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Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites.

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NASA Probe Sees Solar Wind Decline

The 33-year odyssey of NASA's Voyager 1 spacecraft has reached a distant point at the edge of our solar system where there is no outward motion of solar wind. Now hurtling toward interstellar space some 17.4 billion...

Super-Earth Atmosphere

A team of astronomers, including two NASA Sagan Fellows, has made the first characterizations of a super-Earth's atmosphere, by using a ground-based telescope...

Kepler Discovers

NASA's Kepler spacecraft has discovered the first confirmed planetary system with more than one planet crossing in front of, or transiting, the same star...

Pulverized Planet

Tight double-star systems might not be the best places for life to spring up, according to a new study using data from NASA's Spitzer Space Telescope....

Dark Asteroids

NASA is set to launch a sensitive new infrared telescope to seek out sneaky things in the night sky -- among them, dark asteroids that could pose a threat to Earth....

Archive for October 2009

Every 11 years, the sun undergoes a furious upheaval. Dark sunspots burst forth from beneath the sun's surface. Explosions as powerful as a billion atomic bombs spark intense flares of high-energy radiation. Clouds of gas big enough to swallow planets break away from the sun and billow into space. It's a flamboyant display of stellar power.

So why can't we see any of it?

Almost none of the drama of Solar Maximum is visible to the human eye. Look at the sun in the noontime sky and—ho-hum—it's the same old bland ball of bright light.

"The problem is, human eyes are tuned to the wrong wavelength," a solar physicist at the University of Colorado in Boulder. "If you want to get a good look at solar activity, you need to look in the EUV."

EUV is short for "extreme ultraviolet," a high-energy form of ultraviolet radiation with wavelengths between 1 and 120 nanometers. EUV photons are much more energetic and dangerous than the ordinary UV rays that cause sunburns. Fortunately for humans, Earth's atmosphere blocks solar EUV; otherwise a day at the beach could be fatal.

When the sun is active, intense solar EUV emissions can rise and fall by factors of thousands in just a matter of minutes. These surges heat Earth's upper atmosphere, puffing it up and increasing the drag on satellites. EUV photons also break apart atoms and molecules, creating a layer of ions in the upper atmosphere that can severely disturb radio signals.

To monitor these energetic photons, NASA is going to launch a sensor named "EVE," short for EUV Variability Experiment, onboard the Solar Dynamics Observatory as early as this winter.
"EVE gives us the highest time resolution (10 sec) and the highest spectral resolution (<>


For years, researchers have known that the solar system is bounded by a vast bubble of magnetism. Called the "heliosphere," it springs from the sun and extends far beyond the orbit of Pluto, providing a first line of defense against cosmic rays and interstellar clouds that try to enter our local space. Although the heliosphere is huge and literally fills the sky, it emits no light and no one has actually seen it.


NASA's IBEX (Interstellar Boundary Explorer) spaceship has made the first all-sky maps of the heliosphere and the results have taken researchers by surprise. The maps are bisected by a bright, winding ribbon of unknown origin:


Although the ribbon looks bright in the IBEX map, it does not shine in any conventional sense. The ribbon is not a source of light, but rather a source of particles--energetic neutral atoms or ENAs. IBEX's sensors can detect these particles, which are produced in the outer heliosphere where the solar wind begins to slow down and mix with interstellar matter from outside the solar system.


"IBEX is now making a next all-sky map, and we're eager to see if the ribbon is changing," says McComas. "Watching the ribbon evolve--if it is evolving--could yield more clues."



NASA scientists have revealed water molecules in the polar regions of the Moon. Instruments aboard three separate spacecraft revealed water molecules in amounts that are greater than predicted, but still relatively small. Hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom, also was found in the lunar soil.

"Water ice on the Moon has been something of a divine grail for lunar scientists for a very long time," said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. "This surprising finding has come about through the ingenuity, perseverance and international cooperation between NASA and the India Space Research Organization."

"When we say 'water on the Moon,' we are not talking about rivers, oceans or even puddles," explained Carle Pieters, M3's principal investigator from Brown University, Providence, R.I. "Water on the Moon means molecules of water and hydroxyl that interact with molecules of rock and dust specifically in the top millimeters of the Moon's surface.

"With our unlimited spectral range and views over the north pole, we were able to explore the distribution of both water and hydroxyl as a function of temperature, latitude, composition, and time of day," said Jessica Sunshine of the University of Maryland. Sunshine is Epoxi's deputy principal investigator and a scientist on the M3 team. "Our analysis unequivocally confirms the presence of these molecules on the Moon's surface and reveals that the entire surface appears to be hydrated during at least some portion of the lunar day."

The invention of water molecules and hydroxyl on the Moon raises new questions about the origin of "Moon water" and its effect on lunar mineralogy. Answers to these questions will be studied and debated for years to come.