If you’ve been noticing much clearer skies than normal and an unexpected clarity in your nighttime astronomy sessions over the past week or so, part of the reason could be reduced human activity due to coronavirus lockdown.
According to new satellite data from the European Space Agency (ESA), one of the many impacts of the COVID-19 outbreak has been a drop in air pollution.
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ESA’s Copernicus Sentinel-5P satellite has been mapping air pollution across Europe and China, and the data shows a reduction in concentrations of nitrogen dioxide – such as that released by industry, vehicles and air travel – that coincide with lockdown measures imposed by governments across the world.
The ESA satellite images represent concentrations of nitrogen dioxide from 14 to 25 March 2020, compared to average monthly concentrations from 2019.
“The nitrogen dioxide concentrations vary from day to day due to changes in the weather,” says Henk Eskes, a scientist from the Royal Netherlands Meteorological Institute (KNMI), explaining why that specific date range was chosen. “Conclusions cannot be drawn based on just one day of data alone.
“By combining data for a specific period of time, 10 days in this case, the meteorological variability partly averages out and we begin to see the impact of changes due to human activity.”
The Copernicus data could mean clearer skies for astronomers, as a reduction in nitrogen dioxide points to a correlative reduction in heavy industry, traffic and, perhaps most notably for astronomers and astrophotographers, less air traffic leaving trails across the sky.
Lockdown could also mean a reduction in light pollution from towns and cities, as office buildings close, evening traffic jams lessen and large-scale gatherings that would normally require extensive illumination are cancelled.
But while the effects of the lockdown on air pollution are clear, it remains to be confirmed whether astronomers are truly seeing a notable benefit.
An online report in The Times, for example, suggested that Venus is now visibly bright in the night sky because of a drop in pollution, but regular stargazers and astronomers will know the planet has been consistently noticeable in the night sky for the past few months, offering beautiful observing opportunities including conjunctions with a crescent Moon on clear nights.
However, a lack of haze might account for decreased clarity when observing more distant deep-sky objects.
Stargazing aside, ESA’s satellites will continue to monitor air pollution levels across Europe and the rest of the world over the coming weeks, providing even more data into the effects of the coronavirus shutdown on air quality.
“The long-term cooperation between ESA and KNMI proves very valuable and shows the importance of complementary analyses by different partner organisations,” says ESA’s Director of Earth Observation Programmes, Josef Aschbacher.
“As we can see, the Copernicus Sentinel-5P satellite is the best satellite equipped to monitor nitrogen dioxide concentrations on a global scale.”
Keep up to date by with air pollution monitoring via ESA’s dedicated Air Pollution website. And if you have noticed a change in observing conditions, let us know by contacting us at firstname.lastname@example.org.