2017 September 28

**panosol** Πεμ Σεπ 28, 2017 7:22 pm

2017 September 28
Astronomy Picture of the Day - Σελίδα 12 GW170814_orig

LIGO-Virgo GW170814 Skymap
Illustration Credit: LIGO- Virgo Collaboration - Optical Sky Data: A. Mellinger

Explanation: From around planet Earth three gravitational wave detectors have now reported a joint detection of ripples in spacetime, the fourth announced detection of a binary black hole merger in the distant Universe. The event was recorded on 2017 August 14, and so christened GW170814, by the LIGO observatory sites in Hanford, Washington and Livingston, Louisiana, and the more recently operational Virgo Observatory near Pisa, Italy. The signal was emitted in the final moments of the coalescence of two black holes of 31 and 25 solar masses located about 1.8 billion light-years away. But comparing the timing of the gravitational wave detections at all three sites allowed astronomers to vastly improve the location of the signal's origin on the sky. Just above the Magellanic clouds and generally toward the constellation Eridanus, the only sky region consistent with signals in all three detectors is indicated by the yellow contour line in this all-sky map. The all-sky projection includes the arc of our Milky Way Galaxy. An improved three-detector location of the gravitational wave source allowed rapid follow-up observations by other, more conventional, electromagnetic wave observatories that can search for potentially related signals. The addition of the Virgo detector also allowed the gravitational wave polarization to be measured, a property that further confirms predictions of Einstein's general relativity.

**panosol** Παρ Σεπ 29, 2017 8:01 pm

2017 September 29
Astronomy Picture of the Day - Σελίδα 12 Puppis_AWeb_Goldman1024

Puppis A Supernova Remnant
Image Credit & Copyright: Don Goldman

Explanation: Driven by the explosion of a massive star, supernova remnant Puppis A is blasting into the surrounding interstellar medium about 7,000 light-years away. At that distance, this colorful telescopic field based on broadband and narrowband optical image data is about 60 light-years across. As the supernova remnant (upper right) expands into its clumpy, non-uniform surroundings, shocked filaments of oxygen atoms glow in green-blue hues. Hydrogen and nitrogen are in red. Light from the initial supernova itself, triggered by the collapse of the massive star's core, would have reached Earth about 3,700 years ago. The Puppis A remnant is actually seen through outlying emission from the closer but more ancient Vela supernova remnant, near the crowded plane of our Milky Way galaxy. Still glowing across the electromagnetic spectrum Puppis A remains one of the brightest sources in the X-ray sky.

**panosol** Σαβ Σεπ 30, 2017 7:08 pm

2017 September 30
Astronomy Picture of the Day - Σελίδα 12 N281_Coles_Helm

Portrait of NGC 281
Image Credit & Copyright: Eric Coles and Mel Helm

Explanation: Look through the cosmic cloud cataloged as NGC 281 and you might miss the stars of open cluster IC 1590. Still, formed within the nebula that cluster's young, massive stars ultimately power the pervasive nebular glow. The eye-catching shapes looming in this portrait of NGC 281 are sculpted columns and dense dust globules seen in silhouette, eroded by intense, energetic winds and radiation from the hot cluster stars. If they survive long enough, the dusty structures could also be sites of future star formation. Playfully called the Pacman Nebula because of its overall shape, NGC 281 is about 10,000 light-years away in the constellation Cassiopeia. This sharp composite image was made through narrow-band filters, combining emission from the nebula's hydrogen, sulfur, and oxygen atoms in green, red, and blue hues. It spans over 80 light-years at the estimated distance of NGC 281.

**panosol** Κυρ Οκτ 01, 2017 10:46 am

2017 October 1
Astronomy Picture of the Day - Σελίδα 12 Greenmachine_nasa_4800

Concept Plane: Supersonic Green Machine
Illustration Credit: NASA, Lockheed Martin Co.

