Mercury returns to twilight

The inner wanderer graces our evening skies once again this month.

- Charlotte Daniels

When most beginners start out in planetary astronomy, it's easy to default to the holy trinity' of Jupiter, Saturn and our neighbour Mars. Each boasts unique and relatively easy to observe features, from Saturn's rings and Jupiter's bands and Great Red Spot, to Mars's dusty surface. But why stop there? There are eight planets in our Solar System and many can be appreciated with beginner setups. The 'inner planets', Mercury and Venus, present new and exciting challenges to planetary astronomers. We explored Venus in last month's issue and now it's Mercury's turn for the spotlight.

Due to its proximity to the Sun, extra care must be taken to observe Mercury safely, which adds to the challenge. There are particular times that are best to view this elusive, mysterious planet, and this April we can seize the opportunity. Get ready to enjoy one of the Solar System's unsung heroes.

Following Mercury's path 

The fastest planet in the Solar System, Mercury is named after the messenger of the Greek gods, renowned for speed. And time is certainly of the essence with this planet. To catch Mercury, we need to understand how its position relative to the Sun affects its visibility.

Mercury is 0.4 astronomical units (AU) away from the Sun and orbits at speeds of up to 47km per second, compared to Earth's relaxed pace of 30km per second. When it reaches its closest point to the Sun, Mercury is at its fastest and it then slows down slightly the further away it gets. As the innermost planet, it also has the shortest year, taking 88 Earth days to circle the Sun.