This is no supermodel spiral: The NASA/ESA Hubble Space Telescope observes some of the most beautiful galaxies in our skies — spirals sparkling with bright stellar nurseries (heic1403), violent duos ripping gas and stars away from one another as they tangle together (heic1311), and ethereal irregular galaxies that hang like flocks of birds suspended in the blackness of space (heic1114, heic1207). However, galaxies, like humans, are not all supermodels. This little spiral, known as NGC 4102, has a different kind of appeal, with its tightly-wound spiral arms and understated, but charming, appearance. NGC 4102 lies in the northern constellation of Ursa Major (The Great Bear). It contains what is known as a LINER, or low-ionization nuclear emission-line region, meaning that its nucleus emits particular types of radiation — specifically, emission from weakly-ionised or neutral atoms of certain elements. Even in this sense, NGC 4102 is not special; around one third of all nearby galaxies are thought to be LINER galaxies. Many LINER galaxies also contain intense regions of star formation. This is thought to be intrinsically linked to their centres but just why is still a mystery for astronomers — either the starbursts pour fuel inwards to fuel the LINERs, or this active central region triggers the starbursts. NGC 4102 does indeed contain a starburst region towards its centre, where stars are being created at a rate much more furious than in a normal galaxy. This star formation is taking place within a small rotating disc, around 1000 light-years in diameter and with a mass some three billion times the mass of the Sun. This image uses infrared and visible observations taken using Hubble’s Wide Field Planetary Camera 2. A version of this image was submitted to the Hubble's Hidden Treasures image processing competition by contestant Renaud Houdinet. A team of astronomers led by Stephen Smartt of Queen's University Belfast, the Principal Investigator for the observations making up this image, have spent the last 15 years searching for the progenitor stars of supernovae in galaxy images like this. A recent review article explores some of the results from such studies.

Name: NGC 4102
Type: Local Universe : Galaxy : Type : SpiralLocal Universe : Galaxy : Activity : AGN : Liner
Category: Galaxies
Constellation: Ursa Major
Release date: 1 December 2014, 10:00
Credit: ESA/Hubble, NASA and S. Smartt (Queen's University Belfast) Acknowledgement: Renaud Houdinet

All that glitters: This striking new NASA/ESA Hubble Space Telescope image shows a glittering bauble named Messier 92. Located in the northern constellation of Hercules, this globular cluster — a ball of stars that orbits a galactic core like a satellite — was first discovered by astronomer Johann Elert Bode in 1777. Messier 92 is one of the brightest globular clusters in the Milky Way, and is visible to the naked eye under good observing conditions. It is very tightly packed with stars, containing some 330 000 stars in total. As is characteristic of globular clusters, the predominant elements within Messier 92 are hydrogen and helium, with only traces of others. It is actually what is known as an Oosterhoff type II (OoII) globular cluster, meaning that it belongs to a group of metal-poor clusters — to astronomers, metals are all elements heavier than hydrogen and helium. By exploring the composition of globulars like Messier 92, astronomers can figure out how old these clusters are. As well as being bright, Messier 92 is also old, being one of the oldest star clusters in the Milky Way, with an age almost the same as the age of the Universe. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Gilles Chapdelaine.

Name: Messier 92
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Hercules
Distance: 25000 light years
Release date: 8 December 2014, 10:00
Credit: ESA/Hubble & NASA Acknowledgement: Gilles Chapdelaine

A messy star factory: This sprinkle of cosmic glitter is a blue compact dwarf galaxy known as Markarian 209. Galaxies of this type are blue-hued, compact in size, gas-rich, and low in heavy elements. They are often used by astronomers to study star formation, as their conditions are similar to those thought to exist in the early Universe. Markarian 209 in particular has been studied extensively. It is filled with diffuse gas and peppered with star-forming regions towards its core. This image captures it undergoing a particularly dramatic burst of star formation, visible as the lighter blue cloudy region towards the top right of the galaxy. This clump is filled with very young and hot newborn stars. This galaxy was initially thought to be a young galaxy undergoing its very first episode of star formation, but later research showed that Markarian 209 is actually very old, with an almost continuous history of forming new stars. It is thought to have never had a dormant period — a period during which no stars were formed — lasting longer than 100 million years. The dominant population of stars in Markarian 209 is still quite young, in stellar terms, with ages of under 3 million years. For comparison, the Sun is some 4.6 billion years old, and is roughly halfway through its expected lifespan. The observations used to make this image were taken using Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys, and span the ultraviolet, visible, and infrared parts of the spectrum. A scattering of other bright galaxies can be seen across the frame, including the bright golden oval that could, due to a trick of perspective, be mistaken as part of Markarian 209 but is in fact a background galaxy. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.

Name: Mrk 209, UGCA 281
Type: Local Universe : Galaxy : Size : Dwarf
Category: Galaxies
Constellation: Canes Venatici
Release date: 15 December 2014, 10:00
Credit: ESA/Hubble & NASA Acknowledgement: Nick Rose