Fiery young stars wreak havoc in stellar nursery: 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 clouds are strikingly silhouetted against the glowing gas. NGC 2174 lies about 6400 light-years away in the constellation of Orion (The Hunter). It is not part of the much more familiar Orion Nebula, which lies much closer to us. Despite its prime position in a very familiar constellation this nebula is faint and had to wait until 1877 for its discovery by the French astronomer Jean Marie Edouard Stephan using an 80 cm reflecting telescope at the Observatoire de Marseille. This picture was created from images from the Wide Field Planetary Camera 2 on Hubble. Images through four different filters were combined to make the view shown here. Images through a filter isolating the glow from ionised oxygen (F502N) were coloured blue and images through a filter showing glowing hydrogen (F656N) are green. Glowing ionised sulphur (F673N) and the view through a near-infrared filter (F814W) are both coloured red. The total exposure times per filter were 2600 s, 2600 s, 2600 s and 1000 s  respectively and the field of view is about 1.8 arcminutes across.

Name: NGC 2174
Type: Milky Way : Nebula : Appearance : Emission : H II Region
Category: Nebulae
Constellation: Orion
Distance: 6500 light years
Release date: 7 February 2011, 10:00
Credit: ESA/Hubble & NASA

Old stars with a youthful glow: 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 dense globulars, like this one, underwent a process called core collapse, in which gravitational interactions between stars led to many members of the cluster migrating towards the centre. Messier 15 is also the first globular cluster known to harbour a planetary nebula, and it is still one of only four globulars known to do so. The planetary nebula, called Pease 1, can be seen in this image as a small blue blob to the lower left of the globular’s core. This picture was put together from images taken with the Wide Field Channel of Hubble's Advanced Camera for Surveys. Images through yellow/orange (F606W, coloured blue) and near-infrared (F814W, coloured red) filters were combined. The total exposure times were 535 s and 615 s respectively and the field of view is 3.4 arcminutes across.

Name: Messier 15
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Pegasus
Distance: 35000 light years
Release date: 14 February 2011, 10:00
Credit: ESA/Hubble & NASA

Perfect spiral overlaid with Milky Way gems: 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 the ends of their lives in NGC 6384, in the centre, star formation is being fuelled by the galaxy’s bar structure; astronomers think such galactic bars funnel gas inwards, where it accumulates to form new stars. This picture was created from images take with the Wide Field Channel of Hubble’s Advanced Camera for Surveys. An image taken through a blue filter (F435W, coloured blue) was combined with an image taken through a near-infrared filter (F814W, coloured red). The total exposure times were 1050 s through each filter and the field of view is about 3 x 1.5 arcminutes.

Name: NGC 6384
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Ophiuchus
Release date: 21 February 2011, 10:00
Credit: ESA/Hubble & NASA

Orion’s lesser-known nebula takes centre stage: 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 the brilliant hot young stars in this less-studied region and it also reveals many of the curious features around even younger stars that are still cocooned by dust. This picture was created from images taken using the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Images through yellow (F555W, coloured blue) and near-infrared (F814W, coloured red) filters were combined. The exposure times were 1000 s per filter and the field of view is about 3.3 arcminutes across.

Name: Messier 43
Type: Milky Way : Nebula : Type : Star Formation
Category: Nebulae
Constellation: Orion
Distance: 1400 light years
Release date: 28 February 2011, 10:00
Credit: ESA/Hubble & NASA