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| An artist's interpretation of Voyager 1 and Voyager 2 leaving the heliosphere and entering interstellar space. (Image credit: NASA/JPL-Caltech) |
Just in time for Halloween, scientists have discovered something spooky and
strange occurring at the edge of the solar system: The heliopause — the
boundary between the heliosphere (the bubble of solar wind encompassing the
solar system) and the interstellar medium (the material between the stars)
appears to be rippling and creating oblique angles in an unexpected manner.
The general concept that the heliopause changes shape is not new; over the
past decade, researchers have determined that it is not static. They made
this discovery using data from Voyager 1 and Voyager 2, the only two
spacecraft to exit the heliosphere thus far, as well as NASA's Interstellar
Boundary Explorer (IBEX) satellite, which studies the emissions of energetic
neutral atoms (ENAs) that are created when solar winds and the interstellar
medium interact.
"The Voyager spacecraft provide the only direct, in situ measurement of the
locations of these boundaries. But only at one point in space and time,"
Eric Zirnstein, a space physicist at Princeton University, wrote in an
email to Vice. IBEX helps round out that data.
Scientists have used the data to create models that predict how the
heliopause changes. In a nutshell, solar winds and the interstellar medium
push and pull on each other to create an ever-moving boundary.
But recent research into the heliopause has surfaced data that contradict
previous findings. Over a period of several months in 2014, IBEX captured
the brightening of ENAs that indicated asymmetries in the heliopause, and
the team later realized those asymmetries were incongruous with the models,
Vice noted.
Furthermore, in reviewing data from the journeys of Voyager 1 and Voyager 2,
the scientists discovered that the heliopause changed dramatically in a very
short period of time. That helps to explain why there was such a large gap
between the two probes' entrances into interstellar space, which happened in
2012 and 2018, respectively. But that kind of movement by the heliopause
also clashes with the models.
In a paper published Oct. 10 in the journal
Nature Astronomy, the researchers called these discrepancies "intriguing and potentially
controversial." They plan to continue studying the heliopause, hoping to
gain more insight from NASA's Interstellar Mapping and Acceleration Probe, a
new-and-improved satellite that can detect ENAs and is scheduled to launch
in 2025, Zirnstein told Vice.
Until then, we can only ponder this eerie phenomenon happening in the
haunting depths of the solar system.
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Space & Astrophysics