Picture of the Week

14 November 2011: The NASA/ESA Hubble Space Telescope has peered deep into NGC 4631, better known as the Whale Galaxy. Here, a profusion of starbirth lights up the galactic centre, revealing bands of dark material between us and the starburst. The galaxy’s activity tapers off  in its outer regions where there are fewer stars and less dust, but these are still punctuated by pockets of star formation. The Whale Galaxy is about 30 million light-years away from us in the constellation of Canes Venatici (The Hunting Dogs) and is a spiral galaxy much like the Milky Way. From our vantage point, however, we see the Whale Galaxy edge-on, seeing its glowing centre through dusty spiral arms. The galaxy's central bulge and asymmetric tapering disc have suggested the shape of a whale or a herring to past observers. Many supernovae — the explosions of hot, blue, short-lived stars at least eight times the mass …

7 November 2011: The object shown in this beautiful Hubble image, dubbed Messier 54, could be just another globular cluster, but this dense and faint group of stars was in fact the first globular cluster found that is outside our galaxy. Discovered by the famous astronomer Charles Messier in 1778, Messier 54 belongs to a satellite of the Milky Way called the Sagittarius Dwarf Elliptical Galaxy. Messier had no idea of the significance of his discovery at the time, and it wasn’t until over two centuries later, in 1994, that astronomers found Messier 54 to be part of the miniature galaxy and not our own. Current estimates indicate that the Sagittarius dwarf, and hence the cluster, is situated almost 90 000 light-years away — more than three times as far from the centre of our galaxy than the Solar System. Ironically, even though this globular cluster is now understood to lie outside the …

31 October 2011: The pearly wisps surrounding the central star IRAS 10082-5647 in this Hubble image certainly draw the eye towards the heavens. The divine-looking cloud is a reflection nebula, made up of gas and dust glowing softly by the reflected light of nearby stars, in this case a young Herbig Ae/Be star. The star, like others of this type, is still a relative youngster, only a few million years old. It has not yet reached the so-called main sequence phase, where it will spend around 80% of its life creating energy by burning hydrogen in its core. Until then the star heats itself by gravitational collapse, as the material in the star falls in on itself, becoming ever denser and creating immense pressure which in turn gives off copious amounts of heat. Stars only spend around 1% of their lives in this pre-main sequence phase. Eventually, gravitational collapse will heat the star’s …

24 October 2011: The NASA/ESA Hubble Space Telescope has taken this image of the Phoenix Dwarf Galaxy, which is located 1.4 million light-years away from Earth. It is located in the constellation of Phoenix in the southern sky. The object, a dwarf irregular galaxy, features younger stars in its inner regions and older ones at its outskirts. Dwarf galaxies are small galaxies composed of a few billion stars, compared to fully-fledged galaxies which can contain hundreds of billions of stars. In the Local Group, there are a number of such dwarf galaxies orbiting the larger galaxies such as the Milky Way or the Andromeda Galaxy. They are thought to have been created by tidal forces in the early stages of the creation of these galaxies, or as a result of collisions between galaxies, forming from ejected streams of material and dark matter from the parent galaxies. The Milky Way galaxy features at least …

17 October 2011: Supernova SN 1987A, one of the brightest stellar explosions since the invention of the telescope more than 400 years ago, is no stranger to the NASA/ESA Hubble Space Telescope. The observatory has been on the frontline of studies into this brilliant dying star since its launch in 1990, three years after the supernova exploded on 23 February 1987. This image of Hubble’s old friend, retreived from the telescope’s data archive, may be the best ever of this object, and reminds us of the many mysteries still surrounding it. Dominating this picture are two glowing loops of stellar material and a very bright ring surrounding the dying star at the centre of the frame. Although Hubble has provided important clues on the nature of these structures, their origin is still largely unknown. Another mystery is that of the missing neutron star. The violent death of a high-mass star, such as SN …

10 October 2011: Galaxies come in a variety of shapes and sizes, and these features change as they evolve. Some, like the galaxy in the centre of this NASA/ESA Hubble Space Telescope image, are beautiful spirals with graceful curved arms, while others are fuzzy oval-shaped blobs like the large object showing up near the bottom right of the frame. Others still are rather irregular in shape, such as the orange galaxy at the top of the image, which resembles a tiny wobbling string. This picture is one of the few hundred exposures taken with Hubble’s Advanced Camera for Surveys to assemble the “Extended Groth Strip”. This strip, named after the Princeton University astronomer Edward Groth, is a composite picture of a rectangular region of the sky in the constellation of Ursa Major. It covers a relatively small area in the sky — equivalent to roughly the width of a finger stretched at arms’ …

3 October 2011: Thousands and thousands of brilliant stars make up this globular cluster, Messier 53, captured with crystal clarity in this image from the NASA/ESA Hubble Space Telescope. Bound tightly by gravity, the cluster is roughly spherical and becomes denser towards its heart. These enormous sparkling spheres are by no means rare, and over 150 exist in the Milky Way alone, including Messier 53. It lies on the outer edges of the galaxy, where many other globular clusters are found, almost equally distant from both the centre of our galaxy and the Sun. Although they are relatively common, the famous astronomer William Herschel, not at all known for his poetic nature, once described a globular cluster as “one of the most beautiful objects I remember to have seen in the heavens”, and it is clear to see why. Globular clusters are much older and larger than open clusters, meaning they are generally …

26 September 2011: This NASA/ESA Hubble Space Telescope image shows remarkable structures in a galaxy cluster around an object called LRG-4-606. LRG stands for Luminous Red Galaxy, and is the acronym given to a large collection of bright red galaxies found in the Sloan Digital Sky Survey (SDSS). These objects are mostly massive elliptical galaxies composed of huge numbers of old stars. It is sobering to contemplate the sheer number of stars that this image must contain — hundreds of billions — but it also features one of the strangest phenomena known to astronomers. This particular red galaxy and its surrounding galaxies happen to be positioned so that their strong gravitational field has a dramatic effect. Left of centre in the picture, blue galaxies in the background have been stretched and warped out of shape into narrow, pale blue arcs. This is because of an effect called gravitational lensing. The galaxy cluster has …

19 September 2011: In this NASA/ESA Hubble Space Telescope image, NGC 4874 is the brightest object, located to the right of the frame and seen as a bright star-like core surrounded by a hazy halo. A few of the other galaxies of the cluster are also visible, looking like flying saucers dancing around NGC 4874. But the really remarkable feature of this image is the point-like objects around NGC 4874, revealed on a closer look: almost all of them are clusters of stars that belong to the galaxy. Each of these globular star clusters contains many hundreds of thousands of stars. Recently, astronomers discovered that a few of these point-like objects are not star clusters but ultra-compact dwarf galaxies, also under the gravitational influence of NGC 4874. Being only about 200 light-years across and mostly made up of old stars, these galaxies resemble brighter and larger versions of globular clusters. They are thought …

12 September 2011: This NASA/ESA Hubble Space Telescope image shows a compact and distant globular star cluster that lies in one of the smallest constellations in the night sky, Delphinus (The Dolphin). Due to its modest size, great distance and relatively low brightness, NGC 7006 is often ignored by amateur astronomers. But even remote globular clusters such as this one appear bright and clear when imaged by Hubble’s Advanced Camera for Surveys. NGC 7006 resides in the outskirts of the Milky Way. It is about 135 000 light-years away, five times the distance between the Sun and the centre of the galaxy, and it is part of the galactic halo. This roughly spherical region of the Milky Way is made up of dark matter, gas and sparsely distributed stellar clusters. Like other remote globular clusters, NGC 7006 provides important clues that help astronomers to understand how stars formed and assembled in the halo. …

