The planetary alignment: a stargazer’s guide

By Isabella Castel-branco

The night sky appears relatively static. The stars seem to change between summer and winter as the Earth faces different sides of the universe in its orbit around the Sun, but once one knows their constellations, they will hardly have to update them. That is why astronomical phenomena excite us: they provide a new, ephemeral target of observation. Meteor showers, comets, supernovae, and planetary parades are excellent starting points for appreciating and contemplating the night sky. As it happens, a ‘planetary alignment’ or ‘planetary parade’ is currently taking place and will improve as February progresses.

Misconceptions spread easily, and understanding terminology is essential to ensure observations meet expectations. ‘Planetary alignments’ do not refer to planets queued up in a straight line in space. Planets appearing along the same path in the sky are the usual: since they all orbit the Sun on the same disk, which is within a plane, they all follow the same line in the night sky called the ecliptic. This imaginary line also traces the Sun’s path throughout the day. As it is a projection of orbits on a sphere (the sky), it appears curved – the planets, therefore, cannot, no matter the circumstances, rigorously be aligned in a straight line.

Planetary alignments and parades (not technical terms so can be used freely and interchangeably), refer to periods where multiple planets are visible at once. Whilst a nice sight, it is not as rare as sometimes claimed to be – just in June 2022, a more compact parade was visible in the pre-dawn sky. This is not a single-night event, instead extending over many days. The optimal date to view all seven planets at once in the sky is 28th February, but for viewing in the UK, 2nd March. Venus, Jupiter, Saturn, Mercury and Mars will be easily visible to the naked eye – Uranus and Neptune, being much further away, will require a pair of binoculars or a small telescope.

Amateur astronomers can prepare for a stargazing evening by knowing essential tips to acclimatise their eyes to darkness and identify objects

Whilst the event coincides with the New Moon (which entails better visibility), Durham’s hills and latitude lead to considerable constraints. Just after sunset, Venus (the brightest) and Saturn will swiftly set in the southwest. To ensure seeing them, you should seek clear views of the horizon. Moreover, the light pollution in and around Durham also prevents your eye from distinguishing fainter light sources in the sky: to see Uranus and Neptune, you would need a magnifying device and know precisely where to point it. Mars and Jupiter will hang high in the sky throughout the evening and should be the easiest to spot.

Amateur astronomers can prepare for a stargazing evening by knowing essential tips to acclimatise their eyes to darkness and identify objects. To enjoy the night sky to its fullest, one should find a dark area an hour after sunset. Also, whilst observing under a clear sky is relatively obvious, low wind and humidity further allow for crisper images since the air is disturbed to a lesser extent. Most essentially, for the planetary parade, one has to know how to distinguish planets from stars! As planets have a larger apparent size in the sky, since they are so significantly closer, their light appears much less deviated by atmospheric perturbations than stars (which, as a small point source, are, in comparison, more affected). Hence, stars twinkle, and planets do not.

There are various ways in and around Durham to stargaze collectively or under guidance. There are regular observation sessions with telescopes on Observatory Hill. Otherwise, Wynyard observatory – a 20-minute car ride from Durham – offers open observation sessions with experienced volunteers guiding the event. In both cases, you would be in good company to catch as many planets as possible.

Image: Zelch Csaba via Pexels