Cosmic rays from space hit Earth's atmosphere all the time. When a high-energy cosmic ray enters the atmosphere, it can cause an "air shower". The cosmic ray hits a molecule in the atmosphere and "breaks up", producing lots more sub-atomic particles. A real air shower can make millions of particles. This picture shows a simple version of an air shower. The cosmic ray (in red, at the top) makes lots of other particles, many with odd names. The sub-atomic particles shown here include protons (green), neutrons (orange), pions (yellow), muons (purple), photons (blue), and electrons & positrons (pink).
Click on image for full size
Windows to the Universe original artwork by Randy Russell using a photo courtesy UCAR (Nicole Gordon).
Cosmic rays are a type of radiation that comes from space. Cosmic rays aren't really "rays". They are
particles (mostly protons)
that have a lot of energy. They have so much energy that they can be dangerous. We are lucky, though. Earth's magnetic
field and atmosphere protect us; they block most cosmic rays.
A physicist named Victor Hess discovered cosmic rays in 1912. He won the Nobel Prize in 1936 for his discovery.
There are different kinds of cosmic rays, and they come from different places. Some come from solar flares and other explosions on the Sun. Some cosmic rays come from supernova explosions, black holes, and neutron
stars within our own Milky Way galaxy. They are called galactic cosmic rays, and have more energy that the ones that come from the Sun. A third type of cosmic ray has even more energy than galactic cosmic rays. Scientists think they might come from somewhere outside of our galaxy. They are called extragalactic cosmic rays. "Extragalactic" means "outside of our galaxy".
Cosmic rays are made up of tiny particles; pieces of atoms. Most are protons from the nucleus of a hydrogen atom. Some cosmic rays are electrons. Others are from the nucleus of some other kind of atom, like carbon, oxygen, iron, or calcium. All cosmic rays move really, really fast and carry a lot of energy!
Cosmic rays are a kind of particle
radiation, so they can be dangerous to people, animals, and machines. Did you know that you are hit with a small amount of radiation from nature every year? Don't worry, though - it is usually such a tiny amount that it doesn't hurt you at all. About one-tenth of the radiation that hits you each year is from cosmic rays. Earth's magnetic field and atmosphere protect us from most cosmic rays. Astronauts in space need to be careful, though, because they get hit by more cosmic rays. Cosmic rays sometimes damage satellites, too.
When cosmic rays hit Earth's atmosphere, they crash into atoms and molecules of gas. That usually makes even more cosmic ray particles! One cosmic ray particle from space with lots of energy can make lots of low-energy cosmic rays in the atmosphere. When this happens, scientists call it an "air shower" of cosmic rays.
Shop Windows to the Universe Science Store!
Our online store
includes issues of NESTA's quarterly journal, The Earth Scientist
, full of classroom activities on different topics in Earth and space science, ranging from seismology
, rocks and minerals
, and Earth system science
You might also be interested in:
The text for this level hasn't been written yet. Please check the "Intermediate" or "Advanced" level of this page (click on the bar near the top of this page)....more
The Earth has a magnetic field with north and south poles. The magnetic field of the Earth is surrounded by the magnetosphere. The magnetosphere keeps most of the particles from the sun, carried in solar...more
Neutron Stars form when really big stars die. When such a star runs out of fuel its center begins to collapse under gravity. When the center collapses the entire star collapses. The surface of the star...more
When we look up at the night sky, we notice that there are many stars in our sky. Stars must like to live together in star cities - galaxies. Our city of stars is called the Milky Way, and it is home to...more
Text for this level has not been written yet. Please see the "Intermediate" text for this page if you want to learn about this topic. To get to the "Intermediate" text, click on the blue "Intermediate"...more
Most things around us are made of groups of atoms connected together into packages called molecules. Molecules are made from atoms of one or more elements. Some molecules are made of only one type of...more
Scientists have found where cosmic rays come from! The rays are made of atoms. These atoms are flying through space at speeds close to the speed of light. Until now, scientists didn't know where they...more