PSR J1719-1438 b

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PSR J1719-1438 b
Extrasolar planet List of extrasolar planets
Parent star
Star PSR J1719-1438
Constellation Serpens
Right ascension (α) 17h 19m 10s
Declination (δ) −14° 38′ 01″
Distance ~3900 ly
(~1200 pc)
Spectral type Pulsar
Mass (m) ~1.4 M
Age >12.5 Gyr
Orbital elements
Semimajor axis (a) 0.004 AU
Eccentricity (e) < 0.06
Orbital period (P) 0.090706293 d
    (2.176951032 h)
Time of periastron (T0) 2,455,235.51652439 JD
Physical characteristics
Mass (m) ~1.02 MJ
(~330 M)
Radius (r) ≤0.4 RJ
(≤4 R)
Density (ρ) ≥23 g cm−3
Discovery information
Discovery date 25 August 2011
Discoverer(s) Matthew Bailes et al.
Discovery method Pulsar timing
Discovery site Parkes Observatory, Australia
Discovery status Confirmed
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

PSR J1719-1438 b is an extrasolar planet that was discovered on August 25, 2011 in orbit around PSR J1719-1438, a millisecond pulsar. The pulsar planet is most likely composed largely of crystalline carbon, but with a density far greater than diamond.[1][2] PSR J1719-1438 b and PSR J1719-1438 were formerly two stars in a binary star system, but after PSR J1719-1438 went supernova and became a pulsar, PSR J1719-1438 b expanded into its red giant phase and diminished into a white dwarf. The intense conditions of the system converted the white dwarf into a planet composed largely of elements like carbon and oxygen. PSR J1719-1438 b orbits so closely to its host star, the planet's orbit would fit inside the Sun. The existence of such carbon planets had been theoretically postulated.

Observational history[edit]

PSR J1719-1438 was first observed in 2009 by a team headed by Matthew Bailes of Swinburne University of Technology in Melbourne, Australia. The orbiting planet was published in the journal Science on August 25, 2011.[3] The planet was confirmed through pulsar timing, in which small modulations detected in the highly regular pulsar signature are measured and extrapolated.[4] Observatories in Britain, Hawaii, and Australia were used to confirm these observations.[1]


The pulsar was formed when the primary member of a binary star system experienced a supernova, leaving behind its rapidly spinning core, which became the pulsar itself. The secondary, less prominent companion was a main sequence star that became a red giant before shrinking into a white dwarf. During its life, the pulsar siphoned gases from the secondary star, speeding up as more matter was added to it.[3]

The white dwarf, however, did not enter an unstable orbit and merge with the pulsar, which happens to a significant minority of star-pulsar binary systems. Instead, the white dwarf stabilized at an orbit approximately one solar radius away from the pulsar. The proximity caused the white dwarf to lose the majority of its remaining matter, leaving behind a bare core. The intense gravitational pressure caused by the proximity crystallized the carbon-composed planet (because all fusion reactions had stopped, it was reclassified), forming a substance similar to that of diamond.[3]

Host star[edit]

Main article: PSR J1719-1438

PSR J1719-1438 is a pulsar some 4,000 light years away from Earth in the Serpens Cauda constellation, approximately one minute from the border with Ophiuchus. The pulsar completes more than 10,000 rotations a minute. It is approximately 12 miles across, but has a mass that is 1.4 solar masses.[3] The pulsar was originally part of a binary star system, with the other star being PSR J1719-1438 b (when it still completed fusion reactions).[3]


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).[1] It may be partially composed of degenerate matter.[citation needed] It is slightly more massive than Jupiter.[1] Because it is hypothesized to be the remnant of a white dwarf,[5] it is believed to be composed of oxygen and carbon (as opposed to hydrogen and helium, the main components of gas giants like Jupiter and Saturn). However, all known white dwarfs have densities that are on the order of millions of times the density of water and are composed of electron-degenerate matter, which makes this object extremely non-dense for a white dwarf. Also, white dwarfs emit light due to their temperature based on trapped heat from gravitational collapse. It is unknown why this hypothesized white dwarf remnant does not retain enough temperature to emit light.

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 diamond is.[1]

PSR J1719-1438 b orbits its host star with a period of 2.177 hours and at a distance of a little bit less than one (0.89) solar radius.[1]

PSR J1719-1438 b was formerly a star that was a red giant for a period in its lifetime. During this period, gas from PSR J1719-1438 b was pulled onto PSR J1719-1438 after it had become a pulsar, speeding up its rotation significantly. When PSR J1719-1438 b became a white dwarf, over 99.9% of its constituents were blown away because of its proximity to the pulsar, leaving behind a core that could no longer perform fusion reactions. The core was then reclassified as a planet.[3] [6]

See also[edit]

  • WASP-12b, a carbon planet
  • BPM 37093, a carbon star
  • EF Eridani, a star system with a compact star and a degraded planetary-mass former star


  1. ^ a b c d e f Hirschler, Ben (25 August 2011). "Astronomers discover planet made of diamond". Reuters. Retrieved 25 August 2011. 
  2. ^ Bailes, M.; Bates, S. D.; Bhalerao, V.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; d'Amico, N.; Johnston, S.; Keith, M. J. et al. (2011). "Transformation of a Star into a Planet in a Millisecond Pulsar Binary" (PDF). Science 333 (6050): 1717–20. arXiv:1108.5201. Bibcode:2011Sci...333.1717B. doi:10.1126/science.1208890. PMID 21868629. 
  3. ^ a b c d e f Redd, Nola Taylor (25 August 2011). "Surprise! Alien Planet Made of Diamond Discovered". TechMediaNetwork. Retrieved 25 August 2011. 
  4. ^ Hachman, Mark (25 August 2011). "Scientists Discover 'Diamond Planet' Orbiting Pulsar". Ziff Davis. Retrieved 25 August 2011. 
  5. ^
  6. ^ Bailes, M.; Bates, S. D.; Bhalerao, V.; Bhat, N. D. R.; Burgay, M.; Burke-Spolaor, S.; d'Amico, N.; Johnston, S.; Keith, M. J. et al. (2011). "Transformation of a Star into a Planet in a Millisecond Pulsar Binary" (PDF). Science 333 (6050): 1717–20. arXiv:1108.5201. Bibcode:2011Sci...333.1717B. doi:10.1126/science.1208890. PMID 21868629. 

Further reading[edit]

Preceded by
Most dense planet
2011 —present