Astrointerest

Explanation: When did these big galaxies first begin to dance? Really only four of the five of Stephan's Quintet are locked in a cosmic tango of repeated close encounters taking place some 300 million light-years away. The odd galaxy out is easy to spot in this recently reprocessed image by the Hubble Space Telescope -- the interacting galaxies, NGC 7319, 7318B, 7318A, and 7317 (left to right), have a more dominant yellowish cast. They also tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. The mostly bluish galaxy, large NGC 7320 on the lower left, is in the foreground at about 40 million light-years distant, and so is not part of the interacting group. Data and modeling indicate that NGC 7318B is a relatively new intruder. A recently-discovered halo of old red stars surrounding Stephan's Quintet indicates that at least some of these galaxies started tangling over a billion years. Stephan's Quintet is visible with a moderate sized-telescope toward the constellation of Winged Horse (Pegasus).

Explanation: A payload on board the International Space Station, the Neutron star Interior Composition Explorer (NICER) twists and turns to track cosmic sources of X-rays as the station orbits planet Earth every 93 minutes. During orbit nighttime, its X-ray detectors remain on. So as NICER slews from target to target bright arcs and loops are traced across this all-sky map made from 22 months of NICER data. The arcs tend to converge on prominent bright spots, pulsars in the X-ray sky that NICER regularly targets and monitors. The pulsars are spinning neutron stars that emit clock-like pulses of X-rays. Their timing is so precise it can be used for navigation, determining spacecraft speed and position. This NICER X-ray, all-sky, map is composed in coordinates with the celestial equator horizontally across the center.

Explanation: Stars are forming in Lynds Dark Nebula (LDN) 1251. About 1,000 light-years away and drifting above the plane of our Milky Way galaxy, the dusty molecular cloud is part of a complex of dark nebulae mapped toward the Cepheus flare region. Across the spectrum, astronomical explorations of the obscuring interstellar clouds reveal energetic shocks and outflows associated with newborn stars, including the telltale reddish glow from scattered Herbig-Haro objects seen in this sharp image. Distant background galaxies also lurk on the scene, visually buried behind the dusty expanse. The deep telescopic field of view imaged with broadband filters spans about two full moons on the sky, or 17 light-years at the estimated distance of LDN 1251.

Explanation: A prominent impact site anchored in the lunar Oceanus Procellarum, Copernicus crater is at the center of this telescopic portrait in light and shadow. Caught in stacked and sharpened video frames recorded on April 14 at 3:30am UTC, the lunar terminator, or boundary between night and day, cuts across the middle of the 93 kilometer diameter crater. Sunlight is just beginning to strike its tall western walls but doesn't yet shine on lower terrain nearby, briefly extending the crater's outline into the lunar nightside. At that moment standing at Copernicus crater you could watch the sunrise, an event that happens at Copernicus every 29.5 days. Of course that corresponds to a lunar month or a lunation, the time between consecutive Full Moons, as seen from planet Earth.

Explanation: Why do some spiral galaxies have a ring around the center? First and foremost, M95 is one of the closer examples of a big and beautiful barred spiral galaxy. Visible in the featured combination of images from Hubble and several ground based telescopes are sprawling spiral arms delineated by open clusters of bright blue stars, lanes of dark dust, the diffuse glow of billions of faint stars, and a short bar across the galaxy center. What intrigues many astronomers, however, is the circumnuclear ring around the galaxy center visible just outside the central bar. Although the long term stability of this ring remains a topic of research, observations indicate its present brightness is at least enhanced by transient bursts of star formation. M95, also known as NGC 3351, spans about 50,000 light-years, lies about 30 million light years away, and can be seen with a small telescope toward the constellation of the Lion (Leo).

Explanation: Star formation can be colorful. This chromatic cosmic portrait features glowing gas and dark dust near some recently formed stars of NGC 3572, a little-studied star cluster near the Carina Nebula. Stars from NGC 3572 are visible near the bottom of the image, while the expansive gas cloud above is likely what remains of their formation nebula. The image's striking hues were created by featuring specific colors emitted by hydrogen, oxygen, and sulfur, and blending them with images recorded through broadband filters in red, green, and blue. This nebula near NGC 3572 spans about 100 light years and lies about 9,000 light years away toward the southern constellation of the Ship's Keel (Carina). Within a few million years the pictured gas will likely disperse, while gravitational encounters will likely disperse the cluster stars over about a billion years.

