A spiral galaxy in Hydra: This image from the NASA/ESA Hubble Space Telescope shows NGC 4980, a spiral galaxy in the southern constellation of Hydra. The shape of NGC 4980 appears slightly deformed, something which is often a sign of recent tidal interactions with another galaxy. In this galaxy’s case, however, this appears not to be the case as there are no other galaxies in its immediate vicinity. The image was produced as part of a research program into the nature of galactic bulges, the bright, dense, elliptical centres of galaxies. Classical bulges are relatively disordered, with stars orbiting the galactic centre in all directions. In contrast, in galaxies with so-called pseudobulges, or disc-type bulges, the movement of the spiral arms is preserved right to the centre of the galaxy. Although the spiral structure is relatively subtle in this image, scientists have shown that NGC 4980 has a disc-type bulge, and its rotating spiral structure extends to the very centre of the galaxy. Galaxies’ bright arms are the location of new star formation in spiral galaxies, and NGC 4980 is no exception. The galaxy’s arms are traced out by blue pockets of extremely hot newborn stars are visible across much of its disc. This sets it apart from the reddish galaxies visible in the background, which are distant elliptical galaxies made up of much older, and hence redder, stars. This image is composed of exposures taken in visible and infrared light by Hubble’s Advanced Camera for Surveys. The image is approximately 3.3 by 1.5 arcminutes in size.

Name: NGC 4980
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Hydra
Distance: 80 million light years
Release date: 2 April 2012, 10:00
Credit: ESA/Hubble & NASA

Tight and bright: In this image, the NASA/ESA Hubble Space Telescope has captured the brilliance of the compact centre of Messier 70, a globular cluster. Quarters are always tight in globular clusters, where the mutual hold of gravity binds together hundreds of thousands of stars in a small region of space. Having this many shining stars piled on top of one another from our perspective makes globular clusters a popular target for amateur skywatchers and scientists alike. Messier 70 offers a special case because it has undergone what is known as a core collapse. In these clusters, even more stars squeeze into the object's core than on average, such that the brightness of the cluster increases steadily towards its centre. The legions of stars in a globular cluster orbit about a shared centre of gravity. Some stars maintain relatively circular orbits, while others loop out into the cluster's fringes. As the stars interact with each other over time, lighter stars tend to pick up speed and migrate out toward the cluster's edges, while the heavier stars slow and congregate in orbits toward the centre. This huddling effect produces the denser, brighter centres characteristic of core-collapsed clusters. About a fifth of the more than 150 globular clusters in the Milky Way have undergone a core collapse. Although many globular clusters call the galaxy's edges home, Messier 70 orbits close to the Milky Way's centre, around 30 000 light-years away from the Solar System. It is remarkable that Messier 70 has held together so well, given the strong gravitational pull of the Milky Way's hub. Messier 70 is only about 68 light-years in diameter and can be seen, albeit very faintly, with binoculars in dark skies in the constellation of Sagittarius (The Archer). French astronomer Charles Messier documented the object in 1780 as the seventieth entry in his famous astronomical catalogue. This picture was obtained with the Wide Field Camera of Hubble’s Advanced Camera for Surveys. The field of view is around 3.3 by 3.3 arcminutes.

Name: M 70
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Sagittarius
Distance: 30000 light years
Release date: 9 April 2012, 10:00
Credit: ESA/Hubble & NASA

Hubble peeks inside a stellar cloud: These bright stars shining through what looks like a haze in the night sky are part of a young stellar grouping in one of the largest known star formation regions of the Large Magellanic Cloud (LMC), a dwarf satellite galaxy of the Milky Way. The image was captured by the NASA/ESA Hubble Space Telescope’s Wide Field Planetary Camera 2. The stellar grouping is known to stargazers as NGC 2040 or LH 88. It is essentially a very loose star cluster whose stars have a common origin and are drifting together through space. There are three different types of stellar associations defined by their stellar properties. NGC 2040 is an OB association, a grouping that usually contains 10–100 stars of type O and B — these are high-mass stars that have short but brilliant lives. It is thought that most of the stars in the Milky Way were born in OB associations. There are several such groupings of stars in the LMC, including one previously featured as a Hubble Picture of the Week. Just like the others, LH 88 consists of several high-mass young stars in a large nebula of partially ionised hydrogen gas, and lies in what is known to be a supergiant shell of gas called LMC 4. Over a period of several million years, thousands of stars may form in these supergiant shells, which are the largest interstellar structures in galaxies. The shells themselves are believed to have been created by strong stellar winds and clustered supernova explosions of massive stars that blow away surrounding dust and gas, and in turn trigger further episodes of star formation. The LMC is the third closest galaxy to our Milky Way. It is located some 160 000 light-years away, and is about 100 times smaller than our own. This image, which shows ultraviolet, visible and infrared light, covers a field of view of approximately 1.8 by 1.8 arcminutes. A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant Eedresha Sturdivant. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public.

Name: NGC 2040
Type: Local Universe : Star : Grouping : Cluster
Category: Star Clusters
Constellation: Dorado
Distance: 150000 light years
Release date: 16 April 2012, 10:00
Credit: ESA/Hubble, NASA and D. A Gouliermis. Acknowledgement: Flickr user Eedresha Sturdivant