Night Shining Clouds

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A few weeks either side of the summer solstice is the best time to observe ‘noctilucent’ or ‘night shining’ clouds.

These wispy collections of ice crystals are the highest clouds on Earth, located in the mesosphere up to 50 miles overhead. They’re too faint to be seen in daylight and best observed when the Sun is between -6 and -12 degrees below the horizon.

At the moment at Highland latitudes this gives you an approximate window between 11.30pm and 3am in the morning.

Clear skies.

Total Lunar Eclipse 21st January 2019

Look out for a spectacular total lunar eclipse next Monday 21st January, when the full Moon will turn blood red in the sky.  I’ve put together a video guide below with details of the timings for the full event at northern GMT latitudes.

You’ll have to get up early in the morning on the 21st to witness totality, with the best observing times spanning 4.42am – 5.45am.  Set your alarms!

The last total lunar eclipse was only 5 months ago, when I photographed the red Moon briefly emerging from clouds.

Big thanks to Kay Nakayama of Chillscape Art & Music for the accompanying music.

Mercury and Jupiter Conjunction

 

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Have you ever seen the planet Mercury with your own eyes? It’s notoriously difficult to catch being situated so close to the Sun and often hard to pinpoint. You’ll only ever see it as a tiny disc in binoculars, very close to sunrise or sunset.

Over the next couple of days, centred on the Dec 21st solstice, there’s a unique opportunity to see Mercury as it forms a conjunction with bright Jupiter low in the south east in morning skies.

You’ll need a good unobstructed horizon to the SE to catch it. Use Venus as a guide to first find Jupiter, then look through your binoculars and you should see Mercury sitting above.

The window is pretty narrow, from around 7.30pm to 8.30pm. The longer you wait the higher Mercury will rise but the brighter the sky, as the Sun rises.

Good luck and clear skies.

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Mercury through a 10 inch telescope

Star Stories Astronomy Outreach Update

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Starry skies above Abriachan, with Vega and Lyra at the extreme right of the shot.

The Star Stories astronomy programme at Abriachan Forest is going from strength to strength, with tickets selling out far in advance of each event.  Since the last update we’ve hosted two stargazing evenings, involving guest speakers Dr Anthony Luke (UHI) and Professor Martin Hendry (Glasgow University).

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More star studded skies above the classroom, close to brilliant Deneb in the Cygnus region of the Milky Way

The November event was a Leonids special, held near the peak of the annual meteor shower on Nov 16th, with the promise of perhaps observing some early atmosphere skipping Leonids.

Dr Anthony Luke presented a fascinating set of lectures on the chemistry of meteors and stars in the forest classroom, touching on the incredible pressure and heat generated within stellar forges that produce all the elements we see around us.

Meanwhile, I led the stargazing component outside with perfectly clear skies allowing us to take in the brightest stars, and views of the gibbous Moon in video telescope.  The lunar observing was particularly captivating, prompting discussion on the formation lunar maria, the highlands, and the Theia Moon origin hypothesis.

Clelland was also in action over the forest campfire making wooden star models for the younger participants.  There were no dramatic meteor sightings to match October’s spectacle but the event certainly whetted everyone’s appetite.

 

Then on December 5th, Glasgow University’s Professor Martin Hendry (of gravitational wave fame) joined us under dark skies for a Wednesday night special.

Martin is a hard working and inspirational advocate of all things astronomy and space.  Prior to me collecting him at his hotel he had already delivered a packed day of outreach to Inverness schools and hadn’t had a bite to eat since lunch.  Despite this he was incredibly grateful for the cold pizza I offered him on our drive out to Abriachan, and this meagre fare fuelled him sufficiently to deliver two fantastic talks on dark matter and gravitational waves in the forest classroom.  His talk highlighted some of the latest discoveries and simulations from the LIGO (Laser Interferometer Gravitational-Wave Observatory) team.

The following day he was off on the train again to speak to more schools in the far north.