Explanation: What will passenger airplanes be like in the future? To help brainstorm desirable and workable attributes, NASA sponsors design competitions. Shown here is an artist's depiction of a concept plane that was suggested in 2010. This futuristic plane would be expected to achieve supersonic speeds, possibly surpassing the speeds of the supersonic transport planes that ran commercially in the late twentieth century. In terms of noise reduction, the future aircraft has been drawn featuring an inverted V wing stretched over its engines. The structure is intended to reduce the sound from annoying sonic booms. Additionally, future airplanes would aim to have relatively little impact on our environment, including green limits on pollution and fuel consumption. Aircraft utilizing similar design concepts might well become operational by the 2030s.

**panosol** Δευ Οκτ 02, 2017 7:38 pm

2017 October 2
Astronomy Picture of the Day - Σελίδα 12 Pleiades_Comets_Peach_1080_annotated

Two Comets and a Star Cluster
Image Credit & Copyright: Damian Peach

Explanation: Two unusual spots are on the move near the famous Pleiades star cluster. Shifting only a small amount per night, these spots are actually comets in our nearby Solar System that by chance wandered into the field of the light-years distant stars. On the far left is comet C/2017 O1 ASAS-SN, a multi-kilometer block of evaporating ice sporting a bright coma of surrounding gas dominated by green-glowing carbon. Comet ASAS-SN1 shows a slight tail to its lower right. Near the frame center is comet C/2015 ER61 PanSTARRS, also a giant block of evaporating ice, but sporting a rather long tail to its right. On the upper right is the Pleiades, an open cluster dominated by bright blue stars illuminating nearby reflecting dust. This exposure, taken about two weeks ago, is so deep that the filamentary interstellar dust can be traced across the entire field. The Pleiades is visible to the unaided eye, but it should require binoculars to see the comets.

**panosol** Τρι Οκτ 03, 2017 6:54 pm

2017 October 3
Astronomy Picture of the Day - Σελίδα 12 Fomalhaut_Ring_ALMA_2064

Ice Ring around Nearby Star Fomalhaut
Image Credit: ALMA (ESO/NAOJ/NRAO), M. MacGregor; NASA/ESA Hubble, P. Kalas; B. Saxton (NRAO/AUI/NSF)

Explanation: Why is there a large ice ring around Fomalhaut? This interesting star -- easily visible in the night sky -- lies only about 25 light-years away and is known to be orbited by at least one planet, Dagon, as well as several inner dust disks. More intriguing, perhaps, is an outer ring, first discovered about 20 years ago, that has an unusually sharp inner boundary. The featured recent image by the Atacama Large Millimeter Array (ALMA) shows this outer ring with complete and unprecedented detail -- in pink -- superposed on a Hubble image of the Fomalhaut system in blue. A leading theory holds that this ring resulted from numerous violent collisions involving icy comets and planetesimals, the component objects of planets, while the ring boundaries are caused by the gravity of yet unseen planets. If correct, any interior planets in the Fomalhaut system are likely being continually pelted by large meteors and comets -- an onslaught last seen in our own planetary system four billion years ago in an episode called the Late Heavy Bombardment.

**panosol** Τετ Οκτ 04, 2017 7:12 pm

2017 October 4
Astronomy Picture of the Day - Σελίδα 12 Soul_Herschel_960

The Soul Nebula in Infrared from Herschel
Image Credit & License: ESA, Herschel Space Obs., NASA, JPL-Caltech

Explanation: Stars are forming in the Soul of the Queen of Aethopia. More specifically, a large star forming region called the Soul Nebula can be found in the direction of the constellation Cassiopeia, who Greek mythology credits as the vain wife of a King who long ago ruled lands surrounding the upper Nile river. The Soul Nebula houses several open clusters of stars, a large radio source known as W5, and huge evacuated bubbles formed by the winds of young massive stars. Located about 6,500 light years away, the Soul Nebula spans about 100 light years and is usually imaged next to its celestial neighbor the Heart Nebula (IC 1805). The featured image, impressively detailed, was taken last month in several bands of infrared light by the orbiting Herschel Space Observatory.

