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Comets

✨ The dirty snowballs

Comets are celestial objects made mainly of ice, dust, and rocky material that travel through space. They formed about 4.6 billion years ago in the outer regions of the Solar System, where temperatures are low enough for frozen substances to remain preserved.

Most comets come from distant areas such as the Kuiper Belt and the Oort Cloud. They follow elongated orbits around the Sun, and some return regularly after periods that can last from a few years to thousands of years.

When a comet approaches the Sun, its heat causes part of its ice to turn directly into gas, releasing dust and creating a glowing cloud called a coma around the nucleus. Solar radiation and the solar wind can then produce a tail that may stretch millions of kilometers into space.

Contrary to common images, the tail does not trail behind the comet like smoke; it always points away from the Sun. Scientists study comets because they contain ancient material from the early Solar System, which can provide clues about its formation and evolution.

💡 Did you know?

Do you know that a comet's tail can be millions of kilometers long? Yet, it is only made of dust and very light gases. What's even more surprising is that the tail always points away from the Sun, because of the 'solar wind' blowing on it, even when the comet is moving away from the Sun!

Do you know Halley's Comet? It's the most famous one! It comes back to visit us about every 76 years. The last time was in 1986, and it will return around the year 2061. Your grandparents might have seen it, and you will likely see it too when you're older.

Did you know? In 2014, a space mission called 'Rosetta' achieved the feat of landing a small robot named 'Philae' on a comet! It was the first time we touched a comet to study it closely and understand exactly what it was made of.