Approaching the Universe’s origins: This intriguing image from the NASA/ESA Hubble Space Telescope shows a massive galaxy cluster called PSZ2 G138.61-10.84, about six billion light-years away. Galaxies are not randomly distributed in space, but rather aggregated in groups, clusters and superclusters. The latter span over hundreds of millions of light-years and contain billions of galaxies. Our own galaxy, for example, is part of the Local Group, which in turn is part of the giant Laniakea Supercluster. It was thanks to Hubble that we were able to study massive galactic superstructures such as the Hercules-Corona Borealis Great Wall; a giant galaxy cluster that contains billions of galaxies and extends 10 billion light-years across — making it the biggest known structure in the Universe. This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Name: PSZ2 G138.61-10.84
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Andromeda
Distance: 6 billion light years
Release date: 16 April 2018, 06:00
Credit: ESA/Hubble & NASA, RELICS

Stuck in the middle: This pretty, cloud-like object may not look much like a galaxy — it lacks the well-defined arms of a spiral galaxy, or the reddish bulge of an elliptical — but it is in fact something known as a lenticular galaxy. Lenticular galaxies sit somewhere between the spiral and elliptical types; they are disc-shaped, like spirals, but they no longer form large numbers of new stars and thus contain only ageing populations of stars, like ellipticals. NGC 2655’s core is extremely luminous, resulting in its additional classification as a Seyfert galaxy: a type of active galaxy with strong and characteristic emission lines. This luminosity is thought to be produced as matter is dragged onto the accretion disc of a supermassive black hole sitting at the centre of NGC 2655. The structure of NGC 2655’s outer disc, on the other hand, appears calmer, but it is oddly-shaped. The complex dynamics of the gas in the galaxy suggest that it may have had a turbulent past, including mergers and interactions with other galaxies. NGC 2655 is located about 80 million light-years from Earth in the constellation of Camelopardalis (The Giraffe). Camelopardalis contains many other interesting deep-sky objects, including the open cluster NGC 1502, the elegant Kemble’s Cascade asterism, and the starburst galaxy NGC 2146.

Type: Local Universe : Galaxy : Type : Lenticular
Category: Galaxies
Constellation: Camelopardalis
Release date: 23 April 2018, 06:00
Credit: ESA/Hubble & NASA, A. Fillipenko

Monster in the deep: Though the bright, light-speckled foreground galaxy on the left is eye-catching, it is far from the most intriguing object in this NASA/ESA Hubble Space Telescope image. In the upper part of the frame, the light from distant galaxies has been smeared and twisted into odd shapes, arcs, and streaks. This phenomenon indicates the presence of a giant galaxy cluster, which is bending the light coming from the galaxies behind it with its monstrous gravitational influence. This cluster, called SDSSJ0150+2725, lies some three billion light-years away and was first documented by the Sloan Digital Sky Survey (SDSS), hence its name. The SDSS uses a 2.5-metre optical telescope located at the Apache Point Observatory in New Mexico to observe millions of objects and create detailed 3D maps of the Universe. This particular cluster was part of the Sloan Giant Arcs Survey (SGAS), which detected galaxy clusters with strong lensing properties; their gravity stretches and warps the light of more distant galaxies sitting behind them, creating weird and spectacular arcs such as those seen here. The Hubble data on of SDSSJ0150+2725 were part of a study of star formation in brightest cluster galaxies (called BCGs), lying between approximately 2 and 6 billion light-years away. This study found the star formation rate in these galaxies to be low, which is consistent with models that suggest that most stars in such galaxies form very early on. These BCGs also emit strong radio signals thought to be from active galactic nuclei (AGN) at their centers, suggesting that the activity from both the AGN and any ongoing star formation is fuelled by cold gas found within the host galaxies.

Name: SDSSJ0150+2725
Type: Early Universe : Galaxy : Grouping : ClusterEarly Universe : Cosmology : Phenomenon : Lensing
Category: Galaxies
Constellation: Triangulum
Distance: 3 billion light years
Release date: 30 April 2018, 06:00
Credit: ESA/Hubble & NASAAcknowledgement: Judy Schmidt

From toddlers to babies: In the darkness of the distant Universe, galaxies resemble glowing fireflies, flickering candles, charred embers floating up from a bonfire, light bulbs softly shining. This Picture of the Week, captured by the NASA/ESA Hubble Space Telescope, shows a massive group of galaxies bound together by gravity: a cluster named RXC J0032.1+1808. This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3 as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study. Expected to launch in 2018, the JWST is designed to see in infrared wavelengths, which is exceedingly useful for observing distant objects. As a result of the expansion of the Universe, very distant objects are highly redshifted (their light is shifted towards the redder end of the spectrum) and so infrared telescopes are needed to study them. While Hubble currently has the ability to peer billions of years into the past to see “toddler” galaxies, the JWST will have the capability to study “baby” galaxies, the first galaxies that formed in the Universe.

Name: RXC J0032.1+1808
Type: Early Universe : Galaxy : Grouping : Cluster
Category: Galaxies
Constellation: Pisces
Release date: 7 May 2018, 06:00
Credit: ESA/Hubble & NASA, RELICS

A spiral disguised: Resembling a wizard’s staff set aglow, NGC 1032 cleaves the quiet darkness of space in two in this image from the NASA/ESA Hubble Space Telescope. NGC 1032 is located about a hundred million light years away in the constellation Cetus (The Sea Monster). Although beautiful, this image perhaps does not do justice to the galaxy’s true aesthetic appeal: NGC 1032 is actually a spectacular spiral galaxy, but from Earth, the galaxy’s vast disc of gas, dust and stars is seen nearly edge-on. A handful of other galaxies can be seen lurking in the background, scattered around the narrow stripe of NGC 1032. Many are oriented face-on or at tilted angles, showing off their glamorous spiral arms and bright cores. Such orientations provide a wealth of detail about the arms and their nuclei, but fully understanding a galaxy’s three-dimensional structure also requires an edge-on view. This gives astronomers an overall idea of how stars are distributed throughout the galaxy and allows them to measure the “height” of the disc and the bright star-studded core.

Name: NGC 1032
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Cetus
Distance: 100 million light years
Release date: 14 May 2018, 06:00
Credit: ESA/Hubble & NASA