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💫IC1805 Heart Nebula (Cassiopeia) - Nel cuore della Cuore


Lainate, 19 Novembre 2018
Dopo un mese di brutto tempo, finalmente una serata col cielo sereno (anche se con un velo di foschia), purtroppo la festa è finita presto, attorno alle 2 sono tornate le nuvole e oggi è nuovamente brutto.
Dopo un tentativo infruttuoso sulla Helix, troppo vicino alla Luna e troppo bassa sull'orizzonte, tanto da confondersi nella bruma autunnale, la mia attenzione si è rivolta alla Nebulosa Cuore, nella costellazione di Cassiopea.
6x30' bin1 H-alpha 7nm Optolong Filter - AstroProfessional Apo Triplet 115/800 - Moravian G2 8300 - iOptron CEM60

💫Sagittarius A



Astronomers have long known that the supermassive black hole at the center of the Milky Way Galaxy, known as Sagittarius A* (or Sgr A* for short), is a particularly poor eater. The fuel for this black hole comes from powerful winds blown off dozens of massive young stars that are concentrated nearby. These stars are located a relatively large distance away from Sgr A*, where the gravity of the black hole is weak, and so their high-velocity winds are difficult for the black hole to capture and swallow. Scientists have previously calculated that Sgr A* should consume only about 1% of the fuel carried in the winds. However, it now appears that Sgr A* consumes even less than expected - ingesting only about one percent of that one percent. Why does it consume so little? The answer may be found in a new theoretical model developed using data from a very deep exposure made by NASA's Chandra X-ray Observatory. This model considers the flow of energy between two regions around the black hole: an inner region that is close to the so-called event horizon (the boundary beyond which even light cannot escape), and an outer region that includes the black hole's fuel source, the young stars, extending up to a million times farther out.

Collisions between particles in the hot inner region transfer energy to particles in the cooler outer region via a process called conduction. This, in turn, provides additional outward pressure that makes nearly all of the gas in the outer region flow away from the black hole. The model appears to explain well the extended shape of hot gas detected around Sgr A* in X-rays as well as features seen in other wavelengths. This Chandra image of Sgr A* and the surrounding region is based on data from a series of observations lasting a total of about one million seconds, or almost two weeks. Such a deep observation has given scientists an unprecedented view of the supernova remnant near Sgr A* - known as Sgr A East - and the lobes of hot gas extending for a dozen light years on either side of the black hole. These lobes provide evidence for powerful eruptions occurring several times over the last ten thousand years. The image also contains several mysterious X-ray filaments, some of which may be huge magnetic structures interacting with streams of energetic electrons produced by rapidly spinning neutron stars. Such features are known as pulsar wind nebulas.
Credit:     NASA / CXC / MIT/F.K. Baganoff


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💫Abell 1689

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Detailed images from Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) reveal an infant galaxy, dubbed A1689-zD1, undergoing a firestorm of star birth as it comes out of the dark ages, a time shortly after the Big Bang, but before the first stars completed the reheating of the cold, dark Universe. Images from NASA's Spitzer Space Telescope's Infrared Array Camera provided strong additional evidence that it was a young star-forming galaxy in the dark ages. "We certainly were surprised to find such a bright young galaxy 13 billion years in the past", said astronomer Garth Illingworth of the University of California, Santa Cruz, USA and a member of the research team. "This is the most detailed look to date at an object so far back in time." According to the authors, the measurements are "highly reliable'. "This object is the strongest candidate for the most distant galaxy so far", states team member Piero Rosati from ESO, Germany. "The Hubble images yield insight into the galaxy's structure that we cannot get with any other telescope," added astronomer Rychard Bouwens of the University of California, Santa Cruz, one of the co-discoverers of this galaxy.



