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The Hunt for Ancient Antimatter

Antimatter’s great attraction from a propulsion standpoint is the ability to convert 100 percent of its mass into energy, a reaction impossible with fission or fusion methods. The trick, of course, is to find enough antimatter to use. We can produce it in particle accelerators but only in amounts that are vanishingly small. There is evidence that it is produced naturally, at least in trace amounts, in the relativistic jets produced by black holes and pulsars. Indeed, a cloud of antimatter 10,000 light years across has been described around our own galaxy’s center.

And at least one scientist, James Bickford (Draper Laboratory), has worked out ways to extract antimatter produced here in the Solar System, a method that he believes would be five orders of magnitude more cost effective than creating the stuff on Earth. But what about early antimatter, particles left over from the earliest days of the universe? According to prevalent theory, the universe may have been awash with the stuff shortly after the Big Bang, but most of it is assumed to have annihilated with ordinary matter, leaving only the slightly more numerous remnants of matter behind. Could any antimatter have survived?

Image: Antimatter is made up of elementary particles that have the same masses as their corresponding matter counterparts but the opposite charges and magnetic properties. This illustration shows what happens when a particle of antimatter collides with one of matter. The particles annihilate each other and produce energy according to Einstein’s famous equation, E=mc2, mostly in the form of gamma rays, which scientists are looking for using the Compton observatory. Secondary particles are also produced. Credit: CXC/M. Weiss.

Gary Steigman, who has been studying these matters at Ohio State, lays out current thinking on matter/antimatter asymmetry in the early universe in a new paper. A primordial imbalance between matter and antimatter seems to have been essential to the emergence of the universe we see. And the key to the possibility of antimatter surviving from the Big Bang era may be inflation, when spacetime itself seems to have expanded exponentially:

“If clumps of matter and antimatter existed next to each other before inflation, they may now be separated by more than the scale of the observable Universe, so we would never see them meet. But, they might be separated on smaller scales, such as those of superclusters or clusters, which is a much more interesting possibility.”

Usefully, we might be able to observe evidence for such antimatter in collisions between two galactic clusters. That signature would be marked by X-rays from the hot gases involved in the collision and the gamma rays associated with antimatter annihilation. And as we’ve seen in recent times, the Bullet Cluster is an excellent laboratory for such study, being the relatively nearby result of cluster collision. The data thus far garnered from the Chandra X-ray Observatory and the Compton Gamma Ray Observatory are setting strict limits on possible antimatter stores.

At least that’s true in the Bullet Cluster, where the antimatter signature simply does not appear. If antimatter is present, these results mean it amounts to less than three parts per million in this system. The search continues, with Steigman hoping to learn whether other colliding galaxy clusters show a similar paucity of antimatter. It would be helpful if an antimatter signature could tell us about the mysterious period of inflation — how long, for example, did it last? — but even Steigman calls this a long shot. “The collision of matter and antimatter is the most efficient process for generating energy in the Universe, but it just may not happen on very large scales,” says the scientist. “But I’m not giving up yet…”

The paper is Steigman, “When clusters collide: constraints on antimatter on the largest scales,” Journal of Cosmology and Astroparticle Physics 10 (2 October 2008). Available online. Also available at the arXiv site. See as well this Chandra news release.

Comments on this entry are closed.

  • James M. Essig November 3, 2008, 12:26

    Hi Paul;

    This is a most excellent article and a great topic for a thread.

    It may indeed be possible that huge deposits of antimatter lie beyond the extent of the observable universe with respect to Earth.

    Given the possibility that other such deposits may have originated from say an initial ratio of 10,000,000,001/10,000,000,000 antiprotons to protons or similar imbalance due to quantum fluctuations in the mattergy content of our universe before inflation, there might exist an ensemble of patch like alternating cells of matter and antimatter throughout our universe. In the event that our universe might be of infinite extent, the number of such antimatter cells as well as the number of matter cells might be infinite.

    As I am sure much of the readership of Tau Zero/Centauri Dreams is aware, at least some big bang models suggest that our universe may be a patch work of socalled domains wherein each domain would have its unique or rare combination of physical laws, values of fundamental constants, relative strengths of the fundamental forces within, relative mass and force charges of the fundamental particles within, number of fundamental particles etc.. However, if the domain theory is correct, the domains may range in size from much larger than the observable universe to infinite in size. Moreover, there may exist an ensemble of such domains and perhaps even an infinite number of such domains within our universe.

    Regardless of whether the domain theory has any validity or not, the possibility that other regions relatively near by and adjacent to our local would be matter occupied visible universe, might have the same physical laws, number of particle types, and relative strengths of fundamental constants, forces etc. that our would be strictly matter based observable universe has, but almost entirely consist of antimatter, even in terms of baryonic antimatter. If the domain theory is correct, than perhaps within our domain alone, there are numerous, an ensemble of, or even an infinite number of matter and antimatter cells as such.

    The possible existence of antimatter galactic or super-galactic clusters within our observable universe would have outstanding ramifications in terms of a very future advanced humanity to harness them. When one plugs the numbers into the relativistic rocket equation for an Isp of 300,000,000 seconds (not corrected by the value of 9.81) corresponding to an exhaust velocity of C, assumming rocket exhuast energy to ship kinetic energy conversion efficiency of 95 percent, or even somehow a whopping 99 percent, one can see how gamma factors of 1,000 and above can be achieved for sufficient but plausable carried on board supplies of matter and antimatter or antimatter.

    Any assymmetry between matter and antimatter might permit novel space time distortion effects such as those that could be used for space time distortion based interstellar and intergalactic transport system.

    The collection of antimatter within our solar system and within the antimatter cloud within our galaxy might permit a whole new meaning to the word mining.



  • Paul F. Dietz November 4, 2008, 16:56

    Another possibility is that the observed matter/antimatter asymmetry is due to a preferential sequestration of antimatter in nuggets of quark matter. Some recent work suggested that a diffuse x ray background from the center of the galaxy could be consistent with thermal radiation from these nuggets.

    If this is the case, there could be a large number of chunks of antimatter, with masses on the order of perhaps 100 tons, passing through the solar system at any time. Each such nugget would be quite small — maybe 10 microns across — and would be difficult to detect. But if we could detect them, it’s conceivable they could be followed and captured (by charging them up and pushing them around with electric fields.) A single such nugget, immersed in a gas of normal matter, would be a prodigious source of annihilation energy.


  • ljk November 6, 2008, 23:57

    The Bullet Cluster: Searching for Primordial Antimatter

    Scientists are on the hunt for evidence of antimatter – matter’s arch nemesis – leftover from the very early Universe. New results using data from NASA’s Chandra X-ray Observatory and Compton Gamma Ray Observatory suggest the search may have just become even more difficult.


  • ljk January 20, 2009, 0:28

    Baryogenesis and cosmological antimatter

    Authors: A.D. Dolgov

    (Submitted on 14 Jan 2009)

    Abstract: Possible mechanisms of baryogenesis are reviewed. Special attention is payed to those which allow for creation of astronomically significant domains or objects consisting of antimatter. Observational manifestations of cosmological antimatter are discussed.

    Comments: Lectures presented at XIII Mexican School of Particles and Fields, San Carlos, October, 2008, 15pages

    Subjects: High Energy Physics – Phenomenology (hep-ph); Astrophysics (astro-ph)

    Cite as: arXiv:0901.2100v1 [hep-ph]

    Submission history

    From: Alexander Dolgov [view email]

    [v1] Wed, 14 Jan 2009 19:46:57 GMT (20kb)