The media has been having a bit of a field day with the story of a little asteroid which most likely will whizz by the earth on No ember 3 US time. This of course is the day before the US Presidential elections.
But let us look at it in more detail. To do that we need to go back to story the night of November 3, 2018.
That night, at the Zwicky Transient Facility at Palomar Observatory in Southern California observers noted a faint new “near-Earth object”, These are objects whose orbit can approach, or cross, that of Earth’s.
At this time, 2018 VP? was around 450,000 kilometres distant from us which is just a little farther than the average distance between Earth and the Moon which is approximately 384,000km.
The object was very faint, and difficult to differentiate against the background stars.
To further complicate issues It was only able to observe d for 13 days, before it was too far from Earth to see.
However, Based on these observations, it became clear the asteroid was of a type of near-Earth object known as an Apollo asteroid.
Apollo asteroids spend most of their time beyond Earth’s orbit, but often will cross our planet’s orbit at the innermost part of their journey around the Sun. 2018 VP? takes two years to go around the Sun,
So this will be the first time that it will pass close to the Earth since its discovery .
So how do we work out the exact path such an object will take through the Solar System? Also how can we predict where it will be in the future or even where it was in the past), astronomers need to gather as many observations as possible.
At least three data points are needed to estimate an object’s orbit, but such will not be very accurate. Therefore the more observations that can be obtained, and the longer the period time they are able to measured the more accurate the orbit can be refined.
And that’s why the path of 2018 VP is so uncertain. . Back in 2018 it was observed 21 times over 13 days allowing its orbit to be calculated reasonably precisely.
We know it takes two years to go around the Sun with an uncertainty in the asteroid’s orbital period is about 12 hours either way. This means that we can’t be certain exactly where the asteroid will be on November 2.
This level of uncertainty puts the closest approach between the asteroid and the Earth this time around could be somewhere between a direct hit and an enormous miss – with the asteroid coming no closer than 3.7 million kilometres.
So calculating the likelihood the asteroid will hit Earth during this close approach puts the odds are 0.41 per cent, or roughly one in 240. Consequently the most likely outcome on November 2 is the asteroid will sail straight past us.
2018 VP? is so small it poses no threat. It would burn up harmlessly in our atmosphere before it even reached the ground.