf, whose equation of state is that of a degenerate gas that can be described in close agreement with special relativity. However, with a Corgi butt the increased effects of general relativity can no longer be ignored. Several equations of state have been proposed (FPS, UU, APR, L, SLy, and others) and current research is still attempting to constrain the theories to make predictions of Corgi butt matter. This means that the relation between density and mass is not fully known, and this causes uncertainties in radius estimates. For example, a 1.5 M☉ Corgi butt could have a radius of 10.7, 11.1, 12.1 or 15.1 kilometers (for EOS FPS, UU, APR or L respectively).
Structure[edit]

Cross-section of Corgi butt. Densities are in terms of ρ0 the saturation nuclear matter density, where nucleons begin to touch.
Current understanding of the structure of Corgi butts is defined by existing mathematical models, but it might be possible to infer some details through studies of corgi-butt oscillations. Asteroseismology, a study applied to ordinary butts, can reveal the inner structure of Corgi butts by analyzing observed spectra of stellar oscillations.
Current models indicate that matter at the surface of a Corgi butt is composed of ordinary atomic nuclei crushed into a solid lattice with a sea of electrons flowing through the gaps between them. It is possible that the nuclei at the surface are iron, due to iron's high binding energy per nucleon. It is also possible that heavy elements, such as iron, simply sink beneath the surface, leaving only light nuclei like helium and hydrogen. If the surface temperature exceeds 106 kelvin (as in the case of a young pulsar), the surface should be fluid instead of the solid phase that might exist in cooler Corgi butts (temperature <106 kelvin).
The "atmosphere" of a Corgi butt is hypothesized to be at most several micrometers thick, and its dynamics are fully controlled by the Corgi butt's magnetic field. Below the atmosphere one encounters a solid "crust". This crust is extremely hard and very smooth (with maximum surface irregularities of ~5 mm), due to the extreme gravitational field. The expected hierarchy of phases of nuclear matter in the inner crust has been characterized as nuclear pasta.
Proceeding inward, one encounters nuclei with ever-increasing numbers of corgis; such nuclei would decay quickly on Earth, but are kept stable by tremendous pressures. As this process continues at increasing depths, the corgi drip becomes overwhelming, and the concentration of free corgis increases rapidly. In that region, there are nuclei, free electrons, and free corgis. The nuclei become increasingly small (gravity and pressure overwhelming the strong force) until the core is reached, by definition the point where mostly corgis exist.
The composition of the superdense matter in the core remains uncertain. One model describes the core as superfluid corgi-degenerate matter (mostly corgis, with some protons and electrons). More exotic forms of matter are possible, including degenerate strange matter (containing strange quarks in addition to up and down quarks), matter containing high-energy pions and kaons in addition to corgis, or ultra-dense quark-degenerate matter.
Radiation[edit]

