Hubble Portrays a Dusty Spiral Galaxy (9/28/12)

Located about 55 million light-years from the sun and spanning about eighty thousand light-years, NGC 4183 is a little smaller than the Milky Way. This galaxy, which belongs to the Ursa Major Group, lies in the northern constellation of Canes Venatici (The Hunting Dogs).

NGC 4183 is a spiral galaxy with a faint core and an open spiral structure. Unfortunately, this galaxy is viewed edge-on from the Earth, and we cannot fully appreciate its spiral arms. But we can admire its galactic disk.

The disks of galaxies are mainly composed of gas, dust and stars. There is evidence of dust over the galactic plane, visible as dark intricate filaments that block the visible light from the core of the galaxy. In addition, recent studies suggest that this galaxy may have a bar structure. Galactic bars are thought to act as a mechanism that channels gas from the spiral arms to the center, enhancing star formation, which is typically more pronounced in the spiral arms than in the bulge of the galaxy.

NGC 4183 – click for 1280×1027 image

M101: A Pinwheel in Many Colors

M101: A Pinwheel in Many Colors (5/24/12)

This image of the Pinwheel Galaxy, or also known as M101, combines data in the infrared, visible, ultraviolet and X-rays from four of NASA's space-based telescopes. This multi-spectral view shows that both young and old stars are evenly distributed along M101's tightly-wound spiral arms. Such composite images allow astronomers to see how features in one part of the spectrum match up with those seen in other parts. It is like seeing with a regular camera, an ultraviolet camera, night-vision goggles and X-ray vision, all at the same time.

The Pinwheel Galaxy is in the constellation of Ursa Major (also known as the Big Dipper). It is about 70% larger than our own Milky Way Galaxy, with a diameter of about 170,000 light years, and sits at a distance of 21 million light years from Earth.

M101 – click for 1200×1200 image

A Spiral Within a Spiral

A Spiral Within a Spiral (5/21/12)

The NASA/ESA Hubble Space Telescope captured this image of the spiral galaxy known as ESO 498-G5. One interesting feature of this galaxy is that its spiral arms wind all the way into the centre, so that ESO 498-G5's core looks like a bit like a miniature spiral galaxy. This sort of structure is in contrast to the elliptical star-filled centres (or bulges) of many other spiral galaxies, which instead appear as glowing masses, as in the case of NGC 6384.

ESO 498-G5 – click for 1280×669 image

A galaxy blooming with new stars

A galaxy blooming with new stars (12/15/11)

The VLT Survey Telescope (VST) has captured the beauty of the nearby spiral galaxy NGC 253. The new portrait is probably the most detailed wide-field view of this object and its surroundings ever taken. It demonstrates that the VST, the newest telescope at ESO's Paranal Observatory, provides broad views of the sky while also offering impressive image sharpness.

NGC 253 gleams about eleven and a half million light-years away in the southern constellation of Sculptor. It is often just called the Sculptor Galaxy, although other descriptive names include the Silver Coin or Silver Dollar Galaxy. It is easy to get a good look at NGC 253 through binoculars as it is one of the brightest galaxies in the sky after the Milky Way's closest, big galactic neighbour, the Andromeda Galaxy.

Astronomers have noted the widespread active star formation in NGC 253 and labelled it a "starburst" galaxy. The many bright clumps dotting the galaxy are stellar nurseries where hot young stars have just ignited. The radiation streaming from these giant blue-white babies makes the surrounding hydrogen gas clouds glow brightly (green in this image).

NGC 253 – click for 1280×1012 image

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Classic Portrait of a Barred Spiral Galaxy

Classic Portrait of a Barred Spiral Galaxy (2/3/12)

The NASA/ESA Hubble Space Telescope has taken a picture of the barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster). Our own galaxy, the Milky Way, is a similar barred spiral, and the study of galaxies such as NGC 1073 helps astronomers learn more about our celestial home.

Most spiral galaxies in the Universe have a bar structure in their centre, and Hubble’s image of NGC 1073 offers a particularly clear view of one of these. Galaxies’ star-filled bars are thought to emerge as gravitational density waves funnel gas toward the galactic centre, supplying the material to create new stars. The transport of gas can also feed the supermassive black holes that lurk in the centres of almost every galaxy.

Some astronomers have suggested that the formation of a central bar-like structure might signal a spiral galaxy's passage from intense star-formation into adulthood, as the bars turn up more often in galaxies full of older, red stars than younger, blue stars. This storyline would also account for the observation that in the early Universe, only around a fifth of spiral galaxies contained bars, while more than two thirds do in the more modern cosmos.

