Nasa discovers danger zone for asteroids
Astronomers have identified a danger zone from which potentially devastating asteroids can ‘‘sneak up’’ on Earth undetected.
The Nasa-funded scientists found that celestial objects approaching from the east in the night-time sky can appear stationary due to a quirk of the Earth’s daily rotation and its journey around the sun.
It means they are not detected by the network of computerised telescopes intended to look out for such threats.
The research took place after the astronomical community was shaken in 2019 by a ‘‘near miss’’, which saw an asteroid approximately 100 metres across hurtle past Earth at a distance of only 70,000 km.
It was spotted just 24 hours previously.
The US Congress has set Nasa the task of identifying 90 per cent of asteroids 140 metres across or larger, a size which could devastate a region the size of a large city or small state if it hit land.
The agency is also developing methods to prevent Earth impacts.
Last year it launched an experimental mission to smash a heavy spaceship into the moonlet of a comet to see if doing so will knock it off course.
The new discovery comes amid a renewal of public interest in planetary collision in the wake of the hit Netflix film Don’t Look Up, which features Leonardo DiCaprio and Jennifer Lawrence as scientists trying to warn an unreceptive public about a comet that goes on to wipe out mankind.
Professor Richard Wainscoat, who led the research team at the University of Hawaii, said people ‘‘shouldn’t lose sleep’’ over the chances of being hit by a devastating asteroid.
But he added: ‘‘In the event that we find something that is going to hit the earth we would like to do something about it.
‘‘It’s not a matter of finding them and sitting there and letting it hit.’’
The algorithms governing the observation telescopes on the lookout for asteroids are programmed to flag up moving objects, to avoid wrongly identifying phenomena like supernovas and flare stars.
These take account of the fact that objects approaching Earth appear to drift west in the sky because of the Earth’s eastward spin on its axis.
However, when asteroids approach Earth from a portion of the eastern sky, the planet’s spin and its curved orbit around the sun can make the objects appear stationary.
Published in the journal Icarus, the study states that 50 per cent of impactors approaching Earth from the east can be expected to undergo periods of slow motion that may make them difficult to detect.
Were it not for the phenomenon, asteroids of the size of the 2019 body, known as 2019 OK, would be detectable up to four weeks ahead of impact.