Blob: Star Gazers

Shortly before Mars' June 2015 conjunction, the Curiosity Rover celebrated 1000 sols on the red planet. After its August 5, 2012 landing, Curiosity's 1000th sol or martian day on the surface corresponded to planet Earth's calendar date May 31, 2015. Because the line-of-sight to Mars is close to the Sun near the conjunction, radio communications are affected and the six-wheeled, car-sized robotic rover cautiously remains parked at this spot for now. The view looks back toward the stomping grounds for Curiosity's nearly 10.6 kilometer trek so far, with the hazy rim of Gale Crater looming in the distance. The mosaicked panorama was constructed with images from navigation cameras taken on Curiosity's sol 997.

While most spiral galaxies, including our own Milky Way, have two or more spiral arms, NGC 4725 seems to have only one. In this sharp color image, the solo spira mirabilis is tightly wound, traced by bluish, newborn star clusters. The odd galaxy also sports obscuring dust lanes, a prominent ring, and a yellowish central bar structure composed of an older population of stars. NGC 4725 is over 100 thousand light-years across and lies 41 million light-years away in the well-groomed constellation Coma Berenices. Computer simulations of the formation of single spiral arms suggest that they can be either leading or trailing arms with respect to a galaxy's overall rotation.

One million seconds of x-ray image data were used to construct this view of supernova remnant Cassiopeia A, the expanding debris cloud from a stellar explosion. The stunningly detailed image from the Chandra Observatory will allow an unprecedented exploration of the catastrophic fate that awaits stars much more massive than the Sun. Seen in false-color, Cas A's outer green ring, 10 light-years or so in diameter, marks the location of the expanding shock from the original supernova explosion. At about 10 o'clock around the ring, a structure extends beyond it, evidence that the initial explosion may have also produced energetic jets. Still glowing in x-rays, the tiny point source near the center of Cas A is a neutron star, the collapsed remains of the stellar core. While Cas A is about 10,000 light-years away, light from the supernova explosion first reached Earth just over 300 years ago.