First-known interstellar asteroid is a unique and shaped like a cigar...Really???
Since mid-October, the astronomy community has
been buzzing about what might be our Solar System’s first confirmed
interstellar visitor. An automated telescope spotted an object that appeared as
if it had been dropped on the Solar System from above, an angle that suggests
it arrived from elsewhere.
Now the
astronomers have confirmed that the object is from outside our Solar System —
the first interstellar asteroid that’s ever been observed. And it doesn’t look
like any object we’ve ever seen in our cosmic neighbourhood before.
Follow-up
observations, detailed today in Nature, have found that the asteroid is dark
and reddish, similar to the objects in the outer Solar System. It doesn’t have
any gas or dust surrounding it like comets do, and it’s stretched long and
skinny, looking a bit like an oddly shaped cigar.
It’s
thought to be about a quarter-mile long, and about 10 times longer than it is
wide. That makes it unlike any other asteroids seen in our Solar System, none
of which are so elongated.
Astronomers
also think this object — nicknamed `Oumuamua, Hawaiian for “a messenger from
afar arriving first”— travelled for millions of years before stumbling upon our
Solar System. It seems to have come from the direction of the constellation
Lyra, but the asteroid’s exact origin is still unknown. More answers might come
soon, as NASA’s Hubble Space Telescope is observing `Oumuamua this week.
Interstellar
asteroids are thought to be rejects from other planetary systems. When our
Solar System was first formed, for instance, the giant planets tossed around
all the smaller bits of material circulating around the Sun, some of which
landed in the outer edges of the Solar System while others were ejected from
our neighbourhood completely. These outcasts then travelled through
interstellar space, possibly passing by other stars. Conceivably, ejected
material from other planetary systems must make their way to our Solar System
once in a while.
Such
interstellar objects are thought to pass through our Solar System pretty frequently,
but they’re usually moving too fast, and they’re usually too faint to see. With
`Oumuamua, astronomers got lucky: the asteroid entered our Solar System at an
angle, coming in close by the Sun, and then passed by Earth on its way out of
the Solar System. That gave astronomers the chance to catch it with
ground-based telescopes.
Now,
`Oumuamua is 124 million miles from Earth, zooming away at 85,700 miles per
hour. It passed by Mars’ orbit on November 1st and will reach Jupiter’s orbit
sometime in 2018. Soon, it’ll be too hard to track, even with Hubble.
But in
the next few years, we may be able to spot more interstellar objects like
`Oumuamua. Once bigger telescopes start to come online, like the Large Synoptic
Survey Telescope that’s being built in Chile, astronomers will be able to see
even more visiting rocks.
with
inputs from the Verge
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