Pulsar in the Sky, With Diamonds

A new Pulsar Planet has been discovered, and it is a beaut.

In a paper published in Science, Matthew Bailes and collaborators announce the discovery of the third pulsar planet, and this one is a wonder.

Very nice video summary bu Matthew hisself

The first exoplanets discovered, were found around a pulsar: PSR B1257+12.
This is because planets are ubiquitous and pulsars allow precision measurements enabling planet detection.

That was almost 20 years ago, since then one other pulsar planet system has been discovered, PSR B1620-26, which was quite different from 1257+12.

Pulsar observations are a long term game, you do better, generally, by having long time series, and more systems are being continuously discovered and monitored - as opposed to main sequence stars, a lot of those are already known.

Now, finally, yet another exoplanet system around a pulsar, millisecond pulsar, has been discovered, and this one is even more different.
The paper: "Transformation of a Star into a Planet in a Millisecond Pulsar Binary." by Bailes et al. appears in the 26th of August issue of Science, and describes observations of PSR J1719-1438, recently discovered by the Australian Parkes radio observatory

Open Days: Opera at the Dish - image: John Sarkissian, CSIRO

The pulsar is a millisecond pulsar, with a 5.7 ms spin period, it is a little over a kpc away (call it about 4,000 light years). The system is old, most likely several billion years old.

The object orbiting it is Jupiter mass, with some uncertainty in the exact mass due to as yet unmeasured inclination, has an orbital period of 2.2 housrs!
That implies an orbital radius less than a solar radius!
The orbit is, near as we can tell, perfectly circular.

Further, the object is not overflowing its Roche lobe, implying a minimum mean density of 23! Possibly considerably larger.

From both observational constraints, and from theoretical grounds based on models of the origin of the object, it is most likely a pure cold crystalline carbon core of a low mass star, with the rest of the star accreted, blown away and ablated by the millisecond pulsar formation process.

Yes, it is a 1031 carat diamond.
That is 10,000,000 trillion trillion carats of hot sparkly rock!

Probably a yellow diamond, likely has some trace nitrogen inclusions, probably glowing red on one side, as the pulsar radiation blasting out at about 1/3 solar luminosity, is heating the tidally locked near side to a few thousand K (Teff

So, how did we get this?

Well, almost certainly this is the end stage of an ultracompact low mass x-ray binary for a particular combination of masses and orbital parameters.

Basically, the pulsar had a low mass companion whose orbit was close enough to come into contact with the pulsar after it formed, and the star transferred mass onto the pulsar as it evolved, spinning the pulsar up to the current millisecond period in the process.
The orbit of the star moved closer as it evolved, and the interaction became stronger, and some of the stellar mass was blown away, and then as the pulsar lit up, possibly spinning faster than it is now, the pulsar radiation ablated some of the last bit of the star, similar to the Black Widow Pulsar


Then, just before the star was ablated away completely, the compact core of the star, which is essentially pure carbon at that point, fell back into a denser remnant, which could no longer be ablated significantly, as the pulsar luminosity faded, leaving a cold, carbon crystal, the mass of Jupiter.

A different way to make a different planet.

Depending on the exact temperature of the planet, with a bit of luck, it ought to be observable with Hubble, and the nearside and farside temperature differences ought to be quite visible as the planet orbits around the pulsar.

CSIRO press release - with sound files!

Pretty pictures and animation

click to embiggen


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About time for some more pulsar planets. Now we can all have a nice little fight over whether this object actually counts as a genuine planet. :-)

Hm, it is round, "gravitationally dominant", low mass - yup, it is a planet, at least this year...

@V - it'll be tetrahedral diamond in the upper layers to the surface, I think - at higher pressures there are transitions to cubic and hexahedral symmetries, don't have the phase diagram memorized...

That is quite possibly the most awesome thing I have ever heard. :D

By Left_Wing_Fox (not verified) on 25 Aug 2011 #permalink

presumably the outermost layer will be graphite, down to 5 or 6 Gpa. With a density of 23 (diamond is 3.5, and essentially incompressable), most of it will be some sort of degenerate carbon goo.

The diamond/metal transition pressure keeps getting adjusted upward every time a experiment fails to find it; last I checked ( a decade ago), it was thought to be about 1200 GPa

Hi Vagueofgodalming.

We know that most of the inner part of the star is done of crystallized carbon/oxygen and following the wording of the NASA-Goddard web page

"Since a diamond is just crystallized carbon, one may make
the comparison btw a cool carbon/oxygen white dwarf and a diamond."

I believe I asked you this before, but.....

