Quark star
Encyclopedia
A quark star or strange star is a hypothetical type of exotic star
composed of quark matter, or strange matter
. These are ultra-dense phase
s of degenerate matter
theorized to form inside particularly massive neutron star
s.
It is theorized that when the neutron-degenerate matter which makes up a neutron star
is put under sufficient pressure due to the star's gravity, the individual neutron
s break down into their constituent quark
s – up quark
s and down quark
s. Some of these quarks may then become strange quarks and form strange matter. The star
then becomes known as a "quark star" or "strange star", similar to a single gigantic hadron
(but bound by gravity rather than the strong force
). Quark matter/strange matter is one candidate for the theoretical dark matter
that is a feature of several cosmological
theories.
Other theoretical work contends that, "A sharp interface between quark matter and the vacuum would have very different properties from the surface of a neutron star"; and, addressing key parameters like surface tension
and electrical forces that were neglected in the original study, the results show that as long as the surface tension is below a low critical value, the large strangelet
s are indeed unstable to fragmentation and strange stars naturally come with complex strangelet crusts, analogous to those of neutron stars.
on April 10, 2002 detected two candidates, designated RX J1856.5-3754
and 3C58
, which had previously been thought to be neutron stars. Based on the known laws of physics, the former appeared much smaller and the latter much colder than it should be, suggesting that they are composed of material denser than neutron-degenerate matter. However, these observations are met with skepticism by researchers who say the results were not conclusive; and since the late 2000s the possibility that RX J1856 is a quark star has been excluded (see RX J1856.5-3754
).
Another star, XTE J1739-285
, has been observed by a team led by Philip Kaaret of the University of Iowa
and reported as a possible candidate.
It remains to be seen how the question of quark star or strange star existence will play out.
It was reported in 2008 that observations of supernovae SN2006gy, SN2005gj and SN2005ap also suggest the existence of quark stars. It has been suggested that the collapsed core of supernova SN1987A may be a quark star.
Exotic star
An exotic star is a compact star composed of something other than electrons, protons, and neutrons balanced against gravitational collapse by degeneracy pressure or other quantum properties...
composed of quark matter, or strange matter
Strange matter
Strange matter is a particular form of quark matter, usually thought of as a "liquid" of up, down, and strange quarks. It is to be contrasted with nuclear matter, which is a liquid of neutrons and protons , and with non-strange quark matter, which is a quark liquid containing only up and down quarks...
. These are ultra-dense phase
Phase (matter)
In the physical sciences, a phase is a region of space , throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, and chemical composition...
s of degenerate matter
Degenerate matter
Degenerate matter is matter that has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle...
theorized to form inside particularly massive neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
s.
It is theorized that when the neutron-degenerate matter which makes up a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
is put under sufficient pressure due to the star's gravity, the individual neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s break down into their constituent quark
Quark
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...
s – up quark
Up quark
The up quark or u quark is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons and protons of atomic nuclei...
s and down quark
Down quark
The down quark or d quark is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the up quark, forms the neutrons and protons of atomic nuclei...
s. Some of these quarks may then become strange quarks and form strange matter. The star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
then becomes known as a "quark star" or "strange star", similar to a single gigantic hadron
Hadron
In particle physics, a hadron is a composite particle made of quarks held together by the strong force...
(but bound by gravity rather than the strong force
Strong interaction
In particle physics, the strong interaction is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. As with the other fundamental interactions, it is a non-contact force...
). Quark matter/strange matter is one candidate for the theoretical dark matter
Dark matter
In astronomy and cosmology, dark matter is matter that neither emits nor scatters light or other electromagnetic radiation, and so cannot be directly detected via optical or radio astronomy...
that is a feature of several cosmological
Physical cosmology
Physical cosmology, as a branch of astronomy, is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. For most of human history, it was a branch of metaphysics and religion...
theories.
Strange star
Recent theoretical research has found mechanisms by which quark stars with "strange quark nuggets" may decrease the objects' electric fields and densities from previous theoretical expectations, causing such stars to appear very much like—nearly indistinguishable from—neutron stars. However, the team of Prashanth Jaikumar, Sanjay Reddy and Andrew W. Steiner made some fundamental assumptions that led to uncertainties in their theory large enough that the case for it is not yet solid. More research, both observational and theoretical, remains to be done on strange stars in the future.Other theoretical work contends that, "A sharp interface between quark matter and the vacuum would have very different properties from the surface of a neutron star"; and, addressing key parameters like surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...
and electrical forces that were neglected in the original study, the results show that as long as the surface tension is below a low critical value, the large strangelet
Strangelet
A strangelet is a hypothetical particle consisting of a bound state of roughly equal numbers of up, down, and strange quarks. Its size would be a minimum of a few femtometres across . Once the size becomes macroscopic , such an object is usually called a quark star or "strange star" rather than a...
s are indeed unstable to fragmentation and strange stars naturally come with complex strangelet crusts, analogous to those of neutron stars.
