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
- Asteroid ‘2023 NT1’ is an example of a risky rock unnoticed due to the sun’s glare
- READ MORE: Here’s what would happen if a massive asteroid actually hit Earth
NASA usually has a reassuringly close eye on asteroids that come anywhere near our planet, but one has managed to slip through the net.
An asteroid called 2023 NT1 reached as close as around 62,000 miles from Earth – about a quarter the distance between Earth and the moon – on July 13.
But it wasn’t until two days after its close approach that NASA scientists detected it, because it was coming from the direction of the sun and was obscured by light.
2023 NT1, which is now moving away from Earth at a speed of about 25,000 miles per hour, is up to 200 feet in diameter – bigger than the Leaning Tower of Pisa.
This also makes it bigger 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 more than the length of the Leaning Tower of Pisa but smaller than other close approach asteroids
READ MORE: What would happen if an asteroid actually hit us?
Scorching heat, flying debris and towering tsunamis would all occur if an asteroid hit (artist’s depiction)
According to data from NASA and the International Astronomical Union, 2023 NT1 made its closest approach to Earth at 10:12 UTC (11:12 BST) on July 13.
The first reported observation two days later was by ATLAS South Africa, a four-telescope system dedicated to spotting hazardous asteroids.
At up to 200 feet (60 metres) across, 2023 NT1 could be larger than the asteroid that caused Meteor Crater in Arizona, said amateur astronomer Tony Dunn on Twitter.
The historic impact crater near Flagstaff, around 3,900 feet in diameter, is thought to have been caused by a rock that hit Earth around 50,000 years ago.
Despite its close approach, 2023 NT1 isn’t large enough to be considered ‘potentially hazardous’.
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.
At a maximum of 200 feet, 2023 NT1 only fits one of those criteria.
Thankfully 2023 NT1 passed by without issue, but the episode highlights that we have a problem spotting some asteroids due to the glare of the sun.
An asteroid is defined as ‘potentially hazardous’ if it comes within 0.05 astronomical units (4.65million miles) of Earth and is larger than 459 feet (140 meters) in diameter (file image)
READ MORE: Meteor Chelyabinsk may have been involved in forming the MOON
The Chelyabinsk meteorite (pictured) that exploded over Russia in 2013 may also have been involved in the massive impact that formed the moon, a study suggests
Just like 2023 NT1, the Chelyabinsk meteor of a decade ago wasn’t noticed because its ‘radiant’, the point in the sky from which it originated, was close to the sun.
The Chelyabinsk meteor exploded in a fireball over Russia a decade ago with energy estimated to be equivalent to 500,000 tonnes of TNT sending a shockwave twice around the globe.
To combat the threat of space rocks blocked by sunlight, the European Space Agency (ESA) is set to launch its NEOMIR orbiting observatory around 2030.
The observatory will act as an early warning system to detect and monitor any asteroid coming towards Earth from the sun’s direction.
NEOMIR will be stationed at the ‘L1’ Lagrange point – a position in space between Earth and the sun where objects sent there tend to stay put.
Undisturbed by Earth’s atmosphere, its infrared telescope will be able to spot asteroids 65 feet (20 metres) and larger currently lurking in the sunlight.
Planetary defence has been a big topic over the past 12 months, in part because of NASA’s successful Double Asteroid Redirection Test (DART) mission.
In September last year, the DART spacecraft was intentionally crashed into Dimorphos, the asteroid moonlet in the double-asteroid system of Didymos.
To combat the threat of space rocks blocked by sunlight, the European Space Agency (ESA) is set to launch its NEOMIR orbiting observatory around 2030 (artist’s impression)
Although this asteroid posed no threat to Earth, the hope is that the success of humanity’s first ever planetary defence 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 modifying its orbit.
Unfortunately, there are some types of space rock that could prove difficult or impossible to deflect with any such manmade object, a recent study suggests.
‘Rubble pile’ asteroids – such as Itokawa around 1.2 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 any impact energy and carry on its trajectory, the study authors claimed.
POTENTIAL METHODS FOR ELIMINATING THE THREAT OF AN ASTEROID
DART is one of many concepts of how to negate the threat of an asteroid that have been suggested over the years.
Scientists in California have been firing projectiles at meteorites to simulate the best methods of altering the course of an asteroid so that it wouldn’t hit Earth.
According to the results so far, an asteroid like Bennu that is rich in carbon could need several small bumps to charge its course.
‘These results indicate multiple successive impacts may be required to deflect rather than disrupt asteroids, particularly carbonaceous asteroids,’ researchers said.
Another idea, known simply as ‘nuke’, involves blowing up a nuclear explosive close to the asteroid.
However, this could create smaller but still potentially dangerous fragments of rock that could spin off in all directions, potentially towards Earth.
Ion Beam Deflection
With Ion Beam Deflection, plumes from a space probe’s thrusters would be directed towards the asteroid to gently push on its surface over a wide area.
A thruster firing in the opposite direction would be needed to keep the spacecraft at a constant distance from the asteroid.
And yet another concept, gravity tractor, would deflect the asteroid without physically contacting it, but instead by using only its gravitational field to transmit a required impulse.
Professor Colin Snodgrass, an astronomer at the University of Edinburgh, said: ‘There have been a few concepts suggested, such as a ‘gravity tractor’ to slowly tow an asteroid away instead of pushing it with a kinetic impactor.
‘But the kinetic impactor is definitely the simplest technology to use on the sort of timescale that is most likely to be of concern for this size of asteroid, i.e. years to decades’ warning time.’
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