- 3317 - EARTH’S - magnetic bubble? A tiny line in a light spectrum reveals a distant part of the Universe that we may not be able to “see” but can deduce through decades of research, and our imagination, transforming data into accretion disks, giant stars, plasma flying at near light-speeds, powerful X-Rays, and spinning stellar relics.
--------------------- 3317 - EARTH’S - magnetic bubble?
- Our little corner of the universe, our solar system, is nestled inside the Milky Way galaxy with more than 100 billion other stars. We're protected from radiation by the heliosphere, which itself is created by another source of radiation, the Sun.
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- The Sun constantly spews charged particles, called the “solar wind“, from its surface. The solar wind spans 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 mostly particles and magnetic fields from the Sun. Outside this bubble 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.
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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).
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- 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 galactic cosmic radiation .
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- The heliosphere changes in size throughout the “solar cycle“. On Earth, we have three layers of protection from space radiation. The first is the heliosphere, which helps block cosmic radiation from reaching the major planets in the solar system.
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- Earth's magnetic field produces a shield called the magnetosphere, which keeps cosmic radiation out away from Earth and low-orbiting satellites like the International Space Station. Then 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.
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- The effect the heliosphere has on cosmic rays allows for human exploration missions with longer duration. The challenge for us is to better understand the interaction of cosmic rays with the heliosphere and its boundaries.
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- Looking at the heliosphere layers from inside outward:
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-------------------- 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.
-------------------- 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.
-------------------- 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, or ENAs, that cross its path. ENAs form where the interstellar medium and the solar wind meet. Some ENAs stream back toward the center of the solar system - and IBEX. By collecting a lot of those individual atoms, science is able to make this inside out image of our heliosphere.
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- In 2025, NASA will launch the Interstellar Mapping and Acceleration Probe (IMAP). IMAP's 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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- A magnetic tunnel surrounds the Earth. What if our eyes could see radio waves? You look up into the sky and see a tunnel of rope-like filaments made of radio waves. The structure would be about 1,000 light-years long and would be about 350 light-years away.
This tunnel explains two of the brightest radio features in the sky.
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- Astronomers discovered the North Polar Spur and the Fan Region in the 1960s when radio astronomy was getting going. The North Polar Spur is a massive ridge of hot gas that rises above the plane of the Milky Way. It emits x-rays and radio waves.
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- The Fan Region is one of the most dominant polarized radio features in the sky. If we were to look up in the sky, we would see this tunnel-like structure in just about every direction we looked, if we had eyes that could see radio light.”
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- The feature is made up of 1,000 light-years long “ropes,” which themselves are made up of charged particles and a magnetic field.
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- Magnetic fields don’t exist in isolation. They all must connect to each other. So a next step is to better understand how this local magnetic field connects both to the larger-scale Galactic magnetic field and also to the smaller scale magnetic fields of our Sun and Earth.
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- The strongest magnetic field ever recorded in the Universe was discovered at the surface of a neutron star called “GRO J1008-57” with a magnetic field strength of approximately 1 billion Tesla. For comparison, the Earth’s magnetic field clocks in at about 1/20,000 of a Tesla. This is tens of trillions of times weaker than you’d experience on this neutron star.
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- Neutron stars are the “dead cores” of once massive stars which have ended their lives as supernova. These stars exhausted their supply of hydrogen fuel in their core and a power balance between the internal energy of the star surging outward, and the star’s own massive gravity crushing inward, is cataclysmically unbalanced, gravity wins.
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- The star collapses in on itself. The outer layers fall onto the core crushing it into the densest object we know of in the Universe, a neutron star. Even atoms are crushed. Negatively charged electrons are forced into the atomic nuclei meeting their positive proton counterparts creating more neutrons.
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- When the core can be crushed no further, the outer remaining material of the star rebounds back into space in a massive explosion, a supernova. The resulting neutron star, made of the crushed stellar core, is so dense that a single sugar-cube-sized sampling would weigh billions of tons, as much as a mountain.
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- Neutron stars are typically about 20 kilometers in diameter and can still be a million degrees Kelvin at the surface.