5 September 2011: Protoplanetary nebulae offer glimpses of how stars similar to the Sun end their lives and how they make the transition to white dwarfs surrounded by planetary nebulae. As it ages, a Sun-like star eventually sheds its outer layers into space, creating a beautiful and often intricately shaped cloud of gas and dust around it. At first, still relatively cool, the star is unable to ionise this gas, which shines only by reflected and scattered stellar light. Only when the temperature of the star increases enough to ionise this protoplanetary nebula does the pattern of gas and dust become a fully fledged planetary nebula. Protoplanetary nebulae are relatively rare and short-lived objects that provide astronomers with clues into how the often strangely asymmetric planetary nebulae are formed. Clearly visible in this image are five blue lobes that extend away from the central star and give the nebula its asymmetric starfish shape. …

29 August 2011: Peering into the depths of space, the sharp-eyed NASA/ESA Hubble Space Telescope has imaged the nearby but faint dwarf galaxy ESO 540-030. This object itself appears as a huge swarm of dim stars, but ESO 540-030 is actually just one point of interest in the picture. ESO 540-030 is just over 11 million light-years distant, and is part of the Sculptor group of galaxies. This collection is the closest neighbour to our own Local Group of galaxies that includes the Milky Way. Due to its proximity the Sculptor group contains some of the brightest galaxies in the southern skies, although ESO 540-030 is not one of these; dwarf galaxies generally have low surface brightness, which make observations difficult. Hubble has captured a snapshot of galaxy types in the background, with spirals, barred spirals, ellipticals and irregulars on display. Careful examination of this picture should allow examples of each galaxy type …

22 August 2011: NGC 2146 is classified as a barred spiral due to its shape, but the most distinctive feature is the dusty spiral arm that has looped in front of the galaxy's core as seen from our perspective. The forces required to pull this structure out of its natural shape and twist it up to 45 degrees are colossal. The most likely explanation is that a neighbouring galaxy is gravitationally perturbing it and distorting the orbits of many of NGC 2146’s stars. It is probable that we are currently witnessing the end stages of a process which has been occurring for tens of millions of years. NCG 2146 is undergoing intense bouts of star formation, to such an extent that it is referred to as a starburst galaxy. This is a common state for barred spirals, but the extra gravitational disruption that NGC 2146 is enduring no doubt exacerbates the situation, compressing …

15 August 2011: A giant cosmic necklace glows brightly in this NASA/ESA Hubble Space Telescope image.The object, aptly named the Necklace Nebula, is a recently discovered planetary nebula, the glowing remains of an ordinary, Sun-like star. The nebula consists of a bright ring, measuring about two light-years across, dotted with dense, bright knots of gas that resemble diamonds in a necklace. The knots glow brightly due to absorption of ultraviolet light from the central stars.A pair of tightly orbiting stars produced the nebula, also called PN G054.2-03.4. About 25 000 years ago one of the aging stars ballooned to the point where it engulfed its companion star. The smaller star continued orbiting inside its larger companion, increasing the giant’s rotation rate, so that the bloated star span so fast that a large part of its gaseous envelope expanded into space. Most of the gas escaped along the star’s equator, producing a ring. The …

8 August 2011: The NASA/ESA Hubble Space Telescope has imaged part of the Hickson Compact Group 7, or HCG 7 for short. This grouping is composed of one lenticular (lens-shaped) and three spiral galaxies in close proximity. In this image, one of the spirals dominates the foreground, with many more distant galaxies peppering the background. Observing tightly-knit galaxy groups like HCG 7 is important because they evolve in a different way from their more spaced-out counterparts in less crowded regions of the Universe.  A recent study using Hubble data analysed the star clusters in HCG 7. Three hundred young clusters and 150 globular clusters were charted, and their ages and distributions measured. The results suggest that the rate of star formation has been fairly steady through time, although quite high in the central regions. Additional studies, including searches for material between the galaxies, hint that the stars in the HCG 7 galaxies formed …

1 August 2011: The NASA/ESA Hubble Space Telescope has used its powerful optics to separate the globular cluster NGC 6401 into its constituent stars. What was once only visible as a ghostly mist in the eyepieces of astronomical instruments has been transformed into a stunning stellar landscape. NGC 6401 can be found within the constellation of Ophiuchus (The Serpent Bearer). The globular cluster itself is relatively faint, so a telescope and some observational experience are required to see it. Globular clusters are very rich, and generally spherical, collections of stars, hence the name. They orbit the cores of galaxies, with the force of gravity also keeping the stars bound as a group. There are around 160 globular clusters associated with our Milky Way, of which NGC 6401 is one. These objects are very old, containing some of the most ancient stars known. However, there are many mysteries surrounding them, with the origin of …

25 July 2011: NGC 2023 surrounds a massive young B-type star. These stars are large, bright and blue-white in colour, and have a high surface temperature, being several times hotter than the Sun. The energy emitted from NGC2023’s B-type star illuminates the nebula, resulting in its high surface brightness: good news for astronomers who wish to study it. The star itself lies outside the field of view, at the upper left, and its brilliant light is scattered by Hubble’s optical system, creating the bright flare across the left side of the picture, which is not a real feature of the nebula. Stars are forming from the material comprising NGC 2023. This Hubble image captures the billowing waves of gas, 5000 times denser than the interstellar medium. The unusual greenish clumps are thought to be Herbig–Haro objects. These peculiar features of star-forming regions are created when gas ejected at hundreds of kilometres per second …

18 July 2011: The NASA/ESA Hubble Space Telescope has imaged an elongated stream of stars, gas and dust called IC 755, which is actually a spiral galaxy that we are seeing edge-on. In 1999 a star within IC 755 was seen to explode as a supernova and named SN 1999an. The supernova was discovered by the Beijing Astronomical Observatory Supernova Survey and three years later Hubble was used to study the environment in which the explosion took place. The inclination of the galaxy made the supernova a challenging target as many other intervening objects obscured the view. Valuable data were obtained and suggest that before detonation the star may have been around 20 times more massive than our Sun, and that it was likely to have been in the region of 14 million years old. Supernovae like SN 1999an are classified as Type IIs and they are dramatic events that mark the end …

11 July 2011: The NASA/ESA Hubble Space Telescope has been used to capture a striking image of a rare astronomical phenomenon called a protoplanetary nebula. This particular example, called Minkowski’s Footprint, also known as Minkowski 92, features two vast onion-shaped structures either side of an ageing star, giving it a very distinctive shape. Protoplanetary nebulae like Minkowski’s Footprint have short lives, being a preliminary stage to the more common planetary nebula phase. In the middle of the image is a star, soon to be a white dwarf, puffing out material due to intense surface pulsations. Charged particle streams, called stellar winds, are shaping this gas into the interesting shapes that Hubble allows us to see. Technically speaking Minkowski’s Footprint is currently a reflection nebula as it is only visible due to the light reflected from the central star. In a few thousand years the star will get hotter and its ultraviolet radiation will light …

4 July 2011: Looking like an elegant abstract art piece painted by talented hands, this picture is actually a NASA/ESA Hubble Space Telescope image of a small section of the Carina Nebula. Part of this huge nebula was documented in the well-known Mystic Mountain picture (heic1007a) and this picture takes an even closer look at another piece of this bizarre astronomical landscape (heic0707a). The Carina Nebula itself is a star-forming region about 7500 light-years from Earth in the southern constellation of Carina (The Keel: part of Jason’s ship the Argo). Infant stars blaze with a ferocity so severe that the radiation emitted carves away at the surrounding gas, sculpting it into strange structures. The dust clumps towards the upper right of the image, looking like ink dropped into milk, were formed in this way. It has been suggested that they are cocoons for newly forming stars. The Carina Nebula is mostly made from …