**panosol** Πεμ Οκτ 05, 2017 6:47 pm

2017 October 5
Astronomy Picture of the Day - Σελίδα 12 Pluto_02_NH

Pluto's Bladed Terrain
Image Credit: NASA, Johns Hopkins Univ./APL, Southwest Research Institute

Explanation: Imaged during the New Horizons spacecraft flyby in July 2015, Pluto's bladed terrain is captured in this close-up of the distant world. The bizarre texture belongs to fields of skyscraper-sized, jagged landforms made almost entirely of methane ice, found at extreme altitudes near Pluto's equator. Casting dramatic shadows, the tall, knife-like ridges seem to have been formed by sublimation. By that process, condensed methane ice turns directly to methane gas without passing through a liquid phase during Pluto's warmer geological periods. On planet Earth, sublimation can also produce standing fields of knife-like ice sheets, found along the high plateau of the Andes mountain range. Known as penitentes, those bladed structures are made of water ice and at most a few meters tall.

**panosol** Παρ Οκτ 06, 2017 6:41 pm

2017 October 6
Astronomy Picture of the Day - Σελίδα 12 Pia21855-16c1024

Global Aurora at Mars
Image Credit: MAVEN, LASP, University of Colorado, NASA

Explanation: A strong solar event last month triggered intense global aurora at Mars. Before (left) and during (right) the solar storm, these projections show the sudden increase in ultraviolet emission from martian aurora, more than 25 times brighter than auroral emission previously detected by the orbiting MAVEN spacecraft. With a sunlit crescent toward the right, data from MAVEN's ultraviolet imaging spectrograph is projected in purple hues on the night side of Mars globes simulated to match the observation dates and times. On Mars, solar storms can result in planet-wide aurora because, unlike Earth, the Red Planet isn't protected by a strong global magnetic field that can funnel energetic charged particles toward the poles. For all those on the planet's surface during the solar storm, dangerous radiation levels were double any previously measured by the Curiosity rover. MAVEN is studying whether Mars lost its atmosphere due to its lack of a global magnetic field.

**panosol** Σαβ Οκτ 07, 2017 9:52 am

2017 October 7
Astronomy Picture of the Day - Σελίδα 12 TSE2017-_W3035w

Eclipsosaurus Rex
Image Credit & Copyright: Fred Espenak (MrEclipse.com)

Explanation: We live in an era where total solar eclipses are possible because at times the apparent size of the Moon can just cover the disk of the Sun. But the Moon is slowly moving away from planet Earth. Its distance is measured to increase about 1.5 inches (3.8 centimeters) per year due to tidal friction. So there will come a time, about 600 million years from now, when the Moon is far enough away that the lunar disk will be too small to ever completely cover the Sun. Then, at best only annular eclipses, a ring of fire surrounding the silhouetted disk of the too small Moon, will be seen from the surface of our fair planet. Of course the Moon was slightly closer and loomed a little larger 100 million years ago. So during the age of the dinosaurs there were more frequent total eclipses of the Sun. In front of the Tate Geological Museum at Casper College in Wyoming, this dinosaur statue posed with a modern total eclipse, though. An automated camera was placed under him to shoot his portrait during the Great American Eclipse of August 21.

**panosol** Κυρ Οκτ 08, 2017 10:20 am

2017 October 8
Astronomy Picture of the Day - Σελίδα 12 Barnard68v2_vlt_4000

Dark Molecular Cloud Barnard 68
Image Credit: FORS Team, 8.2-meter VLT Antu, ESO

Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured here. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

**panosol** Δευ Οκτ 09, 2017 6:20 pm

2017 October 9
Astronomy Picture of the Day - Σελίδα 12 Ahuna_Mons_Ceres_Dawn_1280

Unusual Mountain Ahuna Mons on Asteroid Ceres
Image Credit: Dawn Mission, NASA, JPL-Caltech, UCLA, MPS/DLR/IDA

Explanation: What created this unusual mountain? Ahuna Mons is the largest mountain on the largest known asteroid in our Solar System, Ceres, which orbits our Sun in the main asteroid belt between Mars and Jupiter. Ahuna Mons, though, is like nothing that humanity has ever seen before. For one thing, its slopes are garnished not with old craters but young vertical streaks. One hypothesis holds that Ahuna Mons is an ice volcano that formed shortly after a large impact on the opposite side of the dwarf planet loosened up the terrain through focused seismic waves. The bright streaks may be high in reflective salt, and therefore similar to other recently surfaced material such as visible in Ceres' famous bright spots. The featured double-height digital image was constructed from surface maps taken of Ceres last year by the robotic Dawn mission.

