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The Washington Post

Alan Duffy was confused. On Thursday, the astronomer’s phone was suddenly flooded with calls from reporters wanting to know about a large asteroid that had just whizzed past Earth, and he couldn’t figure out “why everyone was so alarmed”.
“I thought everyone was getting worried about something we knew was coming,” Duffy, who is also lead scientist at the Royal Institution of Australia, told The Washington Post.
Forecasts had already predicted that a couple asteroids would be passing relatively close to Earth this week.
Then he looked up the details of the hunk of space rock named Asteroid 2019 OK.
“I was stunned,” he said. “This was a true shock.”

This is the video of the close encounter of Asteroid 2019 OK we have been Twitting all day with the Earth: https://t.co/bjT7uhQJuO pic.twitter.com/3e4UyPcdPl
— ASAS-SN (@SuperASASSN) July 25, 2019

This asteroid wasn’t one that scientists had been tracking and it had seemingly appeared from “out of nowhere,” Michael Brown, a Melbourne-based observational astronomer, told The Post.
According to data from Nasa, the craggy rock was large, roughly 100 metres wide, and moving quickly along a path that brought it within about 73,000km (45,000 miles) of Earth. That’s about one-fifth of the distance to the moon and what Duffy considers “uncomfortably close”.
“It snuck up on us pretty quickly,” said Brown, an associate professor with Australia’s Monash University’s School of Physics and Astronomy.
It should worry us all quite frankly. It’s not a Hollywood movie. It is a clear and present danger
Scientist Alan Duffy
“People are only sort of realising what happened pretty much after it’s already flung past us.”
The asteroid’s presence was discovered only earlier this week by separate astronomy teams in Brazil and the United States. Information about its size and path was announced just hours before it rocketed past Earth, Brown said.
“It shook me out my morning complacency,” he said.
“It’s probably the largest asteroid to pass this close to Earth in quite a number of years.”
So how did the event almost go unnoticed?
First, there’s the issue of size, Duffy said. Asteroid 2019 OK is a sizeable chunk of rock, but it’s nowhere near as big as the ones capable of causing an event like the dinosaurs’ extinction.
More than 90 per cent of those asteroids, which are 1km (0.62 miles) or larger, have already been identified by Nasa and its partners.




“Nothing this size is easy to detect,” Duffy said of the asteroid. ″You’re really relying on reflected sunlight, and even at closest approach it was barely visible with a pair of binoculars.“
Brown said the asteroid’s “eccentric orbit” and speed were also likely factors in what made spotting it ahead of time challenging.
Its “very elliptical orbit” takes it “from beyond Mars to within the orbit of Venus,” which means the amount of time it spends near Earth where it is detectable isn’t long, he said.
As it approached Earth, the asteroid was travelling at about 15 miles per second, he said. By contrast, other recent asteroids that flew by Earth clocked in at between 2, 5 and 12 miles per second.
It would have gone off like a very large nuclear weapon. Many megatons, perhaps in the ballpark of 10 megatons of TNT
Alan Duffy
The last-minute detection is yet another sign of how much still remains unknown about space and a sobering reminder of the very real threat asteroids can pose, Duffy said.
“It should worry us all quite frankly,” he said. “It’s not a Hollywood movie. It is a clear and present danger.”
Duffy said astronomers have a nickname for the kind of space rock that just came so close to Earth: “city-killer asteroids”.
If the asteroid had struck Earth, most of it would have likely reached the ground resulting in devastating damage, Brown said.
Japan space explorer arrives at asteroid to search origin of life
“It would have gone off like a very large nuclear weapon” with enough force to destroy a city, he said. “Many megatons, perhaps in the ballpark of 10 megatons of TNT, so something not to be messed with.”
In 2013 a significantly smaller meteor, about 20 metres across, broke up over the Russian city of Chelyabinsk and unleashed an intense shock wave that collapsed roofs, shattered windows and left about 1,200 people injured.
The last space rock to strike Earth similar in size to Asteroid 2019 OK was more than a century ago, Brown said.
That asteroid, known as the Tunguska event, caused an explosion that levelled nearly 500,000 square acres of forest land in Siberia.




Though the chances of a large asteroid landing on a city are “modest”, Brown said it is still worthwhile to devote resources toward detection and prevention.
Brown said Asteroid 2019 OK proves there are “still dangerous asteroids out there that we don’t know of” that “can arrive on our doorstep unannounced.”
Scientists are working on developing at least two approaches to deflecting potentially harmful asteroids, Duffy said.
One strategy involves gently pushing the asteroid slowly over time off its course and away from Earth, he said.
The other, which he called a “very elegant solution”, is the gravity tractor. If an asteroid is detected early enough, it could be possible to divert it using the gravity of a spacecraft, according to Nasa.
Nasa unveils programme aimed at preventing an asteroid apocalypse
People shouldn’t try to “blast it with a nuke,” Duffy said.
“It makes for a great Hollywood film,” he said. “The challenge with a nuke is that it may or not work, but it would definitely make the asteroid radioactive.”
In light of Asteroid 2019 OK, Duffy stressed the importance of investing in a “global dedicated approach” to detecting asteroids because “sooner or later there will be one with our name on it, it’s just a matter of when not if.”
“We don’t have to go the way of the dinosaurs,” he said. “We actually have the technology to find and deflect certainly these smaller asteroids if we commit to now.”


