MAHLI's First Night Imaging of Martian Rock Under Ultraviolet Lighting

This image of a Martian rock illuminated by ultraviolet LEDs (light emitting diodes) is part of the first set of nighttime images taken by the Mars Hand Lens Imager (MAHLI) camera at the end of the robotic arm of NASA's Mars rover Curiosity. MAHLI took the images on Jan. 22, 2012 (PST), after dark on the 165th Martian day, or sol, of the rover's work on Mars. The image covers an area about 1.3 inches by 1 inch (3.4 by 2.5 centimeters).

NASA Radar Images Asteroid Toutatis

This 64-frame movie of asteroid Toutatis was generated from data by Goldstone's Solar System Radar on Dec. 12 and 13, 2012. In the movie clips, the rotation of the asteroid appears faster than it occurs in nature.

Space Rocks Vesta and Ceres Visible in Night Sky This Week

On the morning of Sunday December 9, The brightest asteroid Vesta will be in opposition to the Sun, close to the bright planet Jupiter. CREDIT: Starry Night Software 

On Sunday (Dec. 2), the giant planet Jupiter reached opposition with the sun, lining up directly opposite the sun in the sky. That means it's a great target for stargazers, who can see it shine brightly all night long this week.

The Black Marble

This new global view and animation of Earth's city lights is a composite assembled from data acquired by the Suomi NPP satellite. The data was acquired over nine days in April 2012 and 13 days in October 2012. It took 312 orbits to get a clear shot of every parcel of Earth's land surface and islands. This new data was then mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet. Credit: NASA Earth Observatory/NOAA NGDC

Why Are We Seeing So Many Sungrazing Comets?

People have been hunting for sungrazing comets for hundreds of years, but as of 1979, we only knew of 9. Today we have seen 3,000 thanks to better observation tools. Credit: NASA/Goddard Scientific Visual Studio

Giant Molecular Cloud (GMC) - Definition

Giant Molecular Cloud (GMC)

Massive clouds of gas in interstellar space composed primarily of hydrogen molecules (two hydrogen atoms bound together), though also containing other molecules observable by radio telescopes. These clouds can contain enough mass to make several million stars like our Sun and are often the sites of star formation.

General Relativity - Definition

General Relativity

A geometrical theory of gravity developed by Albert Einstein in which gravity's effects are a consequence of the curvature of four-dimensional space-time. According to this theory, the energy and momentum of all matter and radiation cause curvature in space-time, in a way similar to the creation of electric and magnetic fields by electric charges and currents. This curvature also opens the possibility that the universe is closed, having finite volume but without any boundary. Among the many experimentally confirmed consequences of General Relativity are the perihelion precession of the planet Mercury, the bending of light in a gravitational field, and the slowing of time in a gravitational field.

Source: thefreedictionary.com

Gas - Definition

Gas

A gas is a sample of matter that conforms to the shape of a container in which it is held and acquires a uniform density inside the container, even in the presence of gravity and regardless of the amount of substance in the container. If not confined to a container, gaseous matter, also known as vapor, will disperse into space . The term gas is also used in reference to the state, or condition, of matter having this property.

Gamma Ray Imaging Spectrometer (GRIS) - Definition

Gamma Ray Imaging Spectrometer (GRIS)

A balloon-borne instrument which uses germanium detectors for high resolution gamma-ray spectroscopy.

GRIS has been an extraordinarily successful balloon-borne instrument which uses germanium detectors for high resolution gamma-ray spectroscopy. The maiden flights of GRIS from Alice Springs, Australia in 1988 produced the definitive measurements of gamma-ray lines from Supernova 1987A and the positron annihilation line at 511 keV from the Galactic Center. These extremely important lines were resolved, yielding crucial new clues about the emission processes.

Source: NASA

Gamma Ray Imaging Platform (GRIP) - Definition

Gamma Ray Imaging Platform (GRIP)

A balloon-borne gamma-ray telescope made by a group at the California Institute of Technology. It has had many successful flights.

Source: NASA

Gamma-ray Large Area Space Telescope (GLAST)

Gamma-ray Large Area Space Telescope (GLAST)

An international mission launched on June 11, 2008, GLAST studies the universe in the energy range 10 keV - 300 Gev. In August 2008, NASA renamed the mission the Fermi Gamma-ray Space Telescope.

Source: NASA

Gamma-Ray Bursts - Definition

Gamma-Ray Bursts

Gamma-ray bursts are short-lived bursts of gamma-ray photons, the most energetic form of light. At least some of them are associated with a special type of supernovae, the explosions marking the deaths of especially massive stars.

