Is It Possible To Have Entire Planets Composed of Antimatter

[Dayton3]

I was wondering if it was theoretically possible that somewhere in the galaxy you might have such a mass of naturally occurring antimatter that it formed a planet?

I've always figured that all antimatter in our universe had to be manufactured.

But I'm wondering if there was the possibility (even theoretical) of large amounts being naturally occurring.

I had a fan story that focused on such a world. It was polished into a completely featureless smooth ball surrounded by radiation from normal matter particles in space colliding with it continually.

 

[SamuraiBlue]

Theoretically yes since it is said that at the point of the big bang, there was equal amount of regular matter and anti matter.
I don't think there would be a single planet consisting of anti-matter in a regular matter planetary system though since matter and anti-matter annihilate each other at point of contact.

 

[Ronald Held]

In principle but how would you get an antimatter planet in a matter dominated system?

 

[iguana_tonante]

Re: Is It Possible To Have Entire Planets Composed of Antima

SamuraiBlue said:
Theoretically yes since it is said that at the point of the big bang, there was equal amount of regular matter and anti matter.

Yes, but (for reasons still largely unknown) there was a slight overabundance of matter, so when matter and antimatter collided and annihilated each others into photons, they leaved just a handful of matter (that is all we have today). So it's near impossible that we could have a shitload of antimatter coalesced in a planet in our galaxy: I strongly doubt that there is enough free antimatter in the whole galaxy for the mass-equivalent of a Earth-sized planet, ever.

There are some wild speculations about antimatter galaxies in distant parts of the universe (so that they will not encounter matter in their whole life), but at the current understanding they are little less than bogus.

 

[Christopher]

Dayton3 said:
I've always figured that all antimatter in our universe had to be manufactured.

Actually, small quantities of antimatter (well, antiparticles) are created routinely by cosmic-ray bombardment of planetary atmospheres. Any intense enough burst of energy results in pair production -- by E=MC^2, energy and mass are interchangeable, and when high enough concentrations of energy arise, they turn into particle-antiparticle pairs, like annihilation in reverse. High-energy cosmic-ray collisions are energetic enough to do the trick, producing both normal particles and antiparticles.

In fact, these antiparticles can be captured in planetary magnetic fields, and the planet in our solar system that has the densest concentration of antiparticles in its magnetic field is Earth itself (though Saturn has a larger amount overall, less densely concentrated). Of course, it's only a trace amount, nowhere near enough to power a sci-fi-style matter-antimatter engine, but it could potentially be harvested as a "catalyst" for antimatter-initiated fission or fusion thrusters and used to power interplanetary probes. There's a discussion of it in these two links:

http://www.centauri-dreams.org/?p=1567
http://www.centauri-dreams.org/?p=1569

Full-size antimatter planets are unlikely; of course, given the way planets and stars form, they'd have to be part of entire star systems made of antimatter, which would have to be formed in turn from entire galaxies made of antimatter. It's long been hypothesized that there could be distant, very remote "pockets" of antimatter in the universe, maybe isolated regions where the AM was clumped more densely than the M and "won" the competition, but we've never observed anything of the sort. Of course, it would be difficult to determine by telescopic observation whether a galaxy was made of matter or antimatter, since they only differ in charge and/or spin of the particles.

 

[iguana_tonante]

Re: Is It Possible To Have Entire Planets Composed of Antima

Christopher said:
It's long been hypothesized that there could be distant, very remote "pockets" of antimatter in the universe [...] Of course, it would be difficult to determine by telescopic observation whether a galaxy was made of matter or antimatter, since they only differ in charge and/or spin of the particles.

And unfortunately the only ways we currently know to detect something so far (electromagnetic radiation and gravitational effects) are insensible to the difference between matter and antimatter: antiparticles have the same mass as their matter counterparts, and the quanta of electromagnetic radiation (photons) are the antiparticles of themselves. Tough luck.

 

[Ronald Held]

Re: Is It Possible To Have Entire Planets Composed of Antima

You may be able to detect the radiation coming from the matter/antimatter annihilation coming from the interface between the antimatter and matter zones.

