Today, while you’re having your Valentine’s Day brunch, an asteroid potentially the length of 30 London buses will fly past Earth. And this is just one of five asteroids approaching today. Not one but five asteroids are passing by Earth today, and they’re all getting as close as possible.

The largest was discovered just a few weeks ago; potentially dangerous 2024 BR4. This is a considerable piece of space rock, 140-300 meters long. At maximum estimate, that’s the size of an oil tanker, six Olympic-sized swimming pools from end to end, or the height of the Chrysler Building in New York.

And like the box of chocolates you tucked into, the day had a few more surprises. University of Sussex astronomer Dr. Darren Baskill tells us more:

“On Wednesday, February 14, 2024, five asteroids will pass by Earth – all within a radius of five million kilometers!”

This may seem like a long way to go, but from an astronomical perspective it’s just a stone’s throw away.

“The closest of the five is asteroid 2024 CU1, about 20 meters in diameter, which will be about 52 percent farther from us than the Moon.”

2024 CU1 approaches closest time at 13:31 GMT (+/- 1 minute). However, with a diameter of only 20 meters, the ‘killer city’ that made headlines is much smaller than the 2024 BR4.

How close will asteroid 2024 BR4 come?

Asteroid 2024 BR4, one of a series of asteroids hurtling past Earth today, will make its closest approach to 4.6 million kilometers (2.86 million miles). In terms of astronomical units, this is approximately 0.03 astronomical units; this is within the defined criteria for a potentially hazardous object (see ‘What is a potentially hazardous’ asteroid? below).

(To convert kilometers/miles to AU, divide the distance in km/miles by the distance of 1 AU in the same unit.)

Approach will occur today at 11:03 GMT (+/- 1 minute).

Will asteroid 2024 BR4 hit Earth?

Although the Valentine’s Day asteroid is hurtling through space at about 44,880 km/h (27,887 mph), which is slightly faster than the average speed achieved by Galileo during its six-year mission to reach Jupiter, we’re not worried. about how it affects our heavenly oasis.

It will pass us safely and pose no direct threat to the Earth:

“Asteroid 2024 BR4 will pass Earth 12 times farther from the Moon than the Moon,” Baskill explains.

What do we know about asteroid 2024 BR4?

Unfortunately, very few. In general, the larger the object, the brighter it is (the brighter the object, the lower the brightness), and NASA assigned magnitude 21.457 to asteroid 2024 BR4. It’s not very bright.

But you also need to know the albedo (surface reflectance) of the object, which we do not know at the moment. The best available estimates place the asteroid between 140 and 300 meters in diameter. But we know its orbit with relative certainty. And today’s visit will be the closest 2024 BR4 will come in 120 years.

“We don’t need to worry about 2024 BR4 because of its distance, but it’s interesting that it’s around 200 meters in size,” says Baskill. “This is larger than the 50-metre asteroid that hit Tunguska in Siberia in 1918. “Almost 100 million trees were cut down in the area within a 30 km radius of the asteroid burning up in our atmosphere,” he explains.

As the name suggests, 2024 BR4 was discovered quite recently. It was first observed by the Catalina Sky Survey in Arizona on January 30, 2024, and was classified as an Apollo asteroid. This is a group of asteroids that can cross Earth’s orbit, making them of particular interest to astronomers (and space agencies) who monitor their potential collision risks.

More than 18,000 Apollo-type asteroids are currently known, most of which originate from the asteroid belt between Mars and Jupiter.

What does a “potentially hazardous” asteroid mean?

A “potentially hazardous” object (PHO) could be an asteroid (PHA) or a comet (PHC) that could come dangerously close to Earth. If an asteroid is large enough and its orbit brings it close to Earth, it is considered potentially hazardous. There is a small chance of hitting our planet.

Officially, for a space rock to be classified as “potentially hazardous” it must be 0.05 AU or less from Earth; This translates to approximately 7.48 million kilometers (or 4.65 million miles).

To put this into context, 1 AU is the average distance between the Earth and the Sun; that’s about 93 million miles (150 million kilometers). Mercury is about 0.39 AU from the Sun, Venus is about 0.72 AU from the Sun, and Mars is about 1.52 AU from the Sun.

So if you compare distances to our celestial neighbors, 0.05 AU is a relatively short distance.

What is a “city killer” asteroid?

“City-killer” asteroid refers to asteroids that could cause serious damage to a city (or other densely populated area) if they collided with Earth. These asteroids are generally smaller than asteroids that can cause global catastrophes, but are large enough to pose a serious threat.

About 7,000 asteroids are now known that fall into the category of “city killers”.

How many asteroids are we in close contact with?

More than you think. Dr. Baskill explains:

“Last week alone three asteroids passed us closer than the Moon! 2024 CY1 passed on February 12, 2024, at a distance of only 120,000 km. CJ1 passed us at a distance of 370,000 km (the same distance to the Moon) on February 9, 2024, and 2024 CK1 passed us at a distance of 228,000 km. On February 8, 2024.” .

2024 CY1 is so close to us on Monday that it has actually passed between Earth and Moon. It flew just 121,148 km (75,278 miles) from Earth. But don’t worry; Although we are only six weeks into the year, 10 (known) asteroids have already passed within 1 lunar distance of us without disturbing us (1 lunar distance is the distance between the Earth and the Moon).

“Fortunately, all three of these objects were only 5 to 10 meters in diameter, so while it would be a very impressive sight to watch them burn up in our atmosphere, we don’t have to worry about objects that size,” Baskill adds.