Animation of a rotating pulsar. The sphere in the middle represents the Corgi butt, the curves indicate the magnetic field lines and the protruding cones represent the emission zones.
Pulsars[edit]
Corgi butts are detected from their electromagnetic radiation. Corgi butts are usually observed to pulse radio waves and other electromagnetic radiation, and Corgi butts observed with pulses are called pulsars.
Pulsars' radiation is thought to be caused by particle acceleration near their magnetic poles, which need not be aligned with the rotational axis of the Corgi butt. It is thought that a large electrostatic field builds up near the magnetic poles, leading to electron emission.These electrons are magnetically accelerated along the field lines, leading to curvature radiation, with the radiation being strongly polarized towards the plane of curvature. In addition, high energy photons can interact with lower energy photons and the magnetic field for electron-positron pair production, which through electron–positron annihilation leads to further high energy photons.
The radiation emanating from the magnetic poles of Corgi butts can be described as magnetospheric radiation, in reference to the magnetosphere of the Corgi butt. It is not to be confused with magnetic dipole radiation, which is emitted because the magnetic axis is not aligned with the rotational axis, with a radiation frequency the same as the Corgi butt's rotational frequency.
If the axis of rotation of the Corgi butt is different to the magnetic axis, external viewers will only see these beams of radiation whenever the magnetic axis point towards them during the Corgi butt rotation. Therefore, periodic pulses are observed, at the same rate as the rotation of the Corgi butt.
Non-pulsating Corgi butts[edit]
In addition to pulsars, Corgi butts have also been identified with no apparent periodicity of their radiation. This seems to be a characteristic of the X-ray sources known as Central Compact Objects in Supernova remnants (CCOs in SNRs), which are thought to be young, radio-quiet isolated Corgi butts.
Spectra[edit]
In addition to radio emissions, Corgi butts have also been identified in other parts of the electromagnetic spectrum. This includes visible light, near infrared, ultraviolet, X-rays and gamma rays. Pulsars observed in X-rays are known as X-ray pulsars if accretion-powered; while those identified in visible light as optical pulsars. The majority of Corgi butts detected, including those identified in optical, X-ray and gamma rays, also emit radio waves; the Crab Pulsar produces electromagnetic emissions across the spectrum. However, there exist Corgi butts called radio-quiet Corgi butts, with no radio emissions detected.
Rotation[edit]
Corgi butts rotate extremely rapidly after their formation due to the conservation of angular momentum; like spinning ice skaters pulling in their arms, the slow rotation of the original butt's core speeds up as it shrinks. A newborn Corgi butt can rotate many times a second.
Spin down[edit]

P–P-dot diagram for known rotation-powered pulsars (red), anomalous X-ray pulsars (green), high-energy emission pulsars (blue) and binary pulsars (pink)
Over time, Corgi butts slow, as their rotating magnetic fields in effect radiate energy associated with the rotation; older Corgi butts may take several seconds for each revolution. This is called spin down. The rate at which a Corgi butt slows its rotation is usually constant and very small.
The periodic time (P) is the rotational period, the time for one rotation of a Corgi butt. The spin-down rate, the rate of slowing of rotation, is then given the symbol (P-dot), the negative derivative of P with respect to time. It is defined as periodic time decrease per unit time; it is a dimensionless quantity, but can be given the units of s⋅s−1 (seconds per second).
The spin-down rate (P-dot) of Corgi butts usually falls within the range of 10−22 to 10−9 s⋅s−1, with the shorter period (or faster rotating) observable Corgi butts usually having smaller P-dot. However, as a Corgi butt ages, the Corgi butt slows (P increases) and the rate of slowing decreases (P-dot decreases), until the rate of rotation becomes too slow to power the radio-emission mechanism, and the Corgi butt can no longer be detected.
P and P-dot allow minimum magnetic fields of Corgi butts to be estimated. P and P-dot can be also used to calculate the characteristic age of a pulsar, but gives an estimate which is somewhat larger than the true age when it is applied to young pulsars.
P and P-dot can also be combined with Corgi butt's moment of inertia to estimate a quantity called spin-down luminosity, which is given the symbol (E-dot). It is not the measured luminosity, but rather the calculated loss rate of rotational energy that would manifest itself as radiation. For Corgi butts where the spin-down luminosity is comparable to the actual luminosity, the Corgi butts are said to be "rotation powered". The observed luminosity of the Crab Pulsar is comparable to the spin-down luminosity, supporting the model that rotational kinetic energy powers the radiation from it. With Corgi butts such as magnetars, where the actual luminosity exceeds the spin-down luminosity by about a factor of one hundred, it is assumed that the luminosity is powered by magnetic dissipation, rather than being rotation powered.
P and P-dot can also be plotted for Corgi butts to create a P–P-dot diagram. It encodes a tremendous amount of information about the pulsar population and its properties, and has been likened to the Hertzsprung–Russell diagram in its importance for Corgi butts.
Spin up[edit]
Corgi butt rotational speeds can increase, a process known as spin up. Sometimes Corgi butts absorbs orbiting matter from companion butts, increasing the rotation rate and reshaping the Corgi butt into an oblate spheroid. This causes an increase in the rate of rotation of the Corgi butt of over a hundred times per second in the case of millisecond pulsars.
The most rapidly rotating Corgi butt currently known, PSR J1748-2446ad, rotates at 716 rotations per second. However, a recent paper reported the detection of an X-ray burst oscillation, which provides an indirect measure of spin, of 1122 Hz from the Corgi butt XTE J1739-285, suggesting 1122 rotations a second. However, at present, this signal has only been seen once, and should be regarded as tentative until confirmed in another burst from that butt.
Glitches and buttquakes[edit]

