Star Stories 2021 launch October 31st

I’m very happy to announce the launch of the 2021 Star Stories astronomy programme up at Abriachan Forest on October 30th.

If it’s clear I look forward to guiding you under Abriachan’s Milky Way class dark skies. Otherwise I’ll present an indoor talk on the naked eye planets, covering their observational history right up to the advent of modern astronomy.

Meanwhile the Abriachan team will host an outdoor walk and talk about Bats. A creature of darkness so very appropriate for our first dark sky astronomy event.

Tickets will go on sale September 30th. Please follow my Facebook page for the latest.

2021 Perseids Meteor Shower

A bright meteor captured by Chris Cogan from his home in Sutherland, Scottish Highlands

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

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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.

  1. Firmly attach your camera or phone to the tripod.
  2. Disable autofocus and manually focus on some bright stars (make them as small and pin point as possible in your viewing screen)
  3. Set an ISO range somewhere between 1000-3000 depending on the capabilities of the sensor.  Mid 1000s is a good middle road.
  4. Turn off noise reduction or you’ll get big delays between each shot.
  5. Point your camera at a high and clear part of the sky.
  6. 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.
  7. 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.

Good luck and clear skies!

The Atmosphere of Pluto

One of the most amazing parting shots of the planet Pluto, backlit by our distant Sun. Taken by the New Horizons probe as it rushed away from the planet in 2015. Look closely and Plutonian mountains can be seen casting long shadows through the hazy blue atmosphere.

As of now Pluto is the only trans-Neptunian object with a known atmosphere.

Image credit @nasa

Moon Formation

Modelling suggests the Earth came very close to having a pair of smaller Moons.

According to simulations by Canup and Ida (2014) the Earth came very close to hosting two smaller Moon’s (right) rather than the large single Moon we ended up with (left).

This fascinating ‘what if’ modelling is based on the giant impact hypothesis. A faster rate of rotation of the post impact disk is the main requirement for a two Moon system to take hold.

Of course multiple moon system are very common. Saturn for example has an abundance of them, with the most recent count totalling 82 orbiting bodies.

Colour Image: Artist’s impression of an alien world with two moons by Angela Harburn.

Why do we See what we See?

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.

Night Shining Clouds

Lots of wonderful Night Shining Clouds sighted up in the Highlands of Scotland recently. These Polar Mesospheric Clouds are over 50 miles overhead and are lit by the Sun grazing below the northern horizon during mid summer. You need to be between about 50 and 65 degrees north or south of the equator to see them.