An aurora illuminates the skies over Fairbanks, Alaska, in a 2009 picture released this week.
Auroras occur when large numbers of charged particles from the sun encounter Earth's magnetic shield. Most of these particles get corralled toward the Poles, where they slam into atmospheric gases such as nitrogen and oxygen.
Gray ice covers the surface of Lake Sakakawea, North Dakota, in a picture taken by an astronaut aboard the International Space Station.
A dusting of white snow highlights agricultural fields to the north and northeast, as well as irregularities in the surface of the ice, according to the NASA Earth Observatory, which recently released the picture.
One of the largest artificial reservoirs in the United States, Lake Sakakawea was created in 1954 following the completion of the Garrison Dam on the Missouri River.
In an image released Wednesday, young stars—pictured sparkling in the Orion Nebula—have been caught in the turbulent throes of formation by the European Space Agency's Herschel space observatory and NASA's Spitzer Space Telescope. Through these orbiting observatories, astronomers have now witnessed the stars rapidly heating and cooling as they tumble toward more stable adulthoods.
The motion of a rotating telescope dome is captured in this 26-second exposure released February 27 (see photo tips).
A solar filament stretches near the sun's north pole (at top) in this ultraviolet picture taken by the orbiting SOHO spacecraft. Caused by magnetic forces acting on clouds of cooling gas, the filaments occur regularly on the sun.
Tendrils of blue-green water stream from a larger, similarly colored water mass near Antarctica's Amery Ice Shelf in a satellite image taken in early February and released this week.
The colors may be due to frazils, needle-like crystals that form when deep water wells up beneath the ice shelf and begins to freeze.
Though only 0.12 to 0.16 inch (3 to 4 millimeters) wide, frazils in high enough concentrations can change the color of the surface water.
Ocean-circulation models suggest a plume of deep water is emerging from beneath the shelf at that location. Gradually, as layers of ocean water mix, the frazils melt and the colored streams disappear.
Stars Over Uppsala
The night sky stretches above a ruined castle near Uppsala, Sweden, in a February 21 photograph. A star cluster known as the Pleiades, or Messier 45, can be seen above the castle.
Antlia Dwarf Galaxy
A new Hubble Space Telescope picture shows Antlia, a faint and sparsely populated dwarf galaxy more than four million light-years from Earth. According to the Hubble team, the galaxy is thought to have interacted with its neighbor NGC 3109, as evidenced by rifts of stars moving at similar velocities.