Saturn’s North Pole

north-poleThese two natural color images taken by the Cassini spacecraft show how Saturn’s north polar region has changed between 2012 and 2016. The color change is thought to be an effect of Saturn’s seasons. It suggested that the change from a bluish color to a more golden hue is due to the increased production of smog in the atmosphere as the north pole approaches summer solstice in May, 2017.

The hexagon, Saturn’s six-sided jetstream, may act as a barrier preventing haze particles produced outside it from entering. If that’s the case, the polar atmosphere could have become clear of aerosols produced by photochemical reactions, reactions caused by sunlight, during the winter. After Saturn’s equinox in August, 2009, the north pole polar has been in continuous sunshine, and smog aerosols are being produced inside the hexagon, making the polar atmosphere appear hazy.

Image Credit: NASA

Clouds on Mars

Images from MAVEN’s Imaging UltraViolet Spectrograph were used to make this movie of rapid cloud formation on Mars. The ultraviolet light reflected from the planet has been rendered in false color to show what might be seen with ultraviolet-sensitive eyes. The movie uses four MAVEN images to show about 7 hours of Mars rotation, and it interleaves simulated views that could have been seen between the four images. The length of the Martian day is similar to Earth’s, so the movie shows just over a quarter day. The left part of the planet is in morning and the right side in afternoon. Mars’ prominent volcanoes, topped with white clouds, can be seen moving across the disk.  Olympus Mons, the tallest in the Solar System, appears as a prominent dark region near the top with a small white cloud at the summit that grows during the day. Olympus Mons appears dark because the volcano rises up above much of the hazy atmosphere. Three more volcanoes appear in a diagonal row with their cloud cover merging to span a thousand miles by the end of the “day.”

Video Credit: NASA

NGC 278

Cassiopeia’s unusual residentNGC 278 may look serene, but it isn’t. The galaxy is currently undergoing an terrific burst of star formation. The blue knots speckling the galaxy’s spiral arms mark clumps of hot newborn stars. However, NGC 278’s star formation is very unusual. It does not extend all across the galaxy to its outer edges but is only taking place within an inner ring roughly 6500 light-years across. The galaxy’s center is bright, but its extremities are much darker. This odd configuration may have been caused by a merger with a smaller, gas-rich galaxy which ignited the center of NGC 278 while the dusty remains of the smaller galaxy were dispersed into the galaxy’s outer regions. Whatever happened, such a ring of star formation, called a nuclear ring, is extremely rare in galaxies without bars at their centers.

Image Credit: ESA / NASA

Chandra Archives 2016

chandra_archives2016Each year, NASA’s Chandra X-ray Observatory helps celebrate American Archive Month by releasing a collection of images using X-ray data in its archive. Each of these six new images also includes data from telescopes covering other parts of the electromagnetic spectrum, such as visible and infrared light. From left to right, starting on the top row, the objects are:

Westerlund 2: A cluster of young stars – about one to two million years old – located about 20,000 light years from Earth. Data in visible light from the Hubble Space Telescope (green and blue) reveal thick clouds where the stars are forming. High-energy radiation in the form of X-rays, however, can penetrate this cosmic haze, and are detected by Chandra (purple).

3C31: X-rays from the radio galaxy 3C31 (blue), located 240 million light years from Earth, allow astronomers to probe the density, temperature, and pressure of this galaxy, long known to be a powerful emitter of radio waves. The Chandra data also reveal a jet blasting away from one side of the central galaxy, which also is known as NGC 383. Here, the Chandra X-ray image has been combined with Hubble’s visible light data (yellow).

PSR J1509-5850: Pulsars were first discovered in 1967 and today astronomers know of over a thousand such objects. The pulsar, PSR J1509-5850, located about 12,000 light years from Earth and appearing as the bright white spot in the center of this image, has generated a long tail of X-ray emission trailing behind it, as seen in the lower part of the image. This pulsar has also generated an outflow of particles in approximately the opposite direction. In this image, X-rays detected by Chandra (blue) and radio emission (pink) have been overlaid on a visible light image from the Digitized Sky Survey of the field of view.

Abell 665: Merging galaxy clusters can generate enormous shock waves, similar to cold fronts in weather on Earth. This system, known as Abell 665, has an extremely powerful shockwave, second only to the famous Bullet Cluster. Here, X-rays from Chandra (blue) show hot gas in the cluster. The bow wave shape of the shock is shown by the large white region near the center of the image. The Chandra image has been added to radio emission (purple) and visible light data from the Sloan Digital Sky Survey showing galaxies and stars (white).

RX J0603.3+4214: The phenomenon of pareidolia is when people see familiar shapes in images. This galaxy cluster has invoked the nickname of the “Toothbrush Cluster” because of its resemblance to the dental tool. In fact, the stem of the brush is due to radio waves (green) while the diffuse emission where the toothpaste would go is produced by X-rays observed by Chandra (purple). Visible light data from the Subaru telescope show galaxies and stars (white) and a map from gravitational lensing (blue) shows the concentration of the mass, which is mostly (about 80%) dark matter.

CTB 37A: Astronomers estimate that a supernova explosion should occur about every 50 years on average in the Milky Way galaxy. The object known as CTB 37A is a supernova remnant located in our Galaxy about 20,000 light years from Earth. This image shows that the debris field glowing in X-rays (blue) and radio waves (pink) may be expanding into a cooler cloud of gas and dust seen in infrared light (orange).

Image Credit: NASA

In Daylight on the Night Side

rings-in-daylightThe Cassini spacecraft looked down at the rings of Saturn from above the planet’s nightside to take this picture. The darkened globe of Saturn is on the lower right, along with the shadow it casts across the rings. Even on the planet’s night side, part of the rings remain in sunlight, and they reflect sunlight back onto the night side of the planet, making it appear brighter than it would otherwise appear.

Saturn’s small moon Prometheus ( 86 km across) is faintly visible as a speck near upper left. Earlier in the planet’s year, Saturn’s shadow was once long enough to stretch to the orbit of Prometheus, but as northern summer solstice approaches, the shadow no longer reaches that far. Prometheus won’t be in the planet’s shadow until the progression of the seasons again causes the shadow to lengthen.

Image Credit: NASA