Physics

Tales of Dark Matter

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All the light we see from distant stars and galaxies is made from visible matter, yet evidence from the rotational speeds of other galaxies suggests dark matter outweighs visible matter on a ratio six to one. Image: ‘Our galaxy Over Achnasheen’, Stephen Mackintosh

Join me up at Abriachan Forest (a Dark Sky Discovery site) for an evening of stargazing and astronomy on February 25th with our first guest speaker of the 2022 season – Professor Martin Hendry.

If skies are clear Martin and myself will host an outdoor stargazing session, discussion and Q&A under the stars. Following this Martin will present his indoor guest talk on the very latest discoveries in cosmology, concentrating on the elusive nature of dark matter and dark energy.

Refreshments provided plus binoculars for stargazing. Under 16s with accompanying adults go free. Tickets can be booked via Eventbrite here or you can reserve directly from my Facebook page here.

Martin speaking at the Science on Stage Festival

Martin Hendry is Professor of Gravitational Astrophysics and Cosmology at the University of Glasgow and is a passionate advocate for STEM education and science engagement with schools and public audiences. He is the author of more than 200 scientific articles and is a senior member of the LIGO Scientific Collaboration, the global team of more than 1400 scientists which made the first-ever detection of gravitational waves – a discovery awarded the 2017 Nobel Prize for Physics. Martin is a Fellow of the Institute of Physics and the Royal Society of Edinburgh and is currently a Trustee of the IOP and the James Clerk Maxwell Foundation. In 2015 he was awarded an MBE for services to the public understanding of science.

Why do we See what we See?

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The western highlands of Scotland, bathed in the visible light of our home star.

When we think about the vast array of electromagnetic radiation all around us – from Gamma rays, X-rays , UV, Microwaves and Radio waves – a natural question to ask is why do human eyes see in a very narrow band we call ‘visible light’?

The answer is undoubtably tied to the energy output of our nearest star – the Sun. Its peak radiation just happens to be at this ‘visible’ band of radiation. I’ve illustrated this below with a black body radiation profile of our Sun.

Our eyes have therefore evolved to ‘see’ this particular narrow range of otherwise insignificant wavelengths. There’s nothing inherently important about visible light – in fact it makes up a tiny 0.0035 percent of the entire electromagnetic spectrum.

Understanding this makes me wonder about the potential sensory apparatus of life that might have evolved elsewhere in the universe. Other stars with different stellar classifications to our Sun have different peak radiation profiles.

If we had evolved next to a source of intense gamma rays for instance, we would very likely be completely blind to visible light but adept at observing small granular differences in the intensity of gamma radiation.

The Northern Lights

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The northern lights looking over the Beauly firth towards the Black Isle, Inverness-shire

After reports of a KP6 geomagnetic storm predicted to strike Scotland over the weekend, and clear skies on Sunday evening, I headed out after sunset to try and catch the northern lights.  This was a very early aurora excursion as nights have only just got dark enough for decent views of the night sky, let alone tracking down the faint and elusive northern lights.

My initial outing took my into the hills above Bunchrew where I bagged some lovely views of the summer Milky Way overhead.  Turning my attention north I noticed a faint arc of light on the horizon,  and sure enough some test shots picked up a vibrant band of purple and green auroral light.  However little structure was evident until I moved to lower elevations, reaching the Bunchrew shoreline just after 10.30pm.

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The Milky Way near Cygnus, framed between trees above Bunchrew.

From this new vantage, in the dark looking over the Beauly Firth,  the northern lights stood out much more clearly as distant columns of white light, slowly morphing and scintillating above the horizon.  Some of the images (attached) show nice structure and the suggestion of wave like movement.

As our nights get darker many more opportunities to view the aurora will present themselves.  The best strategy is to simply get out there as often as you can when it’s clear, and try and escape the boundaries of light polluted towns and cities.  Aurora forecasts should only be used as a guide as they’re seldom reliable.  Remember to look north and where possible find some nice low horizons in this direction.

Good luck and clear skies.

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The aurora is caused by the solar wind slamming into the earth’s atmosphere near the poles, ionising chemical elements which produce light at very specific quantised frequencies.

 

 

Space Camp in Thurso

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Some photo highlights from the Summer Space Camp up in Thurso’s band new Newton Room.  I had a great time delivering Mars and astronomy based workshops on day 2.  We covered the observational history of Mars, its surface geology, the night sky, the life and death of stars and spectroscopy.  Interactive sections included Mars cratering, galaxy frisbees, star cluster balloons and DIY spectrascopes.

Picture rights Skills Development Scotland.

