Tag Archives: Astronomy

Contextualising Cosmic Danger


We all delight in some measure of fright. There is some allure in taunting the reaper, something endearing about the dark, deserted and blood-stained that we can’t quite explain. But it’s there. This weekend, fittingly around Halloween, our appetite for horror was indulged by yet another close encounter with a giant mass of rock hurtling through space. If it were to collide with earth, the impact of a meteorite this size would quite literally threaten our species with extinction. However, is such a scenario probable? To what degree has that appetite for horror caused us to distort the degree of danger posed by close encounters of the cosmic kind?

The object in question this time is called Asteroid 2015 TB145, although that may prove to be a misnomer. Some within the scientific community have begun to postulate that TB145 is in fact a comet. As a point of clarity: asteroids are the rocky remnants of planetary formation and orbit the sun, primarily in a belt between Mars and Jupiter. Comets, on the other hand, formed beyond the frost line, far from the warm embrace of our star. They are hence composed of rocky nuclei, blanketed in layers of ice which, upon approaching the sun, birth brilliant tails of dust and plasma. TB145 conspicuously lacks this characteristic coma, pointing to the conclusion that if our visitor is indeed a comet, the sun has eaten into its envelope of ice. The traveller from exile at the fringes of our solar system has, this time around, arrived as a corpse.

At closest approach, TB145, nicknamed Spooky, will pass a mere 480 000 km from our home planet. This ‘close shave’  is what has motivated the recurring narrative of earth narrowly escaping global devastation. Granted, on a scale of Astronomical Units, light-years and parsecs, the distance is indeed relatively miniscule, in much the same way that Alpha Centauri is a relatively close star. However, in assessing the danger, it is imperative to remember that on this astronomical scale, Earth is indeed a speck. To illustrate: suppose that Spooky’s orbit crossed into the space between its actual closest approach and the earth. The odds that it would, at random, collide with the earth can be conceptualised by imagining a ‘dartboard’ of radius 480 000 km, with earth as the bull’s eye. The probability is therefore approximated by taking the ratio of the area of the earth to that of the cosmic ‘dartboard’. From figure 1.1, it is apparent that this probability lies far below 1%. The danger, it seems, has been gravely overstated.

Figure 1.1

Figure 1.1

Admittedly, this model is simplistic and fails to account for the intricacies of celestial mechanics. The probability yielded then, is merely an order of magnitude approximation. It aims to illustrate the tremendous vastness  and pervading emptiness of space – the truth that, in the cosmos, the void reigns supreme. However, even when accounting for these shortcomings, it is evident that the chances of a collision within the closest approach are overwhelmingly slim. Moreover, Spooky – and scores of others like it – were on trajectories which we knew would never result in an impact with our home planet. Declaring that each one of these ‘nearly hit’ us is therefore akin to standing a hundred meters from the edge of a motorway and yelling that you narrowly avoided an accident each time a car whizzed by. When placed in proper context, the sensationalism sounds somewhat like the panicked ramblings of a paranoid mad man. Nonetheless, we cannot afford to be lulled into a false sense of security.

Much of the reason why events of this kind are met with alarm is not because the probability of impact is high, but rather because the consequences of such an improbable impact are so extraordinarily dire. Aware of the fate of those great reptilian beasts who roamed and ruled this planet before us, we know too well that an impact may lead to our extinction – an abrupt end to the anthropocene. Efforts, informed by data from objects like TB145, are underway to craft protocols that deal with the possibility of an asteroid impact. From nuclear detonation to a more understated, trajectory-altering nudge, plans are being developed to save earth from catastrophe. For the mad man, in all his crazed rambling, speaks in the spirit of a threat that, while improbable, is real: we simply cannot afford to find ourselves in the headlights of a car that has veered off the road.

These close encounters then, are a reminder from the cosmos that we cannot afford to neglect our space program, if we wish for our species to survive. They nudge us forward into a space-faring age, in which the repository of human potential will not be concentrated on a single planet. Perhaps most importantly, they provide us with a potent reminder of the vulnerability of our terrestrial home and allow us to contemplate our perilous existence upon it. As each asteroid streaks past earth, the message sent to us is clear: our cosmic neighbourhood, while alluring, is hostile to human life. With each near miss, our resolve to preserve this planet should be bolstered. We must realise that these threats of an existential kind needn’t come from the heavens.

Mesmerised by profit, we continue to deplete earth’s resources. Recklessly, we fuel a runaway greenhouse effect that drives climate change and global warming. Nuclear and biological weapons continue to sit in our stockpiles, straining for release. For as long as these characteristics of the human age continue to exist, the destruction of our species is in no need of any help from a rogue asteroid. So the next time the excessive panic machine begins to rumble, remember that after the threat has disappeared into the void, a danger lingers to our continued existence on this planet. And it springs directly from the sins of our species.


An Invitation to Dream Again, in our Age of Cosmic Apathy

65e732632ca383e919ad6e2d41f48d36-Astrobio Award graphic

And on the 14th of July, the storm that was brewing within them burst forth. It shook the foundations of an Old Order long-assumed to be unshakable. In time, it would come to shape their world.

