Saturn near Opposition

Saturn reached its 2017 opposition on June 16. Of course, opposition means opposite the Sun in Earth's sky and near opposition Saturn is up all night, at its closest and brightest for the year. This remarkably sharp image of the ringed planet was taken only days before, on June 11, with a 1-meter telescope from the mountain top Pic du Midi observatory. North is at the top with the giant planet's north polar storm and curious hexagon clearly seen bathed in sunlight. But Saturn's spectacular ring system is also shown in stunning detail. The narrow Encke division is visible around the entire outer A ring, small ringlets can be traced within the fainter inner C ring, and Saturn's southern hemisphere can be glimpsed through the wider Cassini division. Near opposition Saturn's rings also appear exceptionally bright, known as the opposition surge or Seeliger Effect. Directly illuminated from Earth's perspective, the ring's icy particles cast no shadows and strongly backscatter sunlight creating the dramatic increase in brightness. Still, the best views of the ringed planet are currently from the Saturn-orbiting Cassini spacecraft. Diving close, Cassini's Grand Finale orbit number 9 is in progress. via NASA http://ift.tt/2rmLBAm

Manhattan Moonrise

A Full Moon rose as the Sun set on June 9, known to some as a Strawberry Moon. Close to the horizon and taking on the warm color of reflected sunlight filtered through a dense and dusty atmosphere, the fully illuminated lunar disk poses with the skyscrapers along the southern Manhattan skyline in this telephoto snapshot. The picture was taken from Eagle Rock Reservation, a park in West Orange, New Jersey, planet Earth. That's about 13 miles from southern Manhattan and some 240,000 miles from the Moon. Foreground faces of the modern towers of steel and glass share the Moon's warm color by reflecting the last rays of the setting Sun. The tallest, with the shining triangular facet, is New York City's One World Trade center. via NASA http://ift.tt/2t4zRDR

Red Sprites over the Channel

Mysterious and incredibly brief, red sprites are seen to occur high above large thunderstorms on planet Earth. While they have been recorded from low Earth orbit or high flying airplanes, these dancing, lightning-like events were captured in video frames from a mountain top perch in northern France. Taken during the night of May 28, the remarkably clear, unobstructed view looks toward a multicell storm system raging over the English Channel about 600 kilometers away. Lasting only a few milliseconds, the red sprite association with thunderstorms is known. Still, much remains a mystery about the fleeting apparitions including the nature of their relation to other upper atmospheric lightning phenomena such as blue jets or satellite detected terrestrial gamma flashes. via NASA http://ift.tt/2rvwGmB

M89: Elliptical Galaxy with Outer Shells and Plumes

Can you see them? This famous Messier object M89, a seemingly simple elliptical galaxy, is surrounded by faint shells and plumes. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where a recent collision with another large galaxy created density waves that ripple through this galactic giant. Regardless of the actual cause, the featured image highlights the increasing consensus that at least some elliptical galaxies have formed in the recent past, and that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. M89 is a member of the nearby Virgo cluster of galaxies which lies about 50 million light years distant. via NASA http://ift.tt/2smPVUD

An Unusual Hole in Mars

What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all-but-one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon-dioxide ice. The most unusual hole is on the upper right, spans about 100-meters, and seems to punch through to a lower level. Why this hole exists and why it is surrounded by a circular crater remains a topic of speculation, although a leading hypothesis is that it was created by a meteor impact. Holes such as this are of particular interest because they might be portals to lower levels that extend into expansive underground caves. If so, these naturally-occurring tunnels are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers. via NASA http://ift.tt/2rYV6qA

IC 418: The Spirograph Nebula

What is creating the strange texture of IC 418? Dubbed the Spirograph Nebula for its resemblance to drawings from a cyclical drawing tool, planetary nebula IC 418 shows patterns that are not well understood. Perhaps they are related to chaotic winds from the variable central star, which changes brightness unpredictably in just a few hours. By contrast, evidence indicates that only a few million years ago, IC 418 was probably a well-understood star similar to our Sun. Only a few thousand years ago, IC 418 was probably a common red giant star. Since running out of nuclear fuel, though, the outer envelope has begun expanding outward leaving a hot remnant core destined to become a white-dwarf star, visible in the image center. The light from the central core excites surrounding atoms in the nebula causing them to glow. IC 418 lies about 2000 light-years away and spans 0.3 light-years across. This false-color image taken from the Hubble Space Telescope reveals the unusual details. via NASA http://ift.tt/2r4wFqu

Saturn in the Milky Way

Saturn is near opposition in planet Earth's sky. Rising at sunset and shining brightly throughout the night, it also lies near a line-of-sight to crowded starfields, nebulae, and obscuring dust clouds along the Milky Way. Whitish Saturn is up and left of center in this gorgeous central Milky Way skyscape, a two panel mosaic recorded earlier this month. You can find the bright planet above the bowl of the dusty Pipe nebula, and just beyond the end of a dark river to Antares, alpha star of the constellation Scorpius. For now the best views of the ringed giant planet are from the Saturn-orbiting Cassini spacecraft, though. Diving close, Cassini's Grand Finale orbit number 8 is in progress. via NASA http://ift.tt/2sJ7ECt