Urban Astronomy Inverness

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The formation of a young protostar following the collapse of a previously inert dust cloud

We had a great turnout for March’s Urban Astronomy session last week at the Sea Cadet’s Hall in Inverness.  The indoor presentation massively benefited from our new giant screen, expertly erected by Robbie (pictured below).  Here’s a selection of slides from my presentation on naked eye observing and the life of giant stars.

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Robbie putting the final touches to our new giant screen for indoor astronomy presentations and virtual sky guiding

Topics covered:

– Naked eye and binocular observing
– Satellites: Iridium Flares and ISS
– Colour, temperature and mass of stars
– The Hertzsprung-Russell diagram
– Protostar formation from dark nebulae
– Main sequence burning and final fate of stars
– White dwarfs, supernovae, neutron stars and black holes.

As ever there were some superb questions during and after the talk.  Stay tuned for upcoming events as myself and Caroline roll out the program.

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In the simplest terms stars behave like black body radiators with colour linked to their surface temperatures.

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The brightest stars in the night sky can be close – like Sirius – or giant stars very far away (eg. Betelgeuse, Rigel, Deneb).

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The HR diagram.  An elegant and reliable tool for describing the evolution of stars from main sequence burning into their final stages of life

Solar Day at Abriachan

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We were blessed with a lovely sunny day on Saturday for our day of Solar learning up at Abriachan.  We were fully prepared for indoor activities as forecasts were looking pretty grey.  But as the weekend swung around skies cleared and we ended up seeing plenty of Sun all day.

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A day of fun solar learning

Since conditions were so good we moved everything outside, including the talk I’d prepared which was originally put together on powerpoint.  I demonstrated basic shadow time keeping and direction finding, and how solar eclipses take place using a scale model of the Moon and Earth (with the moon’s orbit inclined at 5 degrees).

Based on our model the Earth and Moon were around 3 meters apart with the former about the size of a large orange.  At this scale the Sun would be 10 meters in diameter and over a mile away!  With this model the relative rarity of total solar eclipses becomes clear (on average one every 18 months).

During the talk we also touched upon:

  • Sun gods and how our ancestors perceived the Sun as a perfect orb with no imperfections
  • The human fear of eclipses
  • The discovery of Sun spots and how they revealed that the Sun is spinning
  • How spectroscopy revealed that our Sun is in fact a star (at very close proximity)
  • Why the Sun is loosing mass – over 600 million tons of hydrogen per second
  • The ultimate fate of our Sun – how it will eventually flare up as a red giant star before cooling and shrinking down to a white dwarf

After the talk Clelland took over for some fun outdoor activities including a scale walk of the solar system, DIY spectroscopes and solar lasers using big magnifiers.  We also did a fun experiment simulating the colour of the sky and sunsets using milk in water bottles.

In terms of solar viewing, I setup the 200mm with a full objective white light filter, and we also had a Sunspotter, kindly on load from Glasgow Science centre.  Both setups produced clear views of the Sun’s photosphere, but unfortunately there were no sunspots to see.  This isn’t entirely surprising given we’re bang in the middle of the 11 year solar cycle minimum, although large spots can appear suddenly at any time.  We hope to one day invest in a good quality hydrogen alpha filter for these events, as these reveal many more interesting features, like edge prominences and coronal loops.

Overall a fun day of learning with great interaction and questions from the adults and little ones alike.

Next Abriachan Astronomy Dates

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I’m excited to be hosting two more astronomy events alongside the Abriachan forest team in March and April 2018.  Details and ticket links below.

Star Cluster Special – March 10th (moved from Feb 10th) 7pm-9pm

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The Hyades and Pleiades Star clusters

Explore the great winter open clusters under moonless dark skies with campfire stories to follow. Outdoor binocular guiding under clear skies. Indoor talk, astronomy activities and virtual guiding in the classroom in the event of poor weather. Refreshments provided.

Ticket link: https://www.eventbrite.co.uk/e/dark-sky-observingwith-a-sta…

Solar Special and the Life of Stars – April 14th 2pm – 4pm

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A typical G-type main sequence star – locals have dubbed this one ‘The Sun’

A Sun special exploring our nearest star and the life of giant stars. Outdoor sun projections and activities, with illustrated talk and refreshments. Suzann even has plans for a solar pizza oven!

Ticket link: https://www.eventbrite.co.uk/e/some-sunny-science-and-the-l…

All stargazing events organised in collaboration with the Abriachan team, astronomer Stephen Mackintosh and learning coordinator Suzann Barr. Campfire tales delivered by forest ranger Clelland.

For group bookings please email: abriachanforest@gmail.com