Our 2023/2024 season of astronomy outreach at Abriachan Forest ended on a high note this Saturday with a visit from Martin Hendry, Professor of Gravitational Astrophysics and Cosmology. Since 2022 Martin has been acting vice principle at the University of Glasgow and was formerly head of the school of Physics and Astronomy.
Martin’s packed talk was broadly about the age of the universe, but touched on the age of stars, stellar classification, cepheid variables, rates of cosmic expansion, and the important work undertaken by female astronomers like Henrietta Leavitt, Annie Jump Cannon and Williamina Fleming, who were instrumental in helping us calculate the distances to star clusters and galaxies. A special tribute was also paid to Lord Kelvin on the 2024 bicentenary of his birth.
Alas, we were not graced with clear skies for open air stargazing, so following Martin’s talk we both hosted a virtual planetarium tour instead, referencing many of the clusters, galaxies and some stars mentioned in the main talk.
Thanks to Suzann for the Kelvin and Constellation witches fingers which captivated some of the younger audience members, and my wife Judith for the excellent home bakes. I look forward to announcing our new new 2024/2025 program in October. Stay tuned for details.
Calculations of the age of the universe using a variety of datasets and methodologies, including galactic red shifts and globular clusters have broadly placed the age of the universe at about 14 billion years old.
Due to heavy snow this winter my Tales of the Moon event (with Steve Owens) has moved to February 17th and our scheduled event with Professor Martin Hendry is now March 9th. The former event has sold out but the Eventbrite links for March have just gone live. Please see details below if you wish to book:
Join us up at Abriachan Forest (a Dark Sky Discovery site) for an evening of stargazing with guest astronomer Martin Hendry, professor of Gravitational Astrophysics and Cosmology at the University of Glasgow.
Event format is weather proofed so please book with confidence. As well as our indoor guest speaker talk from Martin on the Age of the Universe (and Lord Kelvin) we’ll have outdoor (or indoor) night sky guiding with astronomer Stephen Mackintosh, possible telescopic views of Juipter and more family focused activities with the Abriachan team.
Refreshments and home bakes available. Due to site and classroom capacity, booking via Eventbrite is essential. Admission is free for under 16s with accompanying adults but please inform Abriachan of any large booking requests.
I’m delighted to announce the return of three excellent astronomers and guest speakers to Abriachan Forest this season.
On December 9th – Maarten De Vries (talking about Meteor Showers)
On January 20th – Steve Owens (joins me to Explore the Moon)
On February 10th – Martin Hendry (discusses Lord Kelvin and the Age of the Universe)
All guest speaker talks will be followed (or proceeded) by naked eye and binocular stargazing led by myself, or a backup indoor sky tour on planetarium software if clouds roll in. Plus storytelling and other activities led by the Abriachan team. Refreshments and home bakes provided.
Ticket links will go live roughly four weeks prior to each event so please stay tuned to my Facebook page for details as they do sell out very quickly.
The above montage shows six recent images of ‘potentially’ massive galaxies photographed by the James Webb space telescope, going back to epochs around 600 million years after the universe began.
If the six red dots are confirmed to indeed be large galactic structures, these examples contradict almost all known models of galaxy formation from the early history of the universe and would suggest stellar masses over 100 times greater than previously predicted in this early period. Existing models of galaxy formation predict large galaxies would require several billion years to form, so if true these findings will require extensive revisions to our understanding of the large structure evolution of the universe.
Truth told we still know very little about the formation of galaxies. Their evolution is still shrouded in deep mystery, for example what forms the large bars we see in the centre of most mature spiral galaxies, including our own Milky Way?
And of course their rotational dynamics have lead to the conclusion that clouds of invisible matter must surround them in giant halos (dark matter).
Our next stargazing and storytelling session at Abriachan Forest will be on New Moon (Jan 21st) and we welcome back Glasgow Science Centre astronomer Steve Owens to guide us under the stars (or present a backup indoor talk on the planets). Our guest campfire storyteller Fiona Macdonald should also be in attendance.
If you booked for the cancelled December event your tickets will carry over and will be valid for the Jan event.
If you missed out on the last few events we have a February and March events planned so stay tuned. The February tickets links and event details will go up in the next week.
Join me on December 17th up at Abriachan Forest (a Dark Sky Discovery site) for an evening of stargazing and storytelling under Moonless dark skies.
If conditions are clear I’ll guide you under Abriachan’s Milky Way class dark skies (with a backup indoor astronomy presentation if clouds roll in).
Meanwhile we welcome our first guest storyteller of the season. Local gael Fiona Macdonald will lead the campfire storytelling section of the evening with tales steeped in Highland folklore.
Due to site and classroom capacity, booking via Eventbrite is essential. Admission is free for under 16s with accompanying adults but please inform Abriachan of any large booking requests.
Sagittarius A – as imaged by the team at the Event Horizon Telescope.
Imagine taking over 4 million copies of our Sun and cramming the combined mass into a region of space no bigger than the orbit of Mercury.
That’s Sagittarius A, the supermassive black hole at the centre of our own Milky Way galaxy. Evidence for Sagittarius A has been growing since the 1970s but now in 2022 the team at the Event Horizon Telescope have actually imaged it.
The term ‘supermassive’ when attributed to black holes is very misleading as black holes are incredibly low volume but dense regions of space. To give you a feel for this, if you took our Moon and somehow compressed it into a black hole, the resulting anomaly would have a diameter of 0.2 millimetres! That’s probably less than the size of a single pixel on the screen you’re reading this article on.
As black holes grow they can devour more mass and will slowly get bigger with the event horizon radius r defined by the famous Schwarzschild equation:
r = 2GM/c^2
In this equation G is the universal gravitational constant, c is the speed of light and M is the mass of the black hole. This is a simple linear relationship, so for example doubling the mass of a black hole will double its radius.
The bright central region of our Milky Way galaxy where Sagittarius A is located. Telescopes of the Atacama Large Millimeter/submillimeter Array in the foreground. Credit: EHT Collaboration
Given the relatively small volumes and areas of space involved, detecting even the most massive black holes in challenging to say the least. Sagittarius A, despite containing millions of solar masses, occupies a volume smaller than a single star in its giant phase of evolution. This gets compounded by the incredible distances involved. The centre of our Milky Way where Sagittarius A is located is a staggering 26,000 light years away. How then did the team capture the image?
The key was using multiple detectors spread across the planet, effectively constructing an Earth sized telescope. The data collected from these widely spaced arrays was then gathered together, producing many terabytes of data, and processed by banks of supercomputers called ‘correlators’. The final image was constructed using advanced algorithmic and statistical imaging techniques.
EVT’s detectors are spread around the planet effectively creating an Earth sized detection aperture.
Clearly by their nature black holes do not allow any light to escape so what we see in the final image is the infrared signature of super-heated gas rotating close to the black hole. Black holes therefore reveal themselves by their indirect influence on nearby objects rather than direct observation.
Indeed, Sagittarius A’s existence was originally inferred by its influence on nearby stars, which are being thrown about at fantastically high speeds due to its intense gravitational influence. Fast enough for us to produce time lapse images over several years (see animation below).
Time-lapse from the ESO’s Very Large Telescope in Chile shows stars orbiting close to Sagittarius A over a 20 year detection period.
| Modulo | Universe 