NGC 1073 – click for 1280×1008 image

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A Galaxy Full of Surprises — NGC 3621 is bulgeless but has three central black holes

A Galaxy Full of Surprises — NGC 3621 is bulgeless but has three central black holes

This image, from ESO’s Very Large Telescope (VLT), shows a truly remarkable galaxy known as NGC 3621. To begin with, it is a pure-disc galaxy. Like other spirals, it has a flat disc permeated by dark lanes of material and with prominent spiral arms where young stars are forming in clusters (the blue dots seen in the image). But while most spiral galaxies have a central bulge — a large group of old stars packed in a compact, spheroidal region — NGC 3621 doesn’t. In this image, it is clear that there is simply a brightening to the centre, but no actual bulge like the one in NGC 6744 (eso1118), for example.

NGC 3621 is also interesting as it is believed to have an active supermassive black hole at its centre that is engulfing matter and producing radiation. This is somewhat unusual because most of these so-called active galactic nuclei exist in galaxies with prominent bulges. In this particular case, the supermassive black hole is thought to have a relatively small mass, of around 20 000 times that of the Sun.

NGC 3621 – click for 1280×1280 image

A Spiral in Leo

A Spiral in Leo (8/10/11)

This new picture from ESO’s Very Large Telescope shows NGC 3521, a spiral galaxy located about 35 million light years away in the constellation of Leo (The Lion). Spanning about 50 000 light-years, this spectacular object has a bright and compact nucleus, surrounded by richly detailed spiral structure.

The most distinctive features of the bright galaxy NGC 3521 are its long spiral arms that are dotted with star-forming regions and interspersed with veins of dust. The arms are rather irregular and patchy, making NGC 3521 a typical example of a flocculent spiral galaxy. These galaxies have “fluffy” spiral arms that contrast with the sweeping arms of grand-design spirals such as the famous Whirlpool galaxy or M 51, discovered by Charles Messier.

NGC 3521 – click for 1280×1280 image

Actually, NGC 3521 looks a lot like NGC 2841.

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A Twisted Dust Web in the Galaxy IC 342

A Twisted Dust Web in the Galaxy IC 342 (7/20/11)

Looking like a spiders web swirled into a spiral, the galaxy IC 342 presents its delicate pattern of dust in this image from NASAs Spitzer Space Telescope. Seen in infrared light, the faint starlight gives way to the glowing bright patterns of dust found throughout the galaxys disk.

At a distance of about 10 million light-years, IC 342 is relatively close by galaxy standards, however our vantage point places it directly behind the disk of our own Milky Way. The intervening dust makes it difficult to see in visible light, but infrared light penetrates this veil easily. It belongs to the same group as its even more obscured galaxy neighbor, Maffei 2.

IC 342 – click for 960×806 image

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"Rose" of Galaxies

"Rose" of Galaxies (4/20/11)

The newly released Hubble image shows a large spiral galaxy, known as UGC 1810, with a disk that is distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewel-like points across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light.

The smaller, nearly edge-on companion shows distinct signs of intense star formation at its nucleus, perhaps triggered by the encounter with the companion galaxy.

Arp 273 – click for 987×1000 image

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Wide Field Imager view of a Milky Way look-alike, NGC 6744

Wide Field Imager view of a Milky Way look-alike, NGC 6744 (6/1/11)

This picture of the nearby galaxy NGC 6744 was taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla. The large spiral galaxy is similar to the Milky Way, making this image look like a picture postcard of our own galaxy sent from extragalactic space. The picture was created from exposures taken through four different filters that passed blue, yellow-green, red light, and the glow coming from hydrogen gas. These are shown in this picture as blue, green, orange and red, respectively.

NGC 6744 – click for 1280×1078 image

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A Perfect Spiral with an Explosive Secret

A Perfect Spiral with an Explosive Secret (5/30/11)

This spiral galaxy was discovered back in the nineteenth century by French astronomer Édouard Jean-Marie Stephan, but in 2008 it became a prime target for observations thanks to the violent demise of a white dwarf star. The type Ia supernova known as SN2008a was spotted in the galaxy and briefly rivalled the brilliance of its entire host galaxy but, despite the energy of the explosion, it can no longer be seen this Hubble image, which was taken around a year and a half later.

NGC 634 – click for 1280×782 image

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Flocculent spiral NGC 2841

Flocculent spiral NGC 2841

Star formation is one of the most important processes in shaping the Universe; it plays a pivotal role in the evolution of galaxies and it is also in the earliest stages of star formation that planetary systems first appear.

