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

By William On Jul 20, 2023

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.

2023 NT1 is up to 200 feet in diameter greater than the length of the Leaning Tower of Pisa, but smaller than other asteroids approaching nearby

Recently discovered #asteroid 2023 NT1 passed about 1/4 the moon’s distance on July 13, but was not detected until July 15 as it approached Earth in the daytime sky. It could be as much as 200 feet across, possibly bigger than the asteroid that created Meteor Crater in Arizona. pic.twitter.com/VLXB4ChTMJ

—Tony Dunn (@tony873004) July 16, 2023

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.

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 (file image)

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.

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

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.

POSSIBLE METHODS TO ELIMINATE THE THREAT OF AN ASTEROID

DART is one of many concepts to deny the threat of an asteroid that have been suggested over the years.

Multiple bumps

Scientists in California fired projectiles at meteorites to simulate the best methods for altering an asteroid’s course so it wouldn’t hit Earth.

According to the results so far, a carbon-rich asteroid like Bennu could need several small bumps to charge its orbit.

“These results indicate that multiple successive impacts may be needed to deflect rather than disrupt asteroids, particularly carbonaceous asteroids,” the researchers said.

Nuke

Another idea, known simply as “nuke,” is to blow up a nuclear explosive near the asteroid.

However, this could create smaller but still potentially dangerous rock fragments that could spin away in all directions, possibly towards Earth.

Ion beam deflection

With Ion Beam Deflection, plumes from a space probe’s thrusters would be directed toward the asteroid to push gently over a large area on its surface.

A thruster firing in the opposite direction would be necessary to keep the spacecraft at a constant distance from the asteroid.

Gravity trigger

And yet another concept, gravity trigger, would deflect the asteroid without making physical contact with it, instead using only the gravitational field to transmit a required momentum.

Professor Colin Snodgrass, an astronomer at the University of Edinburgh, said: ‘A few concepts have been proposed, such as a ‘gravity trigger’ to slowly drag an asteroid away rather than pushing it with a kinetic impactor.

“But the kinetic impactor is definitely the simplest technology to use on the kind of timescale that is likely to matter for this size of asteroid, that is, years to decades of warning time.”