A computer animation of a gamma-ray burst.

Lasting anywhere from a few milliseconds to several minutes, gamma-ray bursts (GRBs) shine hundreds of times brighter than a typical supernova and about a million trillion times as bright as the Sun, making them briefly the brightest source of cosmic gamma-ray photons in the observable Universe. GRBs are detected roughly once per day from wholly random directions of the sky.

Gamma Rays - Definition

Gamma-Rays

Gamma-rays have the smallest wavelengths and the most energy of any other wave in the electromagnetic spectrum. These waves are generated by radioactive atoms and in nuclear explosions. Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.

Gamma-rays travel to us across vast distances of the universe, only to be absorbed by the Earth's atmosphere. Different wavelengths of light penetrate the Earth's atmosphere to different depths. Instruments aboard high-altitude balloons and satellites like the Compton Observatory provide our only view of the gamma-ray sky.

Galileo Galilei (1564-1642)

Galileo Galilei (1564-1642)

Italian scientist and philosopher. Galileo was a true Renaissance man, excelling at many different endeavors, including lute playing and painting. He attended medical school in Padua. While in a cathedral, he noticed that a chandelier was swinging with the same period as timed by his pulse, regardless of its amplitude. He began to study the isochronism of the pendulum  in 1581, as well as the motion of bodies. Using an inclined plane, he showed that all bodies fall at the same rate. He also investigated cohesion,  and concluded that a waterfall breaks when the weight of the water  becomes too great, the same reason that water  pumps could only raise water by 34 feet.

Galaxy - Definition

Galaxy

A galaxy is, by definition, any large collection of stars that can be recognized as a distinct physical entity. In terms of the number of stars, a small 'dwarf irregular' galaxy like the Small Magellanic Cloud, has about one billion stars in it, but there are even smaller systems that are recognized as galaxies such as the Leo I and II dwarf galaxies with about 1 million stars in them, and the Draco System with a few hundred thousand stars in it. The largest star cluster, a globular cluster called Messier 15 has about 6 million stars, so we see that for small galaxies, there is a blurring together of what we mean by a galaxy and a large star cluster.

In addition to their mass and numbers of stars, a galaxy is a collection of stars and gas which move through the universe independently of the Milky Way. Globular clusters are roundish swarms of stars that orbit the Milky Way, while the Leo and Draco Systems seem to be independent collections of stars.

NGC 4414, a typical spiral galaxy

Many galaxies also continue to form new generations of stars. The Milky Way, and all spiral shaped galaxies like it (see above image of NGC 2997), produce new stars at a rate of one or two stars per year. These stars are formed in the vast interstellar clouds that account for about 1 to 10 percent of the mass of these galaxies. Globular star clusters, on the other hand, are not currently forming stars because this activity happened billions of years ago and then stopped once all of the gas and dust clouds were used up.

Source: wikipedia, astronomycafe.net

Fusion - Definition

Fusion

The process in which atomic nuclei collide so fast that they stick together and emit a large amount of energy. In the center of most stars, hydrogen fuses into helium. The energy emitted by fusion supports the star's enormous mass from collapsing in on itself, and causes the star to glow.

Source: atomicarchive.com, NASA

FTOOLS - Definition

FTOOLS

A suite of software tools developed at NASA's Goddard Space Flight Center for analyzing high-energy astronomy data.

Source: NASA

Frequency - Definition

Frequency

A property of a wave that describes how many wave patterns or cycles pass by in a period of time. Frequency is often measured in Hertz (Hz), where a wave with a frequency of 1 Hz will pass by at 1 cycle per second.

Source: answers.com, NASA

Flux - Definition

Flux

A measure of the amount of energy given off by an astronomical object over a fixed amount of time and area. Because the energy is measured per time and area, flux measurements make it easy for astronomers to compare the relative energy output of objects with very different sizes or ages.

Source: http://astro.unl.edu, NASA

Fermi Gamma-ray Telescope - Definition

Fermi Gamma-ray Telescope

An international mission launched on June 11, 2008, the Fermi Gamma-ray Telescope studies the universe in the energy range 10 keV - 300 Gev.

The Fermi Gamma-ray Space Telescope, formerly GLAST, is opening this high-energy world to exploration and helping us answer these questions. With Fermi, astronomers at long last have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists are able to study subatomic particles at energies far greater than those seen in ground-based particle accelerators. And cosmologists are gaining valuable information about the birth and early evolution of the Universe.

Source: NASA