 

[Jarvis]

Re: Is It Possible To Have Entire Planets Composed of Antima

IMO only in an antimatter universe, because the magnetic field that would need to sustain it would collapse before any planet could form.

Far more likely is a sort of "Gamma field", an area of space where matter and antimatter collide to produce extreme levels of radiation.

Just my opinion though.

 

[Ronald Held]

Re: Is It Possible To Have Entire Planets Composed of Antima

That is one thing I had in mind.

 

[Jarvis]

Re: Is It Possible To Have Entire Planets Composed of Antima

Ronald Held said:
That is one thing I had in mind.

On a much smaller scale this effect has been observed during solar flares from our very own sun.

 

[JGordon]

Re: Is It Possible To Have Entire Planets Composed of Antima

On a side note, Larry Niven had a short story about an anti-matter solar system speeding through our galaxy that almost took out a couple of explorers who didn't know it was an antimatter system. I think it was in the Crashlander collection, but I can't recall exactly.

 

[SamuraiBlue]

Re: Is It Possible To Have Entire Planets Composed of Antima

Jarvis said:
IMO only in an antimatter universe, because the magnetic field that would need to sustain it would collapse before any planet could form.

Just my opinion though.

I don't understand why?
In theory positrons would have the same electro-magnetic force and gravity would be the key force in clumping up matter into a planet.

 

[Jarvis]

Re: Is It Possible To Have Entire Planets Composed of Antima

SamuraiBlue said:

Jarvis said:
IMO only in an antimatter universe, because the magnetic field that would need to sustain it would collapse before any planet could form.

Just my opinion though.

I don't understand why?
In theory positrons would have the same electro-magnetic force and gravity would be the key force in clumping up matter into a planet.

But antimatter decays a such an extreme rate in a matter enviroment that long before it had cooled enough to condense into anything that could clump together it would have turned into Gamma radiation.

On the other hand you may be able to form something within a dyson sphere where you could generate an artificial field.

Fun stuff though.

 

[SamuraiBlue]

Re: Is It Possible To Have Entire Planets Composed of Antima

Jarvis said:

But antimatter decays a such an extreme rate in a matter enviroment that long before it had cooled enough to condense into anything that could clump together it would have turned into Gamma radiation.

On the other hand you may be able to form something within a dyson sphere where you could generate an artificial field.

Fun stuff though.

Anti-matter only decays(annihilate) in contact with matter, anit-matter particle's life time is said to be the same with the matter counter-parts.
Electron - Positron
Neutron - antineutron
Proton - antiproton

Although there is no real vacuum in space with various gaseous particles floating around but if a region of space where antimatter was to win the tug fo war then particles that occupies that space would be in theory antimatter as well, so annihilation would not occur.

 

[Ronald Held]

Re: Is It Possible To Have Entire Planets Composed of Antima

I do not see any major reason, why a large antimatter interstellar cloud could not be collapsed to form a planetary system, if the matter density around it was not too high.

 

[Jarvis]

Re: Is It Possible To Have Entire Planets Composed of Antima

I agree that in an equaly balanced universe you could have anti matter behaving in such a way, but the best prediction would say that CP-violation prevented our universe from from being balanced within the first moments of the Big Bang. Add to this the lack of evidence that enough anti matter events take place(ie lack of 511 Mev gamma events) and that those which have been observed can be explained as having their origin after the time of the Big Bang and from a personal stand point I would have to say that I just don't think that even with inflation taken into account enough antimatter could survive for long enough to form a planet.

 

[Christopher]

Re: Is It Possible To Have Entire Planets Composed of Antima

SamuraiBlue said:
Although there is no real vacuum in space with various gaseous particles floating around but if a region of space where antimatter was to win the tug fo war then particles that occupies that space would be in theory antimatter as well, so annihilation would not occur.

You're right that if such a planet or solar system were to exist within a matter galaxy, it could probably survive for an indefinite period of time, suffering only gradual erosion by contact with the interstellar medium, extrastellar comets, etc.

