PSR J1719−1438 b is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

that was discovered on August 25, 2011, in orbit around

PSR J1719−1438 PSR J1719-1438 is a millisecond pulsar with a spin period of 5.8 ms located about 4,000 ly from Earth in the direction of Serpens Cauda, one minute from the border with Ophiuchus. Millisecond pulsars are generally thought to begin as no ...

, a

millisecond pulsar A millisecond pulsar (MSP) is a pulsar with a rotational period less than about 10 milliseconds. Millisecond pulsars have been detected in radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The leading theory for the origin of ...

. The

pulsar planet Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planets to be discovered were around a millisecond pulsar and were the first extrasolar planets to be confirmed as discovered. History ...

is most likely composed largely of crystalline carbon but with a

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

far greater than

diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the Chemical stability, chemically stable form of car ...

. PSR J1719-1438 b orbits so closely to its host star that its orbit would fit inside the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. The existence of such

carbon planet A carbon planet is a theoretical type of planet that contains more carbon than oxygen. Carbon is the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Marc Kuchner and Sara Seager coined the term "carbon ...

s had been theoretically postulated.

Observational history

PSR J1719−1438 was first observed in 2009 by a team headed by

Matthew Bailes Professor Matthew Bailes is an astrophysicist at the Centre for Astrophysics and Supercomputing, Swinburne University of Technology and the Director of OzGrav, the ARC Centre of Excellence for Gravitational Wave Discovery. In 2015 he won an A ...

Swinburne University of Technology Swinburne University of Technology (often simply called Swinburne) is a public research university based in Melbourne, Australia. It was founded in 1908 as the Eastern Suburbs Technical College by George Swinburne to serve those without access ...

in Melbourne, Australia. The orbiting planet was published in the journal ''

Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence for ...

'' on August 25, 2011. The planet was confirmed through

pulsar timing Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of ...

, in which small modulations detected in the highly regular pulsar signature are measured and extrapolated. Observatories in Britain, Hawaii, and Australia were used to confirm these observations.

Host star

PSR J1719−1438 is a pulsar some away from Earth in the

Serpens Serpens ( grc, , , the Serpent) is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by the 2nd-century astronomer Ptolemy, it remains one of the 88 modern constellations designated by the International ...

Cauda constellation, approximately one minute from the border with

Ophiuchus Ophiuchus () is a large constellation straddling the celestial equator. Its name comes from the Ancient Greek (), meaning "serpent-bearer", and it is commonly represented as a man grasping a snake. The serpent is represented by the constella ...

. The pulsar completes more than 10,000 rotations a minute. It is approximately across but with 1.4

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es.

Characteristics

PSR J1719−1438 b was, at the time of its August 25, 2011, discovery, the densest planet ever discovered, at nearly 20 times the density of Jupiter (about 23 times the density of water). It is slightly more massive than Jupiter. It is thought to be composed of oxygen and carbon (as opposed to hydrogen and helium, the main components of

gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...

s like Jupiter and Saturn). The oxygen is most likely on the surface of the planet, with increasingly higher quantities of carbon deeper inside the planet. The intense pressure acting upon the planet suggests that the carbon is crystallized, much like

is. PSR J1719−1438 b orbits its host star with a period of 2.17 hours and at a distance of 0.89 solar radius ().

Formation

It is highly unlikely that this planet would have formed before its parent pulsar, as the resulting supernova would destroy any nearby planets. It has been proposed that PSR J1719−1438 b is not a planet but a star. Specifically, PSR J1719−1438 b was a

yellow dwarf star A G-type main-sequence star (Spectral type: G-V), also often, and imprecisely called a yellow dwarf, or G star, is a main sequence, main-sequence star (luminosity class V) of stellar classification, spectral type G. Such a star has about 0.9 to 1 ...

similar to the Sun in a binary with PSR J1719−1438, a higher-mass star. PSR J1719−1438 swelled up to become a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Anta ...

, but the yellow dwarf star survived the supernova. Billions of years later, PSR J1719−1438 b became a red giant and then a

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

. The gravity from the pulsar stole hydrogen and helium, and the remaining carbon crystallized, forming the diamond planet.

Observational history

Host star

Characteristics

Formation

See also

References

Further reading