M27 Not a Comet

While hunting for comets in the skies above 18th century France, astronomer Charles Messier diligently kept a list of the things he encountered that were definitely not comets. This is number 27 on his now famous not-a-comet list. In fact, 21st century astronomers would identify it as a planetary nebula, but it's not a planet either, even though it may appear round and planet-like in a small telescope. Messier 27 (M27) is an excellent example of a gaseous emission nebula created as a sun-like star runs out of nuclear fuel in its core. The nebula forms as the star's outer layers are expelled into space, with a visible glow generated by atoms excited by the dying star's intense but invisible ultraviolet light. Known by the popular name of the Dumbbell Nebula, the beautifully symmetric interstellar gas cloud is over 2.5 light-years across and about 1,200 light-years away in the constellation Vulpecula. This spectacular color image incorporates broad and narrowband observations recorded by the 8.2 meter Subaru telescope. via NASA http://ift.tt/2rXPe38

Firefall by Moonlight

On certain dates in February, an elusive firefall can be spotted at sunset in Yosemite National Park, when the weather cooperates and the direction to the setting Sun is just right. Often photographed from vantage points below, at the right moment the park's seasonal Horsetail Fall is isolated in the shadows of the steep walls of El Capitan but still illuminated with rays of sunlight reflected by the angled rockface directly behind the flow, briefly giving the waterfall a dramatic fiery appearance. The Horsetail firefall is more rarely photographed at moonset under a starry night sky, though. Even more elusive by moonlight, the firefall effect can also be seen when skies are clear and a bright Moon sets at the right direction along the western horizon. Skies were clear and stars were shining for this well-planned photograph of the Horsetail firefall lit by a gibbous Moon setting in the early morning hours of May 9. via NASA http://ift.tt/2rUN2ZT

The Case of the Missing Star

What's happened to giant star N6946-BH1? It was there just a few years ago -- Hubble imaged it. Now there's only a faint glow. What's curiouser, no bright supernova occurred -- although the star did brightened significantly for a few months. The leading theory is that, at about 25 times the mass of our Sun, N6946-BH1's great gravity held much of the star together during its final tumultuous death throes, after which most the star sunk into a black hole of its own making. If so, then what remained outside of the black hole likely then formed an accretion disk that emits comparatively faint infrared light as it swirls around, before falling in. If this mode of star death is confirmed with other stars, it gives direct evidence that a very massive star can end its life with a whimper rather than a bang. via NASA http://ift.tt/2rCQc2l

Orion: Belt, Flame, and Horsehead

What surrounds the famous belt stars of Orion? A deep exposure shows everything from dark nebula to star clusters, all embedded in an extended patch of gaseous wisps in the greater Orion Molecular Cloud Complex. The brightest three stars, appearing diagonally on the left of the featured image are indeed the famous three stars that make up the belt of Orion. Just below Alnitak, the lowest of the three belt stars, is the Flame Nebula, glowing with excited hydrogen gas and immersed in filaments of dark brown dust. Just to the right of Alnitak lies the Horsehead Nebula, a dark indentation of dense dust that has perhaps the most recognized nebular shapes on the sky. The dark molecular cloud, roughly 1,500 light years distant, is cataloged as Barnard 33 and is seen primarily because it is backlit by the nearby massive star Sigma Orionis. The Horsehead Nebula will slowly shift its apparent shape over the next few million years and will eventually be destroyed by the high-energy starlight. via NASA http://ift.tt/2rPuLy7

Perijove Passage

On May 19, the Juno spacecraft once again swung by Jupiter in its looping 53 day orbit around the Solar System's ruling gas gaint. Beginning at the top, this vertical 14 frame sequence of enhanced-color JunoCam images follows the spacecraft's rapidly changing perspective during its two hour passage. They look down on Jupiter's north polar region, equatorial, and south polar region (bottom images). With the field-of-view shrinking, the seventh and eighth images in the sequence are close-up. Taken only 4 minutes apart above Jupiter's equator they were captured just before the spacecraft reached perijove 6, its closest approach to Jupiter on this orbit. Final images in the sequence pick up white oval storm systems, Jupiter's "String of Pearls", and the south polar region from the outward bound spacecraft. via NASA http://ift.tt/2svkh3d

Black Holes of Known Mass

Add GW170104 to the chart of black holes with known mass. The extremely energetic merger of two smaller black holes corresponds to the Laser Interferometer Gravitational-wave Observatory's (LIGO) third detection of gravitational waves. The newfound black hole has a mass about 49 times that of the Sun, filling a gap between the masses of the two merged black holes detected previously by LIGO, with solar masses of 62 (GW150914) and 21 (GW151216). In all three cases, the signal in each of the twin LIGO detectors was unambiguously identified as coming from black hole mergers while a fourth case (LVT151012) resulted in a lower confidence detection. GW170104 is estimated to be some 3 billion light-years away, more distant than present estimates for GW150914 and GW151216. The ripples in spacetime were discovered during LIGO's current observing run, which began November 30, 2016 and will continue through the summer. via NASA http://ift.tt/2ron3b5