“NASA Telescope Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around Single Star ” http://buff.ly/2ma2S0T

“Almost Three Tails for Comet Encke Image Credit & Copyright: Fritz Helmut Hemmerich Explanation: How can a comet have three tails? Normally, a comet has two tails: an ion tail of charged particles emitted by the comet and pushed out by the wind from the Sun, and a dust tail of small debris that orbits behind the comet but is also pushed out, to some degree, by the solar wind. Frequently a comet will appear to have only one tail because the other tail is not easily visible from the Earth. In the featured unusual image, Comet 2P/Encke appears to have three tails because the ion tail split just near to the time when the image was taken. The complex solar wind is occasionally turbulent and sometimes creates unusual structure in an ion tail. On rare occasions even ion-tail disconnection events have been recorded. An image of the Comet Encke taken two days later gives a perhaps less perplexing perspective.” http://buff.ly/2kT9YCH

“Penumbral Eclipse Rising Image Credit & Copyright: Bill Jelen Explanation: As seen from Cocoa Beach Pier, Florida, planet Earth, the Moon rose at sunset on February 10 while gliding through Earth's faint outer shadow. In progress was the first eclipse of 2017, a penumbral lunar eclipse followed in this digital stack of seaside exposures. Of course, the penumbral shadow is lighter than the planet's umbral shadow. That central, dark, shadow is easily seen on the lunar disk during a total or partial lunar eclipse. Still, in this penumbral eclipse the limb of the Moon grows just perceptibly darker as it rises above the western horizon. The second eclipse of 2017 could be more dramatic though. With viewing from a path across planet Earth's southern hemisphere, on February 26 there will be an annular eclipse of the Sun.” http://buff.ly/2kT9YCH

Hotness at its peak.

Illustration of relatives sizes, colours and albedos of large plutinos. A plutino is any trans neptunian object having 2:3 mean motion resonance with Neptune. So for every 2 orbits made by a plutino, Neptune completes 3 orbits. The brightest and the largest plutino is Pluto, discovered in 1930 by Clyde Tombaugh at Lowell Observatory.

“Crescent Enceladus Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA Explanation: Peering from the shadows, the Saturn-facing hemisphere of tantalizing inner moon Enceladus poses in this Cassini spacecraft image. North is up in the dramatic scene captured last November as Cassini's camera was pointed in a nearly sunward direction about 130,000 kilometers from the moon's bright crescent. In fact, the distant world reflects over 90 percent of the sunlight it receives, giving its surface about the same reflectivity as fresh snow. A mere 500 kilometers in diameter, Enceladus is a surprisingly active moon. Data collected during Cassini's flybys and years of images have revealed the presence of remarkable south polar geysers and a possible global ocean of liquid water beneath an icy crust.” http://buff.ly/2kyux9L

“NGC 6357: The Lobster Nebula Image Credit: ESO, VLT Survey Telescope Explanation: Why is the Lobster Nebula forming some of the most massive stars known? No one is yet sure. Near the more obvious Cat's Paw nebula on the upper right, the Lobster Nebula, on the lower left and cataloged as NGC 6357, houses the open star cluster Pismis 24, home to these tremendously bright and blue stars. The overall red glow near the inner star forming region results from the emission of ionized hydrogen gas. The surrounding nebula, featured here, holds a complex tapestry of gas, dark dust, stars still forming, and newly born stars. The intricate patterns are caused by complex interactions between interstellar winds, radiation pressures, magnetic fields, and gravity. The full zoomable version of this image contains about two billion pixels, making it one of the largest space images ever released. NGC 6357 spans about 400 light years and lies about 8,000 light years away toward the constellation of the Scorpion.” http://buff.ly/2k5D5l5

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“The Porpoise Galaxy from Hubble Image Credit: NASA, ESA, Hubble, HLA; Reprocessing & Copyright: Raul Villaverde Explanation: What's happening to this spiral galaxy? Just a few hundred million years ago, NGC 2936, the upper of the two large galaxies shown, was likely a normal spiral galaxy -- spinning, creating stars -- and minding its own business. But then it got too close to the massive elliptical galaxy NGC 2937 below and took a dive. Dubbed the Porpoise Galaxy for its iconic shape, NGC 2936 is not only being deflected but also being distorted by the close gravitational interaction. A burst of young blue stars forms the nose of the porpoise toward the right of the upper galaxy, while the center of the spiral appears as an eye. Alternatively, the galaxy pair, together known as Arp 142, look to some like a penguin protecting an egg. Either way, intricate dark dust lanes and bright blue star streams trail the troubled galaxy to the lower right. The featured re-processed image showing Arp 142 in unprecedented detail was taken by the Hubble Space Telescope last year. Arp 142 lies about 300 million light years away toward the constellation, coincidently, of the Water Snake (Hydra). In a billion years or so the two galaxies will likely merge into one larger galaxy.” http://buff.ly/2hy2js5

“Conjunction of Four Image Credit & Copyright: Maxime Oudoux Explanation: On January 31, a waxing crescent Moon, brilliant Venus, and fainter Mars gathered in the fading twilight, hanging above the western horizon just after sunset on planet Earth. In this combined evening skyscape, the lovely celestial triangle is seen through clouds and haze. Still glinting in sunlight, from low Earth orbit the International Space Station briefly joined the trio that evening in skies near Le Lude, France. The photographer's line-of-sight to the space station was remarkably close to Mars as the initial exposure began. As a result, the station's bright streak seems to leap from the Red Planet, moving toward darker skies at the top of the frame.” http://buff.ly/2hy2js5