27 June 2011: The NASA/ESA Hubble Space Telescope has imaged an area so jam-packed with stars that they almost overwhelm the inky blackness of space. This includes the globular star cluster Djorgovski 1, which was only discovered in 1987 Djorgovski 1 is located close to the centre of our Milky Way Galaxy, within the bulge. If the galaxy is thought of as being like a city, then this bulge is the very busiest district at its centre. Djorgovski 1's proximity to this hub — within just a few degrees — explains why the picture is teeming with stars. Globular clusters like Djorgovski 1 formed early in the Milky Way's history, and as such may hold clues about the inner galaxy’s early evolution. However, with so much material in the way, obtaining accurate data is problematic. To make matters worse, these stars are faint. Even the most luminous stars in Djorgovski 1 are fainter …

20 June 2011: In this NASA/ESA Hubble Space Telescope image of NGC 7479 — created from observations at visible and near-infrared wavelengths — the tightly wound arms of the spiral galaxy create an inverted ‘S’, as they spin in an anticlockwise direction. However, at radio wavelengths, this galaxy, sometimes nicknamed the Propeller Galaxy, spins the other way, with a jet of radiation that bends in the opposite direction to the stars and dust in the arms of the galaxy. Astronomers think that the radio jet in NGC 7479 was put into its bizarre backwards spin following a merger with another galaxy. Star formation is reignited by galactic collisions, and indeed NGC 7479 is undergoing starburst activity, with many bright, young stars visible in the spiral arms and disc. The three brightest stars in this image, however, are foreground stars — caught on camera because they lie between the galaxy and Hubble. This striking …

13 June 2011: The NASA/ESA Hubble Space Telescope has made a rare celestial catch. Close to a bright, nearby star in this image, the bizarre, whorl-shaped object known as IRAS 22036+5306 has been captured during a brief tumultuous period late in a star's life.  Inside IRAS 22036+5306 lies an aged star that has coughed off almost all of its outer material, forming a cloud in space. Hidden under this veil, the dense, still-burning, exposed core of the star grows hotter. Encircling the star is a torus consisting partly of castoff material, as well as possibly the grainy remnants of comets and other small, rocky bodies. Twin jets spout from the star’s poles and pierce this dusty waist. The jets contain gobbets of material — typically about ten thousand times the mass of the Earth — hurling outwards at a speed of nearly 800 000 kilometres per hour.  IRAS 22036+5306 is making the transition through …

6 June 2011: The two billowing structures in this NASA/ESA Hubble Space Telescope image of IRAS 13208-6020 are formed from material that is shed by a central star. This is a relatively short-lived phenomenon that gives astronomers an opportunity to watch the early stages of planetary nebula formation, hence the name protoplanetary, or preplanetary nebula. Planetary nebulae are unrelated to planets and the name arose because of the visual similarity between some planetary nebulae and the small discs of the outer planets in the Solar System when viewed through early telescopes. This object has a very clear bipolar form, with two very similar outflows of material in opposite directions and a dusty ring around the star. Protoplanetary nebulae do not shine, but are illuminated by light from the central star that is reflected back to us. But as the star continues to evolve, it becomes hot enough to emit strong ultraviolet radiation that …

30 May 2011: The NASA/ESA Hubble Space Telescope is renowned for its breathtaking images and this snapshot of NGC 634 is definitely that — the fine detail and exceptionally perfect spiral structure of the galaxy make it hard to believe that this is a real observation and not an artist’s impression or a screenshot taken straight from Star Wars. 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. White dwarfs are thought to be the endpoint of evolution …

23 May 2011: Deep within the Milky Way lies the ancient globular cluster Terzan 5. This NASA/ESA Hubble Space Telescope image shows the cluster in wonderful detail, but it is the chaotic motions of its stars that make it particularly interesting to astronomers. Terzan 5 has an exceptionally dense core. As a result, it is thought to have one of the highest stellar collision rates for a globular cluster. And packed in at such close quarters, many stars are pushed so close together that they form tight binary systems. Interestingly, studies of individual stars within the cluster reveal that they can be split into two age groups: 6 and 12 billion years old. Some astronomers have hypothesised that the younger crowd may have been stripped away from a dwarf galaxy. This picture was created from images taken with the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Images through a yellow/red filter …

16 May 2011: Like a Dali masterpiece, this image of Messier 8 from the NASA/ESA Hubble Space Telescope is both intensely colourful and distinctly surreal. Located in the constellation of Sagittarius (The Archer), this giant cloud of glowing interstellar gas is a stellar nursery that is also known as the Lagoon Nebula. Although the name definitely suits the beauty of this object, “lagoon” does suggest tranquillity and there is nothing placid about the high-energy radiation causing these intricate clouds to glow. The massive stars hiding within the heart of the nebula give off enormous amounts of ultraviolet radiation, ionising the gas and causing it to shine colourfully, as well as sculpting the surrounding nebula into strange shapes. The result is an object around four to five thousand light-years away which, on a clear night, is faintly visible to the naked eye. Since it was first recorded back in the 1747 this object has …

9 May 2011: This NASA/ESA Hubble Space Telescope image shows the edge-on profile of the slender spiral galaxy NGC 5775. Although the spiral is tilted away from us, with only a thin slither on view, such a perspective can be advantageous for astronomers because the regions above and below the galaxy’s disc can be seen much more clearly. For instance, astronomers have previously used the high inclination of this spiral to study the properties of the halo of hot gas that is visible when the galaxy is observed at X-ray wavelengths. The mechanism behind such haloes is unclear, but they are found around spirals that have a high star formation rate, like NGC 5775. Some astronomers think that hot gas from the disc is driven into the halo by supernova explosions, which is then returned to the disc as it cools — like a massive galactic fountain. Meanwhile, there is further disruption taking …

2 May 2011: The globular cluster Messier 5, shown here in this NASA/ESA Hubble Space Telescope image, is one of the oldest belonging to the Milky Way. The majority of its stars formed more than 12 billion years ago, but there are some unexpected newcomers on the scene, adding some vitality to this aging population. Stars in globular clusters form in the same stellar nursery and grow old together. The most massive stars age quickly, exhausting their fuel supply in less than a million years, and end their lives in spectacular supernovae explosions. This process should have left the ancient cluster Messier 5 with only old, low-mass stars, which, as they have aged and cooled, have become red giants, while the oldest stars have evolved even further into blue horizontal branch stars. Yet astronomers have spotted many young, blue stars in this cluster, hiding amongst the much more luminous ancient stars. Astronomers think …

25 April 2011: Galaxies come in all sorts of shapes and sizes, with most being classed as either elliptical or spiral. However, some fall into the miscellaneous category known as irregulars, such as UGC 9128 shown here in this NASA/ESA Hubble Space Telescope image. UGC 9128 is a dwarf irregular galaxy, which means that in addition to not having a well-defined shape, it probably contains only around one hundred million stars — far fewer than are found in a large spiral such as the Milky Way. Dwarf galaxies are important in understanding how the Universe has evolved and they are often referred to as galactic building blocks, as galaxies are thought to grow as smaller ones merge. In recent years, astronomers have been trying to find out if dwarf galaxies contain a similar halo and disc structure to their much larger counterparts, whereby older stars are found in the extended spheroidal halo, with …

18 April 2011: The NASA/ESA Hubble Space Telescope usually works as a solo artist to capture awe-inspiring images of the distant Universe. For this picture, though, Hubble had a helping hand from the subject of the image, a galaxy cluster called LCDCS-0829, as the huge mass of the galaxies in the cluster acted like a giant magnifying glass. This strange effect is called gravitational lensing. The object was discovered during the Las Campanas Distant Clusters Survey, which explains the cluster's unusual name. This survey was carried out in March 1995 using a 1-metre telescope at the Las Campanas Observatory in Chile. More than one thousand clusters of galaxies, most of them previously unknown, were found in a dedicated survey of a long, but narrow, section of the southern sky. The bizarre phenomenon of gravitational lensing is a consequence of Albert Einstein’s general theory of relativity, which says that the huge mass of the …

