Cosmic radiation: why we shouldn’t worry

Cosmic radiation: why we shouldn’t worry
Cosmic radiation: why we shouldn’t worry

Cosmic radiation is aptly named: it is radiation coming from space. This article discusses this radiation, why we are protected from it on Earth, how it affects people in certain professions, and how it can help advance cancer treatment techniques.

What are cosmic rays?

Cosmic rays are extremely high-energy subatomic particles – mainly protons and atomic nuclei accompanied by electromagnetic emissions – that travel through space and eventually bombard the Earth’s surface. They move at a speed close to the speed of light, which is around 300,000 kilometers per second.

Where do they come from ?

Cosmic rays can be of two types: galactic or solar. Galactic cosmic radiation emanates from the remnants of supernovas, powerful explosions occurring during the final stages of the life of enormous stars, which then become black holes or are destroyed. The energy released during these explosions accelerates charged particles, sending them out of our solar system and making them extremely penetrating and difficult to stop. In fact, supernovas behave like gigantic natural particle accelerators. The Earth is constantly exposed to galactic cosmic radiation.

Solar cosmic radiation is composed of charged particles emitted by the Sun, which are mainly electrons, protons and helium nuclei. Part of this radiation is emitted continuously by the Sun’s corona, which is why scientists call it the “solar wind.” The rest results from solar particle phenomena – sudden, sporadic bursts of electrically charged particles accompanied by electromagnetic emissions that occur when magnetic fields on the Sun’s surface stretch and twist. Like rubber bands, the Sun’s magnetic fields can snap, suddenly releasing an enormous amount of energy and posing a health risk to astronauts in space. Although rare, strong solar flares can cause radio outages and impact modern communication and ground navigation technology.

Do cosmic rays reach us on the ground?

The Earth is protected by a magnetic field that bounces charged particles from one pole to the other, creating two gigantic ring-shaped belts populated with energetic electrons and protons. The magnetosphere deflects cosmic rays and protects us from solar flares. Sometimes cosmic radiation reaches us but does not harm us, just like other weak radiation to which we are regularly exposed. People are exposed to radiation of about 3.5 millisieverts per year on average. About half of this radiation comes from artificial sources, such as x-rays, mammograms and CT scans, while the other half comes from natural sources, with cosmic radiation accounting for about 10%. The sievert is the unit of measurement of the risk posed by radiation to health: a sievert is associated, for an individual, with a probability of 5.5% of developing radiation-induced cancer over the course of life.

“Particles from cosmic rays entering the atmosphere at the Earth’s magnetic poles can create truly astonishing colorful aurora borealis,” explains Michael Hajek, external dosimetry specialist at the IAEA. Joan Feynman, an astrophysicist who devoted most of her life to studying auroras, found that these magical phenomena, observable mainly at high latitudes, near the Arctic and Antarctica, resulted from collisions between charged particles solar wind and the gaseous constituents of the atmosphere. The characteristic pale yellowish-green color of most auroras results from oxygen molecules, while nitrogen gives rise to blue or purplish-red auroras.

Do these rays reach us on a plane?

Yes. Airplane passengers are exposed to significant levels of cosmic radiation, especially at high altitudes and latitudes, but the radiation they receive during a flight is insignificant. Aircrew and frequent travelers are exposed to higher doses of space radiation because they fly often. The crew of aircraft usually flying at low altitude, like most propeller-driven aircraft, receive a dose that rarely exceeds one millisievert per year. On the other hand, cabin crew on long-haul flights passing near the poles can be exposed to an effective annual dose of up to six millisieverts.

“One section of the IAEA safety standards, Section 5 of GSR Part 3, outlines ways Member States can reduce the exposure of aircrew to radiation,” said Tony Colgan, head of the IAEA Safety Standards. IAEA Radiation Protection Unit. The flight hours of aircrew are controlled by the International Air Transport Association (IATA), which also establishes limits on the radiation doses to which these personnel can be exposed.

What about astronauts?

Space crews receive an even higher dose of radiation. An astronaut on a space station orbiting the Earth at an altitude of 400 kilometers is typically exposed to a dose of more than half a millisievert per day. In 12 days, he could receive the dose that a flight crew member receives in a year. National space agencies have established allowable dose limits for astronauts during their careers. Effects on astronaut health, such as radiocarcinogenesis and certain tissue reactions, could be linked to exposure to cosmic radiation, but the small sample size makes it difficult to quantify these effects.

Can we take advantage of cosmic radiation on Earth?

“It is fascinating to think that if we better understand cell damage induced by strong cosmic radiation, we can advance technology using high-energy particle accelerators for cancer treatment,” says Michael Hajek. Due to their unique properties, beams of charged particles similar to those found in space can destroy deep tumors while minimizing damage to nearby tissues. “The discoveries of ion therapy will allow us to improve radioprotection in space and to address the current limitations in predicting the health risks posed by long-term travel in space. space,” explains Michael Hajek.

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