**panosol** Τρι Οκτ 10, 2017 6:54 pm

2017 October 10
Astronomy Picture of the Day - Σελίδα 12 Zodiacal_Pinnacles_Zhang_5026

Milky Way and Zodiacal Light over Australian Pinnacles
Image Credit & Copyright: Jingyi Zhang

Explanation: What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains a topic of research. The panorama was taken last month. A ray of zodiacal light, sunlight reflected by dust grains orbiting between the planets in the Solar System, rises from the horizon near the image center. Arching across the top is the central band of our Milky Way Galaxy. The planets Jupiter and Saturn, as well as several famous stars are also visible in the background night sky.

**panosol** Τετ Οκτ 11, 2017 6:55 pm

2017 October 11
Astronomy Picture of the Day - Σελίδα 12 Ngc362_Hubble_Heyl_3617

Star Cluster NGC 362 from Hubble
Image Credit: Hubble WFC3, NASA, ESA, J. Heyl, I. Caiazzo, & Javiera Parada (UBC)

Explanation: If our Sun were near the center of NGC 362, the night sky would glow like a jewel box of bright stars. Hundreds of stars would glow brighter than Sirius, and in many different colors. Although these stars could become part of breathtaking constellations and intricate folklore, it would be difficult for planetary inhabitants there to see -- and hence understand -- the greater universe beyond. NGC 362 is one of only about 170 globular clusters of stars that exist in our Milky Way Galaxy. This star cluster is one of the younger globulars, forming likely well after our Galaxy. NGC 362 can be found with the unaided eye nearly in front of the Small Magellanic Cloud, and angularly close to the second brightest globular cluster known, 47 Tucanae. The featured image was taken with the Hubble Space Telescope to help better understand how massive stars end up near the center of some globular clusters.

**panosol** Πεμ Οκτ 12, 2017 6:58 pm

2017 October 12
Astronomy Picture of the Day - Σελίδα 12 NGC1365-_Hager_Benson

NGC 1365: Majestic Island Universe
Image Credit & Copyright: Dietmar Hager, Eric Benson, Torsten Grossmann

Explanation: Barred spiral galaxy NGC 1365 is truly a majestic island universe some 200,000 light-years across. Located a mere 60 million light-years away toward the chemical constellation Fornax, NGC 1365 is a dominant member of the well-studied Fornax galaxy cluster. This impressively sharp color image shows intense star forming regions at the ends of the bar and along the spiral arms, and details of dust lanes cutting across the galaxy's bright core. At the core lies a supermassive black hole. Astronomers think NGC 1365's prominent bar plays a crucial role in the galaxy's evolution, drawing gas and dust into a star-forming maelstrom and ultimately feeding material into the central black hole.

**panosol** Παρ Οκτ 13, 2017 6:26 pm

2017 October 13
Astronomy Picture of the Day - Σελίδα 12 Yuri_LMC_Las_Campanas

Under the Galaxy
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)

Explanation: The Large Magellanic Cloud, a satellite galaxy of the Milky Way, stands above the southern horizon in this telephoto view from Las Campanas Observatory, planet Earth. In the dark September skies of the Chilean Atacama desert, the small galaxy has an impressive span of about 10 degrees or 20 Full Moons. The sensitive digital camera's panorama has also recorded a faint, pervasive airglow, otherwise invisible to the eye. Apparently bright terrestrial lights in the foreground are actually very dim illumination from the cluster of housing for the observatory astronomers and engineers. But the flattened mountain top along the horizon just under the galaxy is Las Campanas peak, home to the future Giant Magellan Telescope.

