Voyager goes intersellar: This artist’s concept puts solar system distances in perspective. The scale bar is in astronomical units,
with each set distance beyond 1 AU representing 10 times the previous distance. One AU is the distance from the sun to the Earth, which
is about 93 million miles or 150 million kilometers. NASA’s Voyager 1, humankind’s most distant spacecraft, is around 125 AU. Scientists
Image: NASA/JPL-Caltech
believe it entered interstellar space - the space between stars - on Aug. 25, 2012.
The hotly contested question has been
answered: Voyager 1 is humanity’s first
object to enter interstellar space! The historic
announcement came from NASA after a
year of review into 2012 and 2013 data points
from the intrepid probe. Officially, Voyager 1
entered interstellar space on 25 August 2012.
The debate
For over a year, scientists have questioned the
analysis of data points returned from Voyager 1 as
it passed through a new and unique region on the
outskirts of the solar system.
Specifically, the debate centered around the
question of whether Voyager 1 was in a previously
unknown region at the outer-most edge of the solar
system (known as the heliopause) or whether Voyager 1
had actually crossed the barrier into interstellar space.
On 25 August 2012, Voyager 1 registered an abrupt,
durable change in the density of the energetic particles
it was traveling through.
Initially, as reported by NASA on 4 December 2012,
it was determined that this shift in particle density was
Authored by Chris Gebhardt, this article
appeared first at NASASpaceFlight.com.
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the mark of Voyager 1’s full entrance into a new region
of the heliopause, called the magnetic superhighway,
at the outer-most edge of the solar system.
It is now understood that this was a far more significant
date and moment than first thought.
Gift of a Coronal Mass Ejection
In March 2012, five months before Voyager 1 would
record the particle density change in August, a Coronal
Mass Ejection (CME), a massive expulsion of charged
particles, released from the sun. While seemingly
routine at the time, the CME event could now be held
as one of the most important and significant CMEs in
recorded history.
Thirteen months after the CME event, on 9 April
2013 (just over seven months after the August particle
density change was recorded), the charged particles
associated with the CME event reached Voyager 1
– which was at a distance of 17 hours 05 minutes 58
seconds light-travel time from Earth.
When the CME charged particles reached Voyager
1, its Plasma Wave Instrument recorded the event and
transmitted the data back to Earth. It is what scientists
saw in these data points that was nothing short of
stunning.
When the CME particles reached the plasma cloud
around Voyager 1, the plasma cloud began oscillating
(vibrating) at a particular pitch that allowed scientists to
determine the density of the plasma field surrounding
the intrepid little probe.
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