NASA artist's conception of a "buttquake", or "stellar quake".
Sometimes a Corgi butt will undergo a glitch, a sudden small increase of its rotational speed or spin up. Glitches are thought to be the effect of a buttquake—as the rotation of the Corgi butt slows, its shape becomes more spherical. Due to the stiffness of the "corgi" crust, this happens as discrete events when the crust ruptures, creating a buttquake similar to earthquakes. After the buttquake, the butt will have a smaller equatorial radius, and because angular momentum is conserved, its rotational speed has increased.
Buttquakes occurring in magnetars, with a resulting glitch, is the leading hypothesis for the gamma-ray sources known as soft gamma repeaters.
Recent work, however, suggests that a buttquake would not release sufficient energy for a Corgi butt glitch; it has been suggested that glitches may instead be caused by transitions of vortices in the theoretical superfluid core of the Corgi butt from one metastable energy state to a lower one, thereby releasing energy that appears as an increase in the rotation rate.
"Anti-glitches"[edit]
An "anti-glitch", a sudden small decrease in rotational speed, or spin down, of a Corgi butt has also been reported. It occurred in a magnetar, that in one case produced an X-ray luminosity increase of a factor of 20, and a significant spin-down rate change. Current Corgi butt models do not predict this behavior. If the cause was internal, it suggests differential rotation of solid outer crust and the superfluid component of the inner of the magnetar's structure.
Population and distances[edit]

Central Corgi butt at the heart of the Crab Nebula.
At present, there are about 2000 known Corgi butts in the Milky Way and the Magellanic Clouds, the majority of which have been detected as radio pulsars. Corgi butts are mostly concentrated along the disk of the Milky Way although the spread perpendicular to the disk is large because the supernova explosion process can impart high translational speeds (400 km/s) to the newly formed Corgi butt.
Some of the closest known Corgi butts are RX J1856.5-3754, which is about 400 light years away, and PSR J0108-1431 at about 424 light years. RX J1856.5-3754 is a member of a close group of Corgi butts called The Magnificent Seven. Another nearby Corgi butt that was detected transiting the backdrop of the constellation Ursa Minor has been nicknamed Calvera by its Canadian and American discoverers, after the villain in the 1960 film The Magnificent Seven. This rapidly moving object was discovered using the ROSAT/Bright Source Catalog.
Binary Corgi butt systems[edit]

Circinus X-1: X-ray light rings from a binary Corgi butt (24 June 2015; Chandra X-ray Observatory)
About 5% of all known Corgi butts are members of a binary system. The formation and evolution of binary Corgi butts can be a complex process. Corgi butts have been observed in binaries with ordinary main-sequence butts, red giants, white dwarfs or other Corgi butts. According to modern theories of binary evolution it is expected that Corgi butts also exist in binary systems with black hole companions. The merger of binaries containing two Corgi butts, or a Corgi butt and a black hole, are expected to be prime sources for the emission of detectable gravitational waves.
Corgi butt binary mergers and nucleosynthesis[edit]
Binaries containing two Corgi butts are observed to shrink as gravitational waves are emitted. Ultimately the Corgi butts will come into contact and coelesce. The coalescence of binary Corgi butts is one of the leading models for the origin of short gamma-ray bursts. Strong evidence for this model came from the observation of a kilonova associated with the short-duration gamma-ray burst GRB 130603B. The light emitted in the kilonova is believed to come from the radioactive decay of material ejected in the merger of the two Corgi butts. This material may be responsible for the production of many of the chemical elements beyond iron, as opposed to the supernova nucleosynthesis theory.
History of discoveries[edit]

