Beacon of Light: This image from the NASA/ESA Hubble Space Telescope shows the galaxy Messier 86. Despite its being discovered over 235 years ago by astronomer Charles Messier, the morphological classification of Messier 86 remains unclear; astronomers are still debating over whether it is either elliptical or lenticular (the latter being a cross between an elliptical and spiral galaxy). Messier 86 is part of the Virgo Cluster of galaxies and is situated about 50 million light-years from Earth. The galaxy is moving through space remarkably quickly  — its current trajectory is bringing it in our direction, back towards the centre of its cluster from the far side, at the incredible speed of over 875 000 kilometres per hour! Because of the speed with which it is moving through the cluster, Messier 86 is undergoing a process known as ram-pressure stripping; the resistive material filling the gaps between individual cluster galaxies is pulling at the gas and dust in Messier 86 and stripping them out as the galaxy moves, creating a long trail of hot gas that is emitting X-ray radiation. Astronomers are using Hubble observations such as this to study elliptical and lenticular galaxies, both of which are often found at the centres of galaxy clusters. By studying the cores of these galaxies, astronomers hope to determine details of the central structure and to analyse both the history of the galaxy and the formation of its core.

Name: Messier 86
Type: Local Universe : Galaxy : Type : Elliptical
Category: Galaxies
Constellation: Virgo
Release date: 23 September 2019, 06:00
Credit: ESA/Hubble & NASA, P. Cote et al.

Snakes and Stones: The galaxy pictured in this Hubble Picture of the Week has an especially evocative name: the Medusa merger. Often referred to by its somewhat drier New General Catalogue designation of NGC 4194, this was not always one entity, but two. An early galaxy consumed a smaller gas-rich system, throwing out streams of stars and dust out into space. These streams, seen rising from the top of the merger galaxy, resembles the writhing snakes that Medusa, a monster in ancient Greek mythology, famously had on her head in place of hair, lending the object its intriguing name. The legend of Medusa also held that anyone who saw her face would transform into stone. In this case, you can feast your eyes without fear on the centre of the merging galaxies, a region known as Medusa's eye. All the cool gas pooling here has triggered a burst of star formation, causing it to stand out brightly against the dark cosmic backdrop. The Medusa merger is located about 130 million light-years away in the constellation of Ursa Major (The Great Bear).

Name: NGC 4194
Type: Early Universe : Galaxy : Type : Interacting
Category: Galaxies
Constellation: Ursa Major
Distance: 130 million light years
Release date: 30 September 2019, 06:00
Credit: ESA/Hubble & NASA, A. Adamo

A Spiral in Profile: The NASA/ESA Hubble Space Telescope sees galaxies of all shapes, sizes, brightnesses, and orientations in the cosmos. Sometimes, the telescope gazes at a galaxy oriented sideways — as shown here. The spiral galaxy featured in this Picture of the Week is called NGC 3717, and it is located about 60 million light-years away in the constellation of Hydra (The Sea Serpent). Seeing a spiral almost in profile, as Hubble has here, can provide a vivid sense of its three-dimensional shape. Through most of their expanse, spiral galaxies are shaped like a thin pancake. At their cores, though, they have bright, spherical, star-filled bulges that extend above and below this disc, giving these galaxies a shape somewhat like that of a flying saucer when they are seen edgeon. NGC 3717 is not captured perfectly edge-on in this image; the nearer part of the galaxy is tilted ever so slightly down, and the far side tilted up. This angle affords a view across the disc and the central bulge (of which only one side is visible).

Name: NGC 3717
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Hydra
Distance: 60 million light years
Release date: 7 October 2019, 06:00
Credit: ESA/Hubble & NASA, D. Rosario

A Galactic Portal: The galaxy NGC 4380 looks like a special effect straight out of a science fiction or fantasy film in this Hubble Picture of the Week, swirling  like a gaping portal to another dimension. In the grand scheme of things, though, the galaxy is actually quite ordinary. Spiral galaxies like NGC 4380 are one of the most common types of galaxy in the Universe. These colossal collections of stars, often numbering in the hundreds of billions, are shaped like a flat disc, sometimes with a rounded bulge in the centre. Graceful spiral arms outlined by dark lanes of dust wind around the bulging core, which glows brightly and has the highest concentration of stars in the galaxy.

Name: NGC 4380
Type: Local Universe : Galaxy : Type : SpiralLocal Universe : Galaxy : Activity : AGN
Category: Galaxies
Constellation: Virgo
Release date: 14 October 2019, 06:00
Credit: ESA/Hubble & NASA, P. Erwin

A Familiar Sight: This image from the NASA/ESA Hubble Space Telescope shows IC 4653, a galaxy just above 80 million light-years from Earth. That may sound like quite a distance, but it’s not that far on a cosmic scale. At these kinds of distances, the types and structures of the objects we see are similar to those in our local area. Thie galaxy's whirling arms tells us a story about what’s happening inside this galaxy. Stars are generally brighter and bluer when they are younger, so the blue patches mark sites of new star formation. Studying the structures of other galaxies is a key way to learn about the structure of our own, given that humans can’t leave the Milky Way to look back and see what it looks like from the outside. It helps to compare our observations of our home galaxy with those of nearby galaxies we can see in their entirety.

Name: IC 4653
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Ara
Distance: 80 million light years
Release date: 21 October 2019, 06:00
Credit: ESA/Hubble & NASA, D. Rosario (CEA, Durham University)

Lonely Hearts Club: Galaxies may seem lonely, floating alone in the vast, inky blackness of the sparsely populated cosmos — but looks can be deceiving. The subject of this Picture of the Week, NGC 1706, is a good example of this. NGC 1706 is a spiral galaxy, about 230 million light-years away, in the constellation of Dorado (The Swordfish). NGC 1706 is known to belong to something known as a galaxy group, which is just as the name suggests — a group of up to 50 galaxies which are gravitationally bound and hence relatively close to each other. Around half of the galaxies we know of in the Universe belong to some kind of group, making them incredibly common cosmic structures. Our home galaxy, the Milky Way, belongs to the Local Group, which also contains the Andromeda Galaxy, the Large and Small Magellanic Clouds, and the Triangulum Galaxy. Groups are the smallest of galactic gatherings; others are clusters, which can comprise hundreds of thousands of galaxies bound loosely together by gravity, and subsequent superclusters, which bring together numerous clusters into a single entity.

Name: NGC 1706
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Dorado
Distance: 230 million light years
Release date: 28 October 2019, 06:00
Credit: ESA/Hubble & NASA, A. Bellini et al.