The limiting factor here, though, is not destruction but creation. The problem is that an antimatter planet couldn't form in the first place in a matter galaxy. Stars and planets are formed out the interstellar gas and dust of the galaxy, much of which comes from the remains of earlier stars in that galaxy. Every atom on the Earth other than hydrogen or helium was formed in the core of some ancient, long-dead star, or during its supernova.

So every star and planet within a galaxy is an integral part of that galaxy, made up of stuff that used to be part of other stars and planets in that galaxy. And star systems don't form individually; they form in nebulae known as stellar nurseries, which spawn "litters" of dozens or hundreds of stars. The whole galactic system is a single interconnected ecology.

So antimatter stars and planets could only form in an entire galaxy made of antimatter.

 

[SamuraiBlue]

Re: Is It Possible To Have Entire Planets Composed of Antima

Christopher said:

The limiting factor here, though, is not destruction but creation. The problem is that an antimatter planet couldn't form in the first place in a matter galaxy. Stars and planets are formed out the interstellar gas and dust of the galaxy, much of which comes from the remains of earlier stars in that galaxy. Every atom on the Earth other than hydrogen or helium was formed in the core of some ancient, long-dead star, or during its supernova.

So every star and planet within a galaxy is an integral part of that galaxy, made up of stuff that used to be part of other stars and planets in that galaxy. And star systems don't form individually; they form in nebulae known as stellar nurseries, which spawn "litters" of dozens or hundreds of stars. The whole galactic system is a single interconnected ecology.

So antimatter stars and planets could only form in an entire galaxy made of antimatter.

Yes I am aware of those aspects and I have no quarrel with it but I once read in a sci-fi novel hypothesize that even if matter/anti-matter where to exist in close proximity within our galaxy the matter/anti-matter borderline will be energetically violent preventing cascade matter/anti-matter interaction. The borderline will be in constant energy eruptions making it difficult for either particle to get close to the boarderline for each other to enteract.
A close analogy would be a droplet of water on a superheated fryingpan, the contact area of the droplet is violently evaporating developing a buffer between the fryingpan and the remaining water within the droplet to make contact making it harder for the droplet of water to evaporate compared to a moderately heated fryingpan.

 

[Christopher]

Re: Is It Possible To Have Entire Planets Composed of Antima

^^So you're proposing that there could have been pockets of antimatter gas/dust that remained separate from the matter gas/dust of the galaxy because of this edge repulsion effect, and formed star systems within them? I don't know... the idea of the edge repulsion sounds plausible, but I'd think that the effect of that would be to push the antimatter pocket out of the galaxy altogether. After all, if it gets repulsed from any region dominated by matter, and it's surrounded by a whole galaxy made of matter, it would tend to be repulsed from the whole thing.

On second thought, though, I'm skeptical about the edge repulsion. That novel was correct about the basics -- if an unconfined M/AM reaction begins, the energy of the initial annihilation would heat the gases enough to blow them apart and halt the reaction before it progresses. But there we're talking about concentrations dense enough for a fair number of annihilations to occur in the first place. Here, we're talking about interstellar gas and dust, where you might have one particle per cubic centimeter. The odds of any one particle hitting an antiparticle would be so low that the particles and antiparticles could intermingle significantly with very little interaction/annihilation. In fact, we know for certain that this happens, because as I said above, there are already plenty of antiparticles up in orbit of Earth, Saturn, and other worlds, held there by their magnetic fields. There are plenty of particles there too, but annihilations are rare because the particles are so tiny and the spaces between them so comparatively huge.

So if you started out with a proto-galaxy containing a mix of matter and antimatter, I think they'd pretty much intermingle rather than being in separate clumps with clear repulsive boundaries between them. If a region of mixed matter/antimatter gas then began to condense -- the first step of forming a star system -- then as it got denser, annihilations would become more frequent, and the proto-system would get blown apart before it could form.

Either way, I still don't believe you could have antimatter stars and planets in a matter galaxy. Only entire galaxies of matter and separate galaxies of antimatter.

 

[Ronald Held]

Re: Is It Possible To Have Entire Planets Composed of Antima

I think it is unclear what is physically realizable, since I have not seen any simulations on this.