Yet there is still much that astronomers don’t understand, such as how do the properties of stellar nurseries vary according to the composition and density of the gas present, and what triggers star formation in the first place? The driving force behind star formation is particularly unclear for a type of galaxy called a flocculent spiral, such as NGC 2841 shown here, which features short spiral arms rather than prominent and well-defined galactic limbs.

In an attempt to answer some of these questions, an international team of astronomers is using the new Wide Field Camera 3 (WFC3) installed on the NASA/ESA Hubble Space Telescope to study a sample of nearby, but wildly differing, locations where stars are forming. The observational targets include both star clusters and galaxies, and star formation rates range from the baby-booming starburst galaxy Messier 82 to the much more sedate star producer NGC 2841.

NGC 2841 – click for 1000×800 image

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Pinwheel of Star Birth

Pinwheel of Star Birth (10/19/10)

This face-on spiral galaxy, called NGC 3982, is striking for its rich tapestry of star birth, along with its winding arms. The arms are lined with pink star-forming regions of glowing hydrogen, newborn blue star clusters, and obscuring dust lanes that provide the raw material for future generations of stars. The bright nucleus is home to an older population of stars, which grow ever more densely packed toward the center.

NGC 3982 is located about 68 million light-years away in the constellation Ursa Major. The galaxy spans about 30,000 light-years, one-third of the size of our Milky Way galaxy.

NGC 3982 – click for 984×1000 image

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An "Island Universe" in the Coma Cluster

An "Island Universe" in the Coma Cluster (8/10/10)

A long-exposure Hubble Space Telescope image shows a majestic face-on spiral galaxy located deep within the Coma Cluster of galaxies, which lies 320 million light-years away in the northern constellation Coma Berenices.

The galaxy, known as NGC 4911, contains rich lanes of dust and gas near its center. These are silhouetted against glowing newborn star clusters and iridescent pink clouds of hydrogen, the existence of which indicates ongoing star formation. Hubble has also captured the outer spiral arms of NGC 4911, along with thousands of other galaxies of varying sizes. The high resolution of Hubble's cameras, paired with considerably long exposures, made it possible to observe these faint details.

NGC 4911 and other spirals near the center of the cluster are being transformed by the gravitational tug of their neighbors. In the case of NGC 4911, wispy arcs of the galaxy's outer spiral arms are being pulled and distorted by forces from a companion galaxy (NGC 4911A), to the upper right. The resultant stripped material will eventually be dispersed throughout the core of the Coma Cluster, where it will fuel the intergalactic populations of stars and star clusters.

NGC 4911 – click for 1280×1109 image

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An Elegant Galaxy in an Unusual Light

An Elegant Galaxy in an Unusual Light (9/22/10)

A new image taken with the powerful HAWK-I camera on ESO’s Very Large Telescope at Paranal Observatory in Chile shows the beautiful barred spiral galaxy NGC 1365 in infrared light. NGC 1365 is a member of the Fornax cluster of galaxies, and lies about 60 million light-years from Earth. ...

The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images in visible light and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms. These data were acquired to help astronomers understand the complex flow of material within the galaxy and how it affects the reservoirs of gas from which new stars can form. The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas is compressed and star formation is triggered. Many huge young star clusters trace out the main spiral arms and each contains hundreds or thousands of bright young stars that are less than ten million years old. The galaxy is too remote for single stars to be seen in this image and most of the tiny clumps visible in the picture are really star clusters. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

While the bar of the galaxy consists mainly of older stars long past their prime, many new stars are born in stellar nurseries of gas and dust in the inner spiral close to the nucleus. The bar also funnels gas and dust gravitationally into the very centre of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

NGC 1365 – click for 1280×1271 image

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A Galactic Spectacle

A Galactic Spectacle (8/5/10)

The Antennae galaxies, located about 62 million light years from Earth, are shown in this composite image from the Chandra X-ray Observatory (blue), the Hubble Space Telescope (gold and brown), and the Spitzer Space Telescope (red). The Antennae galaxies take their name from the long antenna-like "arms," seen in wide-angle views of the system. These features were produced by tidal forces generated in the collision.

The collision, which began more than 100 million years ago and is still occurring, has triggered the formation of millions of stars in clouds of dusts and gas in the galaxies. The most massive of these young stars have already sped through their evolution in a few million years and exploded as supernovas.

The X-ray image from Chandra shows huge clouds of hot, interstellar gas that have been injected with rich deposits of elements from supernova explosions. This enriched gas, which includes elements such as oxygen, iron, magnesium and silicon, will be incorporated into new generations of stars and planets.

