How Do We Find Asteroids Inside Earth's Orbit?

Although researchers think we've found most large asteroids whose orbits bring them near Earth, some are still surprising us. Learn why -- and how we find them -- in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff production of iHeart Radio, Hey brain Stuff,
laurin voge obamb here as fighter pilots in World Wars
one and two were acutely aware attacking an enemy aircraft
from the direction of the Sun was a very effective
tactic to catch your target by surprise. The glare of
sunlight provided cover until it was too late for the
opponent to react. While asteroids don't consciously have this tactic

(00:25):
in mind, we hope astronomers are extremely mindful that the
Sun maybe hiding a cache of undiscovered and potentially hazard
as asteroids within its glare. This concern was highlighted by
the July announcement that is surprisingly big asteroid with the
shortest known year was discovered by this wiki transient facility,
a powerful camera at the Palomar Observatory in California. The asteroid,

(00:48):
designated nine l F six, is point six miles or
one kilometer wide and orbits the Sun entirely inside Earth's orbit.
It completes one orbit every one hundred and fifty one
Earth days. It zooms from within the orbit of Mercury,
which orbits the Sun every eighty eight days, to as
far out as Venus, which has a two twenty five
day orbit in a wonky trajectory that flings it out

(01:10):
of the orbital plane in the process, a sign that
it was once gravitationally disturbed by one of the two
planets in the past. This rare space rock belongs to
a very exclusive group of asteroids known as Tira asteroids,
which orbit the Sun closer than Earth. There are only
twenty known to exist. The fact that they fly between
us and the Sun makes them uniquely difficult objects to detect,

(01:33):
but even for an a Tira asteroid, l F six
didn't make it easy. Most asteroids of its size have
already been found, but it's unique orbit evaded decades of
organized searches. Asteroid l F six was detected as part
of the Twilight Campaign. As the name suggests, the best
time to observe asteroids such as these is during the
short period of twilight, just after sunset but before dark.

(01:57):
The campaign, which was developed by researchers at the National
Central University in Taiwan, discovered another a Tira asteroid designated
twenty nine a Q three in January of a Q
three has a one d and sixty five day orbit
around the Sun in addition these, Wiki transient facility has
identified around two thousand asteroids living in the main asteroid

(02:18):
belt between Mars and Jupiter, plus an impressive hall of
one hundred Near Earth objects or n e o s,
which are commons and asteroids whose orbits bring them within
relatively close proximity to Earth. In addition to the Twilight campaign,
a proposed NASA spacecraft called the Near Earth Object Camera
or NEOCam, will also be able to study the inner

(02:38):
Solar System for more A Tira asteroids by seeking out
their heat signature. We spoke with George Hallow, a researcher
at Caltech and memory of the discovery team. He said,
because A Tira asteroids are closer to the Sun and
warmer than other asteroids, they're brighter in the infrared. Neo
CAM has the double advantage of its location in space

(02:58):
and its infrared capability to find these asteroids more easily
than telescopes working at visible wavelengths from the ground. The
Near Earth objects are of particular interest because, on the
optimistic end, they might potentially be future sites of landings
and research. On the pessimistic end, they could possibly collide
with Earth. Since NASA began it's any O Observations program.

(03:21):
The agency estimates that it's discovered more than of near
Earth asteroids measuring point six miles or one kilometer and larger.
While l F six has been classified as a near
Earth asteroid and is therefore part of a dwindling group
of undiscovered objects of this size, it's not considered a
threat to Earth. Simulations of its future orbits indicate no
eminent likelihood of a future collision. However, it is a

(03:46):
reminder that these substantial asteroids are still out there, and
projects like these Wiki Transient Facility can probe The Inner
Solar System or the Sun may be hiding them. So
for now, while Earth is safe from being smashed by
large space that could cause global damage, astronomers are on
high alert to ensure that we won't get blindsided by
the glare of the Sun. Today's episode was written by

(04:12):
Dr Ian O'Neill and produced by Tyler clay. A Brainstuff
is a production of I Heart Radio's How Stuff Works.
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