ISF Talks – Island Universes

I’ve recently finished delivering two public lectures on Galaxies at this year’s Inverness Science Festival.

The theme of my talks was ‘Island Universes’, telling the tale of when and how we discovered our Milky Way isn’t the only galaxy, and how the teeming multitudes of spiral nebulae, hitherto believed to be collapsing dust clouds, were in fact individual galaxies.

The talk started with some observational astronomy, before discussing the great debate of 1920 between Harlow Shapley and Heber Curtis.  The main unresolved issue here was the distance to the spiral nebulae, particularly Andromeda, which was unknown.  This lead us into pulsating stars and the work of Henrietta Swan Leavitt, who systematically analysed and determined the period luminosity law for cepheid variable stars.

Finally we discussed Edwin Hubble and the ramifications of his observations on the red shift of distance galaxies, and how this has informed our current understanding of the history and future dynamics of the universe.

I’ll let some choice slides do the talking from here on.

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Our own galaxy ‘The Milky Way’ is big.  If you tried to travel from our position to the galactic nucleus at the speed of the Voyager spacecraft it would take you over 400 million years.

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A 1900s image of the Andromeda nebula.  Back then the consensus was these spirals were large collapsing dust clouds, a bit like the star forming Orion nebula.  The idea that they could be separate galaxies like our Milky Way seemed inconceivable, yet that’s where the evidence eventually lead in the 1920s.

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Determining the distance to spiral nebulae (as they were known pre 1900) required a new way of determining distance from so-called ‘standard candles’.  Leavitt’s law was invaluable when Hubble turned his attention to Andromeda in 1922.

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Hubble discovered the galaxies were all rushing away from us.  However this phenomena is actually a metric expansion of space itself, and therefore has no intrinsic centre.  Some of the most distant galaxies are receding away at faster than the speed of light – again due to the expansion of space itself, which has no speed limit imposed.

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There were lots of questions on M87, the giant elliptical galaxy whose black hole was recently imaged by the Event Horizon telescope.

Q&As are always lively after astronomy and space talks, and the younger audience members always surprise me with their amazing knowledge and frank curiosity.  Some choice sample from the two evenings below.  Answers on a postcard please .

1. Is the singularity at the end of a black hole the size of the Planck length?

2. If a giant hole suddenly appeared in the Earth how many Pluto’s could you fit inside it?

3. Do supermassive black holes continue to grow until they devour the host galaxy?

Island Universes – Inverness Science Festival

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Face-on spiral galaxy NGC 6814

I’m looking forward to presenting another astronomy talk for the 2019 Inverness Science Festival.  Talk details below:

Astronomer Stephen Mackintosh from Highland Astronomy will take you on a journey through space and time, looking at the massive stellar structures that make up the observable universe – Galaxies.

How did we discover them, how many are there and what do they tell us about the immense scale and dynamics of the universe?

Plus tips and advice on observing galaxies and other faint deep sky objects for yourself.

Time:  7pm – 8pm,  8th May 2019

Venue:  Main Lecture Theatre, UHI Campus

Booking links:  Eventbrite

 

Dark Sky Observing at Abriachan

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A lovely crescent Moon hung in the West for most of the evening

We enjoyed another superb evening of stargazing and storytelling up at Abriachan Forest last Saturday – the last dark sky session until stargazing returns in October 2019.

There were beautiful crisp skies all evening long, allowing me to guide both groups outside for views of the Milky Way and numerous open star clusters like the Hyades, Pleiades, Beehive and the stunning double cluster in Perseus.

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Orion…of course

We also studied the Orion star forming nebula, the great spiral galaxy in Andromeda and some fainter galaxies in Ursa Major (M81 and M82), and even had a go at sighting the triplet of galaxies in Leo, which some of the keen eyed youngsters successfully glimpsed in the 8×40 binoculars.

Clelland was also back in action with the story of Arden and the birth of Merlin in the roundhouse.

Thanks to everyone who came along.  Please check my Facebook site for details of future summer events.

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Perseus and the double cluster

Star Stories Photography and Aurora Special

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The aurora over Ceannabeinne Beach on the north coast by photographer Graham Bradshaw

Despite the stormy conditions earlier in the evening, skies cleared up beautifully at Abriachan on Saturday night for Star Stories.

Graham Bradshaw of Graham Bradshaw Photography was our guest speaker, talking about his fascinating experiences hunting and photographing aurora in some of the wildest and remotest parts of the Scottish highlands.  His talk included practical advice on seeking out aurora in the north of Scotland (which is much more prevalent than you might think), as well as showing many beautiful still images and stunning time lapses captured all over the highlands and further afield.

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Photographer Graham Bradshaw

Meanwhile I took two groups out stargazing and managed about 20 minutes of clear skies during the first outing until we were rained off by a very brief shower.  After heading back inside I switched to my backup slide deck on the science of aurora, talking about how the differential rotation of stars causes kinks in their magnetic fields, ultimately leading to the coronal mass ejections that produce the aurora.

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I got a nice capture of the Andromeda galaxy over the forest classroom (left), and a passing satellite.  This giant galaxy is over 2.5 million lights years away just visible naked eye.  It looks even more impressive in binoculars.

By the time Graham had finished his first talk, skies had cleared again and my second group had a much longer excursion under the stars.

As usual we took in broad sweeps of the night sky with the wonderful agility of binocular observing, hitting targets like the Orion nebula, Hyades and Pleiades star clusters, the Andromeda galaxy, Beehive cluster as well as numerous bright and massive red and blue giant stars.  The Milky Way was also clearly on display, even with the presence of an enchanting crescent Moon hanging in the South West.  We also saw Mars sitting above the Moon and had a go at finding Uranus (currently observable in the same binocular field as Mars).

During both streams Suzann Barr did some video interviews with some of the younger stargazers who’ve become regulars at the events, and captured feedback on our Star Stories wall chart.  Overall it was another great evening with good feedback from participants.

Our next event in March will be the last dark sky observing session for this season as skies begin to brighten.  The theme for this event will be galaxies, and I’ll have a backup presentation prepared on this topic should skies prove unfavourable.  There’s only a few tickets left available on Eventbrite here.

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Another good catch in my camera, this time the Milky Way in the region of Perseus, with the double cluster clearly visible on the left.

 

 

Galaxy NGC 2841

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Galaxy NGC 2841. Imaged by Hubble nearly 50 million light years away in the constellation Ursa Major. This is an example of a spiral galaxy with no central bar, just a beautiful continuum of overlapping circular dust lanes.

It contains between 400 billion to 1 trillion stars, and like most galaxies outside our local group its receeding away from us, in this case at nearly 500 miles per second.