Cosmic rays

Definition

Cosmic rays are highly energetic particles that originate from outer space and travel at nearly the speed of light. They consist mostly of protons, but also include heavier atomic nuclei and electrons.

5 Must Know Facts For Your Next Test

1. Cosmic rays are primarily composed of protons, with a smaller fraction of helium nuclei and other heavy elements.
2. They originate from supernova explosions, active galactic nuclei, and other high-energy astrophysical events.
3. Cosmic rays can penetrate Earth's atmosphere and are responsible for creating secondary particles when they collide with atmospheric molecules.
4. The energy of cosmic rays can range from a few million electron volts (MeV) to over 10^20 electron volts (eV).
5. Understanding cosmic rays helps astronomers study the processes in massive star evolution and the interstellar medium.

Review Questions

• What are the primary components of cosmic rays?
• How do cosmic rays interact with Earth's atmosphere?
• Why are supernovae significant sources of cosmic rays?

Related terms

Supernova:

A stellar explosion that occurs at the end of a massive star's life cycle, often producing cosmic rays.

Interstellar Medium:

The matter that exists in the space between star systems in a galaxy, including gas, dust, and cosmic rays.

Active Galactic Nucleus:

A compact region at the center of a galaxy with extremely high luminosity due to accreting supermassive black holes, capable of emitting cosmic rays.