Although many projects to track Earth-passing asteroids have been disrupted by the pandemic, astronomers detected nearly 3,000 near-Earth asteroids last year – a record number in a year.
A 340-meter-wide asteroid called Apophis passed safely past Earth on March 6. Its next return, in 2029, will be a special occasion: Apophis will fly over the Earth at less than 40,000 km, just above the orbits of several high-flying satellites. 2029 will be the first time astronomy enthusiasts can see such a large asteroid hovering in the sky.
Apophis’ “visit” last week gave scientists the opportunity to test Earth’s defenses against asteroids – the ability to quickly assess whether an asteroid could hit Earth. “It’s like a fire drill,” said Vishnu Reddy, a planetary scientist at the University of Arizona, Tucson.
This Apophis flight is helping scientists test what they already know about near-Earth asteroids – as well as reveal what needs to be studied further.
Since 1998, when NASA launched its search for near-Earth asteroids, scientists have discovered more than 25,000 asteroids. And 2020 holds the record for the number of asteroids found. Despite the Covid-19 pandemic which disrupts many observation projects, in 2020, astronomers discovered 2,958 near-Earth asteroids previously unknown.
Most of the results come from the Catalina Sky Survey Project, which uses three telescopes in Arizona to hunt asteroids that fly close to Earth. The project was briefly closed last spring due to the pandemic, and closed again shortly after due to a wildfire, in June. However, sightings at Catalina have remained. CD3 – a small asteroid less than 3 meters in diameter that orbits the Earth due to being “captured” by the force of planetary attraction. This “mini moon” then regressed from Earth’s gravity last April.
Another 1,152 finds come from the Pan-STARRS survey telescope in Hawaii. Pan-STARRS discoveries include an object called 2020 SO, which turned out to be not an asteroid, but rather a rocket left in space, which has been spinning ever since it helped make the real ones. NASA launched a mission to the moon in 1966.
Near the button
Several asteroids discovered last year flew very close to Earth – at least 107 of them grazed the planet at a distance closer than the Moon (the Moon is over 380,000 km from Earth). In August 2020, the small asteroid 2020 QG crossed the Indian Ocean at an altitude of just 2,950 km, becoming the closest asteroid to Earth known at the time. But that record was quickly broken just three months later. Another asteroid, 2020 VT4, grazes Earth at an altitude of less than 400 km. If it collided, the asteroid would likely shatter in Earth’s atmosphere.
All of these discoveries make astronomers more aware of the volatile nature of the solar system – there are many active asteroids in near Earth space. According to Reddy, recent efforts to observe Apophis show that astronomers around the world can work together to assess the threat posed by asteroids. “It was a huge international effort,” said Reddy, “and a lot of fun.” By the time Apophis reappears, eight years from now, scientists will have an even more detailed understanding of the space rocks that threaten Earth.