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💫Stellar Fireworks Are Ablaze in Galaxy NGC 4449

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Fireworks blaze over the skies of American cities in the annual Independence Day celebrations. But nearly 12.5 million light-years away in the dwarf galaxy NGC 4449 stellar "fireworks" are going off all the time. Hundreds of thousands of vibrant blue and red stars blaze in this image taken by NASA's Hubble Space Telescope. Hot bluish-white clusters of massive stars are scattered throughout the galaxy, interspersed with numerous dustier, reddish regions of current star formation. Massive dark clouds of gas and dust are silhouetted against the starlight. NGC 4449 has been forming stars for several billion years, but currently it is experiencing a star formation event at a much higher rate than in the past. This unusually explosive and intense star formation activity qualifies as a starburst. At the current rate, the gas supply that feeds the stellar production would only last for another billion years or so.




Starbursts usually occur in the central regions of galaxies, but NGC 4449 has more widespread star formation activity, since the very youngest stars are observed both in the nucleus and in streams surrounding the galaxy. A "global" starburst like NGC 4449 resembles primordial star forming galaxies, which grew by merging with and accreting smaller stellar systems. Since NGC 4449 is close enough to be observed in great detail, it is the ideal laboratory for the investigation of what may have occurred during galactic formation and evolution in the early universe. It's likely that the current widespread starburst was triggered by interaction or merging with a smaller companion. NGC 4449 belongs to a group of galaxies in the constellation Canes Venatici. Astronomers think that NGC 4449's star formation has been influenced by interactions with several of its neighbors.


Credit: NASA, ESA, A. Aloisi (STScI/ESA), and The Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration


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💫The Southern Cross


Shining in the southern sky, the four bright stars portrayed in the left part of this image represent a useful orientation mark which helps identifying the South Celestial Pole. Because of the rather distinctive asterism they form, these stars have been officially classified as the Crux constellation, or the Southern Cross. The vast dark cloud, visible in the lower part of the image, is usually referred to as the Coalsack Nebula; it also has a preeminent role in the Australian Aboriginal culture, representing the head of an emu in the traditional constellation of the "Emu in the Sky". The ruddy object glowing in the upper part of the image owes its colour to the blaze of hydrogen gas. Catalogued as IC 2948, this emission nebula hosts a sparkling cluster of young stars.

Credit:
ESO/Y. Beletsky


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💫Aristarchus Plateau on the Moon

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The Hubble Space Telescope Advanced Camera for Surveys imaged Aristarchus crater and nearby Schroter's Valley rille on Aug. 21, 2005. The Hubble images reveal fine-scale details of the crater's interior and exterior in ultraviolet and visible wavelengths at a scale of approximately 165 to 330 feet (50 to 100 meters) per picture element. Aristarchus crater is 26 miles (42 kilometers) in diameter and approximately 2 miles (3.2 kilometers) in depth, and sits at the southeastern edge of the Aristarchus plateau. The plateau is noted for its rich array of geologic features, including a dense concentration of lunar volcanic rilles (river-valley-like landforms that resulted from the collapse of lunar lava tubes), source vents, and volcanic materials that erupted in giant explosive events.




Aristarchus is one of the youngest large craters on the Moon. It probably formed between 100 and 900 million years ago. This composite image shows that many of the crater's fresh impact features are still well preserved, including a sharp rim, inner crater wall terraces, central uplift structures, and a pattern of excavated and ejected materials, known as ejecta, which blankets the nearby surroundings. This spectacular Hubble image reveals the diversity of ultraviolet- and visible-light signatures of crater ejecta, interior wall deposits, central peak materials, and those of the surrounding plateau.


Credit: NASA, ESA and J. Garvin (NASA/GSFC)


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💫A cosmic flame


Sparkling at the edge of a giant cloud of gas and dust, the Flame Nebula, also referred to as NGC 2024, is in fact the hideout of a cluster of young, blue, massive stars, whose light sets the gas ablaze. Located 1,300 light-years away towards the constellation of Orion, the nebula owes its typical colour to the glow of hydrogen atoms, heated by the stars. The latter are obscured by a dark, forked dusty structure in the centre of the image and are only revealed by infrared observations. This image is based on data acquired with the 1.5-metre Danish telescope at ESO’s La Silla Observatory in Chile, combining three exposures in the filters B (40 seconds), V (80 seconds) and R (40 seconds).

Credit:
ESO/IDA/Danish 1.5 m/R. Gendler, J.-E. Ovaldsen, C. Thöne and C. Féron


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💫Nucleus of Galaxy Centaurus A

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Astronomers have obtained an unprecedented look at the nearest example of galactic cannibalism, a massive black hole hidden at the center of a nearby giant galaxy that is feeding on a smaller galaxy in a spectacular collision. Such fireworks were common in the early universe, as galaxies formed and evolved, but are rare today.




The Hubble telescope offers a stunning unprecedented close-up view of a turbulent firestorm of star birth along a nearly edge-on dust disk girdling Centaurus A, the nearest active galaxy to Earth. The picture at upper left shows the entire galaxy. The blue outline represents Hubble's field of view. The larger, central picture is Hubble's close-up view of the galaxy. Brilliant clusters of young blue stars lie along the edge of the dark dust lane. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars.


Credit: E.J. Schreier (STScI), and NASA


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💫Around the Cat's Paw Nebula


Few objects in the sky have been as well named as the Cat’s Paw Nebula, a glowing gas cloud resembling the gigantic pawprint of a celestial cat out on an errand across the Universe. British astronomer John Herschel first recorded NGC 6334 in 1837 during his stay in South Africa. Despite using one of the largest telescopes in the world at the time, Herschel seems to have only noted the brightest part of the cloud, seen here towards the lower left.

NGC 6334 lies about 5500 light-years away in the direction of the constellation Scorpius (the Scorpion) and covers an area on the sky slightly larger than the full Moon. The whole gas cloud is about 50 light-years across. The nebula appears red because its blue and green light are scattered and absorbed more efficiently by material between the nebula and Earth. The red light comes predominantly from hydrogen gas glowing under the intense glare of hot young stars.

NGC 6334 is one of the most active nurseries of massive stars in our galaxy and has been extensively studied by astronomers. The nebula conceals freshly minted brilliant blue stars — each nearly ten times the mass of our Sun and born in the last few million years. The region is also home to many baby stars that are buried deep in the dust, making them difficult to study. In total, the Cat’s Paw Nebula could contain several tens of thousands of stars.

Credit:
ESO/Digitized Sky Survey 2


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