Sky and Telescope - June 2018 - 4
by Peter Tyson
The Essential Guide to Astronomy
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N ASA / JEFF WILLIA MS
ery that beneﬁts all humankind. The research we write about tends
to be of the pure rather than the applied kind - a new gamma-ray
burst detected, a fresh insight into dark matter, and so on.
This particularly holds true these days, when specialization is
the order of the day, and many scientiﬁc results we astronomy editors cover, if
not put in proper context, might go over lay readers' heads like a shooting star
that fades in seconds. Try as we might to deliver them in clear, accessible prose,
some feature articles even in S&T can feel arcane to those new to the ﬁeld.
But for this issue, I had the pleasure of reporting a story whose most signiﬁcant disclosure all human beings, no matter their age, nationality, education
level, or scientiﬁc literacy, can appreciate in an instant.
The news is simply this: NASA-funded efforts have determined that no
mountain-size asteroid or comet is on a trajectory to hit Earth for at least the
next 100 years.
Even top NASA scientists could not have
stated this with conﬁdence as recently as 20
years ago. We just didn't know what might be
lurking out there unfound. Now, after a diligent search that began in 1998, astronomers
think we have effectively "retired the risk" of
any object larger than a kilometer (0.6 mile)
in diameter colliding with our world in the
foreseeable future (see page 12).
Not that most people worry about such a calamity occurring. But in this
time of uncertainty over our planet's fate as a result of our own doings, it
comes as a relief to learn that at least one natural hazard - in fact, possibly
the gravest of all, just ask the dinosaurs - has been, as one expert told me,
"largely put aside by discovery."
Of course, we have lots more to learn about such immense space rocks and
what they can do to us. See our articles about large meteor craters on Earth
(page 18) - sober reminders of what does happen - and about two missions
now en route to study and sample near-Earth asteroids (page 22).
Such work is important, because despite the reassuring news, it's always possible that one of our surveys could pick up a previously unknown comet, or an
asteroid smaller than 1 km across that still packs a wallop, that might be making a beeline for Earth. We need to know as much as we can about these things
in case we have to try to stop or divert one.
In the meantime, though, we can all breath just a little
bit easier. Kudos to all involved in this achievement.
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