An asteroid the size of a BUS will skim past Earth today - coming within just 140,000 miles of our planet, NASA warns

An asteroid the size of a bus will skim past Earth today – but experts have reassured that there is no cause for alarm. 

The asteroid, called 2024 DW, is expected to come as close as 140,000 miles to our planet today – even closer than the moon. 

It is estimated to be around 42 feet in diameter, which is longer than a London bus and about half the size of a blue whale. 

As 2024 DW flies past Earth, it is travelling at a speed of just over 40,000 miles per hour – roughly 50 times the speed of sound. 

But despite its close proximity to Earth, it shouldn't pose a threat to our planet.  

It is estimated to be around 42 feet in diameter, which is longer than a London bus and about half the size of a blue whale

The asteroid, called 2024 DW, is expected to come as close as 140,000 miles to our planet on Thursday - even closer than the moon (artist's impression of an approaching space rock)

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)

As its name suggests, asteroid 2024 DW was discovered this year by astronomers working on the Mount Lemmon Survey, a project based in Tucson, Arizona. 

NASA lists it as one of the upcoming close approaches on its online tracker, which compiles upcoming objects that are getting closer and closer to Earth. 

But according to Dr Minjae Kim, a space expert at the University of Warwick's astronomy department, it poses no 'real danger' like most of the asteroids that come near us. 

'While the likelihood of a direct hit on land is reduced due to Earth's vast oceans, the potential impact of an asteroid remains a serious concern,' he added. 

Because the moon is on an elliptical orbit of Earth (one that's not perfectly circular), its distance from us gradually changes.  

According to TheSkyLive, the moon is currently 249,768 miles (401,964 km) away from Earth right now.

That means asteroid 2024 DW reaches just over half the distance between Earth and the moon today. 

According to NASA, it made its closest approach today at 04:37 GMT and is now heading back out along its orbit. 

Pictured is the orbit of asteroid 2024 DW (white) in relation to that of Earth (light blue) and Mars (red)

READ MORE: Experts late to notice asteroid the size of the Leaning Tower of Pisa

Asteroid '2023 NT1' is an example of a risky rock unnoticed due to the sun's glare 

Due to its relative proximity to Earth, the asteroid is classed as a near-Earth object (NEO) and is being tracked by the space agency. 

A NEO is defined as such when it comes within 1.3 astronomical units (AU) (120.8million miles) of the sun and hence within 0.3 AU (27.8million miles) of Earth's orbit. 

'NEOs are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to enter the Earth's neighbourhood,' said NASA.

'Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system between the orbits of Mars and Jupiter. 

'The scientific interest in comets and asteroids is due largely to their status as the relatively unchanged remnant debris from the solar system formation process some 4.6 billion years ago.' 

An asteroid is also 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.

Thankfully, 2024 DW is too small to meet the second specification so it is not considered potentially hazardous, but its proximity is still a concern.

On average, Earth is hit by a football pitch-sized rock every 5,000 years, and a civilisation-ending asteroid every one million years, according to NASA's Near-Earth Object Program. 

'Of course, if a significant asteroid threat were imminent, the public would be well-informed by Planetary Defense at NASA,' said Dr Kim. 

'In the event of an asteroid on a collision course with Earth, NASA would provide either a notification of a close encounter or a potential impact.' 

According to a 2017 study, only asteroids that span at least 18 meters (nearly 60 feet) in diameter are potentially lethal if they heading toward Earth. 

The largest known asteroid in the whole of the Solar System, Ceres, is 580 miles in diameter (more than 3million feet) – big enough for humans to live on. 

Thankfully the chances of Ceres hitting Earth are low because its orbit is further out, between Mars and Jupiter, and doesn't intersect with Earth's. 

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.