NASA Astronomy Picture of the Day:

From July of 1997, a ramp from the Pathfinder lander, the Sojourner robot rover, airbags, a couch, Barnacle Bill and Yogi Rock appear together in this 3D stereo view of the surface of Mars. Barnacle Bill is the rock just left of the solar-paneled Sojourner. Yogi is the big friendly-looking boulder at top right. The "couch" is the angular rock shape visible near center on the horizon. Look at the image with red/blue glasses (or just hold a piece of clear red plastic over your left eye and blue or green over your right) to get the dramatic 3D perspective. The stereo view was recorded by the remarkable Imager for Mars Pathfinder (IMP) camera. The IMP had two optical paths for stereo imaging and ranging and was equipped with an array of color filters for spectral analysis. Operating as the first astronomical observatory on Mars, the IMP also recorded images of the Sun and Deimos, the smallest of Mars' two tiny moons. This July saw the launch of NASA's Mars Perseverance Rover on a mission to the Red Planet.

Photo by IMP Team

NASA Astronomy Picture of the Day:

The arms of a grand design spiral galaxy 60,000 light-years across are unwound in this digital transformation of the magnificent 2005 Hubble Space Telescope portrait of M51. In fact, M51 is one of the original spiral nebulae, its winding arms described by a mathematical curve known as a logarithmic spiral, a spiral whose separation grows in a geometric way with increasing distance from the center. Applying logarithms to shift the pixel coordinates in the Hubble image relative to the center of M51 maps the galaxy's spiral arms into diagonal straight lines. The transformed image dramatically shows the arms themselves are traced by star formation, lined with pinkish starforming regions and young blue star clusters. Companion galaxy NGC 5195 (top) seems to alter the track of the arm in front of it though, and itself remains relatively unaffected by this unwinding of M51. Also known as the spira mirabilis, logarthimic spirals can be found in nature on all scales. For example, logarithmic spirals can also describe hurricanes, the tracks of subatomic particles in a bubble chamber and, of course, cauliflower.

Photo by Hubble Heritage Project

NASA Astronomy Picture of the Day:

Shrouded in a thick atmosphere, Saturn's largest moon Titan really is hard to see. Small particles suspended in the upper atmosphere cause an almost impenetrable haze, strongly scattering light at visible wavelengths and hiding Titan's surface features from prying eyes. But Titan's surface is better imaged at infrared wavelengths where scattering is weaker and atmospheric absorption is reduced. Arrayed around this visible light image (center) of Titan are some of the clearest global infrared views of the tantalizing moon so far. In false color, the six panels present a consistent processing of 13 years of infrared image data from the Visual and Infrared Mapping Spectrometer (VIMS) on board the Cassini spacecraft. They offer a stunning comparison with Cassini's visible light view. Experts Debate: How will humanity first discover extraterrestrial life?

NASA Astronomy Picture of the Day:

Does the Sun change as it rotates? Yes, and the changes can vary from subtle to dramatic. In the featured time-lapse sequences, our Sun -- as imaged by NASA's Solar Dynamics Observatory -- is shown rotating though an entire month in 2014. In the large image on the left, the solar chromosphere is depicted in ultraviolet light, while the smaller and lighter image to its upper right simultaneously shows the more familiar solar photosphere in visible light. The rest of the inset six Sun images highlight X-ray emission by relatively rare iron atoms located at different heights of the corona, all false-colored to accentuate differences. The Sun takes just under a month to rotate completely -- rotating fastest at the equator. A large and active sunspot region rotates into view soon after the video starts. Subtle effects include changes in surface texture and the shapes of active regions. Dramatic effects include numerous flashes in active regions, and fluttering and erupting prominences visible all around the Sun's edge. Presently, our Sun is passing an unusually low Solar minimum in activity of its 11-year magnetic cycle. As the video ends, the same large and active sunspot region previously mentioned rotates back into view, this time looking different.

NASA Astronomy Picture of the Day:

Do other stars have planets like our Sun? Previous evidence shows that they do, coming mostly from slight shifts in the star's light created by the orbiting planets. Recently, however, and for the first time, a pair of planets has been directly imaged around a Sun-like star. These exoplanets orbit the star designated TYC 8998-760-1 and are identified by arrows in the featured infrared image. At 17 million years old, the parent star is much younger than the 5-billion-year age of our Sun. Also, the exoplanets are both more massive and orbit further out than their Solar System analogues: Jupiter and Saturn. The exoplanets were found by the ESO's Very Large Telescope in Chile by their infrared glow – after the light from their parent star was artificially blocked. As telescope and technology improve over the next decade, it is hoped that planets more closely resembling our Earth will be directly imaged. Experts Debate: How will humanity first discover extraterrestrial life?

