The colour of a star tells us how hot it burns. From the dull red of Arcturus to the brilliant blue of Rigel, you can actually see these subtle colour differences with your own eyes when looking up at the night sky.
Just like an iron cast into the blacksmith’s forge, which slowly changes from red to white hot, stars emit light at different frequencies depending on their overall luminosity and energy output.
The Planck-Einstein equation E = hf is a basic way of understanding this. E is energy, f is frequency and h is the famous Planck’s constant. Higher frequency light (blue) is more energetic than lower frequency light (red) and therefore hotter and more luminous stars tend to appear more blue. Meanwhile cooler stars whose external atmospheric envelopes has expanded (red giants like Betelgeuse) appear redder.
A simple way to highlight the colour of star light is to take your smartphone camera or DSLR and manually defocus it on a target star. This will emphasise the colour and you can even produce beautiful star trails like the one below by taking a movie or long exposure star trail.
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 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.
Please see confirmed dates for my stargazing tours next February for the 2022 Hebridean Dark Skies Festival. I hope to be hosting a walk and talk under the stars from each location with an indoor fallback in the event of poor weather (so please book with confidence). Ticket links below:
The Hebridean Dark Skies Festival runs from 11-25 February. Look out for lots more programme announcements in the next few days – and for our printed festival programme, available at An Lanntair and across the island from next week! Full listings at https://lanntair.com/events/category/dark-skies/
A fantastic programme of events is coming together for the 2022 Hebridean Dark Skies Festival. I’m really looking forward to delivering stargazing experiences for the festival again, from various dark locations across the Hebrides. The festival programme is directed by Andrew Eaton-Lewis and is always wonderfully eclectic with The Sky At Night’s Chris Lintott rating it “A highlight of the last few years”.
Art, Music, Cinema and food frequently accompany the astronomy and stargazing components and more than this I think it’s just a great opportunity for a winter break under some of Scotland’s remotest and best dark skies.
You can read about my previous experiences at the festival from my 2020 and 2021 posts. This year I hope to once again present in person astronomy and stargazing from various dark places across the island.
The 2021 Perseids meteor shower is now underway with peak activity predicted in the early morning of August 11th, 12th and 13th.
The best times to view the shower will be close to and after midnight, when the Perseus radiant is rising higher in the East. However, you don’t need to look at the radiant to see shooting stars as they’ll appear to come from all directions.
This year a thin crescent Moon won’t impact the shower and will have set in the west before proper darkness sets in. Look out for Jupiter and Saturn burning brightly on the southern horizon as you wait for shooting stars.
Observing the Perseids
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 camping mat and (if it’s cold) a warm blanket and lay out under the darkest conditions you can find, preferably away from urban light pollution. It’s an excellent activity to do alone, with family and friends, 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 phone screens 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 LEDs or touches are best for preserving you night vision.
For optimal viewing, head out close to midnight or in the darkness of the pre dawn sky., when the radiant is highest in the sky.
Don’t Expect Too Much
You need to be patient with meteor showers. Sometimes you’ll see many and other times very few or none at all. Think of it as a great excuse to get out under the stars and take in some fresh air. Even if you don’t see much you probably won’t regret heading out and looking up. Very rarely meteor showers can erupt into storms, like the Leonids in 1833 when over 100,000 shooting stars criss crossed the night sky!
What Causes a Meteor Shower
Meteors are the fine dust and particulates left over from comets and large asteroids which stray into our solar system. Some of these are on predictable orbits and as they whizz around the Sun they melt and shed some of this material into space. The Earth then travels through these giant dust trails as it orbits the Sun, producing predictable meteor showers. The Perseids are generated by Comet Swift-Tuttle, which has a 133 year orbit.
Photographing the Perseids
If your have a DSLR camera and tripod, or a suitable phone app like NightCap, you could try capturing some meteors with this rough guide.
Firmly attach your camera or phone to the tripod.
Disable autofocus and manually focus on some bright stars (make them as small and pin point as possible in your viewing screen)
Set an ISO range somewhere between 1000-3000 depending on the capabilities of the sensor. Mid 1000s is a good middle road.
Turn off noise reduction or you’ll get big delays between each shot.
Point your camera at a high and clear part of the sky.
Shoot long exposures ranging from 10s to 30s, or simply use a remote shutter to take long manual exposures. Note: don’t go crazy with very long exposures or you’ll get amp glow from the sensor.
Take lots and lots of shots and be patient!
If your camera has a time-lapse feature you can automate the shooting process and tell the camera to continually shoot 30 second exposures over a long interval. Just watch out for dew forming on the lens if conditions are cold. Some hand warmers stuffed into a sock wrapped around the lens will solve this particular issue.