Space may seem empty, but it's actually a dynamic place populated with near-invisible matter, and dominated by forces, in particular those created by magnetic fields. Magnetospheres -- the magnetic fields around most planets -- exist throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are spewed out by the Sun or come from interstellar space. Along with atmospheres, they happen to protect the planets' surfaces from this harmful radiation.
But not all magnetospheres are created equal: Venus and Mars do not have magnetospheres at all, while the other planets -- and one moon -- have ones that are surprisingly different.
NASA has launched a fleet of missions to study the planets in our solar system -- many of which have sent back crucial information about magnetospheres. The twin Voyagers measured magnetic fields as they traveled out to the far reaches of the solar system, and discovered Uranus and Neptune's magnetospheres.
Other planetary missions including Galileo, Cassini and Juno, and a number of spacecraft that orbit Earth, provide observations to create a comprehensive understanding of how planets form magnetospheres, as well as how they continue to interact with the dynamic space environment around them.
Earth's magnetosphere is created by the constantly moving molten metal inside Earth. This invisible "force field" around our planet has a general shape resembling an ice cream cone, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the near-constant flow of solar wind and magnetic field from the Sun-facing side.
Earth's and other magnetospheres deflect charged particles away from the planet -- but also trap energetic particles in radiation belts. Auroras are caused by particles that rain down into the atmosphere, usually not far from the magnetic poles.
It's possible that Earth's magnetosphere was essential for the development of conditions friendly to life, so learning about magnetospheres around other planets and moons is a big step toward determining if life could have evolved there.
Mercury, with a substantial iron-rich core, has a magnetic field that is only about 1 percent as strong as Earth's. It is thought that the planet's magnetosphere is compressed by the intense solar wind, limiting its extent. The MESSENGER satellite orbited Mercury from 2011 to 2015, helping us understand our tiny terrestrial neighbor.
After the Sun, Jupiter has by far the strongest and biggest magnetic field in our solar system -- it stretches about 12 million miles from east to west, almost 15 times the width of the Sun. (Earth's, on the other hand, could easily fit inside the Sun -- except for its outstretched tail.) Jupiter does not have a molten metal core; instead, its magnetic field is created by a core of compressed liquid metallic hydrogen.
One of Jupiter's moons, Io, has powerful volcanic activity that spews particles into Jupiter's magnetosphere. These particles create intense radiation belts and auroras around Jupiter.
Ganymede, Jupiter's largest moon, also has its own magnetic field and magnetosphere -- making it the only moon with one. Its weak field, nestled in Jupiter's enormous shell, scarcely ruffles the planet's magnetic field.
Saturn's huge ring system transforms the shape of its magnetosphere. That's because oxygen and water molecules evaporating from the rings funnel particles into the space around the planet. Some of Saturn's moons help trap these particles, pulling them out of Saturn's magnetosphere, though those with active volcanic geysers -- like Enceladus -- spit out more material than they take in. NASA's Cassini mission followed in the Voyagers' wake, and studied Saturn's magnetic field from orbit around the ringed planet between 2004 and 2017.
Uranus' magnetosphere wasn't discovered until 1986, when data from Voyager 2's flyby revealed weak, variable radio emissions and confirmed when Voyager 2 measured the magnetic field directly. Uranus' magnetic field and rotation axis are out of alignment by 59 degrees, unlike Earth's, whose magnetic field and rotation axis are nearly aligned. On top of that, the magnetic field does not go directly through the center of the planet, so the strength of the magnetic field varies dramatically across the surface. This misalignment also means that Uranus' magnetotail -- the part of the magnetosphere that trails behind the planet, away from the Sun -- is twisted into a long corkscrew.
Neptune was also visited by Voyager 2, in 1989. Its magnetosphere is offset from its rotation axis, but only by 47 degrees. Similar to Uranus, Neptune's magnetic field strength varies across the planet. This means that auroras can appear across the planet -- not just close to the poles, like on Earth, Jupiter and Saturn.
Outside of our solar system, auroras, which indicate the presence of a magnetosphere, have been spotted on brown dwarfs -- objects that are bigger than planets but smaller than stars. There's also evidence to suggest that some giant exoplanets have magnetospheres, but we have yet to see conclusive proof. As scientists learn more about the magnetospheres of planets in our solar system, it can help us one day identify magnetospheres around more distant planets as well.
Mara Johnson-Groh | EurekAlert!
Double layer of graphene helps to control spin currents
18.10.2019 | University of Groningen
Analysis of Galileo's Jupiter entry probe reveals gaps in heat shield modeling
17.10.2019 | American Institute of Physics
A very special kind of light is emitted by tungsten diselenide layers. The reason for this has been unclear. Now an explanation has been found at TU Wien (Vienna)
It is an exotic phenomenon that nobody was able to explain for years: when energy is supplied to a thin layer of the material tungsten diselenide, it begins to...
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.
The nanocosmos is constantly in motion. All natural processes are ultimately determined by the interplay between radiation and matter. Light strikes particles...
Particles that are mere nanometers in size are at the forefront of scientific research today. They come in many different shapes: rods, spheres, cubes, vesicles, S-shaped worms and even donut-like rings. What makes them worthy of scientific study is that, being so tiny, they exhibit quantum mechanical properties not possible with larger objects.
Researchers at the Center for Nanoscale Materials (CNM), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE's Argonne National...
A new research project at the TH Mittelhessen focusses on the development of a novel light weight design concept for leisure boats and yachts. Professor Stephan Marzi from the THM Institute of Mechanics and Materials collaborates with Krake Catamarane, which is a shipyard located in Apolda, Thuringia.
The project is set up in an international cooperation with Professor Anders Biel from Karlstad University in Sweden and the Swedish company Lamera from...
Superconductivity has fascinated scientists for many years since it offers the potential to revolutionize current technologies. Materials only become superconductors - meaning that electrons can travel in them with no resistance - at very low temperatures. These days, this unique zero resistance superconductivity is commonly found in a number of technologies, such as magnetic resonance imaging (MRI).
Future technologies, however, will harness the total synchrony of electronic behavior in superconductors - a property called the phase. There is currently a...
02.10.2019 | Event News
02.10.2019 | Event News
19.09.2019 | Event News
18.10.2019 | Power and Electrical Engineering
18.10.2019 | Medical Engineering
18.10.2019 | Physics and Astronomy