Sunday space | All about comets, asteroids and meteors

The week before, asteroid 2023bu skimmed Earth at a distance of around 3500 km - less than the distance between Canberra and Perth.

These objects may seem similar, but their formation, what they are made up of, and where they come from are all quite different.

Comets, like comet ZTF, come from a part of space called the Oort cloud. It has never been observed, as it is on the edge of our solar system - hundreds to thousands of times further from the sun than Pluto. While the gravity of the sun does affect these, it is only barely. The slight bump or knock of a comet can either send it out into space, or towards the sun, into the solar system, passing by planets just like comet ZTF.

Comets are relatively small, usually only 3-10km in size, and are like a dirty snowball - a frozen chunk of rock.

These are leftover bits of the solar system, that being so far out from the sun, freeze. Made mostly of carbon monoxide, carbon dioxide, water ice, methane, pebbles and dust, as they go towards the Sun, they heat up and the ice turns to a gas.

Asteroids, on the other hand, are usually much closer to the sun, with most lying in the asteroid belt between Mars and Jupiter.

Defined as minor planets, they have more in common with planets than comets. They are chunks of rock - which can range from more rocky, to metal, to ice. They also range in sizes, from 1m to nearly 1000km - larger than most comets.

The formation of asteroids is very similar to that of planets and dwarf planets - bits of material that clumped together as the solar system was forming. However, these objects do not have enough mass to pull themselves into spheres like dwarf planets or planets, but they do end up in a regular orbit around the sun.

While comets and asteroids are formed objects orbiting around our sun, meteors are different, and we need to understand the difference between meteoroid, meteor and meteorite.

Meteoroid, meteor, and meteorite are really all names for the same piece of rock - but at difference places and times. A meteoroid is a name for any rock, usually something that is broken off an asteroid through a collision, or some dust or pebbles that come off a comet. The meteoroid is in space, and as it hits the Earth and enters our atmosphere, it turns into a meteor.

We often call meteors shooting stars, and these objects are tiny - sometimes the size of a grain of sand. If this rock is big enough and doesn't completely burn up in the atmosphere, it can land on the ground as a meteorite.

A broken off bit of asteroid or comet turns into a meteoroid, which then becomes a meteor, and then a meteorite. Essentially different ways of saying space rock.

Despite all their differences, they are unique bits of our solar system that provide clues to understanding our place in the universe.