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.
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.
Starry skies over the Moray coast
Amidst a very busy schedule last month I managed to head out to Roseisle (along the Moray coast) for some observing and a wild camp. My original mission was to try and catch a geomagnetic storm predicted by the MET office space weather forecasts. As it happened the promised aurora didn’t arrive but I did manage to get some photos of the starry skies that opened up on Saturday night, starting with the International Space Station.
Not the most fantastic ISS shot but I only had about 20 seconds to set up after running down the dunes to capture the pass!. The station is actually travelling from west to east here, towards Sirius (bright star on left)
From there I took a number of pictures hoping to capture some aurora, but instead imaging the crisp starry skies. I’ll let the photos do the talking from here – please read the caption notes.
This image of the Plough (minus Alkaid) was snapped while I was still under the trees, on my approach to the beach. You can clearly see the naked eye double star Mizar-Alcor at the bottom of the image. The main stars in the Plough are roughly 100 lights years away. Our Sun would not be visible naked eye if placed this far away which tells us something about the scale and luminosity of these titan stars.
Looking north towards Burghead where I hoped to capture some aurora. Instead I picked up the rich star fields within the Milky Way near Cassiopeia.
One of many passing satellites.
An interesting shot looking north west. The bright white light is the Portmahomack lighthouse and the orange light pollution on the right is likely from Helmsdale. Perhaps the most interesting feature in this photo is the faint smudge of light in the top left. That’s the Andromeda galaxy – a separate spiral galaxy (larger than our Milky Way) over 2.5 million light years away.
The dog star ‘Sirius’ is now high and visible in winter skies looking South. Draw a line down and left from Orion’s belt and you can’t miss the brightest star in the night sky.
Sirius means ‘scorching’ and was considered a second Sun of sorts to many ancient cultures. Its incredible brightness is due to its close proximity. At only 9 light years away it’s the 5th closest star system to our Sun and a fairly typical hydrogen fusing main sequence star likely to live a long stable life of several billion years. This is in contrast to short lived giant stars like Rigel and Betelgeuse, which are very distant and appear bright due to their bloated sizes and massive energy output.
Procyon is sometimes mistaken for Sirius but it rises earlier, hence its name which means ‘before the dog’. The Arabs told a tale linking Procyon and Sirius as two sisters, who became separated by a great river (the Milky Way) while searching for their missing brother.