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Monday, January 17, 2011

Thunderstorms Produce Beams of Antimatter Plus Dark Matter Mysteries

Image Source: NASA via BBC.

Caption for the above image: Electrons racing up electric field lines give rise to light, then particles, then light.

BBC is reporting on research findings presented at the meeting of the American Astronomical Society, which state that thunderstorms emit Antimatter.  From the report:
[The Fermi] space telescope has accidentally spotted thunderstorms on Earth producing beams of antimatter. Such storms have long been known to give rise to fleeting sparks of light called terrestrial gamma-ray flashes. But results from the Fermi telescope show they also give out streams of electrons and their antimatter counterparts, positrons. The surprise result was presented by researchers at the American Astronomical Society meeting in the US. It deepens a mystery about terrestrial gamma-ray flashes, or TGFs - sparks of light that are estimated to occur 500 times a day in thunderstorms on Earth. They are a complex interplay of light and matter whose origin is poorly understood.

Thunderstorms are known to create tremendously high electric fields - evidenced by lightning strikes. Electrons in storm regions are accelerated by the fields, reaching speeds near that of light and emitting high-energy light rays - gamma rays - as they are deflected by atoms and molecules they encounter. These flashes are intense - for a thousandth of a second, they can produce as many charged particles from one flash as are passing through the entire Earth's atmosphere from all other processes.
Read the rest of the report here.
Image Credit: NASA's Goddard Space Flight Center. Image Source: NASA.

Caption for the above image:  From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years, or roughly half of the Milky Way's diameter, as shown in this illustration. Hints of the bubbles' edges were first observed in X-rays (blue) by ROSAT, a Germany-led mission operating in the 1990s. The gamma rays mapped by Fermi (magenta) extend much farther from the galaxy's plane.

In other recent news about the Fermi telescope, the telescope has also spotted a giant blob that is mysteriously emiting two huge bubbles of gamma rays and X-rays (one on top of the other) at the centre of our galaxy. NASA reports (including a video) here and here.

ADDENDUM: There's a report out today on i09 that researchers suspect that the Milky Way Galaxy is surrounded by Dark Matter galaxies. (Hat tip: Lee Hamilton's blog)  From i09:
Based on how gravity affects the gases at the edge of our galaxy, we should have a satellite galaxy located about 26,000 light-years away...except nobody's ever seen it. This might be because it's composed almost entirely of dark matter.

Astronomer Sukanya Chakrabarti looked for gravitational effects created by potential satellite galaxies of our home, the Milky Way. Not unlike the gas giants such as Jupiter of Saturn, the Milky Way has a bunch of relatively tiny "moon" galaxies. The most famous of these, the Magellanic Clouds, are about 10 percent the size of our galaxy, but most of these satellite galaxies are less than a hundredth the size of the Milky Way.

Back in the 19th century, astronomers detected the planet Neptune by observing the slight gravitational wobble of Uranus, which could only be caused by an undetected planet further out. The same basic principle is at work here, as this mysterious Galaxy X is creating movement in the gas at the edge of our galaxy. Chakrabarti suspects the galaxy is composed mostly of dark matter, which is part of the reason why we hadn't found it up to this point.

If it exists, Galaxy X would be about 1% the size of the Milky Way, making it the third largest satellite after the Magellanic galaxies. While dark matter would make up most of its mass, there would likely still be some dim stars of regular matter in there as well. The galaxy lies on the same plane as our galactic disc, meaning astronomers need to look through all the bright lights of the Milky Way just to see Galaxy X. Still, now that we know where to look, Chakrabarti says, we should be able to find it.

There's some theoretical basis to think that Galaxy X really is out there. Our understanding of galactic formation tells us that our galaxy should have hundreds of satellite galaxies, but we've only found a few dozen. The idea that "dark" galaxies are hiding out there, unable to be seen in the visible light spectrum, could go a long way to sorting that mystery out. If we can find the dim star lights of Galaxy X, then we might be able to see the darker parts of the galaxy with infrared telescopes.

The search is now on for Galaxy X, and Chakrabarti says that, if we find this galaxy, there's every chance we'll detect the existence of fellow dark matter Galaxies Y and Z and so on. If we can't find this galaxy, then she argues that something must be wrong in the calculations. This might mean the halo of dark matter known to surround the Milky Way is different from what we thought it was, which would open up some new avenues of research. Either way, the hunt for Galaxy X figures to teach us some crucial new information about elusive dark matter.
Original research published in the Astrophysical Journal here (reported via National Geographic).


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