Author: Stephen Mackintosh

Lunar Maria

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Happy New Year everyone.  There’s been a lovely bright full moon on display over the new year, allowing me to venture out for well lit evening walks, stopping every so often to study the bright lunar disc both unaided and with binoculars.

One very obvious thing you can notice from looking at the moon, especially naked eye, is the contrasting dark and light regions.

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The dark regions are called lunar ‘maria’ which is latin for ‘sea’. These regions are relatively smooth and have a low abundance of craters, which suggests they’re younger than the brighter more heavily cratered regions.

But how can the moon, a dead world with no significant geological activity, have younger regions?

The answer is from giant impacts.

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Imagine a massive asteroid hitting the moon. Not only will it generate a huge crater but the heat from the impact will cause the solid rock underneath to become molten and well up in a huge overflowing lava event. This overflow pours across the surface of the moon a bit like applying fresh plaster to a wall, masking all the old craters and creating what we now see as ‘maria’.

I’ll be talking about this and much more at our special moon night on the 27th Jan out at Abriachan Forest.

The Geminids

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One of the most energetic meteor showers of the year is fast approaching with activity predicted between Dec 4th – Dec 16th. With the best possible observing conditions the Geminids can produce displays of up to 120 meteors per hour, although you’ll likely see rates much lower than this in reality.

Occasionally and unpredictably, meteor showers can erupt into storms. One of the most famous ‘storms’ happened in 1833 when the Leonids produced over 100,000 meteors per hour! Who knows what this December will bring.

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Observing Meteor Showers

You don’t need any special equipment to view a meteor shower, in fact binoculars or telescopes will just narrow your field of view. Grab a deck chair or a warm blanket, prepare a hot drink, wrap up warm and lay out under the darkest conditions you can find. It’s an excellent activity to do alone or if you have children they’ll love an excuse to get outside for some after dark play.

Put away any lights or bright mobile phones and simply look up and wait. Remember it takes up to 30 minutes for your eyes to fully dark adapt and any exposure to bright lights will start the process all over again. If you need a light red touches are best for preserving you night vision.

Good luck and clear skies!

 

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Abriachan Forest Trust Gains ‘Milky Way’ Dark Sky Discovery Status

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I was delighted to help Abriachan Forest Trust gain ‘Milky Way’ Dark Sky Discovery status this month after working on a joint nomination with Abriachan’s learning coordinator Suzann Barr.  This is the first site in the Inverness area to be awarded the status and it’ll hopefully attract winter tourism and lots of opportunity for astronomy based public engagement.

The Highlands really are blessed with excellent dark skies – we just need to do more to capitalise on it and perhaps emulate some of the great work that’s been done in the Scottish Borders where the Galloway International Dark Sky Park brings substantial benefits to the local economy.

After the status was formally awarded by Dan Hillier (who leads the Dark Sky Discover network from Edinburgh’s Royal Observatory) I generated a press release which several news bodies picked up, not least BBC Scotland.

Link to  BBC Scotland Article.

The Press and Journal also ran a full page article reproduced below:

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Mercury at Maximum Elongation

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Heavily cratered Mercury

If you have flat and unobstructed views towards the south west there’s a chance of observing one of the most elusive planets this evening – Mercury.

Mercury is hard to see because it orbits so close to the sun, meaning it’s usually lost in the glare of our parent star.

However the planet is currently at its maximum eastern elongation from the Sun, so there’s a small window of opportunity to spot Mercury just after sunset low in the south west. Grab a pair of binoculars and see if you get lucky.

For us high northern latitude observers it’s a tough ask due to the currently flat orientation of the ecliptic, but even if you don’t see Mercury you should catch Saturn sitting just a little higher on the horizon.

Mercury goes through several peak elongations from east to west during a year, providing alternating opportunities to see the planet in pre-dawn or evening skies

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Maximum eastern elongation

Despite being closest to the sun, Mercury isn’t the planet with the highest temperatures – that prize goes to Venus with its thick carbon dioxide cloud base.  This is because Mercury has no atmosphere to trap or distribute heat.  If you were able to stand on Mercury, your daytime temperatures would be a blistering 427C.  However, if you hid in the shadow of a large crater or travelled into the dark half of Mercury, temperatures would plummet to a freezing -173C!  Again, due to a lack of atmosphere to smooth out the temperature extremes.

Stargazing at Balloch Brownies

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I had the great pleasure of helping the 2nd Balloch Brownies gain their Stargazers badge this evening.  Brownie leader Gaener Rodger wanted an astronomer to lead the girls through basic constellations and star navigating, but I came prepared for both outdoor and indoor activities in the event of poor skies.

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A captive and very excitable audience!

The location for stargazing was next to the Balloch hall (beside Balloch Primary) which has some fairly bright street lights nearby.  Thankfully the skies were clear enough to make out the main constellations once we’d shifted our location to the gable end of the hall, away from the worse offending lights.

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The plough or dipper is one of the best asterisms to orientate an audience and begin a stargazing tour with.  Ursa Major is also home to dozens of interesting stars and deep sky objects.