11 April 2011: Astronomers have used the NASA/ESA Hubble Space Telescope to study the young open star cluster IC 1590, which is found within the star formation region NGC 281 — nicknamed the Pacman Nebula due to its resemblance to the famous arcade game character. This image only shows the central part of the nebula, where the brightest stars at the core of the cluster are found, with part of the Pacman’s hungry mouth visible as the dark region below. But Pacman isn’t gobbling up these stars. Instead, the nebula’s gas and dust are being used as raw ingredients to make new stars. However, the stars in IC 1590 are still plotting their escape from the Pacman Nebula, as open clusters are only loosely bound together and the grouping will eventually disperse within a few tens of millions of years. IC 1590 lies about ten thousand light-years from Earth in the constellation of …

4 April 2011: The NASA/ESA Hubble Space Telescope has captured a planetary nebula with unconventional good looks. Planetary nebulae signal the demise of mid-sized stars (up to about eight times the mass of the Sun); when the star’s hydrogen fuel supply is exhausted, its outer layers expand and cool, creating a cocoon of gas and dust. This gas then glows as it is bathed in the strong ultraviolet radiation from the central star. NGC 5882 is a quite bright, but small, example of a planetary nebula that lies deep in the southern Milky Way in the constellation of Lupus (The Wolf). Planetary nebulae sometimes have a perfectly symmetrical appearance, with gas being bellowed out from the dying star evenly in every direction. However, this isn’t the case for NGC 5882, as this Hubble image shows. It appears to have two distinct, but non-uniform regions: an elongated inner shell of gas and a fainter …

28 March 2011: The high concentration of stars within globular clusters, like Messier 12, shown here in an image from the NASA/ESA Hubble Space Telescope, makes them beautiful photographic targets. But the cramped living quarters in these clusters also makes them home to exotic binary star systems where two stars are locked in tight orbits around each other and matter from one is gobbled up by its companion, releasing X-rays. It is thought that such X-ray binaries form from very close encounters between stars in crowded regions, such as globular clusters, and even though Messier 12 is fairly diffuse by globular cluster standards, such X-ray sources have been spotted there. Astronomers have also discovered that Messier 12 is home to far fewer low-mass stars than was previously expected (eso0604). In a recent study, astronomers used the European Southern Observatory’s Very Large Telescope at Cerro Paranal, Chile, to measure the brightness and colours of …

21 March 2011: This view from the NASA/ESA Hubble Space Telescope shows the beautiful spiral galaxy NGC 5584. This galaxy has played a key role in a new study that measures the expansion rate of the Universe to greater accuracy than ever before. NGC 5584 was first spotted as a faint glow in the constellation of Virgo by the great visual observer E. E. Barnard, back in 1881, using just a 12.5-cm telescope. But, by bringing the power of Hubble to bear, the galaxy can be resolved into thousands of separate stars. Some of these stars vary in brightness and are classified as Cepheids. These are brilliant pulsating stars with a remarkable property — once the time it takes a Cepheid to brighten and fade is known, then it is possible to find how bright it actually is. When this information is combined with a measurement of how bright the star appears it …

14 March 2011: Most of the rich globular star clusters that orbit the Milky Way have cores that are tightly packed with stars, but NGC 288 is one of a minority of low-concentration globulars, with its stars more loosely bound together. This new image from the Advanced Camera for Surveys on the NASA/ESA Hubble Space Telescope completely resolves the old stars at the core of the cluster. The colours and brightnesses of the stars in the picture tell the story of how the stars have evolved in the cluster. The many fainter points of light are normal low-mass stars that are still fusing hydrogen in the same way as the Sun. The brighter stars fall into two classes: the yellow ones are red giant stars that are at a later phase in their careers and are now bigger, cooler and brighter. The bright blue stars are even more massive stars that have left …

7 March 2011: The strange and irregular bundle of jets and clouds in this curious image from the NASA/ESA Hubble Space Telescope is the result of a burst of activity late in the life of a star. As its core runs out of nuclear fuel, the star’s unstable outer layers are puffing out a toxic concoction of gases including carbon monoxide and hydrogen cyanide. The Westbrook Nebula — also known as PK166-06, CRL 618 and AFGL 618 — is a protoplanetary nebula, an opaque, dark and relatively short-lived cloud of gas that is ejected by a star as it runs out of nuclear fuel. As the star hidden deep in the centre of the nebula evolves further it will turn into a hot white dwarf and the gas around it will become a glowing planetary nebula, before eventually dispersing. Because this is a relatively brief stage in the evolution process of stars, only …

28 February 2011: The NASA/ESA Hubble Space Telescope has taken a close-up view of an outer part of the Orion Nebula’s little brother, Messier 43. This nebula, which is sometimes referred to as De Mairan’s Nebula after its discoverer, is separated from the famous Orion Nebula (Messier 42) by only a dark lane of dust. Both nebulae are part of the massive stellar nursery called the Orion molecular cloud complex, which includes several other nebulae, such as the Horsehead Nebula (Barnard 33) and the Flame Nebula (NGC 2024). The Orion molecular cloud complex is about 1400 light-years away, making it one of the closest massive star formation regions to Earth. Hubble has therefore studied this extraordinary region extensively over the past two decades, monitoring how stellar winds sculpt the clouds of gas, studying young stars and their surroundings and discovering many elusive objects, such as brown dwarf stars. This view shows several of …

21 February 2011: The NASA/ESA Hubble Space Telescope has produced this finely detailed image of the beautiful spiral galaxy NGC 6384. This galaxy lies in the constellation of Ophiuchus (The Serpent Bearer), not far from the centre of the Milky Way on the sky. The positioning of NGC 6384 means that we have to peer at it past many dazzling foreground Milky Way stars that are scattered across this image. In 1971, one member of NGC 6384 stood out against these bright foreground stars when one of its stars exploded as a supernova. This was a Type Ia supernova, which occurs when a compact star that has ceased fusion in its core, called a white dwarf, increases its mass beyond a critical limit by gobbling up matter from a companion star. A runaway nuclear explosion then makes the star suddenly as bright as a whole galaxy. While many stars have already come to …

14 February 2011: The dazzling stars in Messier 15 look fresh and new in this image from the NASA/Hubble Space Telescope, but they are actually all roughly 13 billion years old, making them some of the most ancient objects in the Universe. Unlike another recent Hubble Picture of the Week, which featured the unusually sparse cluster Palomar 1, Messier 15 is rich and bright despite its age. Messier 15 is a globular cluster — a spherical conglomeration of old stars that formed together from the same cloud of gas, found in the outer reaches of the Milky Way in a region known as the halo and orbiting the Galactic Centre. This globular lies about 35 000 light-years from the Earth, in the constellation of Pegasus (The Flying Horse). Messier 15 is one of the densest globulars known, with the vast majority of the cluster’s mass concentrated in the core. Astronomers think that particularly …

7 February 2011: The NASA/ESA Hubble Space Telescope has imaged a violent stellar nursery called NGC 2174, in which stars are born in a first-come-first-served feeding frenzy for survival. The problem is that star formation is a very inefficient process; most of the ingredients to make stars are wasted as the cloud of gas and dust, or nebula, gradually disperses. In NGC 2174, the rate at which the nebula disperses is further speeded up by the presence of hot young stars, which create high velocity winds that blow the gas outwards. These fiery youngsters also bombard the surrounding gas with intense radiation, making it glow brightly, creating the brilliant scene captured here. The nebula is mostly composed of hydrogen gas, which is ionised by the ultraviolet radiation emitted by the hot stars, leading to the nebula’s alternative title as an HII region. This picture shows only part of the nebula, where dark dust …