The new images should offer insights into the formative years of galaxy birth and evolution and yield information on the types of objects that may have contributed to ending the dark ages. During its lifetime the Hubble telescope has peered ever farther back in time, viewing galaxies at successively younger stages of evolution. These snapshots have helped astronomers create a scrapbook of galaxies from infancy to adulthood. The new Hubble and Spitzer images of A1689-zD1 show a time when galaxies were in their infancy. Current theory holds that the dark ages began about 400,000 years after the Big Bang, as matter in the expanding Universe cooled and formed clouds of cold hydrogen. These cold clouds pervaded the Universe like a thick fog. At some point during this era, stars and galaxies started to form. Their collective light heated and cleared the fog of cold hydrogen, and ended the dark ages about a billion years after the Big Bang.

"This galaxy presumably is one of the many galaxies that helped end the dark ages", said astronomer Larry Bradley of Johns Hopkins University in Baltimore, USA, and leader of the study. "Astronomers are fairly certain that high-energy objects such as quasars did not provide enough energy to end the dark ages of the Universe. But many young star-forming galaxies may have produced enough energy to end it." The galaxy is so far away it did not appear in visible light images taken with Hubble's Advanced Camera for Surveys, because its light is stretched to infrared wavelengths by the Universe's expansion. It took Hubble's NICMOS, Spitzer and a trick of nature called gravitational lensing to see the faraway galaxy. The astronomers used a relatively nearby massive cluster of galaxies known as Abell 1689, roughly 2.2 billion light-years away, to magnify the light from the more distant galaxy directly behind it. This natural telescope is a gravitational lens. Abell 1689 is one of the most spectacular gravitational telescopes known and its gravitational properties are very well known.

Though the diffuse light of the faraway object is nearly impossible to see, gravitational lensing has increased its brightness by nearly 10 times, making it bright enough for Hubble and Spitzer to detect. A telltale sign of the lensing is the smearing of the images of galaxies behind Abell 1689 into arcs by the gravitational warping of space by the intervening galaxy cluster. Piero Rosati says: "This galaxy lies near the region where the galaxy cluster produces the highest magnification -- which was essential to bring this galaxy within reach of Hubble and Spitzer." Spitzer's images show that the galaxy's mass is typical of galaxies in the early Universe. Its mass is equivalent to several billions of stars like our Sun, or just a tiny fraction of the mass of the Milky Way. "This observation confirms previous Hubble studies that star birth happens in very tiny regions compared with the size of the final galaxy", Illingworth said.

The faraway galaxy also is an ideal target for Hubble's successor, the James Webb Space Telescope (JWST), scheduled to launch in 2013. Even with the increased magnification from the gravitational lens, Hubble's sharp "eye" can only see knots of the brightest, heftiest stars in the galaxy. The telescope cannot pinpoint fainter, lower-mass stars, individual stars, or the material surrounding the star-birth region. To see those things, astronomers will need the infrared capabilities of JWST currently being developed by NASA, ESA and CSA in a major international collaboration. The planned infrared observatory will have a mirror about seven times the area of Hubble's primary mirror and will collect more light from faint galaxies. JWST also will be able to view even more remote galaxies whose light has been stretched deep into infrared wavelengths that are out of the reach of NICMOS. 

"This galaxy will certainly be one of the first objects that will be observed by JWST", said team member Holland Ford of Johns Hopkins University. "This galaxy is so bright that JWST will see its detailed structure. This object is a pathfinder for JWST for deciphering what is happening in young galaxies." The astronomers noted that the faraway galaxy also would be an ideal target for the ESO/NRAO/NAOJ Atacama Large Millimeter Array (ALMA), which, when completed in 2012, will be the most powerful radio telescope in the world. "ALMA and JWST working together would be an ideal combination to really understand this galaxy", Illingworth said, noting that: "JWST's images and ALMA's measurement of the gas motions will provide revolutionary insights into the very youngest galaxies." The astronomers will conduct follow-up observations with infrared spectroscopy to confirm the galaxy's distance using ESO's VLT and the Keck telescope atop Mauna Kea in Hawaii.

