Huge asteroid the size of the Leaning Tower of Pisa flew closer to Earth than the MOON this month – and scientists didn’t notice until two days later

NASA usually keeps a reassuringly close eye on asteroids that pass anywhere near our planet, but one has managed to slip through the net.

An asteroid called 2023 NT1 reached about 100,000 kilometers from Earth on July 13 — about a quarter of the distance between Earth and the moon.

But it wasn’t until two days after its approach that NASA scientists discovered it, because it came from the direction of the sun and was obscured by light.

Now moving away from Earth at about 40,000 kilometers per hour, 2023 NT1 is up to 60 meters in diameter – larger than the Leaning Tower of Pisa.

This also makes it taller than the 60-foot Chelyabinsk meteor, which injured more than 1,600 people when it entered Earth’s atmosphere in 2013.

According to data from NASA And the International Astronomical Union2023 NT1 made its closest approach to Earth at 10:12 UTC (11:12 BST) on July 13.

The first reported sighting two days later was by ATLAS South Africa, a four-telescope system dedicated to detecting dangerous asteroids.

At up to 200 feet (60 meters) in diameter, 2023 NT1 could be larger than the asteroid that created Meteor Crater in Arizona, said amateur astronomer Tony Dunn on Twitter.

The historic impact crater at Flagstaff, about 1,200 meters in diameter, is thought to have been caused by a rock that hit Earth about 50,000 years ago.

Despite its close approach, 2023 NT1 is not big enough to be considered “potentially dangerous.”

An asteroid is defined as “potentially hazardous” if it comes within 0.05 astronomical units (4.65 million miles) of Earth and is larger than 459 feet (140 meters) in diameter.

With a maximum of 200 feet, 2023 NT1 meets only one of those criteria.

Fortunately, 2023 NT1 passed without a hitch, but the episode highlights that we have a problem spotting asteroids due to the sun’s glare.

Like 2023 NT1, the Chelyabinsk meteor from a decade ago went unnoticed because its “radiant” point in the sky it came from was close to the sun.

The Chelyabinsk meteor exploded in a fireball over Russia ten years ago with an energy estimated to be equivalent to 500,000 tons of TNT send a shock wave around the world twice.

To counter the threat of sunlight-blocked space rocks, the European Space Agency (ESA) will launch its NEOMIR observatory into orbit around 2030.

The observatory will act as an early warning system to detect and track any asteroid coming toward Earth from the Sun’s direction.

NEOMIR will be stationed at the ‘L1’ Lagrange point – a position in space between the Earth and the Sun where objects sent there tend to stall.

Undisturbed by Earth’s atmosphere, the infrared telescope will be able to spot asteroids 20 meters and larger currently lurking in the sunlight.

Planetary defense has been a big topic for the past 12 months, in part because of NASA’s successful Double Asteroid Redirection Test (DART) mission.

Last September, the DART spacecraft purposely crash-landed into Dimorphos, the asteroid moonlet in the binary asteroid system of Didymos.

While this asteroid posed no threat to Earth, the hope is that the success of humanity’s first-ever planetary defense test could provide a blueprint for defending our planet against future threats from space.

It was the world’s first test of a kinetic impact mitigation technique, using a spacecraft to deflect an asteroid by altering its trajectory.

Unfortunately, there are some types of space rock that are difficult or impossible to deflect with such a man-made object, a recent study suggests.

“Mess” asteroids – like Itokawa some 2 million miles away – are made up of loose boulders and rocks that have clumped together under the influence of gravity, so much of them are empty space.

Such an asteroid would act as a “space cushion” in that it would absorb all of the impact energy and continue its orbit, the study authors claimed.