The Fermi Gamma-ray Space telescope orbits at 550 km - I'm not sure how large its Gamma-ray Burst Monitor is, but, it's probably on the order of magnitude of a square meter.
From the graph, a TGF creates an additional 80 impacts per microsecond. Under the (admittedly incorrect) presumption that a TGF is omnidirectional, that would suggest a TGF is emitting enough positrons to cause in 10^-6 seconds an increase of 80 impacts on the 1 meter section of the surface of a sphere with a 550 * 10^3 meter radius.
If I don't munge the math, that would suggest each of these TGF is emitting approximately:
4*Pi*(550*10^3 )^2*80 /(1*10^-6 )
3*10^20 positron emissions per TGF that make it to the LEO of the satellite.
Divide as appropriate to account for the likely (per the article) non-omnidirectional nature of the burst (they tend upwards)
Not sure how many are normally absorbed in the atmosphere, or, in fact, if 10^20 is a significant number of positrons - but I'm thinking it would be interesting to mount a TGF detector near, or above, a frequently hit lighting target (Empire State Building gets around 100 Hits per year)
Checking Wikipedia - it turns out that lightning has been a well known source of Gamma Rays for at least 15 years - I read about the observations of the Compton Gamma Ray Observatory in 1994 - and compared it to the more recent discovery by the Fermi Gamma Ray Space telescope. It's hard to see what they discovered that was different this time around.
What's new here is the direct observation of a spectral feature--the well-known 511 keV line--which corresponds to annihilation of the positrons produced by the TGF with electrons. Gamma-rays and electrons had been observed before, but it wasn't known that positrons were produced as well.
Compton didn't observe it because its energy resolution was too coarse, and RHESSI (another satellite which has detected many TGFs) doesn't have enough collecting area to do spectroscopy.
There are current ground and airborne experiments looking for high energy emission from lightning.
(I'm a gamma-ray astrophysicist who works with these satellites on other sources.)
The graph in the article is not counting positrons, but gamma photons. A fraction of those photons (not quantified) are from electron-positron annihilations: they infer this because their instrument [1] measures the energy of individual photons, and there is a cluster at/above the lowest possible energy for e-/e+ annihilation photons (511 keV).
Given that this isn't my field, I tried not to make any assumptions. I made my comment based on the following Graph Description:
"Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi's GBM."
I wasn't aware that Gamma Rays were created by anything other than positrons colliding with electrons.
What are the potential implications from this discovery? Since it is so expensive and difficult to create antimatter on Earth (and it only lasts for less than a second), the obvious question to ask is if we can capture or study the antimatter produced in thunderstorms?
The positrons (antimatter electrons) detected in this study are fairly easy to produce on Earth--certainly more cheaply than building satellites. http://en.wikipedia.org/wiki/Positron#Production Positrons are also produced in some radioactive decays as well as in accelerator experiments.
For some reason I feel this is only going to reduce the significance of anti-matter. I remember first hearing about it as some ominous "substance" that only exists in the emptiest depths of the universe. If it happens all of the time on earth, I'm sure we'll be able to conclude that anti-matter is as common here as it is elsewhere in the universe, and won't exhibit any super-interesting properties that we once thought it did.
>I remember first hearing about it as some ominous "substance" that only exists in the emptiest depths of the universe.
It doesn't exist in appreciable amounts anywhere, that anyone knows of. Maybe you're confusing it with dark matter, which has only observed in distant galaxies (because it's only detectable -- to date -- by its gravitational effects).
Antimatter exists on earth. You're generating antimatter right now. One isotope of natural potassium (K-40) emits an antielectron in one in every 10^5 decays [1]. A typical meatbag has enough K-40 for 4,400 decays per second [2] (i.e., 4.4 kBq), so you're spontaneously emitting, on average, about 3 antielectrons per minute from this path.
Sorry but that last sentence of yours doesn't make sense to me. From the discovery that it is created frequently on Earth, it does not follow that it won't exhibit any interesting properties nor that it is common in the universe (except by a generous definition of "common").
Anyhow, the main mystery remains: the Universe should be 50% matter and 50% antimatter, so where has all the antimatter gone?
I think that's a good question.
