Increasing global warming and light pollution levels could severely affect ground telescope observations

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Increasing global warming and light pollution levels could severely affect ground telescope observations
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If you reside within the confines of bumbling cityscapes like Bengaluru or Mumbai, chances are you're more likely to spot stars indulging in casual evening strolls amongst commoners than actually in the skies. In such metropolitan skies, soupy evening smog and brash light pollution rarely allow even a single star to peek out among the clouds at night.
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This is tragic, not only because we stand to lose the vast inherent romanticism of stars that we regularly weave into countless poems and songs, but also because it restricts astronomy enthusiasts from indulging thoroughly in their craft. In many ways, a telescope functions similarly to our eyes. Regrettably, this means that if we're facing strain in our star search, so are the world's largest cosmic observatories — including future ones.

One of the most exciting gossip in current astronomy grapevines is the Thirty-Metre-Telescope (TMT) — an international collaboration between India and four of the world's most astronomically advanced nations — whose scale puts even the James Webb Telescope to shame. However, since the TMT will be a ground-based observatory, new studies have revealed several factors that could threaten its and similar telescopes' functioning.

For starters, there's global warming. Climate change's destructive arms have been creeping into every facet of society over the past few decades. It has threatened to submerge entire coastal cities, worsened illnesses, and now, it has also begun affecting astronomy.

Global warming causing cloudier skies


A recent study has unveiled that long-term atmospheric warming has begun restricting the number of photons (particles of light) that make the arduous trip from distant celestial bodies to the Earth. The perpetrator? Increasing amounts of atmospheric water vapour due to global warming, of course.

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According to the study, a moister atmosphere can lead to more cloud cover and precipitation, leading to observation dome closures in such lousy weather.

What's even more concerning is that this observation was built on measurements of incoming solar radiation from atop Mauna Loa since 1958, which distinctly shows a decline in the number of photons that have passed through to the Earth. And Mauna Loa is just over 50 kilometres from Mauna Kea, where the TMT will be built.

According to study lead author Eric Steinbring, this detriment equals losing 12 centimetres of aperture from the telescopes every year. Over time, this could spell disaster for ground-based telescopes' sensitivity and light-gathering capabilities, especially for smaller ones. In addition, this reduction could also hinder our ability to detect one-off events, such as single flashes from distant celestial sources.

Worsening artificial light pollution levels


The other fault in our search for stars is that we're headed towards a brighter future — but only in the literal sense, unfortunately.

A group of international scientists determined that artificial light pollution over major observatories might be worse than we had thought. Out of 28 of these space observatories, only one had "uncontaminated" skies (light pollution below 1% of the expected natural sky brightness).

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Worse yet, only one-third of major ground-based observatories pass this test even if we consider the 10% maximum limit for allowable artificial brightness threshold set by the International Astronomical Union (IAU). If you're worried about the credibility of the IAU, they're the same organisation that downgraded Pluto from planet status (ergo, a big boy at the planetary organisation dinner table).

Considering that we'll be shovelling an estimated ₹22,000 crores into the TMT (almost 2.5 times as expensive as the James Webb), this might be a good time to assess how climate change and light pollution factors into astronomy in order to delay the retirement of such massively expensive toys.

As Steinberg explains, "the effect of global atmospheric change seems to be detectable in the images themselves. And once you see something in your data, you can no longer ignore it".

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The new Thirty-Metre-Telescope will be an international collaboration between India and four of the world's most astronomically advanced nations, whose scale puts even the James Webb Telescope to shame. However, since the TMT will be a ground-based observatory, new studies have revealed several factors that could threaten its and similar telescopes' functioning.