100 topics · Read, check sources and follow your curiosity.

A little room to wonder

Astronomy

Astronomy investigates objects and processes beyond Earth. It connects observations with models that help explain how worlds and larger systems behave.

What can a model of space show clearly, and what might it hide?

Blue, gold and rust-coloured gas and dark dust in the Keyhole Nebula, dotted with bright stars.
The Keyhole Nebula within the Carina Nebula, photographed with Hubble. This view shows a region beyond our Solar System, not a planet.NASA, The Hubble Heritage Team (AURA/STScI) · Source · Public domain

Systems within systems

The Solar System includes the Sun, eight planets, their moons and many smaller bodies. The Sun is a star; Earth is a planet orbiting it. Our Solar System belongs to the Milky Way galaxy. A nebula, such as the one pictured here, is a cloud of gas and dust, not another name for a planet. Outward from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Names depend on definitions

Astronomers classify objects using shared definitions. The Solar System’s eight planets meet criteria that include orbiting the Sun and gravitationally dominating their orbital neighbourhoods. Pluto is classified as a dwarf planet. A category tells you which definition an object meets, rather than how interesting or valuable it is.

Scale is part of the explanation

A neat row of equally spaced planets is convenient to read but does not represent their real distances. Models often simplify size, spacing or motion. Ask what a diagram is designed to explain and which features are not to scale. A useful model states its limits instead of hiding them.

Only if you feel like trying

Make the missing scale visible

  1. Sketch the Sun and the eight planets in the order named above; use labels rather than trying to show their real sizes.
  2. Add “sizes and distances not to scale” to the drawing.
  3. Choose one distance or size comparison you would need to check before making a scale model.

Optional paper activity. Never look directly at the Sun or point binoculars or a telescope at it.