In a major milestone for astronomers, more than 30,000 near-Earth asteroids (NEAs) have now been discovered in the Solar System.
According to the European Space Agency (ESA), there are now a total of 30,039 near-Earth asteroids known to science, and the number is rapidly increasing.
Near-Earth asteroids are rocky bodies that orbit the Sun on a path that brings them close to Earth’s orbit – and some have the potential to hit our planet.
ESA claims that 1,425 of the total have a ‘non-zero chance of collision’ with our planet and are therefore under the ‘watchful eye’ of a network of telescopes.
Near-Earth asteroids are rocky bodies that orbit the Sun on a path that brings them close to Earth’s orbit. The picture shows an artist’s impression of asteroid 21 Lutetia, which is located in the main asteroid belt
It is estimated that there are about 10,000 NEAs larger than 460 feet (140 meters) in diameter. And there are also an estimated 1,000 NEOs larger than 3,280 feet (one kilometer) in diameter, highlighting the need to keep track of these space rocks.
WHAT ARE NEAR-EARTH ASTEROIDS?
Near-Earth asteroids are rocky bodies that orbit the Sun on a path that brings them close to Earth’s orbit.
An asteroid is called a near-Earth asteroid (NEA) when its orbit brings it within 1.3 astronomical units (AU) of the Sun.
A single astronomical unit is the distance between the Sun and the Earth.
According to ESA, the majority of the 30,000 NEAs were discovered in the last decade, thanks to rapidly improving technology.
“The good news is that more than half of today’s known near-Earth asteroids were discovered in the last six years, which shows how much our asteroid vision has improved,” said Richard Moissl, ESA’s head of planetary defence.
‘As this new 30,000 detection milestone shows, and as new telescopes and detection methods are built, it’s only a matter of time before we find them all.’
Of the 30,039 NEAs, about 10,000 are estimated to be larger than 460 feet (140 meters) in diameter and 1,000 larger than 3,280 feet (one kilometer) in diameter—underscoring the need to keep track of these space rocks.
Currently, NEAs make up about a third of the approximately one million asteroids discovered in the Solar System so far.
Most of them live in the asteroid belt – the ring-shaped region of the solar system that lies roughly between the orbits of Jupiter and Mars.
Most NEAs reside in the asteroid belt – the ring-shaped region of the Solar System roughly between the orbits of Jupiter and Mars
DIFFERENT TYPES OF RUMBBERG
An asteroid is a large chunk of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the Main Belt.
ONE comet is a rock covered in ice, methane and other compounds. Their orbits take them much further out of the solar system.
ONE meteor is what astronomers call a flash of light in the atmosphere when debris burns up.
This waste itself is known as a meteoroid. Most are so small that they evaporate in the atmosphere.
If any of this meteoroid reaches Earth, it is called a meteorite.
Meteors, meteoroids and meteorites usually originate from asteroids and comets.
The first ever NEA to be discovered, called 433 Eros, was first noticed by German astronomer Carl Gustav Witt at the Berlin Observatory on August 13, 1898.
433 Eros’ orbit, noted for its strange, elongated shape and rocky composition, brings it within about 13.5 million miles of Earth – 57 times the distance of the Moon.
In addition to being the first NEA discovered, 433 Eros became the first asteroid to be orbited by a spacecraft and the first to have a spacecraft land on it.
The craft – NEAR Shoemaker – studied Eros from close orbit over a period of one year before landing on its surface in February 2001.
An asteroid is classified as a near-Earth when its orbit brings it within 1.3 astronomical units (AU) of the Sun.
A single astronomical unit is the distance between the Sun and the Earth (93 million miles), so many are still a considerable distance from us.
Fortunately, experts can detect their position and whether they will hit Earth up to hundreds of years into the future.
“Of course, any asteroid discovered near Earth qualifies as a near-Earth asteroid, but many are found far from home,” said Marco Micheli, astronomer at ESA’s Near-Earth Object Coordination Centre.
‘New objects are observed over time, their movements are studied and with just a handful of data points from different nights their future positions can be predicted.
‘Depending on the number and quality of observations, this could extend decades, even hundreds of years into the future.’
433 Eros’ orbit, noted for its strange elongated shape and rocky composition, brings it within about 13.5 million miles of Earth – 57 times the distance of the moon
On average, Earth is hit by a rock the size of a football pitch every 5,000. year and a civilization-ending asteroid every million years, according to NASA’s Near-Earth Object Program.
In an effort to tackle the threat posed by asteroids that may one day get a little too close for comfort, NASA formed a planetary defense program, which includes the Double Asteroid Redirection Test (DART) mission.
DART was launched from California last November – and finally ended its 10-month journey when it hit the asteroid Dimorphos last month.
Dimorphos, about 560 feet in diameter, orbits a larger asteroid called Didymos, both of which are about 6.8 million miles away from our planet.
On September 26, DART smashed into Dimorphos, which orbits a larger asteroid called Didymos. Dimorphos is depicted here in scale with Rome’s Colosseum
DART hit the space rock at more than 14,000 miles per hour and was destroyed on impact, while Dimorphos received a ‘little nudge’ to change its trajectory by a fraction.
NASA announced earlier this month that the mission was a success, as the craft managed to shorten Dimorphos’ orbit by 32 minutes.
Neither Dimorphos nor Didymos pose any danger to Earth; rather, the $325m (£298m) mission was a rehearsal of what might be required if a space rock one day threatens our planet.
NASA’S DART MISSION CONSIDERED A HUGE SUCCESS: CRAFT PUSHED ASTEROID’S ORBIT
NASA’s DART mission, which plowed a spacecraft into a small asteroid 6.8 million miles from Earth, was a ‘huge success’.
Data published on October 11 revealed that the orbit of the space rock was successfully displaced by the impact.
The planetary defense test, conducted on September 26, aimed to see if we could push the path of a massive asteroid heading straight for our planet.
This successful mission marks “humanity’s first time intentionally altering the motion of a celestial body and the first full-scale demonstration of asteroid deflection technology,” NASA said.
Before the impact, Dimorphos took 11 hours and 55 minutes to orbit its parent asteroid, Didymos – but after the impact, its orbit has been shortened by 32 minutes.
The original goal was to shave at least 10 minutes, so the results far exceeded this.