NASA baffled as Voyager 1 enters unknown region of space
June 27, 2013 | Reuters | Irene Klotz
CAPE CANAVERAL, Florida (Reuters) – Reports last summer than NASA’s
long-lived Voyager 1 space probe had finally left the solar system
turned out to be a bit premature, scientists said on Thursday.
Rather, the spacecraft, which was launched in 1977 for a five-year
mission to study Jupiter and Saturn, has found itself in a previously
unknown region between the outermost part of the solar system and
interstellar space.
It is an unusual and unexpected thoroughfare, a place where charged
particles from the sun have virtually disappeared and those coming from
galactic cosmic rays beyond the solar system are plentiful.
By that measure alone, scientists initially thought Voyager 1 did
indeed finally reach interstellar space on August 25, 2012, becoming the
first man-made object to leave the solar system.
But one key measurement killed that theory. The magnetic field in
which Voyager 1 traveled was still aligned like the sun’s. If the probe
were truly in interstellar space, scientists expect that the direction
of the magnetic field would be different.
“You can never exclude a really peculiar coincidence, but this was
very strong evidence that we’re still in the heliosheath” – the bubble
of plasma from the sun that surrounds the solar system, said Voyager
scientist Leonard Burlaga, with NASA’s Goddard Space Fight Center in
Greenbelt, Maryland.
Additional measurements later turned up a second odd reading. The
cosmic ray particles were not uniformly distributed around Voyager 1
like scientists expected them to be in interstellar space. Instead, the
charged particles, which stem from distant supernova explosions, were
oriented in particular directions.
That led scientists to conclude that Voyager 1 was in some sort of
magnetic boundary zone, where particles from inside and outside the
solar system could easily swap places, but where the sun’s influence
still reigns supreme.
“We have no explanation for why we even found this new region,” Burlaga told Reuters.
So far, Voyager’s sister probe, Voyager 2, which is exiting the solar
system in a different direction, has not encountered the same phenomena
– nor may it ever.
“Voyager 2 has seen exactly what the models predicted we would see,
unlike Voyager 1, which didn’t,” said lead scientist Ed Stone, with the
California Institute of Technology in Pasadena, California.
Voyager 1 may be in an unusual place where the heliosheath and interstellar space connect, he added.
Voyager 1 is now about 11 billion miles (18 billion km) from Earth.
At that distance, it takes radio signals, which move at the speed of
light, 17 hours to make a one-way trip to Earth.
Scientists do not know how much farther Voyager has to travel to
reach interstellar space. The spacecraft, which is powered by the slow
decay of radioactive plutonium, will begin running out of energy for its
science instruments in 2020. By 2025, it will be completely out of
power.
The research appears in the journal Science this week.
(Editing by Kevin Gray)
