What are cosmic rays?

Cosmic rays are extremely high-energy subatomic particles – mostly protons and atomic nuclei accompanied by electromagnetic emissions – that move through space, eventually bombarding the Earth’s surface. They’re called rays, but they are actually particles.

Who discovered cosmic rays?

Victor Franz Hess was an Austrian-American physicist, who discovered cosmic rays in 1912 . Hess shared the 1936 Nobel prize in physics for his discovery.

What is the speed of cosmic rays?

They travel at nearly the speed of light, which is approximately 300 000 kilometres per second.

Can we determine exactly from where cosmic rays came from?

Since cosmic rays are charged – positively charged protons or nuclei, or negatively charged electrons – their paths through space can be deflected by magnetic fields. On their journey to Earth, the magnetic fields of the galaxy, the solar system, and the Earth scramble their flight paths so much that we can no longer know exactly where they came from. That means we have to determine where cosmic rays come from by indirect means.

What are the types of cosmic rays?

Cosmic rays are of two types: galactic and solar.

What is Galactic cosmic radiation?

Galactic cosmic radiation comes from the remnants of supernovas, which are powerful explosions during the last stages of massive stars that either collapse to black holes or are destroyed. The energy released in these explosions accelerates charged particles outside our solar system, making them highly penetrating and extremely hard to shield. In essence, supernovas act like huge, natural particle accelerators. The Earth is constantly exposed to galactic cosmic radiation.

What is Solar cosmic radiation?

Solar cosmic radiation is composed of charged particles emitted by the Sun, predominantly electrons, protons and helium nuclei. Some of this radiation is continuously emitted from the Sun’s corona, which led scientists to call it the ‘solar wind’. The remainder comes from solar particle events – sudden and sporadic outbursts of electrically charged particles accompanied by electromagnetic emissions that occur when magnetic fields on the Sun’s surface stretch and twist.

Like a rubber band, the Sun’s fields can snap, suddenly releasing enormous energy and presenting potential health concerns to astronauts in space. Although rare, strong solar flares can eventually create radio blackouts and impact modern communication and navigation technology on ground.

What is the composition of cosmic rays?

All of the natural elements in the periodic table are present in cosmic rays. This includes elements lighter than iron, which are produced in stars, and heavier elements that are produced in violent conditions, such as a supernova at the end of a massive star’s life.

About 90% of the cosmic ray nuclei are hydrogen (protons), about 9% are helium (alpha particles), and all of the rest of the elements make up only 1%. Even in this one percent there are very rare elements and isotopes. Elements heavier than iron are significantly more rare in the cosmic-ray flux but measuring them yields critical information to understand the source material and acceleration of cosmic rays

Do cosmic rays reach the Earth’s surface?

These high-energy particles, also called primary particles, do not reach ground level because they collide with air molecules high up in the atmosphere. Their collisions result in a shower of lower-energy particles (“secondary” particles are ejected from this collision) some of which reach the ground and can be detected.

The Earth is shielded by a magnetic field that makes the charged particles bounce from pole to pole, creating two gigantic donut-shaped belts populated by energetic electrons and protons. The magnetosphere deflects cosmic rays and protects us from solar flares. Sometimes, cosmic radiation does reach us, but without creating any harm, just like other low levels of radiation we are regularly exposed to.

How much of radiation per year people are exposed to on Earth?

On average, people are exposed to around 3.5 millisieverts of radiation per year. About half of this comes from artificial sources such as X-ray, mammography and CT scans, while the other half we get from natural sources, of which about 10 per cent comes from cosmic radiation.

What is Sievert?

Sievert is the measure of health risk from radiation: one sievert carries with it a 5.5 per cent chance of eventually developing radiation-induced cancer later in life.

What are auroras?

Cosmic-ray particles sneaking into the atmosphere at the Earth’s magnetic poles can create truly astonishing, colourful auroral lights.

These magical phenomena predominantly seen at high latitudes around the Arctic and Antarctic are the result of collisions between charged particles of the solar wind and the gaseous constituents of the atmosphere. The most common auroral colour, a pale yellowish-green, is produced by oxygen molecules, while nitrogen gives rise to blue or purplish-red aurora.

Do cosmic rays reach us when we fly?

Yes. While airplanes passengers are exposed to elevated levels of cosmic radiation, especially at higher altitudes and latitudes, the radiation they receive in one flight is quite insignificant. Aircrew and frequent flyers are exposed to higher levels of radiation doses from space, because of how often they fly.

The crew on flights typically operating at low altitude, such as most propellant aircraft, will hardly exceed a dose of one millisievert per year. Crew serving on long-haul polar routes, though, might be exposed to an annual effective dose of up to six millisieverts.

Are astronauts exposed to cosmic radiation?

An astronaut on board a space station orbiting the Earth at an altitude of 400 kilometres is typically exposed to a dose of more than half a millisievert per day. In 12 days, they would get the same dose as aircrew gets in a year. Health effects such as radiation carcinogenesis and certain tissue reactions could have been linked to cosmic radiation exposure in astronauts.

Are cosmic rays harmful?

Cosmic rays are one type of ionizing radiation, meaning they are energetic enough to knock electrons out of atoms, ionizing them. If the atom is part of electronics or computing equipment, this can change the performance of the electronics or cause a one-time error in a computer. If the atom is part of a living being, perhaps part of a DNA molecule, it can damage the biological tissue, perhaps causing a mutation in the DNA.

Can we benefit from cosmic radiation on Earth?

Our understanding of cellular damage induced by high levels of cosmic radiation could help advance technology for cancer treatment using high-energy particle accelerators. Because of their unique properties, beams of charged particles, similar to those encountered in space, can destroy deep-seated tumours while minimizing damage to surrounding tissues.

Insights from ion therapy will enable us to improve radiation protection in space and overcome the current limitations in predicting health risks for long-duration space travel.

PRACTICE QUESTIONS

QUES . Which one of the following has highest frequency? CDS 2007

(a) Cosmic rays

(b) X- rays

(c) Radiowaves

(d) Microwaves

Ans (a)