Because 2018 VP₁’s orbit takes almost exactly two years, in 2020 (two years after discovery), it will once again pass close to Earth.
But how close will it come? Well, that’s the million-dollar question.
Anything from a collision to a very distant miss …
To work out an object’s exact path through the Solar system, and to predict where it will be in the future (or where it was in the past), astronomers need to gather observations.
We need at least three data points to estimate an object’s orbit – but that will only give us a very rough guess. The more observations we can get, and the longer the time period they span, the better we can tie down the orbit.
And that’s why the future of 2018 VP₁ is uncertain. It was observed 21 times over 13 days, which allows its orbit to be calculated fairly precisely. We know it takes 2 years (plus or minus 0.001314 years) to go around the Sun. In other words, our uncertainty in the asteroid’s orbital period is about 12 hours either way.
That’s actually pretty good, given how few observations were made – but it means we can’t be certain exactly where the asteroid will be on November 2 this year.
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However, we can work out the volume of space within which we can be confident that the asteroid will lie at a given time. Imagine a huge bubble in space, perhaps 4 million km across at its largest. We can be very confident the asteroid will be somewhere in the bubble – but that’s about it.
What does that mean for Earth? Well, it turns out the closest approach between the two this year will be somewhere between a direct hit and an enormous miss – with the asteroid coming no closer than 3.7 million km!
We can also work out the likelihood the asteroid will hit Earth during this close approach. The odds are 0.41%, or roughly 1 in 240. In other words, by far the most likely outcome on November 2 is the asteroid will sail straight past us.
But what if it did hit us?
As the great Terry Pratchett once wrote, “Million-to-one chances crop up nine times out of ten”. But have you ever heard someone say “It’s a 240-to-1 chance, but it might just work?”
So should we be worried?
Well, the answer here goes back to how hard it was to spot 2018 VP₁ in the first place. Based on how faint it was, astronomers estimate it’s only about 2 metres across. Objects that size hit Earth all the time.
Bigger asteroids do more damage, as we were spectacularly reminded back in February 2013, when an asteroid around 20 metres across exploded in the atmosphere above the Russian city of Chelyabinsk.
A collection of footage of the Chelyabinsk airburst, and its aftermath, on 15 Feb 2013.
The Chelyabinsk airburst was spectacular, and the shockwave damaged buildings and injured more than 1,500 people. But that was an object ten times the diameter of 2018 VP₁ – which means it was probably at least 1,000 times heavier, and could penetrate far further into the atmosphere before meeting its fiery end.
Read more: Chelyabinsk meteor explosion a 'wake-up call', scientists warn
2018 VP₁ is so small it poses no threat. It would almost certainly burn up harmlessly in our atmosphere before it reached the ground. Most likely, it would detonate in an “airburst”, tens of kilometres above the ground – leaving only tiny fragments to drift down to the surface.
If 2018 VP₁ is particularly robust (a chunk of a metal asteroid, rather than a stony or icy one), it could make it to the ground – but even then, it is way too small to cause significant damage.
Having said that, the fireball as the asteroid entered Earth’s atmosphere would be spectacular. If we were really lucky, it might be captured on camera by the Global Fireball network (led by Curtin University).