It is natural to require that the total charge in the universe was zero at the start of its life (same goes for all quantum numbers). Otherwise, there was something before there was anything!
Seriously, either this matter-antimatter asymmetry was an initial condition (in which case we can't hope to understand it) or it appeared at some point during the course of things.
The problem of finding the exact mechanism that gave us the matter-filled universe we observe today, with all the antimatter gone is an open question. There are a bunch of hypotheses, and experiments coming son to a large hadron collider near you will help physicists gather pieces of the puzzle.
The big-bang did not create particles or atoms, merely energy. In the very initial stages of the big-bang all of the mass of the entire Universe was locked up in bosons (photons, W & Z bosons, etc.), with virtual quarks and other exotic particles existing only ephemerally. At this stage the Universe is essentially an enormously hot photon gas. As the Universe cooled lower energy particles (such as electrons and protons) became more stable, and more and more energy started to become locked up in them. Interactions involving high energy photons can create particle / anti-particle pairs, in theory these should be exactly balanced. However, in practice it appears as though there is much more matter than anti-matter in the Universe. Likely this is due to some slight imbalance in particle/anti-particle pair creation, but we do not sufficiently understand this (though there have been a few hints).
Hm. I'm not sure I'd go so far as to say it's pedestrian. Well understood by theoretical physicists, perhaps. Inherently, though, it's still pretty damn interesting.
Interesting scientifically, sure, just like electrons and protons and Newtonian physics and all sorts of other things. But there's not much mystery to it. I agree with uvdiv, acconrad was almost certainly thinking dark matter/energy.
Or he's been misled by, like, every work of science fiction ever. They almost all portray it as the sort of mysterious, otherworldly stuff he's describing. I've known a lot of people who were kind of disappointed to learn that antiparticles are uncommon, but not that uncommon.
Anti-matter has been created in the laboratory routinely for decades. And it has existed in nature forever. Cosmic rays routinely create showers of particles and anti-particles in the upper atmosphere. Radioactive decay generates positrons continuously throughout nature (in Earth's rocks and soil, in the oceans, in bananas, inside your own body). Every second of every day you are bathing in an ocean of anti-neutrinos, mostly from the Sun.
But that hardly changes the remarkable nature of anti-matter. A single grain of sand of anti-matter would be a sufficient energy source to power a Toyota Prius for an entire century. A chunk of anti-matter the size of an aspirin tablet could be used to create a bomb as powerful as a nuclear weapon or power 100 homes for a year.
And conversely, it would take us the amount of energy sufficient to power a toyota prius for an entire century to create a grain of anti-sand, and we'd have to dump enough power to run 100 homes for a year to create a piece the size of an aspirin tablet.
Antimatter isn't free, and current production efficiencies are actually astronomically low (one trillionth efficient or something like that). My point was that matter/anti-matter reactions are nevertheless remarkable and amazing even though anti-matter reactions are common in nature.
I just realized, doesn't Jupiter have constant lightning storms a couple of orders of magnitude more violent than ours? Just imagine the sort of animatter generation those might be driving!
We gotta get another probe out there! Unless maybe we've got something that could pick up the signs back here...?
From the graph, a TGF creates an additional 80 impacts per microsecond. Under the (admittedly incorrect) presumption that a TGF is omnidirectional, that would suggest a TGF is emitting enough positrons to cause in 10^-6 seconds an increase of 80 impacts on the 1 meter section of the surface of a sphere with a 550 * 10^3 meter radius.
If I don't munge the math, that would suggest each of these TGF is emitting approximately:
Divide as appropriate to account for the likely (per the article) non-omnidirectional nature of the burst (they tend upwards)Not sure how many are normally absorbed in the atmosphere, or, in fact, if 10^20 is a significant number of positrons - but I'm thinking it would be interesting to mount a TGF detector near, or above, a frequently hit lighting target (Empire State Building gets around 100 Hits per year)
Checking Wikipedia - it turns out that lightning has been a well known source of Gamma Rays for at least 15 years - I read about the observations of the Compton Gamma Ray Observatory in 1994 - and compared it to the more recent discovery by the Fermi Gamma Ray Space telescope. It's hard to see what they discovered that was different this time around.