31 January 2011: Hubble's Advanced Camera for Surveys has captured this moment in the ever-changing life of a spiral galaxy called IC 391. Although these massive star cities appear static and unchanging, their stellar inhabitants are constantly moving and evolving, with new stars being born and old stars reaching the ends of their lives —often in spectacular fashion, with an immense supernova explosion that can be viewed from Earth. On 3 January 2001, members of the Beijing Astronomical Observatory discovered such an explosion within IC 391 and it was named SN 2001B. This was a Type Ib supernova, which occurs when a massive star runs out of fuel for nuclear fusion and collapses, emitting vast amounts of radiation and creating a powerful shock wave. Hubble has contributed much to our understanding of supernovae in recent years, and it has made an extensive study of supernova 1987A (heic0704), the brightest such stellar explosion to …

24 January 2011: The NASA/ESA Hubble Space Telescope has captured a clear view of the unusual globular cluster Palomar 1, whose youthful beauty is a puzzle for astronomers. This faint and sparse object is very different from the more familiar brilliant and very rich globular clusters and had to wait until 1954 for its discovery by George Abell on photographs from the Palomar Schmidt telescope. Globular clusters are tightly bound conglomerations of stars, which are found in the outer reaches of the Milky Way, in its so-called halo. They are amongst the oldest objects in a galaxy, containing very old stars and no gas, which means there is no possibility of newborn stars introducing some fresh blood into the cluster. However, at 6.3 to 8 billion years old, Palomar 1 is a youngster in globular cluster terms — little more than half the age of most the other globulars in our Milky Way, …

17 January 2011: The spiral galaxy NGC 1345 and its loose and ragged arms dominate this rich image from the NASA/ESA Hubble Space Telescope. It is a member of the Eridanus Galaxy Cluster — a group of about 70 galaxies that lies 85 million light-years away in the constellation of Eridanus (the River). This region of the night sky is well populated with bright galaxies, with the Fornax Cluster of galaxies also nearby on the celestial sphere, although the two clusters are actually separated by about 20 million light-years. Collectively, they are known as the Fornax Supercluster or the Southern Supercluster. John Herschel discovered NGC 1345 in 1835 from South Africa. He described it as small and very faint and it is still far from easy to see it even with quite a large amateur telescope, where it appears as a small, circular fuzz. Apart from the main galaxy that dominates the picture, …

10 January 2011: Astronomers have used the NASA/ESA Hubble Space Telescope to image the tiny planetary nebula NGC 6886. These celestial objects signal the final death throes of mid-sized stars (up to about eight times the mass of the Sun); when such a star exhausts its supply of hydrogen fuel, the outer layers begin to expand and cool, which creates an envelope of gas and dust that shrouds the dying star. However, the star doesn't go down without a fight, finding alternative ways to prevent it from collapsing under its own gravity and emerging as a white dwarf. In the process, the star's surface temperature increases and it is eventually hot enough to emit strong ultraviolet radiation and make the cocoon of gas glow as a stunning planetary nebula. Stellar death isn't quick and painless: the planetary nebula stage typically lasts several tens of thousands of years. By studying the elements that are …

3 January 2011: A spectacular section of the well-known Eagle Nebula has been targeted by the NASA/ESA Hubble Space Telescope. This collection of dazzling stars is called NGC 6611, an open star cluster that formed about 5.5 million years ago and is found approximately 6500 light-years from the Earth. It is a very young cluster, containing many hot, blue stars, whose fierce ultraviolet glow make the surrounding Eagle Nebula glow brightly. The cluster and the associated nebula together are also known as Messier 16.Astronomers refer to areas like the Eagle Nebula as HII regions. This is the scientific notation for ionised hydrogen from which the region is largely made. Extrapolating far into the future, this HII region will eventually disperse, helped along by shockwaves from supernova explosions as the more massive young stars end their brief but brilliant lives. In this image, dark patches can also be spotted, punctuating the stellar landscape. These …

27 December 2010: An image of the Cartwheel Galaxy taken with the NASA/ESA Hubble Space Telescope has been reprocessed using the latest techniques to mark the closure of the Space Telescope European Coordination Facility (ST-ECF), based near Munich in Germany, and to celebrate its achievements in supporting Hubble science in Europe over the past 26 years. Astronomer Bob Fosbury, who is stepping down as Head of the ST-ECF, was responsible for much of the early research into the Cartwheel Galaxy along with the late Tim Hawarden — including giving the object its very apposite name — and so this image was selected as a fitting tribute. The object was first spotted on wide-field images from the UK Schmidt telescope and then studied in detail using the Anglo-Australian Telescope.Lying about 500 million light-years away in the constellation of Sculptor, the cartwheel shape of this galaxy is the result of a violent galactic collision. A …

20 December 2010: The galaxy captured in this image, called UGC 12158, certainly isn’t camera-shy: this spiral stunner is posing face-on to the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys, revealing its structure in fine detail. UGC 12158 is an excellent example of a barred spiral galaxy in the Hubble sequence — a scheme used to categorise galaxies based on their shapes. Barred spirals, as the name suggest, feature spectacular swirling arms of stars that emanate from a bar-shaped centre. Such bar structures are common, being found in about two thirds of spiral galaxies, and are thought to act as funnels, guiding gas to their galactic centres where it accumulates to form newborn stars. These aren’t permanent structures: astronomers think that they slowly disperse over time, so that the galaxies eventually evolve into regular spirals. The appearance of a galaxy changes little over millions of years, but this image also contains a …

13 December 2010: The NASA/ESA Hubble Space Telescope has turned its eagle eye to the planetary nebula NGC 6572, a very bright example of these strange but beautiful objects. Planetary nebulae are created during the late stages of the evolution of certain stars that eject gas into space and emit intense ultraviolet radiation that makes the material glow. This picture of NGC 6572 shows the intricate shapes that can develop as stars exhale their last breaths. Hubble has even imaged the central white dwarf star, the origin of the dazzling nebula, but now a faint, but hot, vestige of its former glory. NGC 6572 only began to shed its gases a few thousand years ago, so it is a fairly young planetary nebula. As a result the material is still quite concentrated, which explains why it is abnormally bright. The envelope of gas is currently racing out into space at a speed of …

6 December 2010: The star cluster is very bright and was discovered in the mid-eighteenth century. The nebula, however, is much more elusive and it took almost a further two decades for it to be first noted by Charles Messier in 1764. Although it is commonly known as the Eagle Nebula, its official designation is Messier 16 and the cluster is also named NGC 6611. One spectacular area of the nebula (outside the field of view) has been nicknamed “The Pillars of Creation” ever since the Hubble Space Telescope captured an iconic image of dramatic pillars of star-forming gas and dust. The cluster and nebula are fascinating targets for small and medium-sized telescopes, particularly from a dark site free from light pollution. Messier 16 can be found within the constellation of Serpens Cauda (the Tail of the Serpent), which is sandwiched between Aquila, Sagittarius, and Ophiuchus in the heart of one of the …

29 November 2010: Fresh starbirth infuses the galaxy NGC 6503 with a vital pink glow in this image from the NASA/ESA Hubble Space Telescope. This galaxy, a smaller version of the Milky Way, is perched near a great void in space where few other galaxies reside. This new image from Hubble’s Advanced Camera for Surveys displays, with particular clarity, the pink-coloured puffs marking where stars have recently formed in NGC 6503's swirling spiral arms. Although structurally similar to the Milky Way, the disc of NGC 6503 spans just 30 000 light-years, or just about a third of the size of the Milky Way, leading astronomers to classify NGC 6503 as a dwarf spiral galaxy. NGC 6503 lies approximately 17 million light-years away in the constellation of Draco (the Dragon). The German astronomer Arthur Auwers discovered this galaxy in July 1854 in a region of space where few other luminous bodies have been found. …

