The comet is accelerating towards Earth – it may cause a surprise

A comet from the Oort cloud approaches the Sun. But is it bright enough to be visible with the naked eye?

MUNICH – In recent years, a number of comets have appeared in the sky – but the comet currently heading towards Earth could dwarf them: Comet C/2023 A3 (Tsochinchan-Atlas) is named after its discoverers, the observatory at the International Space Center. Purple Mountain in China (Tsouchenshan) and the Atlas Telescope in South Africa. It was discovered on January 9, 2023 and since then the expectations of the scientific community have been high.

Comet C/2023 A3 (Tsuchenshan-Atlas) approaches the Sun and Earth

The comet is currently making its long journey from the farthest parts of the solar system towards the sun. When it was discovered, it was still far beyond Jupiter's orbit, about a billion kilometers from the sun. It is now positioned between the orbits of Mars and Jupiter and will reach the closest point in its orbit to the Sun, perihelion, on September 28. At that point, it will be only 58 million kilometers from the Sun, a distance similar to the distance of the closest planet to the Sun, Mercury and our host star.

About two weeks later, on October 13, the comet will reach its closest point to Earth, which is its perigee, and it will be only 70.5 million kilometers from Earth. Comets are often referred to as “dirty snowballs” because they consist of dust and rock held together by ice. When a comet approaches the Sun, the atmosphere becomes warmer and the ice immediately begins to evaporate, and pieces of rock, dust and gases are released and form the typical comet's tail.

Will comet C/2023 A3 (Tsuchenshan-Atlas) be visible with the naked eye?

Experts expect that the brightness of comet C/2023 A3 (Tuchinshan-ATLAS) will reach the second or even first magnitude, and will be visible to the naked eye. For comparison: the North Star shines with a brightness of 2, while Spica, the main star in the constellation Virgo, has a brightness of 1 (the lower the value, the brighter the object).

A phenomenon called “forward scattering” can help make a comet appear brighter. This phenomenon occurs when the comet is between the Sun and Earth approximately on October 8th. If the comet is very dusty, dust particles can scatter sunlight forward and increase its brightness. Experts say that “forward scattering” could make the comet even brighter than magnitude 1.

Bad sign: The comet is approaching the Sun for the first time

However, there are also factors that prevent comet C/2023 A3 (Tsuchenshan-Atlas) from being seen with the naked eye. The comet comes directly from the Oort Cloud at the edge of the solar system and approaches the sun for the first time. This means that highly volatile materials on the comet's surface would likely evaporate at a great distance from the Sun. This can lead to short-term increases in brightness, but as the comet approaches the Sun, the increase in brightness usually slows or stops completely.

It is very likely that comet C/2023 A3 (Tsuchinshan-Atlas) will also behave this way, but it is not mandatory. In general, it is very difficult to predict the evolution of comets. Amateur astronomer and science writer David Levy put it best when he said: “Comets are like cats: they have tails and they do whatever they want.” (unpaid bill)