‘Not too hot and not too cold’

88177475_2543093119260958_112126439158972416_n.jpg

The Goldilocks zone around three different type of stars

The Goldilocks Zone.  The above image is a great illustration of the relative size of the habitable zone around different types of star, with stars like our Sun at the bottom.

Even very dim M class dwarf stars (pictured top) could harbour planets with liquid water – the planets would just need to be situated much closer in. These stars can have very active magnetic fields however, frequently throwing harmful radiation out towards any orbiting planets.  M class stars are also extremely stable, some destined to burn for over 100 billions years, much longer than our Sun which has around 4 billion years of fuel left.

In the middle we see the K class dwarf stars. These will also out live our Sun (by a factor of 4), have nice wide zones of habitation, and much less magnetic activity than the M class stars.  Potentially these K class stars are the ideal incubators for the slow evolution of life, and there’s plenty of them. Nearly 13% of stars in our galaxy are K class red dwarfs.  That’s approximately 26 billion in our galaxy alone! 

Rocky-Exoplanet-Orbiting-Red-Dwarf-Star.jpg

An artist’s impression of a rocky world orbiting a red dwarf star, like the M and K class stars mentioned above.

Sirius the Glitter-ball

 

A video of Sirius (the brightest star in the night sky) twinkling on the horizon, captured by Steve Brown @sjb_astro. Many people think they’re seeing a low altitude aircraft or UFO when they witness this.

This phenomenon occurs (to a lesser extent) with any bright star low on the horizon due to the vast amount of atmosphere you’re seeing it through. As stars gain elevation, and less atmosphere is between us and them, they shine more steadily, and views are hugely improved.

The difference in the amount of atmosphere you look through with elevation is very striking (as demonstrated in the sketch below).  Particularly for faint deep sky objects like galaxies, high elevations makes a dramatic difference to the quality of visual or photographic images you’ll collect.

9GxqA

How much atmosphere you look through with observing angle.  At the zenith (overhead) you look through over 2/3 less atmosphere than at the horizon.

Star Stories Astrophotography Special

88174012_2540393609530909_7483019853649936384_o-2

Eric presenting his guest talk up at Abriachan

There were only a few stars up at Abriachan Forest tonight for our Star Stories Astrophotography special, but some nice early views of the waxing crescent Moon and Venus before the weather really turned and a mini snowstorm descended.

Many thanks to our guest speaker Eric Walker from the Highlands Astronomical Society for delivering a fantastic talk on astrophotography.  Eric showcased a ton of amazing images he’s taken over the years demonstrating his passion for astronomy and observing.

Clelland also entertained in the round house with storytelling and we had a nice impromptu discussion about the night sky over the campfire between changeovers.

The next Star Stories is our Vernal Equinox special in March, which will be the last opportunity for dark sky observing this season before the return of longer days.

Eventbrite link here

Urban Astronomy Aurora Special

Many thanks to Graham Bradshaw of Graham Bradshaw Photography for tonight’s fascinating guest talk on hunting down and photographing the Aurora. Here’s one of the beautiful time lapses Graham shared with us during his presentation.

 

Graham also provided a lovely selection of his images (see below) along with camera settings to help budding night sky and aurora photographers.

We also took advantage of some clear breaks in the sky after the talk and walked up to the Nature Reserve to view some bright constellations and star clusters.

Thanks to everyone who came along. The next Urban Astronomy event is our Venus special on March 12th. Booking link here.

Stargazing in the Outer Hebrides

DSC_0056.jpeg

Pre dawn Milky Way on the Isle of Lewis, during the 2020 Hebridean Dark Sky Festival

As a family we’ve visited the Western Isles of Scotland during the warmer summer months, attracted by the wild open spaces, stunning beaches and abundant locations for camping.  Unfortunately the long summer days and short nights are too bright to stargaze, so I’ve never had the opportunity to sample the fantastic dark skies the island has to offer.  I therefore jumped at the opportunity of participating in this year’s Hebridean Dark Sky Festival, organised by An Lanntair and programmed by Andrew Eaton-Lewis.

My outreach involved delivering astronomy talks and stargazing events at community hubs across the island of Lewis.  Over three nights on the island I visited communities at Balallan, Comunn Eachdraidh Nis in North Lewis and the aptly named Edge Cafe over in the west at Aird Uig.

Despite some very wild weather both before and during the festival the three events were a big success, with starry skies materialising in some form at each session.  Skies, when clear, were astonishingly dark, with star clusters and galaxies clearly visible with the naked eye and a glorious sweep of Milky Way evident between the fast moving weather.

DSC_0058.jpeg

Starry skies from Ness Beach

When presenting my stargazing talks in Scotland I always try to persuade people of the merits of binocular and naked eye observing over telescopes when weather conditions are changeable.  This mantra was well demonstrated during these events, with the agility of binocular observing allowing us to quickly head in and out when breaks in the sky presented themselves.

Travelling to each event in my camper van and sleeping out in the wilds was also a memorable experience.  Wind, sleet, rain and hail all assailed me at various points during my wild camps, but I was always rewarded with frequent starry skies opening above me when I headed out for fresh air.

The people of the island are also some of the friendliest folk you could meet, with Highland hospitality well in evidence wherever I went.  Bounteous servings of tea and cake were never far away!

I very much look forward to participating in the festival again and encourage anyone with an interest in stargazing to consider the Outer Hebrides as a viable winter destination, particularly if you’re seeking some of the very best dark skies available.

DSC_0057.jpeg

Satellites aplenty

Venus and Mercury

85024035_2842536592490527_233392740522524672_o.jpgThis is how low Mercury grazes the horizon at the moment. A superb shot of Venus and Mercury from Will Cheung this evening.

If you want to sight Mercury for yourself the best chance is right now in the early evenings just after sunset.  Using Venus as a guide, scan the low horizon with binoculars or naked eye.  An unobstructed horizon like the one in the picture above is essential.

Clear skies.

Crab Nebula Composite

84055277_2520165368220400_5095797449084108800_o.jpg

This is an amazing composite image of the Crab Nebula supernova remnant. It shows the neutron star at the center, superimposed over the shockwave nebula (whose outline can be observed dimly in a decent telescope).

This is what happens to high mass stars when they run out of fuel. The atmosphere of the star suddenly collapses inward and dramatically rebounds off the compressed neutron core.

Conservation of angular momentum makes the neutron star spin rapidly (a pulsar) and the rest of the star’s atmosphere expands into space releasing huge quantities of energy (a supernova).

This particular supernova was observed and recorded by Chinese astronomers in 1054 AD as a ‘guest star’, in the constellation Taurus.  It remained visible as a naked eye star for over a year before fading.