**panosol** Σαβ Οκτ 14, 2017 10:03 am

2017 October 14
Astronomy Picture of the Day - Σελίδα 12 Steve_Auroral_Arc_allskyproj

All-Sky Steve
Image Credit & Copyright: Alan Dyer, Amazingsky.com, TWAN

Explanation: Familiar green and red tinted auroral emission floods the sky along the northern (top) horizon in this fish-eye panorama projection from September 27. On the mild, clear evening the Milky Way tracks through the zenith of a southern Alberta sky and ends where the six-day-old Moon sets in the southwest. The odd, isolated, pink and whitish arc across the south has come to be known as Steve. The name was given to the phenomenon by the Alberta Aurora Chasers Facebook group who had recorded appearances of the aurora-like feature. Sometimes mistakenly identified as a proton aurora or proton arc, the mysterious Steve arcs seem associated with aurorae but appear closer to the equator than the auroral curtains. Widely documented by citizen scientists and recently directly explored by a Swarm mission satellite, Steve arcs have been measured as thermal emission from flowing gas rather than emission excited by energetic electrons. Even though a reverse-engineered acronym that fits the originally friendly name is Sudden Thermal Emission from Velocity Enhancement, his origin is still mysterious.

**panosol** Κυρ Οκτ 15, 2017 12:40 pm

2017 October 15
Astronomy Picture of the Day - Σελίδα 12 Nsmerger3_heasarc_3000

On the Origin of Gold
Illustration Credit: Dana Berry, NASA

Explanation: Where did the gold in your jewelry originate? No one is completely sure. The relative average abundance in our Solar System appears higher than can be made in the early universe, in stars, and even in typical supernova explosions. Some astronomers have suggested, and many believe, that neutron-rich heavy elements such as gold might be most easily made in rare neutron-rich explosions such as the collision of neutron stars. Pictured here is an artist's illustration depicting two neutron stars spiraling in toward each other, just before they collide. Since neutron star collisions are also suggested as the origin of short duration gamma-ray bursts, it is possible that you already own a souvenir from one of the most powerful explosions in the universe.

**panosol** Δευ Οκτ 16, 2017 9:40 pm

2017 October 16

GW170817: A Spectacular Multi-Radiation Merger Event Detected
Illustrative Video Credit: NASA's Conceptual Imaging Lab

Explanation: Both gravitational and electromagnetic radiations have been detected in rapid succession for an explosive merging event for the first time. Data from the outburst fit well with a spectacular binary neutron-star death-spiral. The explosive episode was seen on August 17 in nearby NGC 4993, an elliptical galaxy only 130 million light years distant. Gravitational waves were seen first by the ground based LIGO and Virgo observatories, while seconds later the Earth-orbiting Fermi observatory detected gamma-rays, and hours after that Hubble and other observatories detected light throughout the electromagnetic spectrum. Pictured is an animated illustrative movie of the event's likely progenitors. The video depicts hot neutron stars as they spiral in toward each other and emit gravitational radiation. As they merge, a powerful jet extends that drives the short-duration gamma-ray burst, followed by clouds of ejecta and, over time, an optical supernova-type episode called a kilonova. This first coincident detection confirms that LIGO events can be associated with short-duration gamma-ray bursts. Such powerful neutron star mergers are thought to have seeded the universe with many heavy nuclei including the iodine needed for life and the uranium and plutonium needed for nuclear fission power. You may already own a souvenir of one of these explosions -- they are also thought to be the original creators of gold.

**panosol** Τρι Οκτ 17, 2017 7:34 pm

2017 October 17
Astronomy Picture of the Day - Σελίδα 12 Haumea_Rings_IAA_1900

Haumea of the Outer Solar System
Illustration Credit: Instituto de Astrofísica de Andalucía

Explanation: One of the strangest objects in the outer Solar System has recently been found to have a ring. The object, named Haumea, is the fifth designated dwarf planet after Pluto, Ceres, Eris, and Makemake. Haumea's oblong shape makes it quite unusual. Along one direction, Haumea is significantly longer than Pluto, while in another direction Haumea has an extent very similar to Pluto, while in the third direction is much smaller. Haumea's orbit sometimes brings it closer to the Sun than Pluto, but usually Haumea is further away. Illustrated above, an artist visualizes Haumea as a cratered ellipsoid surrounded by a uniform ring. Originally discovered in 2003 and given the temporary designation of 2003 EL61, Haumea was renamed in 2008 by the IAU for a Hawaiian goddess. Besides the ring discovered this year, Haumea has two small moons discovered in 2005, named Hi'iaka and Namaka for daughters of the goddess.