....why the big delay in finding more pulsar planets? It's been, what, 25 years since the original four?

#1 and #3: If the assumptions are correct, this thing started as a star. The issue is to define if and when a star becomes a planet.

#6: I'm not a solid state physicist, but I'm dubious about the density of the object. The Roche lobe is valid for loose piles of rubble, but if the object is a solid lump of coal that has no loose parts, its density need not be 23. It stays together via covalent bonds, not gravity. With a circular orbit and gravitational lock-in there are no tidal forces to worry about.

By Lassi Hippeläinen (not verified) on 26 Aug 2011 #permalink

@Lab - graphite is more stable than diamond at low temperatures and pressures but it is marginal whether this object is cool enough for graphite even at the surface - maybe on the farside there is a graphite layer, and diamond on the nearside.
At higher pressures the carbon ought to transition to cubic lattice, with possibly a higher co-ordination intermediate state, like some bi-cubic. Then at higher temperatures the material is just a fluid.

@Lassi - tidal forces are still there even with a circular orbit, the gradient of the gravitational force across the object is still there. At the energies involved any covalent bonds are irrelevant, astrophysical objects are usually best modeled as fluids when considering gravitational stresses, especially within a million km of a neutron star...

@Matt - only 20 years... discovery pace of PSRs is slow, and the major telescopes were essentially all out of action for several years. PSR planets are moderately rare, O(1%) of MSPs seem to have one.

On the star vs planet issue.
Currently, the definition of a planet is WYSIWYG - there is no consideration for formation mechanism. Further, the formation mechanism is conjectured, not observed.
By current definition this object is unambiguously a planet.

In the latest issue of Science 8/26/11 there is a report by Bailes et al describing the discovery and properties of a new pulsar-planet system, the third so far.

Pulsar-planets were first discovered in 1992.

In 1989, in the International Journal of Theoretical Physics, vol. 28, No. 12, pp. 1503-1532, it was definitively predicted by a new paradigm called the self-similar cosmological paradigm (now referred to as Discrete Scale Relativity) that planetary-mass objects would be discovered orbiting stellar-mass ultracompact objects.

Discrete Scale Relativity was the only theory to ever definitively predict systems like pulsar-planets, explain how they form, and explain why they should not be unusually rare objects.

If you would like to read more about this definitive scientific prediction by Discrete Scale Relativity, see Selected Paper #4 at http://www3.amherst.edu/~rloldershaw , which was also published in IJTP.

It will be most interesting to see the more detailed properties of this system once further research is done on it, especially with the new Russian Spektr-R radio wave satellite that can be linked to Earth-based radio telescopes to give unprecedented resolution of radio sources, like a pulsar-planet system.

Game On!
Fractal Cosmology

Could this object have formed from a carbon dwarf, which partially blown away by supernova explosion of a neighbour star?

By Alex Besogonov (not verified) on 26 Aug 2011 #permalink

Of course according to the IAU:

A "planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

Since this object fails requirement (a), it is unambiguously not a planet.

Incidentally the IAU definition does not make any kind of requirement on the upper mass limit for planet. If a star ended up orbiting the Sun (if the Sun had an encounter with a binary system perhaps), then that star would count as a planet under the definition...

Your way over my head, but I like to think I can learn more that I know today. Awesome! At least I can share this with my young lelatives- might inspire them to persue the field of science, physics, astrophysics, who knows. Thanks.

By Lela Wakely (not verified) on 28 Aug 2011 #permalink

Speaking as someone who was at the IAU meeting in 2006, that definition is set for objects in our Solar System (we didn't worry about other stars orbiting the Sun at the time; if it happens, I promise you we'll have a meeting of the IAU to discuss how to name such an object). Outside the solar system, the definition isn't as clear, but generally it's considered that objects smaller than 13 Jupiter masses orbiting stars are planets. (Haven't got to the point of finding KBO-like things around other stars yet...)

To be honest I disagree with the 13 Jupiter mass limit as being particularly useful. It doesn't work too well when it comes up against, say, Upsilon Andromedae or BD+20°2457, which seem to me to suggest that nature occasionally builds deuterium-burning planets, or the various observations of stellar clusters which might indicate that nature occasionally builds non-deuterium-burning brown dwarfs...

As for this particular object, as I understand it carbon-oxygen white dwarfs (as opposed to theorists' nice simple pure carbon white dwarfs) typically crystallise oxygen at their centres with more carbon-rich material as you go outwards. I don't get why we would expect this thing to be mainly carbon, rather than mainly oxygen?