Astronomy’s Environmental Toll Is Surprisingly High

Itt’s hard not to love the Kepler Space Telescope. Launched in 2009, the venerable spacecraft discovered nearly 5,000 suspected or confirmed exoplanets—or worlds orbiting other stars—during its 11-year lifetime. It was built and launched for a relatively low price at $600 million. The spacecraft produced 4,306 scientific papers by 9,606 authors. It sounds great, right? It’s not so.

In those same eleven years, the telescope, which had discovered other worlds, did not favor ours. The annual carbon dioxide emission from the telescope was 4,784 tonnes. That’s a staggering 52,620 tons. This equates to twelve tons CO2 per piece of paper, and five tonnes per author.

Astronomy is, at times, the most simple of sciences. Astronomy is absolutely free. But both ground-based and space-based observatories extract a huge environmental toll—in terms of construction, launch, energy generation and consumption, and even, at least before the pandemic, in the air miles burned as the world’s estimated 30,000 astronomers flew from conference to conference around the globe.

A new paper is now available Astronomy of NatureThe entire greenhouse gas footprint of skygazing has been measured. To complete the analysis, the researchers analyzed the CO2 output from 46 space-based missions as well as 39 ground observatories. These data ranged back to the 62-year-old Observatoire en Haute Provence (in southeastern France) and the InSight observatory, located in New Mexico. In that time, the researchers—affiliated with the Institut de Recherche en Astrophysique et Planétologie (IRAP), in Toulouse, France—concluded that the 85 observatories have generated a prodigious 20.3 million tons of CO2, or an average of 1.2 million tons per year.

“Astronomers get caught up in the day to day—the next funding grant, the next new project,” said Annie Hughes, IRAP astronomer and a co-author of the paper, at a March 17 news conference announcing the results. “Our colleagues are aware of climate change as a problem, but there’s an enormous amount of inertia in the system.”

Three years ago, the researchers began work on this paper. It used 2019 for the year of reference and did not include new observatories like the James Webb Space Telescope and the enormous Square Kilometer array currently being built in Australia and South Africa. Not included in this work are the three ships, from China and the United States, which reached Mars in 2021. The numbers, even without the addition of new spacecraft to the field are alarming enough.

When it comes to ground-based observatories, the straightforward business of construction dominates the first phase of the CO2 emissions—with the pouring of concrete, which releases 600 kg (1,100 lbs.) an additional 8% of carbon dioxide for every ton material. The cement industry alone is responsible for 8 percent of all annual greenhouse gas emission.

“The VLT [Very Large Telescope]The ALMA [Atacama Large Millimeter/submillimeter Array] are just tremendously big and expensive infrastructure and they come with a huge carbon footprint,” said IRAP astronomer and paper co-author Jürgen Knödlseder at the press conference.

The location of the telescope is important too. After a telescope has been built on the ground, it’s biggest contributor to CO2 is from electricity used for its observation. Chile’s Atacama Desert is home not only to the VLT and the ALMA, but to 14 other observatories, thanks to its exceedingly dry air and its 330 nights of clear skies per year. It makes for spectacular viewing. However, Chile only ranks in the middle of the countries regarding the cleanliness and reliability of its electricity network.

“Chile has a kind of average emission factor for electricity,” said Knödlseder. “So it’s not as high, for example, as Australia, which burns a lot of coal, but it’s not as low as Sweden and France, which use a lot of renewable energy.”

Worse, extremely remote observatories may not even be connected to their home countries’ electrical grids and thus must run on their own diesel-generated electricity. ALMA is one of these observatories. The observatory emitted close to 300,000 tonnes of CO2 in its construction phase.

The overall carbon footprint of space-based observatories is smaller than that of terrestrial observatories. They are also much smaller in size and construction takes place in climate controlled clean-rooms or hangars. The biggest impact on the climate is caused by their electricity use, which increases over time. Hubble Space telescope, still in operation and in use for close to 30 years according to the 2019 paper data, has released approximately 21 tons CO2 per 52,497 papers about its results. Based on the estimates of the authors, James Webb Space Telescope (launched Christmas Day 2021) could leave a carbon footprint similar to that of the Hubble Space Telescope. It is expected to release over 1.22 million tonnes of CO2 during its 20-year life expectancy.

This paper stresses the need for the astronomy community to take drastic steps to reduce its carbon footprint, and not just consider it a cost of doing business. The total 20.3million tons of carbon dioxide emitted by 85 observatories amounts to approximately the entire annual output of countries like Estonia and Bulgaria. You can reduce those figures.

“The first step,” said IRAP astronomer and co-author Lyigi Tibaldo, “is that existing structures are decarbonized, by switching to renewable energy sources.” Sun is abundant in the Atacama, making solar power a viable option. In Europe especially, more of the total energy system will rely on renewables. This means that telescopes located in the Atacama region can operate more efficiently without causing a significant greenhouse effect. While most space-based observatories rely on solar panels for power, a cleaner grid allows them to conduct their observations and analyze their data with less carbon emissions.

The authors suggest that we slow down the building boom at the Atacama, and other observatories, in order to rely more heavily on existing astronomical infrastructure. “The strong reduction of emissions that are required in the next decade will not be achieved if we continue building new infrastructure at the pace that is occurring now,” said Tibaldo. “That will also give us more time to perform more comprehensive exploration of the data we have from existing infrastructure.”

The authors admit that this is unlikely to be popular advice. “Some of our colleagues are a bit shocked at the idea of slowing down,” said Knödlseder. “But the [climate] emergency we are facing is so big that we think this option must indeed be on the table.”

For now, the telescopes will keep on working and the astronomers will keep on observing and the paper will continue to be churned out by the thousands and—academically at least—that is a very good thing. But as the authors noted in the very first paragraph of their paper, United Nations Secretary General António Guterres has warned that the most recent International Panel on Climate Change (IPCC) report is nothing less than a “code red for humanity.” It is well and good to go searching for and studying new worlds. But it’s even more important that we preserve and protect the one we’ve got.

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