An Active Centre: This swirling mass of celestial gas, dust, and stars is a moderately luminous spiral galaxy named ESO 021-G004, located just under 130 million light-years away. This galaxy has something known as an active galactic nucleus. While this phrase sounds complex, this simply means that astronomers measure a lot of radiation at all wavelengths coming from the centre of the galaxy. This radiation is generated by material falling inwards into the very central region of ESO 021-G004, and meeting the behemoth lurking there — a supermassive black hole. As material falls towards this black hole it is dragged into orbit as part of an accretion disc; it becomes superheated as it swirls around and around, emitting characteristic high-energy radiation until it is eventually devoured. The data comprising this image were gathered by the Wide Field Camera 3 aboard the NASA/ESA Hubble Space Telescope.

Name: ESO 021-G004
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Chamaeleon
Distance: 130 million light years
Release date: 23 December 2019, 06:00
Credit: ESA/Hubble & NASA, D. Rosario et al.

Placed Among the Stars: This smattering of celestial sequins is a spiral galaxy named NGC 4455, located in the northern constellation of Coma Berenices (Berenice’s Hair). This might sound like an odd name for a constellation — and in fact it is somewhat unusual; it’s the only modern constellation to be named in honour of a real person from history: Queen Berenice II of Egypt. The story of Queen Berenice II is an interesting one. A ruling queen of the ancient Greek city of Cyrene in modern-day Libya, and later a queen of Ptolemaic Egypt through her marriage to her cousin Ptolemy III Euergetes, Berenice became known for sacrificing locks of her hair as an offering to ensure her husband’s safe return from battle. Her husband did indeed return safely and her hair, which she had left in a Zephyrium temple, had disappeared — it had apparently been stolen and placed among the stars. Should it be located in NGC 4455, it travelled a long way. The galaxy is about 45 million light-years away. This image was taken by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys.

Name: NGC 4455
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Distance: 45 million light years
Release date: 30 December 2019, 06:00
Credit: ESA/Hubble & NASA, I. Karachentsev et al.

Imposter or the Real Deal?: This Picture of the Week, taken by the NASA/ESA Hubble Space Telescope, shows a close-up view of a galaxy named NGC 2770. NGC 2770 is intriguing, as over time it has hosted four different observed supernovae (not visible here). Supernovae form in a few different ways, but always involve a dying star. These stars become unbalanced, lose control, and explode violently, briefly shining as brightly as an entire galaxy before slowly fading away. One of the four supernovae observed within this galaxy, SN 2015bh, is especially interesting. This particular supernova initially had its identity called into question. When it was first discovered in 2015, astronomers classified SN 2015bh as a supernova imposter, believing it to be not an exploding star but simply an unpredictable outburst from a massive star in its final phase of life. Thankfully, astronomers eventually discovered the truth and the object was given its correct classification as a Type II supernova, resulting from the death of a star between eight and 50 times the mass of the Sun.

Name: NGC 2770
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Lynx
Distance: 90 million light years
Release date: 6 January 2020, 06:00
Credit: ESA/Hubble & NASA, A. Filippenko

Catalogues Galore: This bright, somewhat blob-like object — seen in this Picture of the Week as observed by the NASA/ESA Hubble Space Telescope — is a galaxy named NGC 1803. It is about 200 million light-years away, in the southern constellation of Pictor (The Painter’s Easel). NGC 1803 was discovered in 1834 by astronomer John Herschel. Herschel is a big name in astronomy; John, his father William, and his aunt Caroline all made huge contributions to the field, and their legacies remain today. William systematically catalogued many of the objects he viewed in the night sky, named many moons in the Solar System, discovered infrared radiation, and more. Caroline discovered several comets and nebulae. John took this aforementioned catalogue of night-sky objects and reworked and expanded it into his General Catalogue of Nebulae and Clusters of Stars. This was the basis for the cataloguing system still used today by astronomers (Dreyer’s New General Catalogue of Nebulae and Clusters of Stars, or the New General Catalogue for short). This gives rise to the NGC names assigned to a vast number of galaxies — including NGC 1803. This galaxy is one of a galactic pair. It was described by Dreyer as being “faint, small, [and] round”, and located near to a very bright star to the southeast. This star is in fact the nebulous lenticular galaxy PGC 16720 — not visible in this image.

Name: NGC 1803
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Pictor
Distance: 200 million light years
Release date: 13 January 2020, 06:00
Credit: ESA/Hubble & NASA, A. Bellini et al.

Supermassive Influence: This peculiar galaxy, beautifully streaked with tendrils of reddish dust, is captured here in wonderful detail by the NASA/ESA Hubble Space Telescope. The galaxy is known as NGC 1022, and is officially classified as a barred spiral galaxy. You can just about make out the bar of stars in the centre of the galaxy in this image, with swirling arms emerging from its ends. This bar is much less prominent than in some of the galaxy’s barred cousins and gives the galaxy a rather squat appearance; but the lanes of dust that swirl throughout its disc ensure it is no less beautiful. Hubble observed this image as part of a study into one of the Universe’s most notorious residents: black holes. These are fundamental components of galaxies, and are thought to lurk at the hearts of many — if not all — spirals. In fact, they may have quite a large influence over their cosmic homes. Studies suggest that the mass of the black hole sitting at a galaxy’s centre is linked with the larger-scale properties of the galaxy itself. However, in order to learn more, we need observational data of a wider and more diverse range of galaxies — something Hubble’s study aims to provide.

Name: NGC 1022
Type: Local Universe : Galaxy : Type : Spiral
Category: Galaxies
Constellation: Cetus
Release date: 20 January 2020, 06:00
Credit: ESA/Hubble & NASA, A. Seth