The idea of a killer asteroid smashing into Earth might sound like the plot of the latest science fiction blockbuster.
But it could become a reality, according to NASA, which puts the chance of a deadly asteroid striking Earth in any given year at roughly one in 300,000.
Before you panic about our impending doom, there’s good news.
A scientist from the University of Murcia has come up with an equation to spot killer asteroids heading for our planet.
Professor Oscar del Barco Novillo’s equation is based on the gravitational bending of light, and will allow scientists to pinpoint the precise positions of minor objects in the solar system.
This includes objects in the Kuiper Belt – a region of icy objects including Pluto and other dwarf planets beyond the orbit of Neptune – and a vast, frozen, spherical shell called the Oort Cloud, which is the most distant region in our solar system.
In turn, that could allow planetary defence networks to spot and prepare for any asteroids which could collide with Earth.
This advanced warning could be the difference between having time to deflect the asteroid onto a safe path and a cataclysmic impact.
Normally, light takes a straight path from an object to our eyes, meaning where we see the image is where the object really is.
However, this isn’t the case for distant objects like asteroids because of a phenomenon called ‘gravitational deflection’.
When a beam of light passes through a strong gravitational field like the one around our sun it leaves its straight path and follows a curved trajectory.
You can think of this like a ball following a curving path as it rolls over some uneven ground.
The idea that gravity might bend passing beams of light was first proposed by Sir Isaac Newton in 1730.
However, it wasn’t until Albert Einstein proposed his theory of general relativity in 1916 that scientists were able to confirm this was really the case.
The issue for astronomers is that gravitational deflection means that the image we see of a distant object doesn’t line up with where the object really is.
Professor Novillo told MailOnline: ‘When the sunlight is reflected on the minor objects in the solar system, such as asteroids, the light beams we receive on Earth are deflected due to the Sun and major planets such as Jupiter.
‘In this sense, the actual positions of these minor bodies are shifted, so this effect should be taken into account in the equations of motion of these minor bodies.’
For most applications that might not be an issue, but when it comes to calculating the orbit of a potentially hazardous asteroid even a small miscalculation could be fatal.
Professor Novillo’s solution, published in Monthly Notices of the Royal Astronomical Society, is to treat gravity as if it were a physical medium like water to work out how much light bends as it passes through.
Using this formula, Professor Novillo calculated the angle of deflection for light beams coming from Mercury at different points in its orbit.
Comparing the results to those based on Newtonian and Einsteinian equations, he found there was up to a 15.8 per cent difference when Mercury was at its greatest distance from the Sun.
Professor Novillo says that the most important consequence of this discovery is to enable ‘a better calculation of the orbits of minor objects in the solar system, which could be potentially hazardous to the Earth.’
While it won’t help detect asteroids in the first place, it will help determine a more precise location for these objects and, consequently, a better estimation of their orbits.
Space agencies such as NASA and the European Space Agency (ESA) are currently investigating ways that humanity might be able to avoid colliding with an asteroid.
For example, the ESA’s DART mission used a fridge-sized satellite to slam into the space rock Dimorphos to see if an asteroid could be knocked from its path.
While the results are due to be confirmed by the Hera mission late next year, early observations show that the impact did deflect Dimorphos’ orbit.
In theory, humanity could use a similar kamikaze satellite to deflect the orbit of a hazardous asteroid on its way to Earth.
However, doing this would require years of prior warning to give space agencies time to plan the mission and for the asteroid to drift out of Earth’s path.
That is why it is so critical for space agencies to have an accurate way of assessing the locations and orbits of asteroids drifting through the solar system.
Beyond planetary defence, this equation could also be used to deepen our understanding of the universe.
The hope is that scientists will now be able to calculate the exact location of the nearest star to Earth, Proxima Centauri.
Proxima Centauri is 4.25 light-years away and is thought to have three exoplanets orbiting around it.
If its location could be precisely determined, that would also help scientists accurately study the orbits of its planets to learn whether they do indeed sit within their star’s habitable zone.
Additionally, Professor Novillo’s discovery could even help scientists map the most distant reaches of space.
Professor Novillo says: ‘Distant galaxies, which are distorted and magnified by large amounts of intervening mass, such as galaxy clusters, might be precisely located with this new exact equation.’
Over the next six years, the ESA’s Euclid mission will observe the shapes, distances and motions of billions of galaxies out to 10 billion light-years – with the goal of creating the largest cosmic 3D map ever made.
Armed with this equation, scientists could produce even more accurate maps which might help understand how dark matter and dark energy have shaped the Universe into what we see today.
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