Other theorized quark formations
- Jaffe 1977, suggested a four-quark state with strangeness (qs).
- Jaffe 1977 suggested the H dibaryonDibaryonDibaryons are a large family of hypothetical particles that would consist of six quarks of any flavours. They are predicted to be fairly stable once formed...
, a six-quark state with equal numbers of up-, down-, and strange quarks (represented as uuddss or udsuds). - Bound multi-quark systems with heavy quarks (QQ).
- In 1987, a pentaquarkPentaquarkA pentaquark is a hypothetical subatomic particle consisting of four quarks and one antiquark bound together . As quarks have a baryon number of +, and antiquarks of −, it would have a total baryon number of 1, thus being classified as an exotic baryon...
state was first proposed with a charm anti-quark (qqqs). - Pentaquark state with an antistrange quark and four light quarks consisting of up- and down-quarks only (qqqq).
- Light pentaquarks are grouped within an antidecuplet, the lightest candidate, Ө+.
- This can also be described by the diquark model of Jaffe and Wilczek (QCDQuantum chromodynamicsIn theoretical physics, quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
).
- This can also be described by the diquark model of Jaffe and Wilczek (QCD
- Ө++ and antiparticle −−.
- Doubly strange pentaquark (ssdd), member of the light pentaquark antidecuplet.
- Charmed pentaquark Өc(3100) (uudd) state was detected by the H1 collaboration.
Observed overdense neutron stars
Statistically, the probability of a neutron star being a quark star is low, so in the Milky Way Galaxy there will only be a small population of quark stars (but, if it is correct that overdense neutron stars turn into quark stars, that makes the possible number of quark stars higher than was originally thought, as we would be looking for the wrong type of star). Quark stars and strange stars are entirely hypothetical , but observations released by the Chandra X-Ray ObservatoryChandra X-ray Observatory
The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. It was named in honor of Indian-American physicist Subrahmanyan Chandrasekhar who is known for determining the maximum mass for white dwarfs. "Chandra" also means "moon" or "luminous" in Sanskrit.Chandra...
on April 10, 2002 detected two candidates, designated RX J1856.5-3754
RX J1856.5-3754
RX J1856.5-3754 is a nearby neutron star in Corona Australis. It is believed to have been created by a supernova explosion of its companion star about one million years ago and is moving 108 km/s across the sky...
and 3C58
3C58
3C58 or 3C 58 is a pulsar and surrounding synchrotron nebula within the Milky Way that is possibly associated with the supernova SN 1181. There are, however, signs that indicate that it could be several thousand years old, and thus not associated with that supernova...
, which had previously been thought to be neutron stars. Based on the known laws of physics, the former appeared much smaller and the latter much colder than it should be, suggesting that they are composed of material denser than neutron-degenerate matter. However, these observations are met with skepticism by researchers who say the results were not conclusive; and since the late 2000s the possibility that RX J1856 is a quark star has been excluded (see RX J1856.5-3754
RX J1856.5-3754
RX J1856.5-3754 is a nearby neutron star in Corona Australis. It is believed to have been created by a supernova explosion of its companion star about one million years ago and is moving 108 km/s across the sky...
).
Another star, XTE J1739-285
XTE J1739-285
|- style="vertical-align: top;"| Distance | 39.000 LyXTE J1739-285 is a neutron star, in the constellation Ophiuchus, situated approximately 39,000 light-years from Earth...
, has been observed by a team led by Philip Kaaret of the University of Iowa
University of Iowa
The University of Iowa is a public state-supported research university located in Iowa City, Iowa, United States. It is the oldest public university in the state. The university is organized into eleven colleges granting undergraduate, graduate, and professional degrees...
and reported as a possible candidate.
It remains to be seen how the question of quark star or strange star existence will play out.
It was reported in 2008 that observations of supernovae SN2006gy, SN2005gj and SN2005ap also suggest the existence of quark stars. It has been suggested that the collapsed core of supernova SN1987A may be a quark star.