22 November 2010: Smaller, dimmer galaxies appear to flit like moths around a radiant street light in this image captured by the NASA/ESA Hubble Space Telescope. The brilliant central object is a supergiant elliptical galaxy, the dominant member of a galaxy cluster with the mouthful of a name MACSJ1423.8+2404. This great swarm of galaxies is located about five billion light-years away in the constellation Boötes (the Herdsman). MACSJ1423.8+2404 and other distant galaxy clusters offer astronomers a peek into the earlier days of our Universe when these colossal groupings were still taking shape. Over the 13.7 billion-year history of the cosmos, such galaxy clusters have emerged as the largest observed gravitationally bound structures. But there is much more than meets the eye when it comes to galaxy clusters — they also hint at the vast majority of the Universe’s substance that we have not yet directly detected. Astronomers study clusters such as MACSJ1423.8+2404 to …

15 November 2010: The NASA/ESA Hubble Space Telescope has used its Advanced Camera for Surveys to peer closely at the strange cloud of gas and dust that envelops a star at a late stage in its life, a short-lived phenomenon known as a protoplanetary, or pre-planetary nebula. These fascinating celestial objects give astronomers an opportunity to watch the early stages of planetary nebula formation, as the gas and dust is moulded by high velocity winds — like watching a glassblower at work in his factory. Despite their rather confusing names, these objects are unrelated to planets. The name arose because of the superficial visual similarity between planetary nebulae and the small discs of the outer planets in the Solar System when viewed through a telescope.The protoplanetary nebula shown in this image is known as IRAS 20068+4051 and it is found in the constellation of Cygnus. The shell formed when its progenitor star exhausted …

8 November 2010: The NASA/ESA Hubble Space Telescope has imaged a striking galaxy called NGC 4452, which appears to lie exactly edge-on as seen from Earth. The result is an extraordinary picture of billions of stars observed from an unusual angle. The bright nucleus can be seen at the centre, along with the very thin disc that looks like a straight line from our unusual viewing position. To complete the picture, a hazy halo of stars on the periphery of the galaxy makes it seem to glow.NGC 4452 was first seen by William Herschel in 1784 with his 47 cm telescope in England. He described the object as a bright nebula, small and very much elongated. The new Hubble image shows just how elongated this unusual object really is.Galaxies are like star cities, and typically contain many billions of stars. The American astronomer Edwin Hubble, after whom the Hubble Space Telescope is named, …

1 November 2010: At first glance NGC 3077 looks like a typical, relatively peaceful elliptical galaxy. However, as this NASA/ESA Hubble Space Telescope image dramatically reveals it is actually a hotbed of very energetic star formation and the whole galaxy is laced with dusty tendrils. It lies about 13 million light-years from Earth.NGC 3077 was first seen by William Herschel with his 47 cm telescope in England in 1801, when he was close to completing his sky surveys. It is located in the far northern sky in the constellation of Ursa Major (the Great Bear) and forms a triplet with two brighter nearby galaxies, the graceful spiral Messier 81 and the very peculiar and active starburst galaxy Messier 82.Although overshadowed by its brighter neighbours, NGC 3077 is also very active and resembles a less dramatic version of Messier 82. Interactions between the three galaxies have stoked the fires of star formation in the …

25 October 2010: The NASA/ESA Hubble Space Telescope has turned its sharp eye towards a tight collection of stars, first seen 174 years ago. The result is a sparkling image of NGC 1806, tens of thousands of stars gravitationally bound into a rich cluster. Commonly called globular clusters, most of these objects are very old, having formed in the distant past when the Universe was only a fraction of its current age. NGC 1806 lies within the Large Magellanic Cloud, a satellite galaxy of our own Milky Way. It can be observed within the constellation of Dorado (the dolphin-fish), an area of the sky best seen from the Earth’s southern hemisphere. NGC 1806 was discovered in 1836 by the British astronomer John Herschel. He had travelled to South Africa in order to catalogue astronomical objects visible best from southern latitudes, and thereby complete work begun by his father William, the man who coined …

18 October 2010: The NASA/ESA Hubble Space Telescope has taken a striking high resolution image of the curious planetary nebula NGC 6210. Located about 6500 light-years away, in the constellation of Hercules, NGC 6210 was discovered in 1825 by the German astronomer Friedrich Georg Wilhelm Struve. Although in a small telescope it appears only as a tiny disc, it is fairly bright. NGC 6210 is the last gasp of a star slightly less massive than our Sun at the final stage of its life cycle. The multiple shells of material ejected by the dying star form a superposition of structures with different degrees of symmetry, giving NGC 6210 its odd shape. This sharp image shows the inner region of this planetary nebula in unprecedented detail, where the central star is surrounded by a thin, bluish bubble that reveals a delicate filamentary structure. This bubble is superposed onto an asymmetric, reddish gas formation where …

11 October 2010: The beautiful spiral galaxy NGC 406 was discovered in 1834 by John Herschel and is here imaged in great detail by the NASA/ESA Hubble Space Telescope. Located some 65 million light-years away, in the southern constellation of Tucana (the Toucan), NGC 406 is about 60 000 light-years across, roughly half the diameter of our galaxy, the Milky Way. It is a spiral galaxy quite similar to the well known Whirlpool galaxy (Messier 51, see http://www.spacetelescope.org/images/opo0110a/). In a moderate-sized amateur telescope NGC 406 would appear as a faint hazy blob, like thousands of others across the sky, and none of the spectacular fine detail in the Hubble picture could be made out. In this image the galaxy exhibits spiral arms that are mainly populated by young, massive, bluish stars and crossed by dark dust lanes. As is typically observed in this kind of spiral galaxy, the yellowish central bulge, dominated by …

4 October 2010: The keen eye of the NASA/ESA Hubble Space Telescope has often peered deeply into the Orion Nebula to see the processes occurring there and revealed many dramatic tableaux of young stars hurling material into space and entire solar systems forming. This image shows the spectacular region around an object known as Herbig-Haro 502, a very small part of the vast stellar nursery. The entire picture is filled with the rich colourful glow of the nebula and, just left of the centre, a star embedded in a pinkish glow can be also seen. This fascinating object is an example of a very young star surrounded by the cloud of gas from which it formed. This leftover material may accrete to form planets and eventually solar systems as intricate as our own. It is highly likely that the material that now forms our own planet Earth was part of a similar gaseous …

27 September 2010: This bright spray of stars in the small but evocative constellation of Delphinus (the Dolphin) is the globular cluster NGC 6934. Globular clusters are large balls of (typically) a few hundred thousand ancient stars that exist on the edges of galaxies. Lying 50 000 light-years from Earth, in the outer reaches of our Milky Way galaxy, NGC 6934 is home to some of the most distant stars still to be part of our galactic system — in a sense, it is a far-flung suburb to the Milky Way’s city centre. NGC 6934 was first seen by William Herschel in the late eighteenth century. He classified it as a “bright nebula” and was not able to resolve it into stars. The cluster is not bright enough to see with the naked eye, and even in ideal conditions it is very difficult to view with binoculars. However, it is a popular target …

20 September 2010: The NASA/ESA Hubble Space Telescope snapped this striking image of an aging star whose outer layers of gas have blown off into space. These gases glow in the fierce ultraviolet glare from the hot, small remnant of the star at the cloud's centre. This object, which is designated NGC 6741, also known as the Phantom Streak Nebula, is located about 7000 light-years away in the constellation of Aquila (the Eagle). NGC 6741 is classed as a planetary nebula, though no planets are responsible for this billowy cloud; the term came about in the 18th century because the round gas shells resembled the Solar System's outer giant planets in astronomers' telescopes. Although fairly bright, this object appears very small though a typical telescope and was missed by early surveyors of the skies and only spotted in 1882 by Edward Charles Pickering. Stars with sizes that are somewhat smaller than our Sun …

