Nasa is going asteroid hunting - in our backyard


Nasa is going asteroid hunting - in our backyard

US space agency to build observatory in SA after space rock scare, and to avert a dinosaur wipe-out scenario

Cape Town bureau chief

Ten weeks after an asteroid narrowly missed SA before smashing into Botswana, Nasa has hit the panic button.
The US space agency says it will build an observatory in SA to boost its efforts to hunt down asteroids and save the world from the kind of impact that wiped out the dinosaurs 66 million years ago.
The new telescope, the exact location of which has not yet been confirmed, will be one of two Nasa will build in the southern hemisphere in the next four years. The location of the second one has not yet been decided.
The $3.8m (R54m) project will fill the gaps in Nasa’s Asteroid Terrestrial-impact Last Alert System (ATLAS), which relies on three northern hemisphere observatories.The system spotted 95% of near-Earth asteroids discovered in 2017 but cannot see 30% of the southern sky. That’s why there was panic on June 2 when an asteroid 1.8m across was detected only eight hours before impact.
When the alarm was sounded by the Nasa-funded Catalina Sky Survey, in Tucson, Arizona, the asteroid was the same distance from Earth as the moon.
The asteroid, later named 2018 LA, had its trajectory calculated by the Center for Near-Earth Object Studies at Nasa’s Jet Propulsion Laboratory in Pasadena, California, and it  was deemed harmless.It entered Earth’s atmosphere at 61,000km/h (about 17km per second) and its rapid deceleration meant its back travelled faster than its front, causing it to explode 50km above the ground with the equivalent force of between 300 and 500 tons of TNT.Fragments smashed into Botswana and astronomers and geoscientists teamed up in search for meteorites. Their search began with an analysis of video footage of the fireball, then they hit the ground in Botswana’s Central Kalahari Game Reserve.
“The challenge was to search for a meteorite in 200 square kilometres of uncharted wild in a park teeming with elephants, lions and snakes,” said Professor Alexander Proyer of the Botswana International University of Science and Technology.
After five days of searching, a student found the first rock on June 23 – only the second time that a meteorite has been recovered from an asteroid first spotted in space.Farmer Barend Swanepoel caught 2018 LA on CCTV footage as it flew over Ottosdal, in North West, and his nine-second video has racked up more than 1.8 million views on YouTube.Lindley Johnson, a Nasa planetary defence officer, said 2018 LA was much smaller than the agency was “tasked to detect and warn about”.
“However, this real-world event allows us to exercise our capabilities and gives some confidence our impact-prediction models are adequate to respond to the potential impact of a larger object.”
Johnson said the new southern hemisphere observatories would enable the agency “to cover the entire night sky every day or two to provide as much warning as we can”.
After they come online, “we’ll have close to round-the-clock coverage of the night sky”, said Larry Denneau, an ATLAS co-principal investigator at the University of Hawaii. “The more eyes you have looking, the better.”Out of this world
The first known asteroid was Ceres, discovered by Giuseppe Piazzi in 1801. The solar system contains more than 600,000 known asteroids. Most of them orbit in the Asteroid Belt, a series of rings between the orbits of Mars and Jupiter.
The asteroid that hit Botswana in June, 2018 LA, belonged to the Apollo group of near-Earth asteroids – a type of near-Earth object – which travel within 1.3 astronomical units of the sun. An astronomical unit is the average Earth-sun distance of 150 million kilometres.Near-Earth objects are classified as potentially hazardous objects if they have characteristics that could cause significant destruction on impact.
An asteroid becomes a potentially hazardous object if it is at least 140m in diameter and approaches Earth’s orbit within 7.5 million kilometres.
2018 LA, at 1.8m, was not large enough to be considered a potentially hazardous object, even though it was just outside the moon’s orbit (about 384,000km) when discovered.
Source: Astronomy.comUS astronomy consultant Tim Spahr told Nature: “By placing telescopes in the southern hemisphere, you’ll enhance the ability to protect the planet. There will always be things we can’t see from the north.”
The additional observatories will not only spot asteroids that could harm people, but also detect comets, supernovae and other benign celestial objects.
The asteroid that scientists believe wiped out the dinosaurs was 9km in diameter, but much smaller examples can also inflict serious damage.
“The mid-air explosion of a 20m asteroid in 2013 resulted in burns, cuts and broken bones for people in the Chelyabinsk region of Russi,” Nature reported. “And researchers think that a 50m asteroid devastated thousands of square kilometres of Russian forest in the 1908 Tunguska event.”ATLAS telescopes in Hawaii are designed to find asteroids within 7.5 million kilometres of Earth. They scan the sky rapidly and have software that looks for fast-moving objects.
John Tonry, the founder and principal investigator of ATLAS, said the network could spot asteroids roughly the size of the Chelyabinsk and Tunguska rocks a few days to a week before impact.
Since it started making observations in 2015, ATLAS has discovered 171 asteroids whose path brings them close to Earth’s orbit.

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