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The Pleiades and red giant Aldebaran

We were also blessed with lots of clear breaks on the 5th, so I once again led the observing component outdoors, this time taking groups further back into the darker areas above the classroom where the Milky Way was ablaze, and fainter fuzzies like the Andromeda galaxy leapt out at us in our binocular and naked eye views.  Amongst many things we discussed the evolution of hot massive stars like Betelgeuse and the Kepler exoplanet survey, which has been scanning vast numbers of star systems close to Cygnus and Vega, cataloging extrasolar planets.

Prior to packing away the binoculars I snapped some pictures of the starry skies close to the forest classroom (attached).

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Orion rising in the east from Abriachan Forest

Both evenings have garnered fantastic feedback and we’re looking forward to the next events, listed below.

As always a big thanks to learning coordinator Suzann Barr, Ronnie, Clelland and the rest of the Abriachan team who help make these events so welcoming and successful.  We’re also grateful to grant funding from the STFC, allowing us to invest in observing equipment, free transport and to extend the scope of this year’s programme.

Future Star Stories Events

Winter Solstice Special (21st December 2018) – Solstice talk and Moon observing with astronomer Stephen Mackintosh, turn of the year campfire twists with Clelland.

Stargazing with Dark Sky Man Steve Owens (12th Jan 2019) – Stargazing with author of Stargazing for Dummies Steve Owens

Star Stories Photography Special with guest Graham Bradshaw (9th Feb 2019) – Local landscape, aurora and night sky photographer Graham Bradshaw shares his stories of nights spent on exposed hillsides and offers tips to budding photographers.

Solstice Special at Abriachan

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The summer Solstice goes largely unmarked these days. Join me up at Abriachan forest on the longest day to learn all about the Sun’s standstill and why it resonated so deeply with our ancestors.

Join us at Abriachan Forest to celebrate the longest day with a Solstice evening of anicent astronomy and storytelling.

We’ll kick off with a talk from local astronomer Stephen Mackintosh, learning about solar and lunar time keeping, horizon calendars & henges, seasonal constellations and more. Stephen will also give an overview of June’s night skies, including a feast of planetary opportunities and tips on how to get the best views.

We’ll then step back in time and sample the entertainment of our ancestors, as storyteller and countryside ranger Clelland McCallum recounts an ancient tale around the flames of an open campfire.

A warm welcome from the Abriachan Staff with refreshments to toast the Sun’s standstill.  All ages welcome. Tickets are £6 per person. Children 8 years and younger go free.

Booking essential via Eventbrite.  Ticket link here.

Exoplanet Hunting and other Habitable Worlds

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Artists impression of a giant exoplanet occulting part of its parent star.

Recent advances in telescope and sensor technology have finally allowed us to start answering one of the great unknowns of the 21st century – how many habitable worlds are there in our Milky Way galaxy?

Until recently it was simply assumed that a fairly high fraction of stars ‘probably’ contained planets, and that some further fraction of those would be in the so-called habitable zone.  These assumptions were based from simple extrapolation from our own solar system (along with some inconclusive inferential data gathered in the 1990s).  But as has been painfuly demonstrated with the hunt for life in our solar system, assumptions like this need careful confirmation, and extrapolating from a sample size of one is seldom convincing.  Often, what we want to believe is, regrettably, not compatible with reality.  The video link from the late Carl Sagan at the end of the piece will give you a flavour for what people ‘guessed’ in the 1980s.

The good news is we now have concrete evidence that an abundance of other planets are out there orbiting other suns – in fact roughly 70% of all stars are accompanied by other worlds.  How do we know this?  There are two simple detection methods which I’d like to explain in more detail, which both ‘indirectly’ detect the presence of other planets.  These are:

  1. Transit Photometry
  2. Radial velocity

Transit Photometry

The first method involves closely observing a star over a period of time with a photometer, looking for any subtle changes in its brightness.  Any dip in brightness which is periodic and cannot be explained by general stellar dynamics is then assumed to be a large body passing between us and the star.

