The Solar System is whirling through an interstellar soup of hydrogen.
Where is the end of the solar system?
There’s no planetary exit sign that thanks you for visiting, no fence, or physical boundary.
The closest thing our Solar System has to an “end” is the point where the Sun’s solar wind no longer has influence — we call this interstellar space, or the space between stars.
This place starts at about 90 AU, which is 90 times the distance between Earth and the Sun (or 3 times the distance between Pluto and the Sun).
At this distance, we get to the edge of the heliosphere, or the “bubble” caused by charged particles streaming from the Sun (known as solar wind).
One of the Voyager spacecraft has even been there.
The heliosphere can be compared to Earth’s magnetic field, which forms a bubble around our planet and protects us from the Sun’s radiation.
The heliosphere blocks about 75 percent of high energy cosmic rays from entering our Solar System.
NASA’s New Horizons spacecraft, which took the first up-close pictures of Pluto back in 2015, has been observing interstellar space from the Kuiper Belt.
New Horizons studies particles from those cosmic rays that have interacted with the solar wind as they stream into our Solar System from interstellar space.
With those measurements, New Horizons scientists recently discovered that the Sun whirls around the Milky Way in a relatively thick soup of interstellar medium.
They figured out that the interstellar medium outside our Solar System contains much more hydrogen than scientists originally thought.
This is the first time we’ve studied these particles from so close (relatively) to the edge of our cosmic neighborhood.
The interstellar medium is where new stars form. Without it, there’d be no Sun, no us.
Studying this region, although it seems very far from our everyday lives, is vital to understanding the origins of the very universe itself.
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