Skip to Content
Uncategorized

Antiproton Radiation Belt Discovered Around Earth

Physicists have long suspected that antiprotons must become trapped in a belt around Earth. Now they’ve found it.

The Earth is constantly bombarded by high energy particles called cosmic rays. These are generated by the Sun and by other sources further afield. (The source of the highest energy cosmic rays is still a mystery).

The particles are generally protons, electrons and helium nuclei and when they collide with nuclei in the Earth’s upper atmosphere they can produce showers of daughter particles. These showers can be so extensive that they can easily be observed from the ground.

Astronomers long ago realised that these collisions must produce antiprotons, just as they do in particle accelerators on Earth. But this raises an interesting question: what happens to the antiprotons after they are created?

Clearly, many of these antiparticles must be annihilated when they meet particles of ordinary matter. But some astronomers always suspected that the remaining antiprotons must become trapped by the Earth’s magnetic field, forming an antiproton radiation belt.

Now astrophysicists say they’ve finally discovered this long-fabled belt of antiprotons.

In 2006, these guys launched a spacecraft called PAMELA into low Earth orbit, specifically to look for antiprotons in cosmic rays.

But, like most spacecraft in low Earth orbit, PAMELA must pass daily through the South Atlantic Anomaly, a region where the Van Allen Radiation Belts come closest to the Earth’s surface. It’s here that energetic particles tend to become trapped. So if any antiprotons are caught up in the mix, that’s where PAMELA ought to find them.

Now the PAMELA team has analysed the 850 days of data, looking only at the times when the spacecraft was in the South Atlantic Anomaly (about 1.7 per cent of this time).

Lo and behold, these guys found 28 antiprotons. That’s about three orders of magnitude more than you’d expect to find in the solar wind, proving that the particles really are trapped and stored in this belt.

This constitutes “the most abundant source of antiprotons near the Earth”, say the PAMELA team.

The South Atlantic Anomaly is well known as a thorough nuisance. Because of the high energy particles here, the Hubble Space Telescope must be switched off when it passes through several times a day; and the International Space Station has extra shielding to protect astronauts from its effects.

The discovery of an additional belt of antiprotons won’t have much impact on the danger it represents–the number of antiprotons is tiny compared to the electrons and protons trapped there.

But it’s always interesting to have theoretical predictions confirmed. That’s good science at work.

Ref: arxiv.org/abs/1107.4882: The Discovery Of Geomagnetically Trapped Cosmic Ray Antiprotons

Keep Reading

Most Popular

AV2.0 autonomous vehicles adapt to unknown road conditions concept
AV2.0 autonomous vehicles adapt to unknown road conditions concept

The big new idea for making self-driving cars that can go anywhere

The mainstream approach to driverless cars is slow and difficult. These startups think going all-in on AI will get there faster.

biomass with Charm mobile unit in background
biomass with Charm mobile unit in background

Inside Charm Industrial’s big bet on corn stalks for carbon removal

The startup used plant matter and bio-oil to sequester thousands of tons of carbon. The question now is how reliable, scalable, and economical this approach will prove.

AGI is just chatter for now concept
AGI is just chatter for now concept

The hype around DeepMind’s new AI model misses what’s actually cool about it

Some worry that the chatter about these tools is doing the whole field a disservice.

images created by Google Imagen
images created by Google Imagen

The dark secret behind those cute AI-generated animal images

Google Brain has revealed its own image-making AI, called Imagen. But don't expect to see anything that isn't wholesome.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.