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Asteroid to sweep close to Earth October 11-12 |
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October 6, 2017 |
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Illustration of a possible orbit for
asteroid 2012 TC4, via NASA. |
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By Eddie Irizarry and Deborah Byrd
EarthSky.org
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| Image of
asteroid 2012 TC4 (center) from 2012,
via G. Masi and F. Nocentini/ Virtual
Telescope Project. |
The Center for Near Earth Object Studies (CNEOS)
at NASA’s Jet Propulsion Laboratory in Pasadena,
California, and other astronomers and
observatories around the globe have had their
eye on a small asteroid, designated 2012 TC4.
It’ll pass close to Earth on October 11-12.
Last summer, experts were already saying they
knew the rock wouldn’t hit us, but they thought
2012 TC4 might give us a close shave, passing as
close as 4,200 miles. In late July, though,
astronomers recovered the space rock – picked it
up telescopically again, after not seeing it for
some years – and the new observations let them
refine their knowledge of 2012 TC4’s orbit and
better compute its closest distance to Earth
later this month. Thus we now know the object
will pass around 30,000 miles above Earth’s
surface.
2012 TC4 will come closest to Earth at around
10:42 a.m. October 12. It’ll come close enough
that Earth’s gravity will slightly alter the
asteroid’s path. Later in the day on October 12
– at 12:19 p.m., the asteroid will pass some
172,000 miles from the moon.
The asteroid is currently travelling at a speed
of about 30,000 mph, and while it appears very
dim at the moment, it’ll get brighter as it gets
closer.
Can you see asteroid 2012 TC4 as it sweeps past?
Not with the eye alone, surely.
But experienced observers with telescopes and
charting software will be able to pick it up,
and you can watch online as the asteroid passes.
The Virtual Telescope Project in Italy will
offer two online observing sessions, on October
11 and 12, in cooperation with Tenagra
Observatories in Arizona. Click here to go to
Virtual Telescope’s observing page for 2012 TC4.
https://www.virtualtelescope.eu/webtv/
Experienced backyard observers have a shot at
the asteroid, too. To see it, you’ll need to
make your own tracking map using sky charting
software. AstroBob has instructions on how to do
that at his blog. He wrote:
"Observers in the Americas (especially South
America) will get the best views as 2012 TC4
hurtles from Capricornus across Microscopium and
into southern Sagittarius during early evening
hours. [The locator map below], with stars to
magnitude 8, shows the asteroid’s trajectory
across the evening sky on the evening of October
11. Positions are shown every hour starting at
6:30 p.m. PDT. 2012 TC4 will be much fainter,
around magnitude 13."
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| Chart
showing the path across our sky of
asteroid 2012 TC4, created with Chris
Marriott’s SkyMap, via AstroBob. |
Find instructions for how to create your
tracking map on AstroBob’s October 3
blog post.
Meanwhile, CNEOS is working with astronomers of
the International Asteroid Warning Network on a
plan to utilize asteroid 2012 TC4 in an exercise
to test NASA’s network for planetary defense
against asteroids. They’ve said they intend to
test out their ability to recover, characterize
and report on a potentially hazardous object
approaching Earth.
Recover, in this sense, doesn’t mean recovering
a sample from an asteroid; it means recovering
the object via telescopes as it moves across the
heavens, using tracking data from an earlier
pass.
The calculations on the October, 2017, pass of
asteroid 2012 TC4, for example, were originally
based on only seven days of tracking it, shortly
after it was discovered in 2012. Then we lost
the object again, in the depths of space, as it
sped away from us.
That’s an exceedingly common scenario for
close-passing asteroids, which are, after all,
just flying chunks (some more like flying
mountains) of rock in space. They sweep past
then go their way.
These astronomers are trying out their planetary
defense systems – a global protection against
asteroids on a possible collision course with
Earth – which they’ve been discussing for
decades and developing over the last few years.
Brightness measurements made during the week it
was observed in 2012 gave an estimated size of
30 to 100 feet for asteroid 2012 TC4. That’s
comparable to the meteor that caused a shock
wave and explosion in Earth’s atmosphere, over
the Russian city of Chelyabinsk, in February
2013, injuring 1,500 people and damaging over
7,000 buildings.
The Chelyabinsk meteor, before it struck Earth’s
atmosphere, is estimated to have been about 20
meters wide.
Astronomers also know that 2012 TC4 is an
elongated and rapidly rotating asteroid. And
they know that asteroid 2012 TC4 has made many
close approaches to Earth in the past.
Bottom line: A small asteroid designated 2012
TC4 will pass Earth safely – but closely – on
October 12, 2017. Experts are certain it won’t
hit Earth. This summer, an international
collaboration of telescopes is trying to
reacquire the asteroid – that is, find it again
in space – with the goal of precisely
determining its orbit.
To learn more,
click here. |
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