Astronomers just discovered a comet that could be brighter than most stars when we see it next year. Or will it?

The comet is currently between the orbits of Jupiter and Saturn, a billion kilometres from Earth

Hot on the heels of the disappointing Green Comet, astronomers have just discovered a new comet with the potential to be next year’s big story – C/2023 A3 (Tsuchinshan-ATLAS).

Although it is still more than 18 months from its closest approach to Earth and the Sun, comet Tsuchinshan-ATLAS already has social media buzzing, with optimistic articles being written about how it could be a spectacular sight. What’s the full story on this new icy wanderer?

Every year, a few dozen new comets are discovered – dirty snowballs moving on highly elongated paths around the Sun. The vast majority are far too faint to see with the unaided eye. Perhaps one comet per year will approach the edge of naked-eye visibility.

Occasionally, however, a much brighter comet will come along. Because comets are things of ephemeral and transient beauty, the discovery of a comet with potential always leads to excitement.

Comet C/2023 A3 (Tsuchinshan-ATLAS) certainly fits the bill. Discovered independently by astronomers at Purple Mountain Observatory in China and the Asteroid Terrestrical-impact Last Alert System, ATLAS, the comet is currently between the orbits of Jupiter and Saturn, a billion kilometres from Earth.

It is falling inwards, moving on an orbit that will bring it to within 59 million kilometres of the Sun in September 2024. The fact the comet was found while it’s so far away is part of the reason for astronomers’ excitement. Although currently some 60,000 times too faint to see with the naked eye, the comet is bright for something so far from the Sun. And observations suggest it’s following an orbit that could allow it to become truly spectacular.

It’s all down to a combination of the comet’s path through the Solar System, and the potential size of its nucleus – the solid centre. As comets swing closer to the Sun, they heat up, and their surface ices sublime (turn from a solid to a gas). Erupting from the comet’s surface, this gas carries along dust, shrouding the nucleus in what’s called a coma – a giant cloud of gas and dust. The coma is then pushed away from the Sun by solar wind, resulting in a tail (or tails) pointing directly away from the Sun.