The lowdown on the highest energy light

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Incredible hulking facts about gamma rays

From lightning to the death of electrons, the highest-energy form of light is everywhere

For Symmetry Magazine:

Gamma rays are the most energetic type of light, packing a punch strong enough to pierce through metal or concrete barriers. More energetic than X-rays, they are born in the chaos of exploding stars, the annihilation of electrons and the decay of radioactive atoms. And today, medical scientists have a fine enough control of them to use them for surgery. Here are seven amazing facts about these powerful photons. [Read the rest at Symmetry Magazine]

Some light reading about light

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

As I mentioned before, I’m branching out a bit and writing some listicles for Symmetry Magazine this year. The first covered gravity, and the second covers… light!

Eight things you might not know about light

Light is all around us, but how much do you really know about the photons speeding past you?

For Symmetry Magazine:

1. Photons can produce shock waves in water or air, similar to sonic booms.

Nothing can travel faster than the speed of light in a vacuum. However, light slows down in air, water, glass and other materials as photons interact with atoms, which has some interesting consequences.

The highest-energy gamma rays from space hit Earth’s atmosphere moving faster than the speed of light in air. These photons produce shock waves in the air, much like a sonic boom, but the effect is to make more photons instead of sound. Observatories like VERITAS in Arizona look for those secondary photons, which are known as Cherenkov radiation. Nuclear reactors also exhibit Cherenkov light in the water surrounding the nuclear fuel. [Read the rest at Symmetry Magazine…]

No quantum foam seen in the cosmic beer glass

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Light from distant black holes doesn’t surf on waves of quantum foam

Strongest check yet on quantum gravity effects in astronomy turns up nothing

For Ars Technica:

Quantum gravity is notoriously slippery. While the Standard Model successfully describes three forces of nature, it doesn’t include gravity, so gravity still has no consistent quantum theory. To make matters worse, gravity is so weak that it’s difficult to probe at the sorts of energies where any minuscule quantum effects would pop out. However, some researchers predict that those tiny effects could accumulate over cosmological distances: light traveling from far-off quasars would be changed by the “quantum foam” of spacetime, producing blurry images in our telescopes—or even making objects seem to disappear.

A new report by E. S. Perlman and colleagues examines the disappearance hypothesis using gamma-ray data from quasars. In particular, they investigated a possibility suggested by the holographic principle, the idea that all the information in the cosmos can be encoded on the two-dimensional boundary that encloses it. Disappointingly for fans of quantum foam, the gamma ray data did not show any measurable fading or blurring of the quasars.

As the authors point out, these results don’t rule out anything general regarding quantum gravity, quantum foam, or the holographic principle. But they do provide the tightest constraint yet on cumulative effects of quantum foam on light traveling across the Universe. [Read the rest at Ars Technica…]

Where do cosmic rays originate? Cosmic rays are mostly high-energy protons from deep space that hit Earth’s upper atmosphere, creating showers of other particles that can be detected at the surface. Some of these protons are so incredibly high energy—meaning they’re moving just a whisker slower than the speed of light—that only exceptional astronomical events could accelerate them. The prime suspect: supernova explosions. Up until now, though, nobody had confirmed this suspicion. However, a new observation using gamma ray emissions from supernova remnants found the telltale signature of particle collisions, which could only be present if protons were getting that extra boost of energy.

On October 15, 1991, a high-energy proton from deep space struck Earth’s upper atmosphere. Known as the “Oh My God Particle”, this proton was by far the highest energy cosmic ray ever seen. This one proton’s energy was equivalent to a regulation soccer ball traveling at 15 meters per second (34 miles per hour). In the two decades following, observers spotted several similarly energetic cosmic rays, which left a big question: what was accelerating these protons to higher speeds than anything we can achieve in on Earth? [Read more….]

High-energy cosmic rays are sped on their way by exploding stars

Pulsars are rapidly rotating neutron stars—the dense remnants of stars much more massive than the Sun. Some pulsars are in binary systems, and when they feed off their companion star, their rotation rate can increase until they’re spinning hundreds of times per second. Known as millisecond pulsars, these are often also strong emitters of gamma rays, but no one had identified one through gamma ray observation alone…until now.

Astronomers have now used the Fermi Gamma-Ray Space Telescope to identify a “black widow” pulsar that’s stripping mass off a close companion star while simultaneously evaporating it by emitting intense radiation. It’s having these dramatic effects because the pulsar and its companion orbit each other so closely that they complete an orbit once every 93 minutes, making this the tightest black widow binary yet discovered. [Read more….]

Pulsar eats companion star, burps gamma rays