The Sky This Month
Welcome to our night-time sky.
Please enjoy this monthʼs tidbits of
knowledge. We are lucky to live in
a dark-sky area where the heavens
can shine through. I hope you
enjoy the sky and perhaps learn a
thing or two. Happy star gazing!
CLOSE ENCOUNTERS – There
may be aliens up there buzzing
around our solar system, but this discussion is about a
verifiable group of objects – asteroids. In May alone,
there will be 34 cataloged asteroids zipping nearby
Earth. Anyone of them could cause a massive fireball or
destroy life on Earth if the asteroid is large enough and if
the asteroid hits directly. There is no need to fear though.
Mayʼs asteroids are traveling by at a large distance from
Earth. The farthest asteroid in this list (there are many
more further out) will pass us at a distance of 0.19 AU.
AU stands for Astronomical Unit, which corresponds to
the average distance between the Earth and the Sun, so
0.19 AU is pretty far away. To put that into perspective,
we can use Lunar Distance (LD), which is the average
distance between the Earth and the Moon. There are
6
May 2017
pccnews
roughly 389 LDs in an AU. So, the farthest asteroid
in this list will be 74 times further than the distance
between the Earth and the Moon. The nearest will pass
at 8 LD. Occasionally, asteroids pass between the Earth
and Moon (or at least less than the distance between
the two). On April 4 th , a 15 foot long asteroid passed
by at 0.04 LD or about 10,000 miles, which is half the
distance between the Earth and a geostationary satellite.
An asteroid of that size would break up and burn in our
atmosphere.
Too Close for Comfort – There have been some recent
asteroids that have made it through our atmosphere. The
most recent one occurred in Chelyabinsk, Russia on
February 15 th , 2003. A meteor with an estimated mass
of about 10 tons broke apart in the sky and produced a
blinding light. The shock wave shattered windows and
985 people sought medical treatment. One large piece
of the meteor remained intact and created a 20 foot
wide crater. On June 30, 1908 in Tunguska, Russia,
an even larger meteor blasted apart about a forest in
Siberia. The ensuing shock wave knocked down 770
square miles of trees. More recently and closer to home,
on October 9, 1992, a meteor shot across the sky from
Kentucky to New York. A 27-pound piece of meteorite
from the fireball landed in Peekskill, New York. The
meteorite punched a hole through the trunk of a car and
created a shallow depression beneath it. NASAʼs Near
Earth Object Program is currently tracking over 16,000
asteroids and comets. There are currently 568 asteroids
that have some potential for hitting the Earth in the next
100 years and causing some amount of damage. The two
most likely objects are 23 feet in diameter and have a
0.5% chance of striking the Earth. Donʼt worry though;
the first potential impacts are in the years 2073 and 2095,
so youʼre safe for now.
— Brian Biggs
Amateur Astronomer