Monday, July 29, 2019

After Last Week We Can Truly Say The Asteroid Peril Isn't just Science Fiction

Image of the Chelyabinsk asteroid's exploded trail  over Chelyabinsk, Russia,  in 2013.

An interesting article by Gordon L. Dillow ('The Asteroid Peril Isn't Science Fiction', WSJ, p. C4, July 6-7) appeared barely two weeks before a real asteroid scare, which few humans may know about. This near hit concerned the asteroid 2019 OK  which was definitely not "ok" in terms of its near collision with Earth.  This is also given  no one picked it up until it had already passed.

Alan Duffy  - lead astronomer at the Royal Institution of Australia-   was  particularly confused in the aftermath.  This was given  a couple of forecasts had already predicted a couple asteroids were to pass close to the Earth  last week.   So, in Duffy's mind, everyone was getting hysterical over something already known to be coming, but evidently not. Because most did not know as 2019 OK whizzed past Earth.
That led Duffy to say:
I was stunned.  This was a true shock.”


So what happened and why wasn't it on more astronomers 'radars' so to speak?  According to Michael Brown - a Melbourne-based observational astronomer- this particular beast wasn't one that astronomers had been tracking. And it "seemingly appeared from out of nowhere". 

Let's back up here. By 'out of nowhere' he means from the direction of the Sun which of course will obscure any relatively small rock headed for us. In this case, we're talking of an object weighing in at nearly  6 x 10 14  kg and wider than an NFL football field. The trouble is, as Gordon Dellow's article makes clear, there are "hundreds of thousands of other near Earth asteroids both large and small which up to now haven't been identified." If they haven't been identified that means we don't have their orbital elements and hence can't predict what tracks they will take, including how close to Earth in the future.   The other not so sanguine news?  The funding allocated for asteroid defense this year is barely 1 percent of NASA's total budget of $21.5 billion.

Certainly, before planing expeditions back to the Moon and Mars we ought to be shoring up our defenses against oncoming asteroids that could wipe out whole cities - or islands - no?

Our previous asteroid wake up call occurred with the  Chelyabinsk object (est. 66 feet in diameter)  that blew up over that Russian city in 2013.  That event was energetic enough to injure over  1,000 people by flying debris as the shock wave from the explosion swept across the Russian city, shattering windows and leaving a trail of damage.  The explosion was estimated to have had a force greater than 30 Hiroshima atomic bombs, according to NASA scientists.  

By contrast, the object that just missed us would have been in the 1- 2 megaton energy range and had it struck a city like New York or Philly, would have incinerated it, reduced it to ashes. If it had struck Barbados, as I pointed out to Janice, it would have flatted that little 21 by 14 miles island. 

According to data from NASA, the craggy rock was large, an estimated 57 to 130 meters wide (187 to 427 feet), and moving fast along a path that brought it within about 73,000 kilometers (45,000 miles) of Earth. That’s less than one-fifth of the distance to the moon and what Duffy considers “uncomfortably close.”
It snuck up on us pretty quickly,” said Brown, an associate professor in with Monash University’s School of Physics and Astronomy. He later noted, “People are only sort of realizing what happened pretty much after it’s already flung past us.
Not good enough my Astro friends!   The asteroid’s presence was discovered only earlier this past week by separate astronomy teams in Brazil and the United States. Information about its size and path was announced just hours before it shot past Earth, Prof. Brown said.  He added:

It shook me out my morning complacency. It’s probably the largest asteroid to pass this close to Earth in quite a number of years.”

So how did the event almost go unnoticed?  Nothing this size is easy to detect,” Duffy said of Asteroid 2019 OK. ″You’re really relying on reflected sunlight, and even at closest approach it was barely visible with a pair of binoculars.”

Brown said the asteroid’s “eccentric orbit” and speed were also likely factors in what made spotting it ahead of time challenging. Its “very elliptical orbit” takes it “from beyond Mars to within the orbit of Venus,” which means the amount of time it spends near Earth where it is detectable isn’t long, he said. As it approached Earth, the asteroid was traveling at about 24 kilometers per second, he said, or nearly 54,000 mph. By contrast, other recent asteroids that flew by Earth clocked in between 4 and 19 kilometers per second (8,900 to 42,500 mph).

Regarding the elusive 2019 OK object, Prof. Brown went on to say:

It’s faint for a long time.  With a week or two to go, it’s getting bright enough to detect, but someone needs to look in the right spot. Once it’s finally recognized, then things happen quickly, but this thing’s approaching quickly so we only sort of knew about it very soon before the flyby.
Basically summarizing why we desperately need thousands, hell, millions, more asteroid detection volunteers with basic astronomy principles guiding them and the telescopes needed for the job.  Such an instrument would be along the lines of the Celestron-14 shown below:

Ironically in May, barely two months before the close pass of 2019 OK, a hypothetical  asteroid impact exercise had been conducted.   This was as part of the International Academy of Astronautics Sixth Planetary Defense Conference held in College Park, MD.

As described by Dellows (ibid.) the exercise began when astronomers in Hawaii detected an 800 foot wide asteroid they dubbed 2019 PDC.  In other words, roughly twice the maximum estimated diameter (427' )  of the actual 2019 OK that just brushed past us.   The decision of the team was then to try to "reduce its speed by a tiny fraction" using missile "kinetic impactors".   Then:  "By the time it reaches its predicted rendezvous point with Earth, our planet will have already moved in its orbit."  All well and good, right?  Not really, as Dellows continues:

"Three of the impactor ships smashed into the asteroid.  The main body was destroyed and would miss Earth.  Denver (the original target) was saved. Unfortunately, one of the kinetic impacts inadvertently broke off a 200-foot wide chunk of the asteroid - and that hurtling fragment was now on track to hit New York City,"

Let's pause here to point out the size of the fragment was smaller (by up to a factor 2)  than the estimated size of 2019 OK that just missed Earth.  Anyway, as we read on (ibid.):
"The only hope was to destroy the fragment with a nuclear device.  But existing ground -launched nuclear missiles were not designed to take on an space and there wasn't time to launch a nuclear armed device to intercept the asteroid chunk.  New York would just have to take the hit."

So what was done in the exercise?

"Millions of people were evacuated.  The asteroid exploded in a fireball over Central Park.- and Manhattan was wiped off the map."

Two takeaways:  First, at least the exercise saw a partial success in that the population of Manhattan was evacuated in time, though they had nothing to return to but ashes. Second, The much larger REAL asteroid that appeared last week, and would have REALLY destroyed Manhattan (or Barbados) missed us by an astronomical hair's breadth.

The consolation? "The chances of a civilization- destroying asteroid are exceedingly small".  Well, true, but they are not zero.  After one hit in 2013 and another near collision this month, I suspect it's time we get a real plan in place especially for these smaller, city-killer asteroids that emerge at the last minute.    As Dellows ends his piece:
"It isn't a question of whether humankind will have to confront the prospect of a destructive asteroid hurtling our way; it is only a question of when."

Let's hope that 'when' is still a long, long time away.

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