13 September 2010: Astronomers are used to encountering challenges in their work, but studying the prosaically-named galaxy PGC 39058 proves more difficult than usual. Due to a stroke of bad luck, a bright star happens to lie between the galaxy and the Earth, meaning our view is partly obscured by the glare of the star. The astounding image from the NASA/ESA Hubble Space Telescope shows the nearby star easily outshining the more distant galaxy PGC 39058. The galaxy is about 14 million light-years away and contains millions of stars — many of them not unlike the bright star in the foreground. The bright foreground star seems to shine with incredible intensity due to the power of Hubble. Most Earth-bound observers would however consider the star to be quite faint. At magnitude 6.7, binoculars or a small telescope are needed to see it at all. That the image manages to capture both objects serves …

6 September 2010: This remarkable picture from the Advanced Camera for Surveys on the NASA/ESA Hubble Space Telescope shows one of the most perfect geometrical forms created in space. It captures the formation of an unusual pre-planetary nebula, known as IRAS 23166+1655, around the star LL Pegasi (also known as AFGL 3068) in the constellation of Pegasus (the Winged Horse). The striking picture shows what appears to be a thin spiral pattern of astonishingly regularity winding around the star, which is itself hidden behind thick dust. The spiral pattern suggests a regular periodic origin for the nebula’s shape. The material forming the spiral is moving outwards a speed of about 50 000 km/hour and, by combining this speed with the distance between layers, astronomers calculate that the shells are each separated by about 800 years.The spiral is thought to arise because LL Pegasi is a binary system, with the star that is losing …

30 August 2010: A billowing cloud of hydrogen in the Triangulum galaxy (Messier 33), about 2.7 million light-years away from Earth, glows with the energy released by hundreds of young, bright stars. This NASA/ESA Hubble Spare Telescope image provides the sharpest view of NGC 604 so far obtained. Some 1500 light-years across, this is one of the largest, brightest concentrations of ionised hydrogen (H II) in our local group of galaxies, and is a major centre of star formation. The gas in NGC 604, around nine tenths of it hydrogen, is gradually collapsing under the force of gravity to create new stars. Once these stars have formed, the vigorous ultraviolet radiation they emit excites the remaining gas in the cloud, making it glow a distinct shade of red. This colour is typical not only of NGC 604 but of other H II regions too. Although it is part of Messier 33 this object …

23 August 2010: This spectacular NASA/ESA Hubble Space Telescope image shows a bright scattering of stars in the small constellation of Sagitta (the Arrow). This is the centre of the globular cluster Messier 71, a great ball of ancient stars on the edge of our galaxy around 13 000 light-years from Earth. M71 is around 27 light-years across. Globular clusters are like galactic suburbs, pockets of stars that exist on the edge of major galaxies. These clusters are tightly bound together by their gravitational attraction, hence their spherical shape and their name: globulus means “little sphere” in Latin. Around 150 such globular clusters are known to exist around our Milky Way, each one of them containing several hundred thousand stars. Messier 71 has been known for a long time, having been first spotted in the mid eighteenth century by Swiss astronomer Jean-Philippe de Cheseaux. Cheseaux discovered a number of nebulae in his career, …

16 August 2010: At first glance, the scatter of pale dots on this NASA/ESA Hubble Space Telescope image looks like a snowstorm in the night sky. But almost every one of these delicate snowflakes is a distant galaxy in the cluster MACS J0717.5+3745 and each is home to billions of stars. This apparently placid scene also hides a storm of epic scale. This picture shows a region where three galaxy clusters are merging and releasing enormous amounts of energy in the form of X-rays. These distant objects are around 5.4 billion light-years from Earth, and were imaged during the Massive Cluster Survey, a project to study distant clusters of galaxies using Hubble. The amount of mass in this sea of galaxies is huge, and is great enough to visibly bend the fabric of spacetime. The strange distortion in the shapes of many of the galaxies in this picture, which appear stretched and bent …

9 August 2010: Haro 11 appears to shine gently amid clouds of gas and dust, but this placid facade belies the monumental rate of star formation occurring in this “starburst” galaxy. By combining data from the NASA/ESA Hubble Space Telescope and ESO’s Very Large Telescope, astronomers have created a new image of this incredibly bright and distant galaxy. The team of astronomers from Stockholm University, Sweden, and the Geneva Observatory, Switzerland, have identified 200 separate clusters of very young, massive stars. Most of these are less than 10 million years old. Many of the clusters are so bright in infrared light that astronomers suspect that the stars are still emerging from the cloudy cocoons where they were born. The observations have led the astronomers to conclude that Haro 11 is most likely the result of a merger between a galaxy rich in stars and a younger, gas-rich galaxy. Haro 11 is found to …

2 August 2010: This dramatic image from the NASA/ESA Hubble Space Telescope shows the planetary nebula NGC 3918, a brilliant cloud of colourful gas in the constellation of Centaurus, around 4900 light-years from Earth. In the centre of the cloud of gas, and completely dwarfed by the nebula, are the dying remnants of a red giant. During the final convulsive phase in the evolution of these stars, huge clouds of gas are ejected from the surface of the star before it emerges from its cocoon as a white dwarf. The intense ultraviolet radiation from the tiny remnant star then causes the surrounding gas to glow like a fluorescent sign. These extraordinary and colourful planetary nebulae are among the most dramatic sights in the night sky, and often have strange and irregular shapes, which are not yet fully explained. NGC 3918’s distinctive eye-like shape, with a bright inner shell of gas and a more …

26 July 2010: This NASA/ESA Hubble Space Telescope picture depicts the galaxy NGC 1533 in the southern constellation of Dorado (the Dolphin-fish). Around 62 million light-years from Earth, NGC 1533, which is classed as a lenticular galaxy, is a transitional type that shows characteristics of both spiral and elliptical galaxies. Like elliptical galaxies, NGC 1533 is largely made up of older and redder stars and vast numbers of them create the smooth glow across the whole picture. However, it also has a residual level of star formation and some young blue stars, which are revealed by its weak barred spiral structure that is faintly visible in this image. Astronomers studying star formation in this type of galaxy are able to subtract the bright light of the stars to reveal the details of a subtle spiral structure that cannot be well seen in less heavily processed images such as this one. John Herschel, son …

19 July 2010: This spectacular NASA/ESA Hubble Space Telescope picture shows NGC 1872, a rich cluster of thousands of stars lying in our small neighbouring galaxy, the Large Magellanic Cloud. This little-studied cluster is located in the constellation of Dorado (the Dolphinfish, a fish unrelated to the dolphin and which often appears on dinner menus under its Hawaiian name mahi-mahi). The Scottish astronomer James Dunlop was probably the first to spot NGC 1872 in 1826 with a small telescope near Sydney in Australia. Clusters are very interesting to astronomers because the stars in them all formed together in both space and time and hence the stars we see now are of similar ages and similar initial composition. Cluster studies have been vital in working out how stars evolve and the power of Hubble allows these studies to be taken beyond our own Milky Way and out into the Local Group of our neighbouring …

12 July 2010: This Hubble Space Telescope picture captures a brief but beautiful phase late in the life of a star. The curious cloud around this bright star is called IRAS 19475+3119. It lies in the constellation of Cygnus (the Swan) about 15 000 light-years from Earth in the plane of our Milky Way galaxy. As stars similar to the Sun age they swell into red giant stars and when this phase ends they start to shed their atmospheres into space. The surroundings become rich in dust and the star is still relatively cool. At this point the cloud shines by reflecting the brilliant light of the central star and the warm dust gives off lots of infrared radiation. It was this infrared radiation that was detected by the IRAS satellite in 1983 and brought the object to the attention of astronomers. Jets from the star may create strange hollow lobes, and in …