Credit: NASA; ESA; L. Bradley (Johns Hopkins University); R. Bouwens (University of California, Santa Cruz); H. Ford (Johns Hopkins University); and G. Illingworth (University of California, Santa Cruz)


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💫NGC 1399


Evidence from NASA's Chandra X-ray Observatory and the Magellan telescopes suggest a star has been torn apart by an intermediate-mass black hole in a globular cluster. In this image, X-rays from Chandra are shown in blue and are overlaid on an optical image from the Hubble Space Telescope. The Chandra observations show that this object is a so-called ultraluminous X-ray source (ULX). An unusual class of objects, ULXs emit more X-rays than any known stellar X-ray source, but less than the bright X-ray sources associated with supermassive black holes in the centers of galaxies. Their exact nature has remained a mystery, but one suggestion is that some ULXs are black holes with masses between about a hundred and a thousands times that of the Sun.  Data obtained in optical light with the Magellan I and II telescopes in Las Campanas, Chile, also provides intriguing information about this object, which is found in the elliptical galaxy NGC 1399 in the Fornax galaxy cluster.

The spectrum reveals emission from oxygen and nitrogen but no hydrogen, a rare set of signals from within globular clusters. The physical conditions deduced from the spectra suggest that the gas is orbiting a black hole of at least 1,000 solar masses. To explain these observations, researchers suggest that a white dwarf star strayed too close to an intermediate-mass black hole and was ripped apart by tidal forces. In this scenario the X-ray emission is produced by debris from the disrupted white dwarf star that is heated as it falls towards the black hole and the optical emission comes from debris further out that is illuminated by these X-rays.  Another interesting aspect of this object is that it is found within a globular cluster, a very old, very tight grouping of stars. Astronomers have long suspected globular clusters contained intermediate-mass black holes, but there has been no conclusive evidence of their existence there to date. If confirmed, this finding would represent the first such substantiation.

Credit:     X-ray: NASA/CXC/UA/J. Irwin;     Optical: NASA/STScI


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💫NGC 1132 in visible and X-Ray

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This image of the elliptical galaxy NGC 1132 combines an image from NASA's Chandra X-Ray Observatory obtained in 2004 with images from the NASA/ESA Hubble Space Telescope made in 2005 and 2006 in green and near-infrared light.


The blue/purple in the image is the X-ray glow from hot, diffuse gas. The giant foreground galaxy, numerous dwarf galaxies in its neighbourhood, and many much more distant galaxies in the background are seen in visible light.

Credit: NASA, ESA, M. West (ESO, Chile), and CXC/Penn State University/G. Garmire


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💫Galaxy Collision Switches on Black Hole


This composite image of data from three different telescopes shows an ongoing collision between two galaxies, NGC 6872 and IC 4970 (roll your mouse over the image above). X-ray data from NASA's Chandra X-ray Observatory is shown in purple, while Spitzer Space Telescope's infrared data is red and optical data from ESO's Very Large Telescope (VLT) is colored red, green and blue. Astronomers think that supermassive black holes exist at the center of most galaxies. Not only do the galaxies and black holes seem to co-exist, they are apparently inextricably linked in their evolution. To better understand this symbiotic relationship, scientists have turned to rapidly growing black holes, so-called active galactic nucleus (AGN), to study how they are affected by their galactic environments.

The latest data from Chandra and Spitzer show that IC 4970, the small galaxy at the top of the image, contains an AGN, but one that is heavily cocooned in gas and dust. This means in optical light telescopes, like the VLT, there is little to see. X-rays and infrared light, however, can penetrate this veil of material and reveal the light show that is generated as material heats up before falling onto the black hole (seen as a bright point-like source). Despite this obscuring gas and dust around IC 4970, the Chandra data suggest that there is not enough hot gas in IC 4970 to fuel the growth of the AGN. Where, then, does the food supply for this black hole come from? The answer lies with its partner galaxy, NGC 6872. These two galaxies are in the process of undergoing a collision, and the gravitational attraction from IC 4970 has likely pulled over some of NGC 6872's deep reservoir of cold gas (seen prominently in the Spitzer data), providing a new fuel supply to power the giant black hole.

Credit:     X-ray: NASA/CXC/SAO/M.Machacek;     Optical: ESO/VLT;     Infrared: NASA/JPL/Caltech


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