Knots and bursts: In the northern constellation of Coma Berenices (Berenice's Hair) lies the impressive Coma Cluster — a structure of over a thousand galaxies bound together by gravity. Many of these galaxies are elliptical types, as is the brighter of the two galaxies dominating this image: NGC 4860 (centre). However, the outskirts of the cluster also host younger spiral galaxies that proudly display their swirling arms. Again, this image shows a wonderful example of such a galaxy in the shape of the beautiful NGC 4858, which can be seen to the left of its bright neighbour and which stands out on account of its unusual, tangled, fiery appearance.
NGC 4858 is special. Rather than being a simple spiral, it is something called a “galaxy aggregate”, which is, just as the name suggests, a central galaxy surrounded by a handful of luminous knots of material that seem to stem from it, extending and tearing away and adding to or altering its overall structure. It is also experiencing an extremely high rate of star formation, possibly triggered by an earlier interaction with another galaxy. As we see it, NGC 4858 is forming stars so frantically that it will use up all of its gas long before it reaches the end of its life. The colour of its bright knots indicates that they are formed of hydrogen, which glows in various shades of bright red as it is energised by the many young, hot stars lurking within.
This scene was captured by the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3), a powerful camera designed to explore the evolution of stars and galaxies in the early Universe.

Name: NGC 4858, NGC 4860
Type: Local Universe : Galaxy : Type : SpiralLocal Universe : Galaxy : Type : EllipticalLocal Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Coma Berenices
Distance: 300 million light years
Release date: 17 September 2018, 06:00
Credit: ESA/Hubble & NASA

Warped and distorted: This NASA/ESA Hubble Space Telescope image contains a veritable mix of different galaxies, some of which belong to the same larger structure: At the middle of the frame sits the galaxy cluster SDSS J1050+0017. The gigantic mass of this cluster creates the fascinating phenomenon of strong ravitational lensing. The gravity of the cluster bends light coming from behind it in a similar way to how the base of a wine glass bends light. The effects of this lensing can be clearly seen as curved streaks forming a circular shape around the centre of the frame. Astronomers can use these distorted galaxies to calculate the mass of the cluster — including the mass of the dark matter within it — and to peer deeper into the Universe as otherwise possible. Gravitational lensing does not only distorts the views of galaxies, it also enlarge their appearance on the sky and magnifies their light. Hubble has viewed gravitational lensing many times, and produced truly stunning images. Astronomers even set up a dedicated programme to study different galaxy clusters which show a great number of lensed galaxies: The Frontier Fields programme. This way some of the most distant galaxies in the Universe were found. With each additional cluster being observed some more distant galaxies are added to this list, slowly completing our picture of how galaxies looked and evolved in the early Universe.

Name: ClG J1050+0017, SDSS J1050+0017
Type: Early Universe : Galaxy : Grouping : ClusterEarly Universe : Cosmology : Phenomenon : Lensing
Category: Galaxies
Constellation: Sextans
Release date: 24 September 2018, 06:00
Credit: ESA/Hubble & NASAAcknowledgement: Judy Schmidt

Celestial fairy lights: This glittering ball of stars is the globular cluster NGC 1898, which lies towards the centre of the Large Magellanic Cloud — one of our closest cosmic neighbours. The Large Magellanic Cloud is a dwarf galaxy that hosts an extremely rich population of star clusters, making it an ideal laboratory for investigating star formation. Discovered in November 1834 by British astronomer John Herschel, NGC 1898 has been scrutinised numerous times by the NASA/ESA Hubble Space Telescope. Today we know that globular clusters belong to the oldest known objects in the Universe and that they are relics of the first epochs of galaxy formation. While we already have a pretty good picture on the globular clusters of the Milky Way — still with many unanswered questions — our studies on globular clusters in nearby dwarf galaxies just started. The observations of NGC 1898 will help to determine if their properties are similar to the ones found in the Milky Way, or if they have different features, due to being in a different cosmic environment. This image was taken by Hubble’s Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). The WFC3 observes light ranging from near-infrared to near-ultraviolet wavelengths, while the ACS explores the near-infrared to the ultraviolet.

Name: Large Magellanic Cloud, NGC 1898
Type: Local Universe : Star : Grouping : Cluster : Globular
Category: Star Clusters
Constellation: Dorado
Distance: 170000 light years
Release date: 1 October 2018, 06:00
Credit: ESA/Hubble & NASA

Rings upon rings: This image from the NASA/ESA Hubble Space Telescope reveals a spiral galaxy named Messier 95 (also known as M95 or NGC 3351). Located about 35 million light-years away in the constellation of Leo (The Lion), this swirling spiral was discovered by astronomer Pierre Méchain in 1781, and catalogued by French astronomer Charles Messier just four days later. Messier was primarily a comet hunter, and was often left frustrated by objects in the sky that resembled comets but turned out not to be. To help other astronomers avoid confusing these objects in the future, he created his famous catalogue of Messier objects. Most definitely not a comet, Messier 95 is actually a barred spiral galaxy. The galaxy has a bar cutting through its centre, surrounded by an inner ring currently forming new stars. Also our own Milky Way is a barred spiral. As well as hosting this stellar nursery, Messier 95 is a known host of the dramatic and explosive final stages in the lives of massive stars: supernovae. In March 2016 a spectacular supernova named SN 2012aw was observed in the outer regions of one of Messier 95’s spiral arms. Once the light from the supernova had faded, astronomers were able to compare observations of the region before and after the explosion to find out which star had “disappeared” — the progenitor star. In this case, the star was an especially huge red supergiant up to 26 times more massive than the Sun.

Name: Messier 95
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Leo
Distance: 35 million light years
Release date: 8 October 2018, 06:00
Credit: ESA/Hubble & NASA