How many moons do you see? Many people would say one, referring to the Earth’s Moon, prominent on the lower left. But take a closer look at the object on the upper right. That seeming-star is actually the planet Jupiter, and your closer look might reveal that it is not alone – it is surrounded by some of its largest moons. From left to right these Galilean Moons are Io, Ganymende, Europa and Callisto. These moons orbit the Jovian world just like the planets of our Solar System orbit the Sun, in a line when seen from the side. The featured single shot was captured from Cancun, Mexico last week as Luna, in its orbit around the Earth, glided past the distant planet. Even better views of Jupiter are currently being captured by NASA’s Juno spacecraft, now in a looping orbit around the Solar System’s largest planet. Earth’s Moon will continue to pass nearly in front of both Jupiter and Saturn once a month (moon-th) as the two giant planets approach their own great conjunction in December. via NASA https://ift.tt/2EOSHJR

Does Ceres have underground pockets of water? Ceres, the largest asteroid in the asteroid belt, was thought to be composed of rock and ice. At the same time, Ceres was known to have unusual bright spots on its surface. These bright spots were clearly imaged during Dawn’s exciting approach in 2015. Analyses of Dawn images and spectra indicated that the bright spots arise from the residue of highly-reflective salt water that used to exist on Ceres’ surface but evaporated. Recent analysis indicates that some of this water may have originated from deep inside Ceres, indicating Ceres to be a kindred spirit with several Solar System moons, also thought to harbor deep water pockets. The featured video shows in false-color pink the bright evaporated brine named Cerealia Facula in Occator Crater. In 2018, the mission-successful but fuel-depleted Dawn spacecraft was placed in a distant parking orbit, keeping it away from the Ceres’ surface for at least 20 years to avoid interfering with any life that might there exist. via NASA https://ift.tt/2Dm7Ula

SS 433 is one of the most exotic star systems known. Its unremarkable name stems from its inclusion in a catalog of Milky Way stars which emit radiation characteristic of atomic hydrogen. Its remarkable behavior stems from a compact object, a black hole or neutron star, which has produced an accretion disk with jets. Because the disk and jets from SS 433 resemble those surrounding supermassive black holes in the centers of distant galaxies, SS 433 is considered a micro-quasar. As illustrated in the animated featured video based on observational data, a massive, hot, normal star is locked in orbit with the compact object. As the video starts, material is shown being gravitationally ripped from the normal star and falling onto an accretion disk. The central star also blasts out jets of ionized gas in opposite directions – each at about 1/4 the speed of light. The video then pans out to show a top view of the precessing jets producing an expanding spiral. From even greater distances, the dissipating jets are then visualized near the heart of supernova remnant W50. Two years ago, SS 433 was unexpectedly found by the HAWC detector array in Mexico to emit unusually high energy (TeV-range) gamma-rays. Surprises continue, as a recent analysis of archival data taken by NASA’s Fermi satellite find a gamma-ray source — separated from the central stars as shown — that pulses in gamma-rays with a period of 162 days – the same as SS 433’s jet precession period – for reasons yet unknown. via NASA https://ift.tt/2EwsCiR

How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known. This star is the brightest object located just above the gas front in the featured image. Close inspection of images taken with the Hubble Space Telescope, however, have shown that Pismis 24-1 derives its brilliant luminosity not from a single star but from three at least. Component stars would still remain near 100 solar masses, making them among the more massive stars currently on record. Toward the bottom of the image, stars are still forming in the associated emission nebula NGC 6357. Appearing perhaps like a Gothic cathedral, energetic stars near the center appear to be breaking out and illuminating a spectacular cocoon. via NASA https://ift.tt/31D4Lqn

