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rfmcdonaldThe newly-discovered planet of millisecond pulsar PSR J1719-1438 has gotten quite a lot of attention. In an era when exoplanets are found daily, it seems there's still room for surprises.
Sources give planet J1719-1438b a density in the area of 23 gram per cubic centimetre. This is dense. Earth, at standard pressure and temperature, has a density of some 5.5 grams per cubic centimetre, and diamond itself has a density of 3.5 grams per cubic centimetre. Who knows what sorts of conditions reign on that world?
J1719-1438b is just one body of many illustrating that the term "planet", as denoting a specific class of bodies that formed in specific ways distinct from other classes of bodies forming in other specific ways, is useless. J1719-1438b probably started off as a star.
The image of a glistening diamond planet is irresistible. What would it look like? astronomers have been asked in the various articles?
From what I know of colour in diamonds, Stappers is right. Diamonds' colours are lent by pollutants, hard radiation (like that produced by pulsars, say) turning diamonds green, the diamonds made up of irregularly-sized and -shaped carbon crystals known as carbondados being black in colour, and so on. J1719-1438b is a wonder, but its wonders are going to be far subtler than non-stop shine.
The new planet is far denser than any other known so far and consists largely of carbon. Because it is so dense, scientists calculate the carbon must be crystalline, so a large part of this strange world will effectively be diamond.
"The evolutionary history and amazing density of the planet all suggest it is comprised of carbon -- i.e. a massive diamond orbiting a neutron star every two hours in an orbit so tight it would fit inside our own Sun," said Matthew Bailes of Swinburne University of Technology in Melbourne.
Lying 4,000 light years away, or around an eighth of the way toward the center of the Milky Way from the Earth, the planet is probably the remnant of a once-massive star that has lost its outer layers to the so-called pulsar star it orbits.
Pulsars are tiny, dead neutron stars that are only around 20 kilometers in diameter and spin hundreds of times a second, emitting beams of radiation.
In the case of pulsar J1719-1438, the beams regularly sweep the Earth and have been monitored by telescopes in Australia, Britain and Hawaii, allowing astronomers to detect modulations due to the gravitational pull of its unseen companion planet.
The measurements suggest the planet, which orbits its star every two hours and 10 minutes, has slightly more mass than Jupiter but is 20 times as dense, Bailes and colleagues reported in the journal Science on Thursday.
In addition to carbon, the new planet is also likely to contain oxygen, which may be more prevalent at the surface and is probably increasingly rare toward the carbon-rich center.
Sources give planet J1719-1438b a density in the area of 23 gram per cubic centimetre. This is dense. Earth, at standard pressure and temperature, has a density of some 5.5 grams per cubic centimetre, and diamond itself has a density of 3.5 grams per cubic centimetre. Who knows what sorts of conditions reign on that world?
J1719-1438b is just one body of many illustrating that the term "planet", as denoting a specific class of bodies that formed in specific ways distinct from other classes of bodies forming in other specific ways, is useless. J1719-1438b probably started off as a star.
[J1719-1438b] orbits the pulsar in just 2 hours and 10 minutes, and the distance between the two objects is [600,000 kilometers] — a little less than the radius of our Sun. Second, the companion is so close to the pulsar that if its diameter was any larger than [60,000 km] — less than half the diameter of Jupiter — it would be ripped apart by the gravity of the pulsar.
“The density of the planet is at least that of platinum and provides a clue to its origin”, said Matthew Bailes from Swinburne University of Technology in Australia.
The team thinks that the planet is the tiny core that remained of a once-massive star after narrowly missing destruction by its matter being siphoned off toward the pulsar.
[. . .]
Pulsar J1719-1438 is a fast-spinning pulsar that’s called a millisecond pulsar. Amazingly, it rotates more than 10,000 times per minute, has a mass of about 1.4 times that of our Sun, but is only [20 km] in radius. About 70 percent of millisecond pulsars have companions of some kind: Astronomers think it is the companion that, as a star, transforms an old, dead pulsar into a millisecond pulsar by transferring matter and spinning it up to a very high speed. The result is a fast-spinning millisecond pulsar with a shrunken companion-most often a white dwarf.
“We know of a few other systems, called ultra-compact low-mass X-ray binaries, that are likely to be evolving according to the scenario above and may likely represent the progenitors of a pulsar like J1719-1438,” said Andrea Possenti, of INAF.
The image of a glistening diamond planet is irresistible. What would it look like? astronomers have been asked in the various articles?
Just what this weird diamond world is actually like close up, however, is a mystery.
"In terms of what it would look like, I don't know I could even speculate," said Ben Stappers of the University of Manchester. "I don't imagine that a picture of a very shiny object is what we're looking at here."
From what I know of colour in diamonds, Stappers is right. Diamonds' colours are lent by pollutants, hard radiation (like that produced by pulsars, say) turning diamonds green, the diamonds made up of irregularly-sized and -shaped carbon crystals known as carbondados being black in colour, and so on. J1719-1438b is a wonder, but its wonders are going to be far subtler than non-stop shine.
