Islands of stars in the river: 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, lots more distant galaxies of many shapes and sizes can be seen in this image, some shining right through the foreground galaxy. NGC 1345 itself features an elongated bar extending from the nucleus and spiral arms that emanate outwards, making it a barred spiral type. Classifying galaxy shapes is an important part of astronomical research as it tells us much about how the Universe has evolved. But computers aren’t really ideal for the task; people are much better at recognising shapes, which is why a citizen-science project called Galaxy Zoo: Hubble is asking members of the public to help sift through the vast archive of images and classify galaxies by type. If you would like to join the cause, there’s a link to the project below. This picture was created from images taken with the Wide Field Channel of Hubble’s Advanced Camera for Surveys. Images taken through a blue filter (F435W) were coloured blue and images through a near-infrared filter (F814W) were coloured red. The exposure times were 17.5 minutes per filter in total and the field of view is 3.2 by 1.6 arcminutes. Links

Name: NGC 1345
Type: Local Universe : Galaxy : Type : Barred
Category: Galaxies
Constellation: Eridanus
Distance: 85 million light years
Release date: 17 January 2011, 10:00
Credit: ESA/Hubble & NASA

The secret of stellar youth: 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, which formed during our galaxy’s violent early history. However, astronomers suspect that globular youngsters, such as Palomar 1, formed in a more sedate manner. Possibly a gas cloud meandered around in the Milky Way’s halo until a trigger kick-started star formation. Another possibility is that the Milky Way captured the stellar group; perhaps it was adrift in the Universe before it was gravitationally attracted to our galaxy, or maybe it had a violent beginning after all and is the remnant of a dwarf galaxy that was devoured by the Milky Way. Behind the sparsely populated Palomar 1 several background galaxies are seen and a few nearby bright foreground Milky Way stars are also visible. Together with Palomar 1 these objects make up an attractive “family portrait”. This picture was created from images taken with the Wide Field Channel of the Advanced Camera for Surveys. Images through orange (F606W, coloured blue) and near-infrared (F814W, coloured red) filters were combined. The exposure times were 1965 s per filter and the field of view is 3.0 arcminutes across.

Name: Palomar 1
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Cepheus
Release date: 24 January 2011, 10:00
Credit: ESA/Hubble & NASA

The star city that never sleeps: 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 be seen from Earth in over 400 years. IC 391 lies about 80 million light-years away in the constellation of Camelopardalis (the Giraffe) in the far northern part of the sky. The British amateur observer William Denning discovered it in the late nineteenth century, and described it as faint, small and round. This picture was assembled from images taken with Hubble’s Wide Field Channel on the Advanced Camera for Surveys. Images through a blue filter (F435W) were coloured blue, those through a green filter (F555W) are shown as green and those through a near-infrared filter (F814W) are shown in red. The exposure times were 800 s, 700 s and 700 s respectively and the field of view is 2.1 by 1.4 arcminutes.

Name: IC 391
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Camelopardalis
Distance: 80 million light years
Release date: 31 January 2011, 10:00
Credit: ESA/Hubble & NASA