A nearly full Rhea shines in the sunlight in this recent Cassini image. Rhea (949 miles, or 1,527 kilometers across) is Saturn’s second largest moon.
Lit terrain seen here is on the Saturn-facing hemisphere of Rhea. North on Rhea is up and rotated 43 degrees to the left. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 10, 2013.
The view was obtained at a distance of approximately 990,000 miles (1.6 million kilometers) from Rhea. Image scale is 6 miles (9 kilometers) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.
Image Credit: NASA/JPL-Caltech/Space Science Institute
On Aug. 3, 2004, NASA’s Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft began a seven-year journey, spiraling through the inner solar system to Mercury. One year after launch, the spacecraft zipped around Earth, getting an orbit correction from Earth’s gravity and getting a chance to test its instruments by observing its home planet.
This image is a view of South America and portions of North America and Africa from the Mercury Dual Imaging System’s wide-angle camera aboard MESSENGER. The wide-angle camera records light at eleven different wavelengths, including visible and infrared light. Combining blue, red, and green light results in a true-color image from the observations. The image substitutes infrared light for blue light in the three-band combination. The resulting image is crisper than the natural color version because our atmosphere scatters blue light. Infrared light, however, passes through the atmosphere with relatively little scattering and allows a clearer view. That wavelength substitution makes plants appear red. Why? Plants reflect near-infrared light more strongly than either red or green, and in this band combination, near-infrared is assigned to look red.
Apart from getting a clearer image, the substitution reveals more information than natural color. Healthy plants reflect more near-infrared light than stressed plants, so bright red indicates dense, growing foliage. For this reason, biologists and ecologists occasionally use infrared cameras to photograph forests.
Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Caption: Holli Riebeek
Mars’ northern-most sand dunes are beginning to emerge from their winter cover of seasonal carbon dioxide (dry) ice. Dark, bare south-facing slopes are soaking up the warmth of the sun.
The steep lee sides of the dunes are also ice-free along the crest, allowing sand to slide down the dune. Dark splotches are places where ice cracked earlier in spring, releasing sand. Soon the dunes will be completely bare and all signs of spring activity will be gone.
This image was acquired by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter on Jan. 16, 2014. The University of Arizona, Tucson, operates the HiRISE camera, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project for the NASA Science Mission Directorate, Washington.
Image Credit: NASA/JPL-Caltech/Univ. of Arizona
Caption: Candy Hansen
The Stories That Galaxies Tell on @NautilusMag
The biggest merger to ever hit these parts is coming—a union that promises to be more tumultuous than that of Richard Burton and Elizabeth Taylor, offer more star power than Brangelina, and deliver more jet propulsion than the new American Airlines–US Airways conglomerate. We’re talking about the coming together of the Milky Way galaxy and its nearest large neighbor, Andromeda, in a collision that scientists now deem inevitable. This celestial amalgamation will begin in about 4 billion years and finish within another 2 billion, producing a new, larger elliptical galaxy in place of the two spirals that originally conjoined.
Illustration by Mikel Jaso
On Feb. 24, 2014, the sun emitted a significant solar flare, peaking at 7:49 p.m. EST. NASA’s Solar Dynamics Observatory (SDO), which keeps a constant watch on the sun, captured images of the event. These SDO images from 7:25 p.m. EST on Feb. 24 show the first moments of this X-class flare in different wavelengths of light — seen as the bright spot that appears on the left limb of the sun. Hot solar material can be seen hovering above the active region in the sun’s atmosphere, the corona.
Solar flares are powerful bursts of radiation, appearing as giant flashes of light in the SDO images. Harmful radiation from a flare cannot pass through Earth’s atmosphere to physically affect humans on the ground, however — when intense enough — they can disturb the atmosphere in the layer where GPS and communications signals travel.
Image Credit: NASA/SDO
Roguish runaway stars can have a big impact on their surroundings as they plunge through the Milky Way galaxy. Their high-speed encounters shock the galaxy, creating arcs, as seen in this newly released image from NASA’s Spitzer Space Telescope.
In this case, the speedster star is known as Kappa Cassiopeiae, or HD 2905 to astronomers. It is a massive, hot supergiant moving at around 2.5 million mph relative to its neighbors (1,100 kilometers per second). But what really makes the star stand out in this image is the surrounding, streaky red glow of material in its path. Such structures are called bow shocks, and they can often be seen in front of the fastest, most massive stars in the galaxy.
Bow shocks form where the magnetic fields and wind of particles flowing off a star collide with the diffuse, and usually invisible, gas and dust that fill the space between stars. How these shocks light up tells astronomers about the conditions around the star and in space. Slow-moving stars like our sun have bow shocks that are nearly invisible at all wavelengths of light, but fast stars like Kappa Cassiopeiae create shocks that can be seen by Spitzer’s infrared detectors.
The Sun, photos by Pepe Manteca via @InvaderXan
"Sun, the nearest star, an inferno of hydrogen and helium gas engaged in thermonuclear reactions, flooding the Solar System with light."
First geologic map of Ganymede via @fadesingh
More details: Global Geologic Map of Ganymede by Geoffrey C. Collins, G. Wesley Patterson, James W. Head, Robert T. Pappalardo, Louise M. Prockter, Baerbel K. Lucchitta, and Jonathan P. Kay
The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.
This Chandra X-Ray Observatory image of the young star cluster NGC 346 highlights a heart-shaped cloud of 8 million-degree Celsius gas in the central region. Evidence from radio, optical and ultraviolet telescopes suggests that the hot cloud, which is about 100 light years across, is the remnant of a supernova explosion that occurred thousands of years ago.
The progenitor could have been a companion of the massive young star that is responsible for the bright X-ray source at the top center of the image. This young star, HD 5980, one of the most massive known, has been observed to undergo dramatic eruptions during the last decade. An alternative model for the origin of the hot cloud is that eruptions of HD 5980 long ago produced the cloud of hot gas, in a manner similar to the gas cloud observed around the massive star Eta Carinae. Future observations will be needed to decide between the alternatives. Until then, the nature of the heart in the darkness will remain mysterious.
Image Credit: NASA/CXC/U.Liege/Y.Nazé et al.