The largest of the trio could cause catastrophe if it smashes into our planet, and is as large as the leaning tower of Pisa.

That’s according to NASA, which has listed the asteroids on its “near-Earth objects” alert page.

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The first will pass Earth around 3:20am tomorrow (Tuesday, January 15, 2.20pm AEDT) at speeds of over three miles per second (17,380 km/h).

Known as 2019 AT6, the 17-metre object will skim within two million miles of Earth, or about eight times the distance between our planet and the moon.

The second space rock to fly past Earth tomorrow, 2019 AM8, is far larger than its predecessor, and is approaching us at twice the speed.

As big as a blue whale, it will hit speeds of almost seven miles per second (40,555km/h) as it passes Earth on Tuesday at 4:03pm (Wednesday, January 16, 3.03am AEDT).

The asteroid will pass our planet just over 2 million miles (3.22 million kilometres) from its surface, or eight and a half times the distance between the moon and Earth.

The third asteroid scheduled for a close shave with Earth is 2019 AG7 – and it’s the biggest of the lot.

Measuring 51 metres in diameter – meaning it’s as wide as the leaning tower of Pisa is tall – 2019 AG7 is scheduled for a 10:43pm fly-by tomorrow evening (Wednesday, November 16, 9.43am AEDT).

Reaching speeds of 4.2 miles per second (24,333 km/h), it will pass closer than its predecessors, zipping within 950,000 miles (1.53 million kilometres) of our planet – about four times the distance between Earth and the moon.

As many as twelve near-Earth objects are expected to fly past our planet between now and the end of this month, meaning tomorrow’s trio are not unusual.

The good news is that the astWeroids are actually classified as “small bodies” by NASA, which does not believe the objects pose any threat to life on Earth.

Even if they were on a collision course with our planet, asteroids of this size often break up in our atmosphere long before they reach its surface.

“Global catastrophes” are only triggered when objects larger than 1000 metres smash into Earth, according to NASA.

WHAT’S THE DIFFERENCE BETWEEN AN ASTEROID, METEOR AND COMET?

Asteroid: An asteroid is a small rocky body that orbits the Sun. Most are found in the asteroid belt (between Mars and Jupiter) but they can be found anywhere (including in a path that can impact Earth)

Meteoroid: When two asteroids hit each other, the small chunks that break off are called meteoroids

Meteor: If a meteoroid enters the Earth’s atmosphere, it begins to vapourise and then becomes a meteor. On Earth, it’ll look like a streak of light in the sky, because the rock is burning up

Meteorite: If a meteoroid doesn’t vapourise completely and survives the trip through Earth’s atmosphere, it can land on the Earth. At that point, it becomes a meteorite

Comet: Like asteroids, a comet orbits the Sun. However rather than being made mostly of rock, a comet contains lots of ice and gas, which can result in amazing tails forming behind them (thanks to the ice and dust vaporising)

This story originally appeared on The Sun and is republished with permission.