Unveiling the Secrets of Star and Planetary System Formation with the Sharpest Eyes on the Sky, by Dr Claire Davies

And so, just like that, we arrived at our final lecture of the 2025/26 season.

Firstly, Mike Meynell treated us to a short talk on the Caldwell Catalogue, compiled by the late Sir Patrick Moore in 1995. Mike outlined that, as well as being a broadcasting legend, Patrick Moore had a background as an expert cartographer whose lunar maps were used by both NASA and the Soviets. Astronomical catalogues are inventories of the sky and date back over 2,000 years. They provide a universal language or ‘address’ for every object. Patrick Moore created the Caldwell Catalogue as an alternative to the Messier Catalogue, believing that there were many objects of equal importance and interest in the night sky that were being neglected by casual observers.

Paul May hosts the evening and Mike Meynell talks about the Caldwell Catalogue.

The aim of the Caldwell Catalogue was to identify objects that could be observed visually. When launched, it was hugely popular. The objects are more evenly distributed across the sky than the Messier objects, which are largely visible from northern latitudes. The Caldwell Catalogue includes C20 – the North America Nebula, C49 – the Rosette Nebula, C4 – the Iris Nebula, C11 – the Bubble Nebula, C31 – the Flaming Star Nebula and C12 – the Fireworks Galaxy. Due to increased light pollution, many are now hard to see without assistance, but smartscopes are bringing new life to viewing.

Many FAS members have submitted their own photos of Caldwell objects to our members’ photo compilations and Mike confirmed that the 2026/27 Blackheath observing season will aim to focus on Caldwell objects alongside other targets.

We then turned our attention to our main topic for the evening: a fantastic exploration of star formation by Dr Claire Davies, from the University of Exeter.

Dr Davies began by outlining the inherent consistency that the stars provide as a backdrop to our lives. The lifetimes of stars are so long that we need to use a range of techniques to understand them.

Dr Claire Davies, during her talk to the Flamsteed. Pictures by Mike Meynell.

Stars are massive, hot spheres of gas which produce light and heat through nuclear fusion at their core. They vary significantly in terms of temperature, ranging from blue-white to red, and magnitude, with these factors often represented in the Hertzsprung-Russell diagram. Some stars, like our Sun, are referred to as main-sequence stars – stars in the stable phase of their life, balancing gravity and outward pressure.

Dr Davies went on to explain the wonders of star development by looking at a specific star-forming region – NGC 604 in the Triangulum Galaxy, M33. Essentially, stars form inside vast clouds of cold gas and dust. NGC 604 has a dense molecular area which has a filamentary structure and this is where stars grow. The process of star formation involves the collapse of a molecular cloud, with gravity pulling part of the cloud together. As the gas and dust fall inwards, the material becomes denser and hotter. Both gravitational and centrifugal forces come into play to create a circumstellar disc, also known as a protoplanetary disc. These are the building blocks of stars, planets, moons and asteroids. The high-density region is at the centre and outer edges of the disc, with more diffuse regions in between. Within the protoplanetary disc, circumplanetary discs also exist, with satellites forming around planets. Material flows between the protoplanetary and circumplanetary discs. These processes are connected and multiple forces affect the accretion onto a protostar.

As the process of formation takes many hundreds of thousands of years, we have created simulations to illustrate how this happens. In addition, distance and size of objects are significant challenges to observation. Dr Davies reminded members how we measure astronomical distances, converting miles/kilometres into astronomical units, the distance from Earth to the Sun, or parsecs, enabling us to more easily carry out calculations. This is critical as the nearest region of star formation from us is in the Taurus Molecular Cloud at 29,000,000 AU, or 140 pc! Over this distance, our target is likely to be just 0.000002 degrees in the sky, or 7 milliarcseconds. So how can we begin to view these events?

Dr Davies outlined that, whilst a single telescope does not have enough resolution to see the detail in the middle of a protoplanetary/circumstellar disc, arrays of telescopes can help. Key observatory sites are:

• ALMA – Atacama Large Millimeter/submillimeter Array, Chajnantor Plateau, Atacama Desert, northern Chile

• VLTI – Very Large Telescope Interferometer, ESO Paranal Observatory, Chile

• CHARA – Center for High Angular Resolution Astronomy array, Mount Wilson Observatory, California

Whilst arrays initially produce incomplete images because they sample the sky sparsely, repeated observations as the Earth rotates help fill in the detail. The ability to see elements previously only simulated is remarkable.

Dr Davies closed her session by highlighting extraordinary progress to date by ALMA, which can currently see discs including gaps and spiral arms. In the PDS 70 system, ALMA has detected a circumplanetary disc around a forming planet. ALMA can also see other things such as asteroid and Kuiper belt analogues around other stars. We expect that these are shepherded into being by planets, just like Jupiter has done for our Solar System. Through these discoveries, researchers can ‘weigh’ the material visible and predict the planets needed to create these conditions. These hypotheses can be followed by using other instruments such as the James Webb Space Telescope to try to find the actual planets. This is an area for continued evolution and development as we explore where stars come from. Huge thanks to Dr Davies for her presentation.

We closed the evening with our Chair, Bobby Manoo, reflecting on the 2025/26 season, noting that we have had almost full houses at lectures. Our next season begins on 14 September 2026, with a full programme already available through to June 2027. As usual, recordings are available on the members’ website. Bobby offered thanks to all who have contributed to the main lecture programme, especially Paul May for compiling the schedule, all our speakers and the RMG membership team for their ongoing partnership working with FAS. A special thanks also goes to Barry Cassels for his fantastic work creating the members’ photos slideshow set to music that opens each lecture. Barry is stepping down for next season and will be much missed, but his approach will continue. Please keep sharing images for inclusion!

Flamsteed chair, Bobby Manoo, closes the 2025/26 lecture season. Picture by Mike Meynell.

We wish all our members a fantastic summer and hope to see you at our Summer Social on Wednesday 8 July 2026, from 7pm onwards at the Old Brewery in Greenwich.