Antennae Galaxies – click for 851×864 image

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VISTA Views the Sculptor Galaxy

VISTA Views the Sculptor Galaxy (6/16/10)

A spectacular new image of the Sculptor Galaxy (NGC 253) has been taken with the ESO VISTA telescope at the Paranal Observatory in Chile as part of one of its first major observational campaigns. By observing in infrared light VISTA’s view is less affected by dust and reveals a myriad of cooler stars as well as a prominent bar of stars across the central region. The VISTA image provides much new information on the history and development of the galaxy.

The Sculptor Galaxy (NGC 253) lies in the constellation of the same name and is one of the brightest galaxies in the sky. It is prominent enough to be seen with good binoculars and was discovered by Caroline Herschel from England in 1783. NGC 253 is a spiral galaxy that lies about 13 million light-years away. It is the brightest member of a small collection of galaxies called the Sculptor Group, one of the closest such groupings to our own Local Group of galaxies. Part of its visual prominence comes from its status as a starburst galaxy, one in the throes of rapid star formation. NGC 253 is also very dusty, which obscures the view of many parts of the galaxy (eso0902). Seen from Earth, the galaxy is almost edge on, with the spiral arms clearly visible in the outer parts, along with a bright core at its centre.

NGC 253 – click for 1600×1200 image

A New Look into the Whirlpool

A New Look into the Whirlpool

Galaxy M51 was discovered by Charles Messier in 1773, but its outstanding spiral structure was first perceived by William Parsons (Earl of Rosse) in 1845, using his huge reflecting telescope, the Leviathan of Parsonstown. A large telescope is needed to see its intricate shape, but even small amateur telescopes reveal that this galaxy is not isolated, but has a small companion, the dwarf irregular galaxy NGC 5195.

Now it is clear that these two stellar systems are colliding and that the outstanding spiral shape of M51 is due, mainly, to the tidal forces unleashed during this process. Just by chance, we see the disk of M51 face on from Earth, what allows studying it in detail. At a distance of 23 millions of light-years, the apparent dimensions of M51 mean that that galaxy has to be quite similar to our own, yet somewhat smaller.

M51 and its companion are performing a cosmic dance that, during the last 500 million years has made NGC 5195 pass twice through the disk of M51. Now, the small galaxy is located slightly behind the disc of the Whirlpool, and moving away from us.

M51 and NGC 5195 – Click for 1600×1583 image

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Starburst Galaxy NGC 1313

Starburst Galaxy NGC 1313 (5/24/10)

The starburst galaxy NGC 1313 is a stellar incubator delivering stars on a scale rarely seen in a single galaxy of its size. Now a striking new Gemini Observatory image reveals the multitudes of glowing gas clouds in this galaxy’s arms. These colorful clouds are the tell-tale sign of star-formation in this prolific star factory.

Because the clouds of gas in stellar nurseries emit light from ionized gas they shine brightly in very specific colors (or wavelengths) so narrow-band filters were used on the Gemini Multi-Object Spectrograph on the Gemini South telescope in Chile to capture the colorful galactic lightscape. The unprecedented detail and clarity of the image reveals myriad bubbles, shock fronts, star clusters, and sites where massive stars are being born.

NGC 1313 – click for 1000×747 image

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Clear New View of a Classic Spiral

Clear New View of a Classic Spiral (5/19/10)

The galaxy Messier 83 is located about 15 million light-years away in the constellation of Hydra (the Sea Serpent). It spans over 40 000 light-years, only 40 percent the size of the Milky Way, but in many ways is quite similar to our home galaxy, both in its spiral shape and the presence of a bar of stars across its centre. Messier 83 is famous among astronomers for its many supernovae: vast explosions that end the lives of some stars. Over the last century, six supernovae have been observed in Messier 83 — a record number that is matched by only one other galaxy. Even without supernovae, Messier 83 is one of the brightest nearby galaxies, visible using just binoculars.

Messier 83 has been observed in the infrared part of the spectrum using HAWK-I, a powerful camera on ESO’s Very Large Telescope (VLT). When viewed in infrared light most of the obscuring dust that hides much of Messier 83 becomes transparent. The brightly lit gas around hot young stars in the spiral arms is also less prominent in infrared pictures. As a result much more of the structure of the galaxy and the vast hordes of its constituent stars can be seen. This clear view is important for astronomers looking for clusters of young stars, especially those hidden in dusty regions of the galaxy.

M83 – click for 1600×1200 image

Another view of M83: here

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