Hubble spies NGC 4394: Discovered in 1784 by the German–British astronomer William Herschel, NGC 4394 is a barred spiral galaxy situated about 55 million light-years from Earth. The galaxy lies in the constellation of Coma Berenices (Berenice's Hair), and is considered to be a member of the Virgo Cluster. NGC 4394 is the archetypal barred spiral galaxy, with bright spiral arms emerging from the ends of a bar that cuts through the galaxy’s central bulge. These arms are peppered with young blue stars, dark filaments of cosmic dust, and bright, fuzzy regions of active star formation. At the centre of NGC 4394 lies a region of ionised gas known as a LINER. LINERs are active regions that display a characteristic set of emission lines in their spectra— mostly weakly ionised atoms of oxygen, nitrogen and sulphur. Although LINER galaxies are relatively common, it’s still unclear where the energy comes from to ionise the gas. In most cases it is thought to be the influence of a black hole at the centre of the galaxy, but it could also be the result of a high level of star formation. In the case of NGC 4394, it is likely that gravitational interaction with a nearby neighbour has caused gas to flow into the galaxy’s central region, providing a new reservoir of material to fuel the black hole or to make new stars.

Name: NGC 4394
Type: Local Universe : Galaxy : Type : Barred
Category: Galaxies
Constellation: Coma Berenices
Distance: 55 million light years
Release date: 2 May 2016, 06:00
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (Geckzilla)

A spiral snowflake: Spiral galaxies together with irregular galaxies make up approximately 60% of the galaxies in the local Universe. However, despite their prevalence, each spiral galaxy is unique — like snowflakes, no two are alike. This is demonstrated by the striking face-on spiral galaxy NGC 6814, whose luminous nucleus and spectacular sweeping arms, rippled with an intricate pattern of dark dust, are captured in this NASA/ESA Hubble Space Telescope image. NGC 6814 has an extremely bright nucleus, a telltale sign that the galaxy is a Seyfert galaxy. These galaxies have very active centres that can emit strong bursts of radiation. The luminous heart of NGC 6814 is a highly variable source of X-ray radiation, causing scientists to suspect that it hosts a supermassive black hole with a mass about 18 million times that of the Sun. As NGC 6814 is a very active galaxy, many regions of ionised gas are studded along  its spiral arms. In these large clouds of gas, a burst of star formation has recently taken place, forging the brilliant blue stars that are visible scattered throughout the galaxy.

Name: NGC 6814
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Aquila
Distance: 75 million light years
Release date: 9 May 2016, 06:00
Credit: ESA/Hubble & NASA  Acknowledgement: Judy Schmidt (Geckzilla)

Busy bees: This NASA/ESA Hubble Space Telescope image shows star clusters encircling a galaxy, like bees buzzing around a hive. The hive in question the an edge-on lenticular galaxy NGC 5308, located just under 100 million light-years away in the constellation of Ursa Major (The Great Bear). Members of a galaxy type that lies somewhere between an elliptical and a spiral galaxy, lenticular galaxies such as NGC 5308 are disc galaxies that have used up, or lost, the majority of their gas and dust. As a result, they experience very little ongoing star formation and consist mainly of old and aging stars. On 9 October 1996, one of NGC 5308’s aging stars met a dramatic demise, exploding as a spectacular Type la supernova. Lenticular galaxies are often orbited by gravitationally bound collections of hundreds of thousands of older stars. Called globular clusters, these dense collections of stars form a delicate halo as they orbit around the main body of NGC 5308, appearing as bright dots on the dark sky. The dim, irregular galaxy to the right of NGC 5308 is known, rather prosaically, as SDSS J134646.18+605911.9

Name: NGC 5308
Type: Local Universe : Galaxy : Type : Lenticular
Category: Galaxies
Constellation: Ursa Major
Distance: 100 million light years
Release date: 16 May 2016, 06:00
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (Geckzilla)

A galactic gathering: Nearly as deep as the Hubble Ultra Deep Field, which contains approximately 10 000 galaxies, this incredible image from the NASA/ESA Space Telescope reveals thousands of colourful galaxies in the constellation of Leo (The Lion). This vibrant view of the early Universe was captured as part of the Frontier Fields campaign, which aims to investigate galaxy clusters in more detail than ever before, and to explore some of the most distant galaxies in the Universe. Galaxy clusters are massive. They can have a tremendous impact on their surroundings, with their immense gravity warping and amplifying the light from more distant objects. This phenomenon, known as gravitational lensing, can help astronomers to see galaxies that would otherwise be too faint, aiding our hunt for residents of the primordial Universe. MACS J1149.5+2223 is a galaxy cluster located approximately five billion light-years away. In 2012, it helped astronomers uncover one of the most distant galaxies ever discovered. Light from the young galaxy, magnified 15 times by the galaxy cluster, first shone when our 13.7-billion-year-old Universe was a mere 500 million years old — just 3.6 per cent of its current age! In 2014 and 2015, MACS J1149.5+2223 was observed as part of the Frontier Fields campaign. While one of Hubble’s cameras observed the galaxy cluster itself, another simultaneously captured the spectacular scene pictured above, of an “unremarkable” patch of space. Referred to as a parallel field, this image — when compared to other similar fields — will help astronomers understand how the Universe looks in different directions.

Type: Unspecified : Cosmology : Morphology : Deep Field
Category: Galaxies
Constellation: Leo
Release date: 23 May 2016, 06:00
Credit: ESA/Hubble & NASA  Acknowledgement: Judy Schmidt (Geckzilla)

A heavy-metal home: This 10.5-billion-year-old globular cluster, NGC 6496, is home to heavy-metal stars of a celestial kind! The stars comprising this spectacular spherical cluster are enriched with much higher proportions of metals — elements heavier than hydrogen and helium, are in astronomy curiously known as metals — than stars found in similar clusters. A handful of these high-metallicity stars are also variable stars, meaning that their brightness fluctuates over time. NGC 6496 hosts a selection of long-period variables — giant pulsating stars whose brightness can take up to, and even over, a thousand days to change — and short-period eclipsing binaries, which dim when eclipsed by a stellar companion. The nature of the variability of these stars can reveal important information about their mass, radius, luminosity, temperature, composition, and evolution, providing astronomers with measurements that would be difficult or even impossible to obtain through other methods. NGC 6496 was discovered in 1826 by Scottish astronomer James Dunlop. The cluster resides at about 35 000 light-years away in the southern constellation of Scorpius (The Scorpion).

Name: NGC 6496
Type: Milky Way : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Scorpius
Distance: 35000 light years
Release date: 30 May 2016, 06:00
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (Geckzilla)