Deep shadows create dramatic contrasts between light and dark in this high-resolution close-up of the martian surface. Recorded on January 24, 2014 by the HiRISE camera on board the Mars Reconnaissance Orbiter, the scene spans about 1.5 kilometers. From 250 kilometers above the Red Planet the camera is looking down at a sand dune field in a southern highlands crater. Captured when the Sun was about 5 degrees above the local horizon, only the dune crests were caught in full sunlight. A long, cold winter was coming to the southern hemisphere and bright ridges of seasonal frost line the martian dunes. The Mars Reconnaissance Orbiter, one of the oldest operating spacecraft at the Red Planet, celebrated the 15th anniversary of its launch from planet Earth on August 12. via NASA https://ift.tt/3lvjsna

This exciting and unfamiliar view of the Orion Nebula is a visualization based on astronomical data and movie rendering techniques. Up close and personal with a famous stellar nursery normally seen from 1,500 light-years away, the digitally modeled frame transitions from a visible light representation based on Hubble data on the left to infrared data from the Spitzer Space Telescope on the right. The perspective at the center looks along a valley over a light-year wide, in the wall of the region’s giant molecular cloud. Orion’s valley ends in a cavity carved by the energetic winds and radiation of the massive central stars of the Trapezium star cluster. The single frame is part of a multiwavelength, three-dimensional video that lets the viewer experience an immersive, three minute flight through the Great Nebula of Orion. via NASA https://ift.tt/34EgAP1

This intergalactic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent right of center, the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470. The faint, wide arcs or shells of NGC 474 could have been formed by a gravitational encounter with neighbor NGC 470. Alternately the shells could be caused by a merger with a smaller galaxy producing an effect analogous to ripples across the surface of a pond. The large galaxy on the top lefthand side of the deep image, NGC 467, appears to be surrounded by faint shells too, evidence of another interacting galaxy system. Intriguing background galaxies are scattered around the field that also includes spiky foreground stars. Of course, those stars lie well within our own Milky Way Galaxy. The field of view spans 25 arc minutes or about 1/2 degree on the sky. via NASA https://ift.tt/31vbKBt

What would it look like to circle a black hole? If the black hole was surrounded by a swirling disk of glowing and accreting gas, then the great gravity of the black hole would deflect light emitted by the disk to make it look very unusual. The featured animated video gives a visualization. The video starts with you, the observer, looking toward the black hole from just above the plane of the accretion disk. Surrounding the central black hole is a thin circular image of the orbiting disk that marks the position of the photon sphere — inside of which lies the black hole’s event horizon. Toward the left, parts of the large main image of the disk appear brighter as they move toward you. As the video continues, you loop over the black hole, soon looking down from the top, then passing through the disk plane on the far side, then returning to your original vantage point. The accretion disk does some interesting image inversions — but never appears flat. Visualizations such as this are particularly relevant today as black holes are being imaged in unprecedented detail by the Event Horizon Telescope. via NASA https://ift.tt/3gmOee9

How come the crescent Moon doesn’t look like this? For one reason, because your eyes can’t simultaneously discern bright and dark regions like this. Called earthshine or the da Vinci glow, the unlit part of a crescent Moon is visible but usually hard to see because it is much dimmer than the sunlit arc. In our digital age, however, the differences in brightness can be artificially reduced. The featured image is actually a digital composite of 15 short exposures of the bright crescent, and 14 longer exposures of the dim remainder. The origin of the da Vinci glow, as explained by Leonardo da Vinci about 510 years ago, is sunlight reflected first by the Earth to the Moon, and then back from the Moon to the Earth. via NASA https://ift.tt/3glE0dZ

How did a star create the Helix nebula? The shapes of planetary nebula like the Helix are important because they likely hold clues to how stars like the Sun end their lives. Observations by the orbiting Hubble Space Telescope and the 4-meter Blanco Telescope in Chile, however, have shown the Helix is not really a simple helix. Rather, it incorporates two nearly perpendicular disks as well as arcs, shocks, and even features not well understood. Even so, many strikingly geometric symmetries remain. How a single Sun-like star created such beautiful yet geometric complexity is a topic of research. The Helix Nebula is the nearest planetary nebula to Earth, lies only about 700 light years away toward the constellation of Aquarius, and spans about 3 light-years. via NASA https://ift.tt/2Qfo16D