See also
- Quark-novaQuark-novaA quark-nova is a hypothetical type of supernova that could occur if a neutron star spontaneously collapsed to become a quark star. The concept of quark-novae was suggested by Dr. Rachid Ouyed and Drs. Dey and Dey...
- Quantum chromodynamicsQuantum chromodynamicsIn theoretical physics, quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons . It is the study of the SU Yang–Mills theory of color-charged fermions...
- Neutron stars - neutron matter - neutron-degenerate matterDegenerate matterDegenerate matter is matter that has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle...
- neutronNeutronThe neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... - deconfinementDeconfinementIn physics, deconfinement is the property of a phase in which certain particles are allowed to exist as free excitations, rather than only within bound states...
- Tolman-Oppenheimer-Volkoff limitTolman-Oppenheimer-Volkoff limitThe Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of stars composed of neutron-degenerate matter . The TOV limit is analogous to the Chandrasekhar limit for white dwarf stars.-History:...
on the mass of a neutron star. - Compact starCompact starIn astronomy, the term compact star is used to refer collectively to white dwarfs, neutron stars, other exotic dense stars, and black holes. These objects are all small for their mass...
- Exotic starExotic starAn exotic star is a compact star composed of something other than electrons, protons, and neutrons balanced against gravitational collapse by degeneracy pressure or other quantum properties...
- Neutron starNeutron starA neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
- PulsarPulsarA pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...
- MagnetarMagnetarA magnetar is a type of neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious high-energy electromagnetic radiation, particularly X-rays and gamma rays...
- White dwarfWhite dwarfA white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
- Stellar black holeStellar black holeA stellar black hole is a black hole formed by the gravitational collapse of a massive star. They have masses ranging from about 3 to several tens of solar masses...
- Exotic star
- Degenerate matterDegenerate matterDegenerate matter is matter that has such extraordinarily high density that the dominant contribution to its pressure is attributable to the Pauli exclusion principle. The pressure maintained by a body of degenerate matter is called the degeneracy pressure, and arises because the Pauli principle...
- QCD matterQCD matterQuark matter or QCD matter refers to any of a number of theorized phases of matter whose degrees of freedom include quarks and gluons. These theoretical phases would occur at extremely high temperatures and densities, billions of times higher than can be produced in equilibrium in laboratories...
- Quark-gluon plasmaQuark-gluon plasmaA quark–gluon plasma or quark soup is a phase of quantum chromodynamics which exists at extremely high temperature and/or density. This phase consists of asymptotically free quarks and gluons, which are several of the basic building blocks of matter...
- StrangeletStrangeletA strangelet is a hypothetical particle consisting of a bound state of roughly equal numbers of up, down, and strange quarks. Its size would be a minimum of a few femtometres across . Once the size becomes macroscopic , such an object is usually called a quark star or "strange star" rather than a...
- Quark matter
- NeutroniumNeutroniumNeutronium is a proposed name for a substance composed purely of neutrons. The word was coined by scientist Andreas von Antropoff in 1926 for the conjectured "element of atomic number zero" that he placed at the head of the periodic table...
- Preon matter
- QCD matter
External links
- Neutron Star/Quark Star Interior (image to print)
- Quark star glimmers, NatureNature (journal)Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
, April 11, 2002. - Debate sparked on quark stars, CERN Courier 42, #5.
- Wish Upon a Quark Star, Paul Beck, Popular Science, June 2002.
- Curious About Astronomy: What process would bring about a quark star?
- RX J185635-375: Candidate Quark Star, Astronomy Picture of the Day, April 14, 2002.
- Quarks or Quirky Neutron Stars?, Mark K. Anderson, Wired News, April 19, 2002.
- Strange Quark Stars, Ask an Astrophysicist, question submitted April 12, 2002.
- Seeing "Strange" Stars, physorg.com, February 8, 2006.
- Quark Stars Could Produce Biggest Bang, spacedaily.com, June 7, 2006.
- Meissner Effect in Strange Quark Stars, Brian Niebergal, web page, University of CalgaryUniversity of CalgaryThe University of Calgary is a public research university located in Calgary, Alberta, Canada. Founded in 1966 the U of C is composed of 14 faculties and more than 85 research institutes and centres.More than 25,000 undergraduate and 5,500 graduate students are currently...
. - Quark Stars Involved in New Theory of Brightest Supernovae - The first-ever evidence of a neutron star collapsing into a quark star is announced, Space.com, 3 June 2008
- Quark Stars, Alternate View Column AV-114, John G. Cramer, Published in the November-2002 issue of Analog Science Fiction & Fact Magazine
