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An object that revolves around a larger object. Planetary moons are natural satellites.

A break in pressure, density, and particle velocity, carrying forward through a medium such as plasma.

Having to do with the Sun.

Solar Cell
Also known as a photovoltaic cell. A solar cell is a battery that uses energy from the Sun as its source of energy.

More about solar cells...

Solar energetic particles (SEPs)
Particles that are associated with solar flares. They move away from the Sun due to plasma heating, acceleration and many other forces.

More about SEPs...

Solar flare
Solar flareAn enormous explosion of gas in the solar atmosphere resulting in a sudden burst of particle acceleration, the heating of plasma and the eruption of large amounts of solar mass. This image of a solar flare is courtesy of NASA JSC.

More about solar flares...

Solar minimum
The lowest level in solar activity. It occurs between solar maxima.

Solar plumes
Long, feathery jets that expel a high-speed stream of electrified gas from the corona. They extend from near the solar poles to more than 13 million miles into space.

More about solar plumes...

Solar system
A star, and its associated planets and their moons, asteroids, comets, and meteoroids, and interplanetary dust and gas that are held by the star's gravity and orbit around it.

More about the solar system...

Solar wind
The plasma of charged particles coming out of the Sun in all directions at supersonic speeds.

More about solar wind...

Solar wind termination shock
The shock caused by the sudden slowing of solar wind as it approaches the heliopause.

The area between all of the bodies in the universe. It is not empty! It contains magnetic fields, electromagnetic radiation, gases, dust and other particles.

Space weather
The effects on Earth produced by solar activity which causes changes in energetic particle flux due to magnetic storms from the Sun.

More about space weather...

An instrument that separates measurements into different energies or frequencies, producing a spectrum.

(plural = spectra) The distribution of energy wavelengths and frequencies.

More about the energy spectrum...

Speed of light
The speed of light in a vacuum (the way the term is normally used) is defined as about 300,000,000 m/s (186,000 miles/second). It is considered to be the fastest speed anything can reach. It is expressed as "c" in Einstein's famous equation: E=mc2

Starbirth -- Hubble Space TelescopeA glowing ball of gas that uses a nuclear reaction to produce energy. This image from the Hubble Space Telescope is of star birth in the Eagle Nebula, November 2, 1995.

Slower than the speed of sound. In air, the speed of sound is about 340 m/sec (~1100 ft/sec).

The SunThe star at the center of our solar system. It is made mostly of hydrogen and helium with traces of heavier elements. This image of the Sun is courtesy of SOHO/EIT.

More about the Sun...

Temporary magnetic disturbances in the photosphere. They appear dark because temperatures are considerably lower than in surrounding areas.

More about sunspots...

(plural = supernovae) The death explosion of a massive star whose core has completely burned out. Supernova explosions can temporarily outshine a galaxy. The outer layers are blasted out in an expanding cloud. This cloud is visible long after the initial explosion fades, and is called a supernova remnant (SNR).

Faster than the speed of sound. In air, the speed of sound is about 340 m/sec (~1100 ft/sec).


Radio signals to and from a spacecraft used to encode and exchange data with a ground station.

An analysis of a set of facts in their relation to one another, offered to explain events.

An instrument system that uses the difference in travel time through a chamber to separate particles or photons with differing properties. A time-of-flight system is in both the SWIMS and ULEIS instruments onboard the ACE spacecraft.

Having to do with three axes (x, y, and z). It is used to describe a three-dimensional system. Triaxial magnetometers are used on the MAG instrument on the ACE spacecraft.

TRACE sun mosaic Supernova 1006 (ASCA) 30
Doradus ACE
spacecraft TRACE solar flare IMAGE magnetosphere
Click on images above to learn more about them

A service of the Heliophysics Science Division at NASA's GSFC

Questions and comments to:
Curator: Dr Eric R. Christian, NASA
Responsible NASA Official: Dr Eric R. Christian

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This file was last modified: December 29, 2006