There’s an interesting astronomical event coming up on 12 October 2017: the close approach of asteroid 2012 TC4.
What’s interesting about it is that astronomers don’t really know how close it’s going to come to the Earth.
And this is because they only got a few days of observations of it the last time it came close to the Earth in October 2012, and were unable to accurately determine its orbit. And so this time around they simply don’t know where it’s going to go. It could pass by 400,000 km away (as distant as the Moon) – or it could come as close as 13,200 km (twice the radius of the Earth).
There’s been some uneasiness about this asteroid for years:
Will asteroid 2012 TC4 hit Earth in October 2017?
“It is something to keep an eye on,” Judit Györgyey-Ries, astronomer at the University of Texas’ McDonald Observatory, told astrowatch.net. “We could see an airburst maybe broken windows, depending on where it hits.”
They don’t even know how big it is either.
“There is one in a million chance that it could hit us,” Detlef Koschny, head of the Near-Earth Object (NEO) Segment in the Space Situational Awareness (SSA) programme office at ESA, told astrowatch.net. He also tried to estimate the exact size of the celestial body. “The size was estimated from the brightness, but we don’t know the reflectivity. So it could be smaller or larger, assume from 10 m to 40 m. A 40 m iron object would go through the atmosphere and make a crater; a 10 m rocky object would be hardly noticed.”
The upshot is that a big international effort is going to be made in September to find out exactly where it is, and where it’s going.
Professor Vishnu Reddy of the University of Arizona’s Lunar and Planetary Laboratory in Tucson leads the campaign to reacquire 2012 TC4 and sees it as an opportunity for the collaborative observation campaign to utilize the international aspect of the network. “This is a team effort that involves more than a dozen observatories, universities and labs across the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities,” said Reddy. The goal of the TC4 campaign is to recover, track and characterize 2012 TC4. “This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications.”
And yesterday I fired up my orbital simulation model, and got hold of NASA’s current estimate of its orbit, and took a look myself. I found that its orbit dips just inside the orbit of the Earth in October.
And then I put a cloud of rocks around it, and ran it round the Sun from October 2012 to October 2017. And I got a rock that lay just 550 km away from TC4 in 2012 to pass directly under the Earth in 2017, 13,233 km from its centre. In the image below, b is 2012 TC4:
I also found that the Pacific ocean was facing the approaching rock cloud, so if there actually was any impact, it would mostly likely cause a tsunami in the Pacific as the asteroid punched through the atmosphere at a speed of about 7 km/second.
Most likely TC4 will come nowhere near the Earth. But as more and more of these asteroids are discovered by automated observatories like the Pan-STARRS project (which found TC4), there’ll be more and more of these false alarms. And some of them won’t be false alarms.
In fact, I can imagine a time in the fairly near future when there will be calendars detailing which rocks are expected to impact or skim very close to the Earth on each day. There will be millions of them, all with their orbits well established, and there will be warnings broadcast each day telling people in one city or other to stay indoors between 8:07 am and 8:10 am, with pillows over their heads. If people are worried enough, there will be regular exoduses elsewhere from danger zones. There’ll even be Safe Spaces where no asteroids are ever predicted to impact.
In 20 or 30 years time, the whole world will probably be in the grip of a Great Asteroid Panic, which will rival and probably surpass our current Secondhand Smoke Panic and Global Warming Panic. Governments will be pumping trillions of dollars into asteroid science and Asteroid Control. Everyone will have computer apps like my simulation model, which will show them the daily impacts of rocks down to the size of 1 metre in diameter (or even smaller) all over the world.
And there’ll be helmet-wearing Asteroid Threat Alarmists arguing furiously with Asteroid Threat Denialists that There’s No Safe Diameter Of Asteroid. And there’ll be devotees of particular asteroids, like 99942 Apophis, with a diameter of 370 metres, and due to make a close approach to the Earth in 2029.
There was a reason that the Ancients worshipped sky gods like Jupiter and Mars and Venus. They were powerless in the face of them, particularly when they came too close, and hurled thunderbolts from the sky.