Last week, at the edge of our planetary neighbourhood, New Horizons made history. For nearly a decade, the small spacecraft has barrelled towards the fringes of our solar system, with a helpful nudge from the colossal gravity of Jupiter. Beyond the orbit of Neptune, lies Pluto and its largest moon, Charon, tidally locked into a perpetual stare as they whirl in a grand cosmic waltz. Back on earth, we watched through the lens of New Horizons as this captivating image slowly grew sharper. On Bastille Day this year, it whizzed by Pluto, returning the clearest images ever of the mysterious icy world. Once again, the public eye was allowed to feast on the majesty of a world never before seen in such dazzling clarity.

The momentous nature of this occasion has not been lost on the public. The flyby has been treated with the reflective nostalgia one would expect from the final addition to our solar system’s family portrait. A family which stubbornly clings on to its misfit of a ninth member. As understandable as this attachment to the ‘nine we all learnt in school’ may be, the notion that the last box has been ticked is a problematic one. The issue is rather aptly highlighted by Dennis Overbye, who recently wrote in the New York Times, “None of us alive today will see a new planet up close for the first time again.”

Overbye’s assertion underlines a gloomy, despondent perspective – that the trailblazing eras of space exploration lie either behind us, in the moon landing euphoria of the 60s and 70s, or so far ahead of us that we will have perished before it becomes a reality. By this seemingly prevalent perspective, we are the Limbo Generation – born too late to witness the excitement of manned missions to the moon, but too early to witness us traverse interstellar space. Apathy is the well-fed beast that sleeps at our feet. Indeed, if we concede to this perspective, it will become a self-fulfilling prophecy.

But why concede now? Despite all our affection for the public’s planetary underdog, it would be foolish to allow our nostalgia to obscure reality. There are worlds beyond Pluto, in the icy wasteland of the Kuiper Belt, that have as much a right to being called planets as Pluto does (one of the reasons for the dwarf planet’s infamous demotion). After the hype has died down, New Horizons will continue to hammer on into the Kuiper Belt with the intention of further discovery. Those worlds beckon us, as do our neighbours, their moons and the endless potential they hold. Within the solar system, there are still many worlds for us to explore, many caves for us to bravely enter, many more oceans into which we will boldly set sail. The most groundbreaking discoveries then, lie ahead of us, well within our reach (something which, to his credit, Overbye acknowledges as a possibility). Still, why concede to the notion that we are confined to the solar system?

Admittedly, the assumption that we are limited to our planetary neighbourhood is not without reason. With our current technology, attempting to cross the chasm of nothingness which separates us from even the nearest stars would take longer than the age of human civilisation. It makes about as much sense as Magellan grabbing an old broomstick as his oar and opting to circumnavigate the globe on a four-poster bed with some floaties strapped to it. For now, interstellar space travel is beyond our capabilities. However, that may change more quickly than we expect.

At the turn of the twentieth century, when the Wright brothers first gave humanity wings, it was scarcely imaginable that we will have walked on the moon before that century had ended. The New Horizons mission, trekking across an astronomical distance so vast that it takes light more than five hours to make the same trip, was once confined to the territory of science fiction – as interstellar exploration is now. It takes a level of undue boldness, masquerading as rationality, to declare that the jump from science fiction to science fact will not occur in our lifetimes. Unfortunately, the impulse to smugly dismiss even a visit to an exoplanet is one that is frequently indulged in our time. Somewhere along the line, we seem to have lost something.

Space is the great repository of human dreams. As the Cold War ended and the momentum from the moon missions died down, our dreaming masses seem to have tragically dwindled. Cynicism has seeped in and our exploratory endeavour has been displaced by distraction. While skepticism has its place, it is high time we hand power back to the imagination. It would be a grave judgement on our species if we are incapable of caring about the exploration of the universe in the absence of a beating war drum and an adversary on the other side of the Iron Curtain.

The Cold War is over, yet our world is no utopia in its wake. One may ask then why we should turn our eyes to the stars when our own terrestrial home is in such fantastic disarray. While the pursuit of space science has many a benefit to a nation and economy, not least of which is the creation of a realm in which dreams can be pursued (as championed gloriously by Neil deGrasse Tyson), the desire to explore space runs deeper. We wade into the dark cosmic waters, because it is who we are.

We are the clay, mixed by the hands of giants long fallen, birthed from the remnants of stars long dead, moulded by the grand forces of sex and death. We were brought forth in chaos, from the precision of randomness. We are a manifestation of the universe’s self-contemplation – “A way for the Cosmos to know itself,” as Carl Sagan famously declared. We are drawn to discovery, enchanted by exploration. The will to wander is written into our DNA. In our age of cosmic apathy, we must rekindle that will…


Pluto and its moons are named after the deities, features and creatures of the Ancient Greek underworld. In the final lines of his famed work, Inferno, Dante Aligieri emerges with the Poet Virgil from Hell, that popular underworld of Christian mythology, to rebehold the stars. As New Horizons sails away from Pluto, we too must unshackle our capacity to dream and turn our faces to the stars. Once again, we must indulge our will to wonder about wandering.