- 3902 - SUN'S - magnetic bubble? The Sun’s Magnetic Bubble is a heliosphere pelted with cosmic rays. Our corner of the universe, the solar system, is nestled inside the Milky Way galaxy, home to more than 100 billion stars. Our solar system is encased in a bubble called the “heliosphere”, which separates us from the vast galaxy beyond and some of its harsh space radiation.
-------------------- 3902 - SUN'S - magnetic bubble?
- We’re
protected from that radiation by the heliosphere, which itself is created by
another source of radiation: the Sun. The Sun constantly spews charged
particles, called the “solar wind”, from its surface. The solar wind flings out
to about four times the distance of Neptune, carrying with it the magnetic
field from the Sun.
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- Magnetic
fields tend to push up against each other, but not mix. Inside the bubble of the heliosphere are
pretty much all particles and magnetic fields from the Sun. Outside are those
from the galaxy.
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- “Heliosphere”
is the combination of two words: “Helios,” the Greek word for the Sun, and
“sphere,” a broad region of influence, though, scientists aren’t sure of the
heliosphere’s exact shape.
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- The
heliosphere was discovered in the late 1950s, and many questions about it
remain. As scientists study the heliosphere, they learn more about how it
reduces astronauts’ and spacecrafts’ exposure to radiation and more generally,
how stars can influence their nearby planets.
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- Some
radiation surrounds us every day. When we sunbathe, we’re basking in radiation
from the Sun. We use radiation to warm leftovers in our kitchen microwaves and
rely on it for medical imaging.
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- Space
radiation, however, is more similar to the radiation released by radioactive elements
like uranium. The space radiation that comes at us from other stars is called
“galactic cosmic radiation” (GCR). Active areas in the galaxy, like supernovae,
black holes, and neutron stars, can strip the electrons from atoms and
accelerate the nuclei to almost the speed of light, producing radiastion.
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- On Earth,
we have three layers of protection from space radiation. The first is the
heliosphere, which helps block radiation from reaching the major planets in the
solar system.
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- Next, the
Earth’s magnetic field produces a shield called the “magnetosphere”, which
keeps radiation out away from Earth and low-orbiting satellites like the
International Space Station.
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- Finally, the
gases of Earth’s atmosphere absorb radiation.
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- When
astronauts head to the Moon or to Mars, they won’t have the same protection we
have on Earth. They’ll only have the protection of the heliosphere, which
fluctuates in size throughout the Sun’s 11-year cycle.
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- In each
solar cycle, the Sun goes through periods of intense activity and powerful
solar winds, and quieter periods. Like a balloon, when the wind calms down, the
heliosphere deflates. When it picks up, the heliosphere expands.
-
- The effect
the heliosphere has on cosmic rays allows for human exploration missions with
longer duration. In a way, it allows humans to reach Mars. The challenge for us is to better understand
the interaction of cosmic rays with the heliosphere and its boundaries.
-
- There is
some debate about the precise shape of the heliosphere. However, scientists
agree that it has several layers. Let’s look at the layers from inside outward.
-
---------------------- Termination shock:
All of the
major planets in our solar system are located in the heliosphere’s innermost layer.
Here, the solar wind emanates out from the Sun at full speed, about a million
miles per hour, for billions of miles, unaffected by the pressure from the
galaxy. The outer boundary of this core layer is called the termination shock.
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---------------------- Heliosheath:
Beyond the termination shock is the heliosheath. Here,
the solar wind moves more slowly and deflects as it faces the pressure of the
interstellar medium outside.
-
---------------------- Heliopause:
The heliopause marks the sharp, final plasma boundary
between the Sun and the rest of the galaxy. Here, the magnetic fields of the
solar and interstellar winds push up against each other, and the inside and
outside pressures are in balance.
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---------------------- Outer Heliosheath:
The region just beyond the heliopause, which is still
influenced by the presence of the heliosphere, is called the outer heliosheath.
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- Many NASA
missions study the Sun and the innermost parts of the heliosphere. But only two
human-made objects have crossed the boundary of the solar system and entered
interstellar space.
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- In 1977,
NASA launched Voyager 1 and Voyager 2. Each spacecraft is equipped with tools
to measure the magnetic fields and the particles it is directly passing
through. After swinging past the outer planets on a grand tour, they exited the
heliopause in 2012 and 2018 respectively and are currently in the outer
heliosheath. They discovered that cosmic rays are about three times more
intense outside the heliopause than deep inside the heliosphere.
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- The Voyagers
work with the Interstellar Boundary Explorer (IBEX) to study the heliosphere.
IBEX is a 176-pound, suitcase-sized satellite launched by NASA in 2008. Since
then, IBEX has orbited Earth, equipped with telescopes observing the outer
boundary of the heliosphere.
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-
IBEX captures and analyzes a class of particle called energetic neutral
atoms, that cross its path. energetic neutral atoms form where the interstellar
medium and the solar wind meet. Some energetic neutral atoms stream back toward
the center of the solar system, and IBEX.
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-
In 2025, NASA will launch the z'Interstellar Mapping and Acceleration
Probe” (IMAP). IMAP’s “energetic neutral atoms”, ENA, cameras are higher resolution and more
sensitive than IBEX’s.
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- In 2009,
IBEX returned a finding so shocking that researchers initially wondered if the
instrument may have malfunctioned. That discovery became known as the IBEX
Ribbon, a band across the sky where ENA emissions are two or three times
brighter than the rest of the sky.
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- Our Sun is
a star like billions of other stars in the universe. Some of those stars also
have astrospheres, like the heliosphere, but this is the only astrosphere we
are actually inside of and can study closely.
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- We need to
start from our neighborhood to learn so much more about the rest of the
universe.”
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March 5, 2023 SUN'S
- magnetic bubble? 3902
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---------------------
--- Monday, March 6, 2023
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