Picture of the Week

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 …