A star's colourful final splash: 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 this image come from the material glowing under the action of the fierce ultraviolet radiation from the still hot central star. This picture was created from images taken using the Hubble Space Telescope’s Wide Field Planetary Camera 2. The red light was captured through a filter letting through the glow from hydrogen gas (F658N). The blue glow comes from ionised oxygen and was recorded through a green filter (F502N). The green layer of the image, which shows the stars well, was taken through a broader yellow filter (F555W). The total exposure times were 1400 s, 360 s and 260 s respectively. The field of view is about 30 arcseconds across.

Name: NGC 6326
Type: Milky Way : Nebula : Type : Planetary
Category: Nebulae
Constellation: Ara
Distance: 11000 light years
Release date: 28 June 2010, 10:00
Credit: ESA/Hubble and NASA

The crowded heart of the Hercules globular cluster: 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 existence to possible extraterrestrial intelligences. However, more recent studies suggest that planets are very rare in the dense environments of globular clusters. Messier 13 has also appeared in literature. In his 1959 novel, The Sirens of Titan, Kurt Vonnegut wrote “Every passing hour brings the Solar System forty-three thousand miles closer to Globular Cluster M13 in Hercules — and still there are some misfits who insist that there is no such thing as progress.” The step from Halley’s early telescopic view to this Hubble image indicates some measure of the progress in astronomy in the last three hundred years. This picture was created from images taken with the Wide Field Channel of the Advanced Camera for Surveys on the Hubble Space Telescope. Data through a blue filter (F435W) are coloured blue, data through a red filter (F625W) are coloured green and near-infrared data (through the F814W filter) are coloured red. The exposure times are 1480 s, 380 s and 567 s respectively and the field of view is about 2.5 arcminutes across.

Name: Messier 13
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Hercules
Distance: 25000 light years
Release date: 5 July 2010, 10:00
Credit: ESA/Hubble and NASA

A dying star starts shedding its skin: 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 the case of IRAS 19475+3119 two such features appear at different angles. These curious objects are rare and short-lived. As the star continues to shed material the hotter core is gradually revealed. The intense ultraviolet radiation causes the surrounding gas to glow brilliantly and a planetary nebula is born. The objects that come before planetary nebulae, such as IRAS 19475+3119, are known as preplanetary nebulae, or protoplanetary nebulae. They have nothing to do with planets — the name planetary nebula arose as they looked rather like the outer planets Uranus and Neptune when seen through small telescopes. This image was created from images taken using the High Resolution Channel of the Hubble Space Telescope’s Advanced Camera for Surveys. The red light was captured through a filter letting through yellow and red light (F606W) and the blue was recorded through a standard blue filter (F435W). The green layer of the image was created by combining the blue and red images. The total exposure times were 24 s and 245 s for red and blue respectively. The field of view is about twenty arcseconds across.

Name: IRAS 19475+3119
Type: Milky Way : Nebula : Type : Planetary
Category: Nebulae
Constellation: Cygnus
Distance: 15000 light years
Release date: 12 July 2010, 10:00
Credit: ESA/Hubble and NASA.

NGC 1872: open or globular cluster?: 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 galaxies. Star clusters are usually classed as either open or globular but NGC 1872 has characteristics of both — it is as rich as a typical globular but is much younger, and, like many open clusters, has bluer stars. Such intermediate clusters are common in the Large Magellanic Cloud. This image was acquired using the Wide Field Channel of the Advanced Camera for Surveys on the Hubble Space Telescope. It was created from images taken through yellow (F555W) and near-infrared (F814W) filters, coloured blue and red in the image. The exposure times were 115 s and 90 s respectively and the field of view is about 3.0 by 1.5 arcminutes.

Name: Large Magellanic Cloud, NGC 1872
Type: Local Universe : Star : Grouping : Cluster
Category: Star Clusters
Constellation: Dorado
Distance: 170000 light years
Release date: 19 July 2010, 10:00
Credit: ESA/Hubble and NASA