Skip to content
Skip to main content

About this free course

Download this course

Share this free course

In the night sky: Orion
In the night sky: Orion

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Orion Glossary

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL


carbon burning

The process by which carbon nuclei undergo nuclear fusion to form a neon nucleus (and a new helium nculeus) in massive stars.


The lower part of the Sun’s atmosphere situated immediately above the photosphere.


A relatively small (typically a few kilometres across) body made of icy materials and rocky materials. Comets are found mainly in the Oort cloud, and also in the Kuiper Belt, and some enter the inner Solar System.


The central very hot region of a star (such as the Sun) where nuclear reactions occur during the Main Sequence lifetime.


The upper part of the Sun’s atmosphere. It is very hot, very tenuous and very extensive.

cosmological constant

A constant (often written as a capital lambda or Λ) introduced into the equations of general relativity by Albert Einstein. It was originally conceived as a property of space and time that counteracts the predicted expansion or contraction of the Universe. It is now sometimes thought of as a content of the Universe, rather than a property of space itself. See also dark energy.