NASA Astronomy Picture of the Day:

Why would meteor trails appear curved? The arcing effect arises only because the image artificially compresses (nearly) the whole sky into a rectangle. The meteors are from the Perseid Meteor Shower that peaked last week. The featured multi-frame image combines not only different directions from the 360 projection, but different times when bright Perseid meteors momentarily streaked across the sky. All Perseid meteors can be traced back to the constellation Perseus toward the lower left, even the seemingly curved (but really straight) meteor trails. Although Perseids always point back to their Perseus radiant, they can appear almost anywhere on the sky. The image was taken from Inner Mongolia, China, where grasslands meet sand dunes. Many treasures also visible in the busy night sky including the central arch of our Milky Way Galaxy, the planets Saturn and Jupiter toward the right, colorful airglow on the central left, and some relatively nearby Earthly clouds. The Perseid Meteor Shower peaks every August. Perseid Meteor Shower: Notable images submitted to APOD

Photo by Jingyi Zhang

NASA Astronomy Picture of the Day:

In the center of this serene stellar swirl is likely a harrowing black-hole beast. The surrounding swirl sweeps around billions of stars which are highlighted by the brightest and bluest. The breadth and beauty of the display give the swirl the designation of a grand design spiral galaxy. The central beast shows evidence that it is a supermassive black hole about 10 million times the mass of our Sun. This ferocious creature devours stars and gas and is surrounded by a spinning moat of hot plasma that emits blasts of X-rays. The central violent activity gives it the designation of a Seyfert galaxy. Together, this beauty and beast are cataloged as NGC 6814 and have been appearing together toward the constellation of the Eagle (Aquila) for roughly the past billion years. Pereid Meteor Shower: Notable images submitted to APOD

NASA Astronomy Picture of the Day:

Does the Moon ever block out Mars? Yes, the Moon occasionally moves in front of all of the Solar System's planets. Just this past Sunday, as visible from some locations in South America, a waning gibbous Moon eclipsed Mars. The featured image from Córdoba, Argentina captured this occultation well, showing a familiar cratered Moon in the foreground with the bright planet Mars unusually adjacent. Within a few seconds, Mars then disappeared behind the Moon, only to reappear a few minutes later across the Moon. Today the Moon moves close to, but not in front of, Venus. Because alignments will not have changed by much, the next two times the Moon passes through this part of the sky – in early September and early October – it will also occult Mars, as seen from parts of South America. Pereid Meteor Shower: Notable images submitted to APOD

Photo by Sergio Scauso

NASA Astronomy Picture of the Day:

Why is this nebula so complex? When a star like our Sun is dying, it will cast off its outer layers, usually into a simple overall shape. Sometimes this shape is a sphere, sometimes a double lobe, and sometimes a ring or a helix. In the case of planetary nebula NGC 5189, however, besides an overall "Z" shape (the featured image is flipped horizontally and so appears as an "S"), no such simple structure has emerged. To help find out why, the Earth-orbiting Hubble Space Telescope has observed NGC 5189 in great detail. Previous findings indicated the existence of multiple epochs of material outflow, including a recent one that created a bright but distorted torus running horizontally across image center. Hubble results appear consistent with a hypothesis that the dying star is part of a binary star system with a precessing symmetry axis. NGC 5189 spans about three light years and lies about 3,000 light years away toward the southern constellation of the Fly (Musca).

NASA Astronomy Picture of the Day:

What planets are those behind that unusual rock spire? Saturn (lower left) and Jupiter.  This month, after sunset, the bright planetary duo are quite prominent toward the southeast.  Now your view of our Solar System's largest planets might not include a picturesque hoodoo in the foreground, nor the spectacular central band of our Milky Way Galaxy across the background, but should be quite eye-catching anyway.  The featured image is a composite of consecutive foreground and background exposures all taken in late May with the same camera and from the same location -- the badlands of the  Ah-Shi-Sle-Pah Wilderness in the San Juan Basin in New Mexico, USA.  The rock spire, informally dubbed 'Alien Throne', stands about 3 meters tall. Saturn and Jupiter will remain visible together after sunset for several months.

Photo by Marcin Zając