ST. GEORGE — Four asteroids, including a 394-foot space boulder the size of a 40-story skyscraper, recently hurtled past Earth at more than 30,000 mph, including one icy rock that NASA says crossed Earth’s orbit as it shot through this neck of the cosmic neighborhood and one that was closer than the moon. But don’t worry. If you’re reading this, everything worked out fine.
The first near-Earth object, 2019 UT1, has been hurtling toward the Earth at a speed of almost 20,000 mph. The rogue space rock has an estimated diameter of around 69 feet and was estimated to have come within about a million miles of the planet’s surface at its closest approach Monday morning.
A near-Earth object is anything that comes within about 30 million miles of the planet’s orbit, according to NASA.
Based on calculations, NASA scientists predicted the asteroid would pass within a few million miles of the planet’s surface, and while that may sound like it’s a safe distance from Earth, in astronomical terms it is fairly close.
The asteroid is roughly the same size as the rock that flattened millions of trees near the Tunguska River in Russia in 1908, after exploding about 3 miles above Earth’s surface with energy about 1,000 times greater than the atomic bomb dropped on Hiroshima, Japan, during World War II.
The second asteroid, dubbed 2019 TR2, has a diameter of 394 feet, which is the size of a 40-story building. The rock made its flyby within a few million miles of the planet’s surface Monday shortly after 9 p.m. MDT.
The icy rock is categorized as an Apollo asteroid, or one that crosses Earth’s orbit as it completes its trip around the sun. These asteroids typically have a wider orbit than Earth does, and also pass near other planets, including Mars and Mercury, according to NASA’s Center for Near-Earth Object Studies.
The closest flyby was the third near-Earth asteroid, dubbed 2019 UB8, a 14- to 31-foot asteroid that came within about 120,000 miles from Earth at its closest approach shortly after midnight Tuesday morning, which is roughly half the distance between Earth and the moon.
The fourth asteroid, UL-5, is set to fly by at 6 a.m. Tuesday and will come within a million miles of the Earth’s surface at its closest approached. The asteroid is between 18-60 feet in diameter and will also come close to Venus and Mercury.
October’s heavenly encounters
October has had a number of cosmic visitors, including four space rocks that whizzed by Oct. 1. While none of them were close enough to the planet to cause any harm, three of the asteroids were discovered just hours before making their appearance, giving little time to prepare for an emergency should any one of the icy rocks have found themselves on a collision course with Earth.
Asteroid 2019 SM8 was discovered by astronomers at the Mount Lemmon Observatory in Arizona, and at its closest, it was less than 100,000 miles from Earth. Just over an hour later, a second newly-discovered space rock, 47-foot Asteroid 2019 SE8, flew within 674,000 miles of the Earth’s surface, while a third newfound asteroid, 2019 SD8, passed about 331,000 miles from Earth and was discovered the day before.
The final nearby visit, Asteroid 2018 FK5, was the only expected asteroid, flying by Earth on Oct. 1, and was well-known to NASA long before its arrival. It was also the most distant space rock — passing more than 3 million miles from Earth. Astronomers at Mt. Lemmon discovered the 24-foot-wide asteroid in March of last year.
Asteroids and chance encounters with Earth
While none of these asteroids have much of a chance of hitting the planet today, NASA still classifies them as “potentially hazardous asteroids” since the rocks could still pose a threat in the future when their orbits cross paths with Earth’s again. This is why NASA and other agencies around the world are actively scanning the skies for dangerous asteroids.
The space rocks that worry NASA scientists are the really big ones, or those that are at least half a mile in diameter. So far, more than 880 of these mountain-size space rocks are known, with possibly 50 more or so left to be discovered — none of which pose a threat to Earth for the foreseeable future.
Space agencies are also working on ways to stop an asteroid in its tracks by developing an emergency response to address any threats posed by a rogue asteroid should it be on a collision course with Earth.
NASA says that if an asteroid’s approached is too close, it can be affected by the gravitational pull of the planet, altering the space rock’s trajectory which could theoretically place it on a collision course with the Earth.
To date, astronomers have spotted more than 8,000 near-Earth asteroids that are at least 460 feet wide or larger — big enough to wipe out a state-size section of the planet. Even though space agencies around the globe are making progress, that only accounts for one-third of the more than 25,000 space rocks that are thought to be frequent travelers in the neighborhood.
The biggest known asteroid is 4 Vesta – a giant rocky body more than 460-miles across that resides in the main asteroid belt, only surpassed in size by the dwarf planet Ceres.
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