If you’ve noticed a surge in reports of asteroids zooming near Earth in the past few years, it seems like our planet is more in danger than ever of being hit by a space rock. But the number of asteroids threatening Earth hasn’t really increased – our ability to detect these asteroids has improved dramatically.
Thanks to technological improvements such as increased computing power and more powerful telescopes, astronomers can now scan the sky in more detail than ever before and discover more objects orbiting the sun and approaching the earth. However, this work cannot be carried out by just one country or agency. To protect the planet, we need a global network of telescopes and researchers working together.
To learn more about how to identify and track asteroids approaching Earth and how global cooperation can protect our planet, we spoke to comet expert Olivier Hainaut from the European Southern Observatory.
Tools of the trade
When it comes to spotting asteroids, there are two main types of tools astronomers use: First, there are all-sky surveys. These surveys scan the entire sky to look for various objects, including asteroids, that could potentially threaten Earth. When a survey detects an asteroid, it can usually track it and determine its trajectory to see if it is approaching our planet.
There is a catch, however. Most surveying telescopes are built in the northern hemisphere as most of the rich countries that build telescopes are in the north. However, you cannot see the entire sky from the northern hemisphere. From Hawaii, where there are many telescopes, for example, you can see about three-quarters of the sky. And that means that some objects are approaching in our blind spot, like a giant asteroid that recently passed Earth and was discovered by an amateur astronomer from Brazil.
Sometimes an asteroid is too weak for an all-sky survey to track, or it looks particularly interesting or as if it could threaten Earth. In these cases, the all-sky surveys relay information about the object to astronomers who use the second important tool, large telescopes. These devices are distributed over the northern and southern hemisphere, such as the two Keck telescopes in Hawaii or the Very Large Telescope in Chile.
These large telescopes have a smaller field of view – so they can only look at a small area of the sky at a time – but they can look in much more detail so they can be used to track asteroids once they have been identified.
Where to build a big telescope
In practice, it would be easiest for businesses to build telescopes in their literal backyard, but that won’t change it with large telescopes. This is why the European Southern Observatory has telescopes in Chile, even though it is a European organization.
These large telescopes have to cover both hemispheres, as Hainaut explained: “In the southern hemisphere, some things are visible that are not visible from the north: the galactic center as the center of our galaxy in the south and the two magellanic clouds that are the two satellites [galaxies] to our Milky Way. These are three very important objects and it has not been possible to study them properly from the north. “
But not just any place in the southern hemisphere will. Sites for large telescopes must meet very specific parameters, e.g. B. far from cities to avoid light pollution and minimal cloud cover so that visibility is not impaired. Another problem is turbulence. If the wind is turbulent in a particular location, the images collected by a telescope there will be distorted.
It is also helpful to have a location that is at high altitude and has little water in the atmosphere. These factors tend to coincide with low cloud cover and low turbulence.
After a long search, ESO found the ideal location in Chile with locations in and on the edge of the Atacama Desert. “Northern Chile is completely magical,” said Hainaut. “It’s a desert, it’s high, and it’s close to the sea.” Being near the ocean means that the wind is generally one-way and flowing in a straight line rather than turbulent.
It’s the perfect place for astronomy, so it’s now home to ESO’s Paranal Observatory, which houses the Very Large Telescope, and the La Silla Observatory, which houses a number of smaller telescopes.
Using telescopes to track asteroids
As catchy as it sounds, very large asteroids, like the ones believed to have killed the dinosaurs, aren’t the top worry right now when it comes to protecting the planets. These huge boulders, more than a kilometer tall, are relatively easy to track. “The dinosaur killers, I’d say we’re in pretty good shape,” said Hainaut. “Because we still know most of these asteroids today, because they are big enough.”
At the other end of the scale, asteroids about the size of a soccer ball burn up in the atmosphere and become a shooting star. The asteroids that are most dangerous for our planet from today’s perspective are in the middle range. “The dangerous ones for the coming years are roughly between a hundred and a kilometer,” said Hainaut. “We have a lot to discover there.”
We have even had close contact with such effects over the past decade. In 2013, an asteroid about 20 meters wide entered the Earth’s atmosphere near the Russian city of Chelyabinsk and exploded about 30 kilometers above the ground. The resulting explosion shone brighter than the sun, creating a shock wave that blew out windows in buildings in six different cities. Thousands of people were injured, but luckily no one died.
Fortunately, the object exploded high in the atmosphere and didn’t hit the ground or the damage would have been much, much worse. The object was estimated to weigh between 12,000 and 13,000 tons and exploded with 25 times the energy of the atomic bomb detonated on Hiroshima.
The next generation of sky surveys
Although great strides have been made in the discovery of asteroids in recent years, astronomers recognize that there is more work to be done. The task of discovering asteroids will be taken over by upcoming projects such as the Vera C. Rubin Observatory, which will be performing all-sky surveys with its 8.4-meter Simonyi survey telescope.
The observatory is located in the Chilean province of Elqui and will take its first photo with the world’s largest digital camera next year. This will help offset the northerly bias of surveying telescopes by capturing the sky from the south.
“This is really a game changer,” said Hainaut. “It’s a big telescope, 8 meters, which means it’s really the same class as that [Very Large Telescope], as perky, as Subaru, as twin. Except that it is a wide-field survey telescope. “That means it will see the entire sky, but also down to the smallest detail, so that astronomers can see smaller or faint objects.
Identifying potentially dangerous asteroids is a central goal of the project, as Hainaut explained: “There will be an extremely aggressive schedule that covers the entire sky every few days and processes everything in real time, including an algorithm to find an asteroids.”
Planet protection is a global endeavor
If we can detect asteroids before they arrive on Earth, then we can take steps to protect ourselves. With a few hours’ warning of where an impact might occur, we could save thousands of lives by turning off gas and electricity in the area. And with years or even decades of warning, we could take steps to deflect or destroy an incoming asteroid using technologies like the Hera mission, a planetary defense collaboration between NASA, ESA (European Space Agency) and many other countries and agencies.
One thing is clear: when it comes to identifying and tracking asteroids and mitigating the damage caused by potential impacts, no country can act alone. Protecting the planet is a truly global endeavor.