April was unusually good for viewing the heavens. Not only did we have about 20 clear, or nearly-clear nights, we also had a more stable atmosphere than is often the case.
The tell-tale sign for this is the twinkling of the stars, and during April the twinkling seemed less pronounced.
This type of behaviour is not unheard of and is unrelated to the lockdown, but it reminds us of one of the key reasons why astronomers go to great lengths to put massive feats of telescope engineering in some of the highest, most hostile environments on the planet, namely, the tops of mountains.
And not just your average grassy knoll, but seriously large mountains like Mauna Kea in Hawaii and in the Atacama Desert in Chile. These great observatories are so high that it becomes difficult to breathe and in many instances astronomers are not even allowed up to the telescopes themselves but have to work from a remote location at lower altitude where they communicate with support astronomers sited up at the telescopes themselves.
High altitude means low temperatures, devoid of the warming blanket of the atmosphere above to moderate the cold. Instead, most of the atmosphere is below. It can be a strange sight.
I recall being at the top of La Palma in the Canary Islands using one of the telescopes to measure the brightness of quasars. When I looked down and across the sea I could see the lights of Tenerife twinkling in the distance, but when I looked up the stars were solid beacons. This was a reminder that we can, with relative ease, simply drive or cycle to altitudes which take us above most of our atmosphere. This in turn should alert us to just how thin the atmosphere is and the consequent ease with which it can be changed by emissions from within.
And speaking of such emissions, the atmosphere of Venus has been considerably augmented over time, probably by high levels of internal volcanic activity, and it now has 93 times the mass of the Earth’s atmosphere, even though the planet itself is physically similar in size to Earth.
Venus continues to shine to the west in the evening, by far the brightest object in the night sky,although it fades during May. Since the planet is permanently covered in a thick mantle of clouds, an observer on the surface would never see stars or any of the beauty of the Universe that we can enjoy.
As the nights hopefully get warmer, you never can be sure in May, they also get brighter, mostly because the Sun’s rays continue to illuminate the upper atmosphere and its light, even at night, continues to be scattered into our eyes. Onthe night of May 4 the Eta Aquarids meteor shower will peak, but viewing will be compromised by the presence of the almost-full Moon and the brighter skies.
Nevertheless, if you want to watch as the Earth ploughs through the trail left by Comet Halley, thenthis is the night to do so as the Equ Aquarids consist of tiny particles emitted by Halley that now burn up in the Earth’s atmosphere.
Meteors are best viewed with just your eyes, so no need to feel telescope-envy if your socially-distanced neighbour is setting up an impressive looking telescope in their back garden. Alternatively, if you wait until May 7 you’ll have the chance to see the last of the four SuperMoons. In my opinion, SuperMoons are best viewed just as the Moon rises, which corresponds to just when the Sun sets.
The brightness of May’s skies and the twinkling of the stars can be thought of as comforting in these difficult times. Although not related to Covid-19 they are evidence that our atmosphere remains in a largely healthy state. With the right decisions we can keep it that way.