5 July 2010: This image, taken by the Advanced Camera for Surveys on the Hubble Space Telescope, shows the core of the great globular cluster Messier 13 and provides an extraordinarily clear view of the hundreds of thousands of stars in the cluster, one of the brightest and best known in the sky. Just 25 000 light-years away and about 145 light-years in diameter, Messier 13 has drawn the eye since its discovery by Edmund Halley, the noted British astronomer, in 1714. The cluster lies in the constellation of Hercules and is so bright that under the right conditions it is even visible to the unaided eye. As Halley wrote: “This is but a little Patch, but it shews it self to the naked Eye, when the Sky is serene and the Moon absent.” Messier 13 was the target of a symbolic Arecibo radio telescope message that was sent in 1974, communicating humanity’s …

28 June 2010: The Hubble Space Telescope captured this beautiful image of NGC 6326, a planetary nebula with glowing wisps of outpouring gas that are lit up by a central star nearing the end of its life. When a star ages and the red giant phase of its life comes to an end, it starts to eject layers of gas from its surface leaving behind a hot and compact white dwarf. Sometimes this ejection results in elegantly symmetric patterns of glowing gas, but NGC 6326 is much less structured. This object is located in the constellation of Ara, the Altar, about 11 000 light-years from Earth. Planetary nebulae are one of the main ways in which elements heavier than hydrogen and helium are dispersed into space after their creation in the hearts of stars. Eventually some of this outflung material may form new stars and planets. The vivid red and blue hues in …

21 June 2010: The small spiral galaxy NGC 2758 is captured in great detail in this image from the Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope. It was first seen by the American astronomer Frank Muller, at the McCormick Observatory in Virginia in the 1880s. This galaxy lies in the constellation of Hydra (the Sea Serpent), the largest and longest constellation in the sky. This very sharp Hubble image shows many of the bright blue stars within the galaxy’s loosely wound spiral arms as well as a bright companion dwarf galaxy to the upper left. Many more distant galaxies lie in the background. NGC 2758 is a fine example of a spiral galaxy that is close enough for the structure to be seen very clearly. In this case the Hubble images were obtained as part of a study of the central redder “bulge” component of galaxies and how they …

14 June 2010: The little-known nebula IRAS 05437+2502 billows out among the bright stars and dark dust clouds that surround it in this striking image from the Hubble Space Telescope. It is located in the constellation of Taurus (the Bull), close to the central plane of our Milky Way galaxy. Unlike many of Hubble’s targets, this object has not been studied in detail and its exact nature is unclear. At first glance it appears to be a small, rather isolated, region of star formation and one might assume that the effects of fierce ultraviolet radiation from bright young stars probably were the cause of the eye-catching shapes of the gas. However, the bright boomerang-shaped feature may tell a more dramatic tale. The interaction of a high velocity young star and the cloud of gas and dust may have created this unusually sharp-edged bright arc. Such a reckless star would have been ejected from …

7 June 2010: The star HD 44179 is surrounded by an extraordinary structure known as the Red Rectangle. It acquired its moniker because of its shape and its apparent colour when seen in early images from Earth. This strikingly detailed new Hubble image reveals how, when seen from space, the nebula, rather than being rectangular, is shaped like an X with additional complex structures of spaced lines of glowing gas, a little like the rungs of a ladder. The star at the centre is similar to the Sun, but at the end of its lifetime, pumping out gas and other material to make the nebula, and giving it the distinctive shape. It also appears that the star is a close binary that is surrounded by a dense torus of dust — both of which may help to explain the very curious shape. Precisely how the central engine of this remarkable and unique object …

31 May 2010: The bright galaxy NGC 3810 demonstrates classical spiral structure in this very detailed image from Hubble. The bright central region is thought to be forming many new stars and is outshining the outer areas of the galaxy by some margin. Further out the galaxy displays strikingly rich dust clouds along its spiral arms. A close look shows that Hubble’s sharp vision also allows many individual stars to be seen. Hot young blue stars show up in giant clusters far from the centre and the arms are also littered with bright red giant stars. The original images were acquired by astronomers studying a supernova discovered late in the year 2000. It was the second supernova found in the galaxy in quick succession following another discovered in 1997. NGC 3810 is located about 50 million light-years from Earth in the constellation of Leo (the lion). It was discovered by William Herschel in …

24 May 2010: This remarkable and unique image of the space shuttle Atlantis and the NASA/ESA Hubble Space Telescope silhouetted against the dazzling disc of the Sun was captured from the ground near the start of the Servicing Mission 4 on 13 May 2009. The picture was taken from Florida, 100 kilometres south of the Kennedy Space Center as Hubble was about to be grappled by the Shuttle’s robot arm. The Shuttle and Hubble appear as small black specks at the lower left, the Shuttle is the larger of the two. The solar disc was unusually quiet in a deep solar minimum and there are no sunspots visible. The image was acquired with a 130 mm aperture refracting telescope equipped with a special solar prism to reduce the intensity along with a standard digital camera. The transit across the disc of the Sun took less than one second and the path across the …

17 May 2010: That galaxies come in very different shapes and sizes is dramatically demonstrated by this striking Hubble image of the Hickson Compact Group 59. Named by astronomer Paul Hickson in 1982, this is the 59th such collection of galaxies in his catalogue of unusually close groups. What makes this image interesting is the variety on display. There are two large spiral galaxies, one face-on with smooth arms and delicate dust tendrils, and one highly inclined, as well as a strangely disorderly galaxy featuring clumps of blue young stars. We can also see many apparently smaller, probably more distant, galaxies visible in the background. Hickson groups display many peculiarities, often emitting in the radio and infrared and featuring active star-forming regions. In addition their galaxies frequently contain Active Galactic Nuclei powered by supermassive black holes, as well large quantities of dark matter. The NASA/ESA Hubble Space Telescope's Advanced Camera for Surveys, using …

10 May 2010: This striking Hubble image of the planetary nebula IC 4634 reveals two shining, S-shaped ejections from a dying star. This star, awash in glowing material at the centre of the picture, bloated as it aged and launched its outer layers off into space. The star’s very hot, exposed core has since beamed intense ultraviolet radiation at these lost shells of gas, making them glow in rich colours. This process has been far from orderly or calm, however, as revealed by the distinct, separate waves of thrown-off gases. One is more distant and therefore was spewed first, followed by a more recently ejected tide of matter that formed the tighter S-shape. The result is remarkably symmetric on each side of the central star. The NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2 (WFPC2) captured this image of IC 4634, which is found more than about 7500 light-years away in the …

3 May 2010: The richly textured spiral galaxy NGC 2082 is found about 60 million light-years away in the constellation of Dorado (the Swordfish), deep in the southern sky. As seen here in a very detailed image from the Advanced Camera for Surveys on the NASA/ESA Hubble Space Telescope, filaments of dark dust splay across NGC 2082’s luminous curved arms and dense central bulge of stars. Hubble’s sharp vision also reveals many of the individual bright blue stars dotting the galaxy’s rather ragged spiral arms as well as many much more distant galaxies in the background. This galaxy is faintly visible in backyard telescopes and was first recorded by Sir John Herschel during his visit to the Cape of Good Hope in South Africa in the 1830s. NGC 2082 was also the host of a bright supernova that was spotted by the great visual supernova discoverer Rev R. Evans back in 1992. This …

22 April 2010: As the first in the new weekly series of spectacular images from the NASA/ESA Hubble Space Telescope, the Hubble Picture of the Week, ESA/Hubble presents a stunning image of an unfamiliar star cluster. This rich collection of scattered stars, known as Messier 72, looks like a city seen from an airplane window at night, as small glints of light from suburban homes dot the outskirts of the bright city centre. Messier 72 is actually a globular cluster, an ancient spherical collection of old stars packed much closer together at its centre, like buildings in the heart of a city compared to less urban areas. As well as huge numbers of stars in the cluster itself the picture also captures the images of many much more distant galaxies seen between and around the cluster stars. French astronomer Pierre Méchain discovered this rich cluster in August of 1780, but we take Messier …