Doing cartwheels to celebrate the end of an era: 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 smaller galaxy has passed right through a large disc galaxy and produced shock waves that swept up gas and dust — much like the ripples produced when a stone is dropped into a lake — and sparked regions of intense star formation (appearing blue). The outermost ring of the galaxy, which is 1.5 times the size of our Milky Way, marks the shock wave’s leading edge. This object is one of the most dramatic examples of the small class of ring galaxies.This image was produced after Hubble data was reprocessed using the free open source software FITS Liberator 3, which was developed at the ST-ECF. Careful use of this widely used state-of-the-art tool on the original Hubble observations of the Cartwheel Galaxy has brought out more detail in the image than ever before. Although the ST-ECF is closing, ESA’s mission to bring amazing Hubble discoveries to the public will be unaffected, with Hubblecasts, press and photo releases, and Hubble Pictures of the Week continuing to be regularly posted on spacetelescope.org.

Name: Cartwheel Galaxy
Type: Local Universe : Galaxy : Type : Ring
Category: Galaxies
Constellation: Sculptor
Distance: 500 million light years
Release date: 27 December 2010, 10:00
Credit: ESA/Hubble & NASA

Stellar powerhouses in the Eagle Nebula: 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 areas of apparent nothingness are actually very dense regions of gas and dust, which obstruct light from passing through. Many of these may be hiding the sites of the early stages of star formation, before the fledgling stars clear away their surroundings and burst into view. Dark nebulae, large and small, are dotted throughout the Universe. If you look up to the Milky Way with the naked eye from a dark, remote site, you can easily spot some huge dark nebulae blocking the background starlight.This picture was created from images from Hubble’s Wide Field Channel of the Advanced Camera for Surveys through the unusual combination of two near-infrared filters (F775W, coloured blue, and F850LP, coloured red). The image has also been subtly colourised using a ground-based image taken through more conventional filters. The Hubble exposure times were 2000 s in both cases and the field of view is about 3.2 arcminutes across.

Name: NGC 6611
Type: Local Universe : Star : Grouping : Cluster : Open
Category: Star Clusters
Constellation: Serpens Cauda
Distance: 6500 light years
Release date: 3 January 2011, 10:00
Credit: ESA/Hubble & NASA

Dying star cocooned within its own gases: 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 present in the nebula today, astronomers can determine the original chemical make-up of the star. Studies suggest that the star belonging to NGC 6886 may have originally been similar to the Sun, containing similar quantities of carbon, nitrogen and neon, although heavier elements, such as sulphur, were less plentiful. Keen amateur astronomers with mid-level telescopes will find it a rewarding challenge to track down NGC 6886 in the small constellation of Sagitta. It is tiny, but not particularly faint: high magnification, a good chart, a dark site and averted vision are needed to spot this elusive celestial jewel. This picture was created by combining images taken using the Wide Field Planetary Camera 2 on Hubble. Filters that let through emission from ionised nitrogen gas (F658N, coloured red), ionised oxygen (F502N, coloured blue) and a broadband yellow filter (F555W, coloured green, and also contributing to the blue) were used. The exposure times were 700 s, 600 s and 320 s respectively. The field of view is merely 30 arcseconds across.

Name: NGC 6886
Type: Local Universe : Nebula : Type : Planetary
Category: Nebulae
Constellation: Sagitta
Distance: 11000 light years
Release date: 10 January 2011, 10:00
Credit: ESA/Hubble & NASA