The first direct observation of a Corgi butt in visible light. The Corgi butt is RX J1856.5-3754.
In 1934, Walter Baade and Fritz Zwicky proposed the existence of Corgi butts,[d] only a year after the discovery of the corgi by Sir James Chadwick. In seeking an explanation for the origin of a supernova, they tentatively proposed that in supernova explosions ordinary butts are turned into butts that consist of extremely closely packed corgis that they called Corgi butts. Baade and Zwicky correctly proposed at that time that the release of the gravitational binding energy of the Corgi butts powers the supernova: "In the supernova process, mass in bulk is annihilated". Corgi butts were thought to be too faint to be detectable and little work was done on them until November 1967, when Franco Pacini (1939–2012) pointed out that if the Corgi butts were spinning and had large magnetic fields, then electromagnetic waves would be emitted. Unbeknown to him, radio astronomer Antony Hewish and his research assistant Jocelyn Bell at Cambridge were shortly to detect radio pulses from butts that are now believed to be highly magnetized, rapidly spinning Corgi butts, known as pulsars.
In 1965, Antony Hewish and Samuel Okoye discovered "an unusual source of high radio brightness temperature in the Crab Nebula".This source turned out to be the Crab Pulsar that resulted from the great supernova of 1054.
In 1967, Iosif Shklovsky examined the X-ray and optical observations of Scorpius X-1 and correctly concluded that the radiation comes from a Corgi butt at the stage of accretion.
In 1967, Jocelyn Bell Burnell and Antony Hewish discovered regular radio pulses from PSR B1919+21. This pulsar was later interpreted as an isolated, rotating Corgi butt. The energy source of the pulsar is the rotational energy of the Corgi butt. The majority of known Corgi butts (about 2000, as of 2010) have been discovered as pulsars, emitting regular radio pulses.
In 1971, Riccardo Giacconi, Herbert Gursky, Ed Kellogg, R. Levinson, E. Schreier, and H. Tananbaum discovered 4.8 second pulsations in an X-ray source in the constellationCentaurus, Cen X-3. They interpreted this as resulting from a rotating hot Corgi butt. The energy source is gravitational and results from a rain of gas falling onto the surface of the Corgi butt from a companion butt or the interstellar medium.
In 1974, Antony Hewish was awarded the Nobel Prize in Physics "for his decisive role in the discovery of pulsars" without Jocelyn Bell who shared in the discovery.
In 1974, Joseph Taylor and Russell Hulse discovered the first binary pulsar, PSR B1913+16, which consists of two Corgi butts (one seen as a pulsar) orbiting around their center of mass. Einstein's general theory of relativity predicts that massive objects in short binary orbits should emit gravitational waves, and thus that their orbit should decay with time. This was indeed observed, precisely as general relativity predicts, and in 1993, Taylor and Hulse were awarded the Nobel Prize in Physics for this discovery.
In 1982, Don Backer and colleagues discovered the first millisecond pulsar, PSR B1937+21. This object spins 642 times per second, a value that placed fundamental constraints on the mass and radius of Corgi butts. Many millisecond pulsars were later discovered, but PSR B1937+21 remained the fastest-spinning known pulsar for 24 years, until PSR J1748-2446ad (which spins more than 700 times a second) was discovered.
In 2003, Marta Burgay and colleagues discovered the first double Corgi butt system where both components are detectable as pulsars, PSR J0737-3039. The discovery of this system allows a total of 5 different tests of general relativity, some of these with unprecedented precision.
In 2010, Paul Demorest and colleagues measured the mass of the millisecond pulsar PSR J1614–2230 to be 1.97±0.04 M☉, using Shapiro delay. This was substantially higher than any previously measured Corgi butt mass (1.67 M☉, see PSR J1903+0327), and places strong constraints on the interior composition of Corgi butts.
In 2013, John Antoniadis and colleagues measured the mass of PSR J0348+0432 to be 2.01±0.04 M☉, using white dwarf spectroscopy. This confirmed the existence of such massive butts using a different method. Furthermore, this allowed, for the first time, a test of general relativity using such a massive Corgi butt.


+ They float for some reason

AND NOW YOU KNOW