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Science and technology
A
stronomers have confirmed Earth’s first known
visitor from another star: a half-metre-wide
space rock that plunged into the atmosphere at more
than 170 times the speed of sound in January 2014.
The rock exploded into tiny fragments high in the air
near the island of Papua New Guinea in the Pacific
Ocean, but scientists have reconstructed its path after
persuading the US government to reveal
secret information from a spy satellite.
Small chunks of rock are
scattered across our solar
system. These are left over
from when the planets formed
about 4.5 billion years ago,
and others thrown out when
larger rocky bodies called
asteroids collide. Sometimes
they cross paths with Earth
and occasionally even crash
into it. The rock plunges into the upper
atmosphere, heating up and breaking apart to create
a brief trail of light called a meteor or “shooting star”.
Bigger chunks can survive to land on Earth’s surface;
scientists call these meteorites and use them to study
material from space.
The 2014 meteor stood out because its speed
and direction weren’t the same as most rocks. AmirSiraj and Avi Loeb, from Harvard University in the
US, spotted it in 2019 while searching through a
list of meteor sightings on the hunt for objects that
might have come from another solar system. Many
of these sightings come from satellites run by the
US Department of Defense (DoD). Their automated
cameras watch Earth’s surface to spot missiles being
launched by other countries but most
of the time they only see the bright
fireballs from meteors entering the
atmosphere. The DoD gave some
information for the list but the
team needed more to be sure
where the meteor came from.
The missing data on the
meteor has been released,
confirming that it did indeed
come from outside our solar
system. Siraj and Loeb think the
space rock began its life close
to another star in the densely packed disc of our
own Milky Way galaxy, before being ejected into
interstellar space on its long journey to Earth. They
are now trying to work out whether small bits of
the meteorite could have survived the impact and
whether it would be possible to find them if they’d
landed in the sea and sunk to the ocean floor.Earth gets an interstellar visit
In 2017, astronomers discovered an object
called ‘Oumuamua on a path that came from
somewhere outside our solar system. It
passed closer to the Sun than the innermost
planet, Mercury. Most astronomers think it is
a chunk of ice a few hundred metres long but
many of ‘Oumuamua’s features are puzzling.
It is 10 times longer than it is wide, much
more elongated than any known space object,
and what’s more, it sped up after passing the
Sun. One group of scientists have suggested
sending a robot probe that could catch up
with ‘Oumuamua and take a closer look.Mysterious ‘Oumuamua
An artist’s view of a space
rock heading to Earth.The strange object
‘Oumuamua.RAIN
FROM
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year.The Week Junior • 23 April 2022
A meteorite from our
own solar system.