| 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) | 0.0004 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. | |
| Detection method | Pulsar timing | |
| Discovery site | Melbourne, Australia | |
| Discovery status | Confirmed | |
| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | 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, or diamond.[1] 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 heavy 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 diamond planets had been theoretically postulated.
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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.[2] The planet was confirmed through pulsar timing, in which small modulations detected in the highly regular pulsar signature are measured and extrapolated.[3] 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.[2]
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 (now that all fusion reactions have stopped, it was reclassified), forming a substance similar to that of diamond.[2]
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.[2] 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).[2]
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] Thus, it must be partially composed of degenerate matter. It is slightly more massive than Jupiter.[1] Because it is hypothesized to be the remnant of a white dwarf, it is believed to be composed of oxygen and carbon (as opposed to hydrogen and helium, which composes 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] and according to Bailes "If you could grab big chunks and bring it home you could turn it into a pretty useful diamond.".
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], and would thus fit inside the Sun if compared to the Solar System.[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.[2][better reference needed]
| Preceded by Kepler-10b |
Most dense planet 2011 — |
Succeeded by current |
| Preceded by Kepler-10b |
Most dense exoplanet 2011 — |
Succeeded by current |