The stargazing tour lasted about 30 mins and covered the following:

  • Ursa Major and the big dipper pointers stars
  • Polaris and circumpolar constellations
  • The story of Callisto and Arkos (The greater and lesser bears)
  • Cassiopeia and the story of Queen Cassiopeia and Cepheus
  • The great square of Pegasus and the legend of Perseus
  • The Northern Cross (Cygnus)
  • Stellar physics on the differences between the stars Vega, Deneb and our Sun

Although it was quite a large group (around 20 brownies), I was amazed at the number of really interesting questions the girls kept throwing at me – what’s a light year,  what causes a supernova, how many stars are there?  The science behind the stars seems to really engage the minds and imaginations of children.

After stargazing we headed back inside for some of the indoor activities I’d prepared.  These included:

  • Demonstrating Moon phases using spheres on sticks and bright head torches
  • A competition to guess the distance from the moon to the earth (using scale ‘chocolate’ models)
  • Mars and Moon cratering using trays of flower, coca powder and lots of marbles!
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Laying down the lunar soil

The latter experiment was messy but well worth the effort, and was a good opportunity to discuss planetary evolution – why the moon and inner planets have such clear cratering and what it tells us about their age and history.

All in all it was a great evening and more importantly the Brownies seemed to have a fantastic time.

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Discussing the impact craters

Cairngorm Stargazing Weekend and the Ghoul Star ‘Algol’

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Algol in Perseus – an eclipsing binary star system

I had a great two nights of stargazing with guests at the Grant Arms Hotel in Grantown-on-Spey this weekend.  The Grant Arms is a 3 star gold hotel located on the main street of Grantown-on-Spey, and a superb base for adventure holidays within the Cairngorms National Park.  The Cairngorms also doubles as one of Scotland’s best stargazing locations due to the area’s superb dark skies and elevated position.

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The Grant Arms Hotel in Grantown-on-Spey

After dinner on Friday I met my guests and we travelled out to the remote moors beside Lochindorb, where the skies were ablaze with stars and the Milky Way soared overhead.

Most of the main autumn constellations were on display with only the low western flank of the sky obscured by some distant weather fronts.  Some of my guests had never seen the Milky Way under really dark conditions before and were amazed at the clarity of the galactic disc soaring overhead.

We opted for naked eye and binocular observing and had stunning views of objects like the Pleiades, Hyades and the Andromeda galaxy, which was a clear naked eye target and resolved into a lovely oval haze in binoculars.  Most of the bright stars shone with stunning intensity under these conditions, allowing us to pick out clear colour differences in Orion’s main stars (just rising in the east), and within constellations like Aries and Andromeda.

During my tour I told the story of Algol, the ghoul star in Perseus, and how the ancients were mystified by its queer dimming every few days lasting several hours.  What I didn’t realise was that at that moment we were looking up at Algol during its lowest brightness, which only happens around 3% of the time you care to look at it.

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How to find Algol

The reason for Algol’s periodic dimming is because it has a larger but dimmer companion star in a relatively tight orbit.  Every three days the larger companion occults Algol, reducing the intensity of light reaching an observer.  Algol is therefore classified as an eclipsing binary system.

We headed out into the darkness again on Saturday evening for more fleeting but equaly rewarding observing, with scattered cloud providing tantalising glimpses of clusters and constellations.   Afterwards we packed up and headed back to the Grant Arms for some hot chocolate, and I concluded the weekend with an astronomy presentation in the lecture theatre.

I’d like to thank my guests for being such great company and making it an enjoyable and memorable weekend.  I’ll be operating more Stargazing weekends out of the Grant Arms in the near future so keep a look out for new dates.

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I met some lovely and interesting people during the weekend

Albireo and Double Stars

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A beautiful exposure of Albireo A and B  by astro-photographer Minos Kritikos

One of the best applications of a good telescope is the viewing of a wide range of double stars. While there are many double stars that can be split in a pair of binoculars, some of the most beautiful examples require more magnification, and that’s where telescopes excel with their narrower fields and greater resolving power.

One of the best double stars to view at northern latitudes lies in the head of the constellation Cygnus the swan – Albireo.

This beautiful indigo and gold double star really dazzles in a telescope eyepiece, and is easily resolved in a small telescope with at least 30x magnification.

The contrast between amber Albireo A and sapphire Albireo B is readily apparent in the above striking image, taken by my friend and astro-photographer Minos Kritikos.

There is still some speculation surrounding whether or not the Albireo pair are gravitationally bound – most evidence suggests they are. If so, their orbital period would be around 75,000 years.

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There are many interesting double stars you can try observing with even a modestly sized telescope – remember that most stars we can see in our galaxy (over 60%) are either double or multiple star systems.  Here’s a list of some other visually pleasing doubles to look out for.

  • Epsilon Lyrae – Lyra (binocular friendly)
  • Polaris – Ursa Minor (high magnification needed)
  • Mitaka – Orion
  • Alpha Capricorni – Capricorn (binocular friendly)
  • Epsilon Pegasi – Pegasus
  • Gamma Delphini – Delphinus
  • Eta Cassiopéia – Cassiopeia (high magnification needed)
  • Gamma Aries – Aries