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- GRO J1008-57 is a spinning neutron star or “pulsar.” Pulsars were first discovered in 1967 by Jocelyn Bell through observations of a regular radio “pulse” of 1.33 seconds. The pulses were determined not to be of human origin so the object was designated, though facetiously, LGM1 (Little Green Men 1).
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- A spinning neutron star projects a beam of energy along its magnetic poles that sweeps across space as the star rotates, like the beams from a turning lighthouse. Depending on the orientation of the star, those beams can sweep along Earth’s field of view resulting in a “pulse” of energy with each of the star’s rotations.
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- But why do neutron stars have incredibly powerful magnetic fields? Seems counterintuitive given that they are made of neutrally charged particles (where neutron gets its name).
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- If you were to cut away a neutron star, it is formed of several layers. A cloud of remaining electrons near the surface, further down traces of charged “impurities” of various atomic nuclei remaining after the formation of the neutron star, a crust of neutrons, and a core of a theorized frictionless neutron fluid further mixed with impurities.
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- The combination of layers makes the star incredibly conductive. Spin a very conductive object and you create a churning flow of charged particles which generates a powerful magnetic field.
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- Our planet’s own magnetic field is itself created by the rotation of the Earth’s nickel-iron core.
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- Neutron star rotations are astonishingly fast. Like a figure skater retracting their arms to spin more quickly, the “angular momentum” of the original giant star, millions of kilometers in radius, is preserved and transferred to an ever faster spinning compact object only 10 km wide. Imagine a spinning figure skater with arms millions of kilometers long pulling them all the way to the center of their body.
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- The first neutron star discovered had a rotation period of 1.33 seconds. GRO J1008-57 is 93.3 seconds . Some rotate in milliseconds. So, these “dead” stars are the size of a city, denser than any material in the universe, are a million degrees, and spin at a good fraction of the speed of light.
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- How can we measure the strength of a pulsar’s magnetic energy? A special technique can be used with a specific class of pulsars which GRO J1008-57 belongs to called “accretion powered X-Ray pulsars“.
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- GRO J1008-57, about 20,000 light years from Earth, is actually in a binary gravitational relationship with a living class B companion star. B’s are hefty stars, a dozen or so times the mass of our Sun and thousands of times brighter.
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- GRO J1008-57’s super density creates a powerful gravitational pull 100 billion times more powerful than Earth’s which rips stellar material off its companion. That material falls toward the neutron star. It becomes entangled in the neutron star’s magnetic field flowing along the “lines” of that field to the north and south magnetic poles where it accumulates or accretes on the surface.
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- The stellar material slams into the surface at half the speed of light releasing tremendous X-Ray energy. These X-Rays, before radiating away from the neutron star, pass through the magnetic field at the neutron star’s surface.
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- The magnetic field scatters some of the X-Rays leaving a gap or “absorption line” in the spectrum of the X-Rays. It’s like a fingerprint left by the magnetic field on the X-Ray energy that we can see with our telescopes. Where that absorption line appears along the X-Ray spectrum directly relates to the strength of the magnetic field at the neutron star’s surface where the stellar material is falling. The line is known as a “Cyclotron Resonance Scattering Feature“.
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- In 2017, the brightest X-Ray outburst ever observed from GRO J1008-57 was recorded by the Chinese Insight-HXMT satellite. Scientists analyzed the Cyclotron abortion lines in the X-Ray spectrum received.
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- They had discovered lines in the spectrum corresponding to a 1-billion Tesla magnetic field. That is the most powerful ever recorded in the Universe. Powerful enough to literally pull atoms apart.
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- So, if it doesn’t vaporize you with its immense heat, or obliterating gravity, your atomic structure would basically dissolve in the magnetic forces.
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- A tiny line reveals a distant part of the Universe that we may not be able to “see” but can deduce through decades of research, and our imagination, transforming data into accretion disks, giant stars, plasma flying at near light-speeds, powerful X-Rays, and spinning stellar relics. SCIENCE!! What can it tell you?
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- October 27, 2021 EARTH’S - magnetic bubble? 3310
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--------------------- --- Thursday, October 28, 2021 ---------------------------
