Predicting eclipses with lunar nodes
Earth follows a year-long elliptical orbit around the Sun, while the Moon follows a 27.3-day tilted elliptical orbit around Earth. Comparing these orbits allows us to predict when solar and lunar eclipses will occur, and from where on Earth they will be visible.
There are two special points along Earth’s orbit around the Sun, called ‘lunar nodes’, where the Moon’s orbit crosses through the Sun-Earth line (yellow dashed lines) in the ecliptic, the plane of Earth’s orbit around the Sun. Solar and lunar eclipses can only happen around these nodes, in what’s known as an ‘eclipse season’. Each eclipse season lasts around 35 days and occurs twice a year (every 173 days).
For example, there are two eclipse seasons in 2026, with one solar and one lunar eclipse in each: an annular solar eclipse on 17 February, a total lunar eclipse on 3 March, a total solar eclipse on 12 August, and a partial lunar eclipse on 28 August.
During a solar eclipse, the Moon passes directly between the Sun and Earth. As a result, the Moon entirely or partially blocks the Sun, casting a shadow on Earth. Solar eclipses only happen during a new moon because the Moon passes between the Sun and Earth during that Moon phase.
During a lunar eclipse, Earth passes directly between the Sun and the Moon. The resulting shadow on the Moon turns it dark red. Lunar eclipses only happen around a full moon.
Away from lunar nodes (left and right of the image), the Moon’s tilted orbit means the Sun, Earth and Moon never directly align. No eclipses can occur here, because the Moon and Earth can’t cast a shadow on each other. In a ‘high moon’, the Moon flies up to five degrees above the ecliptic on the sunny side of Earth; in a ‘low moon’, it flies up to five degrees below the ecliptic.
The 2026–2028 ‘European solar eclipses’
Remember: never look directly at the Sun, even when partially eclipsed, without proper eye protection such as special solar eclipse glasses, or you risk permanent eye damage.
[Image description: This infographic explains how lunar nodes can be used to predict solar eclipses. At the centre of the diagram is the Sun, with the Earth drawn orbiting the Sun. Within this oval-shaped orbit, the location of Earth and the orbiting Moon are shown four times, above, below, left and right of the Sun. The Earth-Moon systems on the left and right of the orbit are labelled 'High moon' and 'Low moon' respectively. The ones at the top and bottom of the orbit are labelled 'Nodes'; for each one a solar eclipse and lunar eclipse is indicated, showing that eclipses can take place during these node periods. A heading at the top says 'Lunar nodes' and the European Space Agency logo sits at the top right of the infographic.]