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Space

Earth’s near miss with a ‘city-killer asteroid’ leaves scientists shaken

An undated image of an asteroid in space. Nasa confirmed that on July 25, Asteroid 2019 OK passed about 73,000km (45,000 miles) from Earth, roughly one-fifth the distance to the moon. File photo: AP

Are asteroids humanity’s ‘greatest challenge’? Maybe, and we have nothing to protect us against them

In this combination of photos made from frame grabs from dashboard camera video, a meteor streaks through the sky over Chelyabinsk, about 1500 km east of Moscow, on February 15, 2013. Photo: AP

Trees lay strewn across the Siberian countryside 45 years after a meteorite struck the Earth near Tunguska, Russia in 1953. The 1908 explosion leveled everything for miles near the impact site. The results of the air collision are similar, although much less severe, than they would be if asteroid 1997 XF11 struck the planet as the International Astronomical Union warned was a possibility on Wednesday, March 11, 1998. (AP Photo)

A Russian policeman works near an ice hole, said by the Interior Ministry department for Chelyabinsk region to be the point of impact of a meteor seen earlier in the Urals region, at lake Chebarkul some 80 kilometers (50 miles) west of Chelyabinsk February 15, 2013. The meteor streaked across the sky and exploded over central Russia on Friday, sending fireballs crashing to earth which shattered windows and damaged buildings, injuring more than 500 people. REUTERS/Chelyabinsk region Interior Ministry/Handout (RUSSIA - Tags: DISASTER SCIENCE TECHNOLOGY ENVIRONMENT TPX IMAGES OF THE DAY) ATTENTION EDITORS - THIS IMAGE WAS PROVIDED BY A THIRD PARTY. FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS

(FILES) This file computer generated handout image taken on May 15, 2015 and released by the European Space Agency (ESA) on May 15, 2015 shows the impact of the DART (Double Asteroid Redirection Test) projectile on the binary asteroid system (65803) Didymos observed by the AIM (Asteroid Impact Mission) satellite. The Asteroid Impact Mission (AIM) is a European Space Agency’s mission, scheduled to be launched in 2020. AIM will travel to a binary asteroid system – the paired Didymos asteroids, which will come a comparatively close 11 million km to Earth in 2022. For a successful joint mission, one spacecraft, DART would impact the secondary of the Didymos binary system in October 2022 while AIM would first characterize the target asteroid (surface and internal properties), observe the impact event and measure any change in the relative orbit. / AFP PHOTO / EUROPEAN SPACE AGENCY / Handout / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / EUROPEAN SPACE AGENCY " - NO MARKETING

Apocalyptic asteroid impact was bigger than the one that killed the dinosaurs, scientists say

An aerial view of the remote Pilbara region of Western Australia, where evidence of a massive asteroid strike has been found. Photo: Reuters

An asteroid like a 10-storey building just missed Earth by only half the distance to the Moon. We barely saw it coming

A graphic created by the Slooh space observatory depicts asteroid 2017 AG13. Graphic: Slooh

Asteroid photos sent by Japan’s jumping robotic rovers offer a glimpse of celestial body’s surface

The unmanned Hayabusa2 spacecraft took more than two years to reach the vicinity of the asteroid

The rocky surface of asteroid Ryugu. Photo: AP

China plans ambitious space mission to hunt and ‘capture’ asteroids by 2020

A conceptual image of Nasa’s Orion spacecraft approaching a robotic asteroid capture vehicle. Image: Nasa

This conceptual image shows NASA’s Orion spacecraft approaching the robotic asteroid capture vehicle. The trip from Earth to the captured asteroid will take Orion and its two-person crew an estimated nine days. Image Credit: NASA

epa05917216 A 'Long March CZ-7' rocket carrying the cargo spacecraft 'Tianzhou-1', China's first cargo spacecraft, at the Wenchang Spacecraft Launch Site in Wenchang, south China's Hainan province, 20 April 2017. The cargo ship is developed by the China Academy of Space Technology with a length of 10.6 meters and a diameter of 3.35 meters and a lift-off mass is about 13 tons. EPA/WU HONG

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If the asteroid had struck Earth, most of it would have likely reached the ground resulting in devastating damage


Asteroid that whizzed past Earth this week seemingly appeared from out of nowhere.


Earth’s near miss with a ‘city-killer asteroid’ leaves scientists shaken

.css-1mniedq{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;}If the asteroid had struck Earth, most of it would have likely reached the ground resulting in devastating damage

If the asteroid had struck Earth, most of it would have likely reached the ground resulting in devastating damage