Incredibly, even amateurs with 12 inch backyard telescopes have been able to detect these illumination changes for very large planets, producing crude light curve plots that have later been verified by professional astronomers.

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As the exoplanet passes in front of the host star the number of photons reaching the objective lens of the telescope drops in a characteristic way.

This method of detection works out to distances of several thousand light years, and allows an approximate calculation of the planet’s size, or radius.  Additionally, for certain nearby stars (if clear spectra can be obtained), drops in light from specific elements can be detected, telling us about the possible composition of the planet’s atmosphere.  For example, if the planet contained a Nitrogen rich atmosphere, we might detect a dip in the intensity of the spectrum corresponding to the wavelength of Nitrogen – this process is called ‘absorption spectrometry’.

The main disadvantage of the transit method is that it relies on a nearly perfect edge-on view of the planet-sun ecliptic from our earth bound position.   Otherwise we simply would not detect any occultation.  Thankfully, we can calculate roughly how often this orientation occurs and account for it statistically.  There’s no shortage of candidate stars out there with systems well aligned for detection.

Radial Velocity

The second method is similar, but instead focuses on the relative motion of the star.  Despite the huge difference in mass between a star and its satellites, as a planet orbits it will impart enough of a gravitational tug to make the star  rotate about a small local axis – tiny but detectable.  The larger the planet the bigger this wobble will be.

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An exaggerated illustration of how a large star will rotate about a local axis due to the gravitational influence of a planet.

To detect this regular movement we can look at the light emanating from the star over time and try and detect if its spectra is being shifted by tiny amounts.  By the doppler effect, if the wavelengths of the star’s spectra appear shifted towards the red it must be moving away from us, and the opposite if the spectra is shifted towards the blue.  In this way the sun’s speed and local orbital radius can be calculated, and from that a determination made of the mass of the orbiting planet.

As a quick example, the Sun moves by about 13 m/s due to the influence of Jupiter, but only about 12 cm/s due to Earth.  Incredibly, velocity variations down to 1 m/s or even less can be detected with modern spectrometers, such as the HARPS.  The major limitation of this method is distance.  At the moment it’s generally only useful for star systems up to 200 light years away.

Bringing both methods together, however, lets us form a picture of an exoplanet’s size and mass, and therefore it’s overall density.  From that,  inferences can even be made about the internal structure of the planet.  All this information without even observing the planet!

The Complete Picture

So what do these methods tell us, so far, about the likely number of habitable or earth like planets in our Milky Way galaxy?  The answer is absolutely staggering.

Based on Kepler mission data, as many as 40 billion earth like planets in the habitable zone could be orbiting around red dwarf and sun-like stars.   Taking away the red dwarfs leaves an upper calculation of 11 billion around Sun like stars.  Just think about those numbers for a moment.

That’s as many as one earth-like planet in the habitable zone for every 10 stars in our local galaxy!  A stupendously high number of candidate worlds from which life may have originated.

But here again, we must be cautious.  11 billion is 11×10^9.  But what if the probability of life forming on rocky planets within the habitable zone was actually as low as low as 11 x 10^-9,  or even 11 x 10^-99?  Then there might only be one or no candidate planets containing life.  A depressing possibility, but one we should never allow our natural bias to discount.  The lesson here is that any large number can quickly be diminished in stature by an equally small probability.

At the moment we simply don’t know what this probability of emergent life is.  Some biologists are more optimistic and consider it relatively high for simple single cell life, but other figures, for more complex multi cellular organisms, are much more pessimistic.  But when we do know this figure, calculating the number of planets on which life has arisen will be comparatively simple, and Frank Drake’s famous equation for estimating the number of ‘technical civilisations’ will be one step closer to a final solution.

 

How did we view the question of ‘other planets’ in the context of life outside Earth in the 1980s.  Watch the late Carl Sagan to find out.