**panosol** Τετ Οκτ 18, 2017 6:20 pm

2017 October 18
Astronomy Picture of the Day - Σελίδα 12 NGC6726_Coles_Pugh_960

Stars and Dust in Corona Australis
Image Credit & Copyright: Eric Coles & Martin Pugh

Explanation: Blue dust clouds and young, energetic stars inhabit this telescopic vista, less than 500 light-years away toward the northern boundary of Corona Australis, the Southern Crown. The dust clouds effectively block light from more distant background stars in the Milky Way. But the striking complex of reflection nebulas cataloged as NGC 6726, 6727, and IC 4812 produce a characteristic blue color as light from the region's bright blue stars is reflected by the cosmic dust. The dust also obscures from view stars still in the process of formation. At the left, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis. Just below it, glowing arcs and loops shocked by outflows from embedded newborn stars are identified as Herbig-Haro objects. On the sky this field of view spans about one degree, corresponding to almost nine light-years at the estimated distance of the nearby star forming region.

**panosol** Πεμ Οκτ 19, 2017 6:50 pm

2017 October 19
Astronomy Picture of the Day - Σελίδα 12 M51_Kerry_Lecky_Hepburn_1600

M51: The Whirlpool Galaxy
Image Credit & Copyright: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)

Explanation: Find the Big Dipper and follow the handle away from the dipper's bowl until you get to the last bright star. Then, just slide your telescope a little south and west and you'll come upon this stunning pair of interacting galaxies, the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with well defined spiral structure is also cataloged as NGC 5194. Its spiral arms and dust lanes clearly sweep in front of its companion galaxy (bottom), NGC 5195. The pair are about 31 million light-years distant and officially lie within the angular boundaries of the small constellation Canes Venatici. Though M51 looks faint and fuzzy to the eye, deep images like this one can reveal striking colors and the faint tidal debris around the smaller galaxy.

**panosol** Παρ Οκτ 20, 2017 7:06 pm

2017 October 20
Astronomy Picture of the Day - Σελίδα 12 M020_rooisand_cdk_3500x2500

A Beautiful Trifid
Image Credit & Copyright: Chamaeleon Team - Franz Hofmann, Wolfgang Paech

Explanation: The beautiful Trifid Nebula is a cosmic study in contrasts. Also known as M20, it lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid does illustrate three different types of astronomical nebulae; red emission nebulae dominated by light from hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. But the red emission region roughly separated into three parts by obscuring dust lanes is what lends the Trifid its popular name. Pillars and jets sculpted by newborn stars, below and left of the emission nebula's center, appear in famous Hubble Space Telescope close-up images of the region. The Trifid Nebula is about 40 light-years across. Just too faint to be seen by the unaided eye, it almost covers the area of the Moon in planet Earth's sky.

**panosol** Σαβ Οκτ 21, 2017 12:48 pm

2017 October 21
Astronomy Picture of the Day - Σελίδα 12 Ldn183neyer_l1

Lynds Dark Nebula 183
Image Credit & Copyright: Fabian Neyer

Explanation: Beverly Lynds Dark Nebula 183 lies a mere 325 light-years away, drifting high above the plane of our Milky Way Galaxy. Obscuring the starlight behind it when viewed at optical wavelengths, the dark, dusty molecular cloud itself seems starless. But far infrared explorations reveal dense clumps within, likely stars in the early stages of formation as enhanced regions of the cloud undergo gravitational collapse. One of the closest molecular clouds, it is seen toward the constellation Serpens Caput. This sharp cosmic cloud portrait spans about half a degree on the sky. That's about 3 light-years at the estimated distance of Lynds Dark Nebula 183.

**panosol** Κυρ Οκτ 22, 2017 10:43 am

2017 October 22
Astronomy Picture of the Day - Σελίδα 12 3c75_chandraNRAO_576

Two Black Holes Dancing in 3C 75
Image Credit: X-Ray: NASA/CXC/D. Hudson, T. Reiprich et al. (AIfA); Radio: NRAO/VLA/ NRL

Explanation: What's happening at the center of active galaxy 3C 75? The two bright sources at the center of this composite x-ray (blue)/ radio (pink) image are co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves.