Science & Technology

Blurring the Universe-Eos

When selected by the European Southern Observatory (ESO) SeroparanalA 2,664 meter mountain in the Atacama Desert, Chile. Extremely large telescope (VLT) has touted the site as “the best continental site known in the world for optical astronomical observations, both in terms of number of sunny days and atmospheric stability over the sky.”

Ceropanal is one of the most observed places on Earth. Still, it’s not as pristine as it was when it was chosen in 1990. A study published last September Showed that temperatures have risen, jet streams have become more annoying, and VLT’s observations of distant stars, galaxies, and exoplanets have become a bit vague.

“The main motivation for this study was to raise awareness of the astronomical community that climate change is affecting the quality of observations,” he said. Faustine Cantalloube, Laboratoire d’Astrophysique de Marseille astrophysicist and lead author of the report.

“Atmospheric conditions affect astronomical measurements, so it is important to be prepared for climatic changes,” he agreed. Sae Yamamoto Clewell, Cologne University of Cologne and Professor of Meteorology. These preparations are especially important as ESO is building a very large telescope (ELT), A huge telescope of 39 meters, which is the largest telescope in the world, located on the mountaintop about 20 km from Paranal. ELT is expected to be a “hard worker” for decades, Crewell said.

Astronomers are just beginning to consider how these changes affect observations, or may affect them in the coming years. Potential problems include reduced “seeing” (the clarity with which the telescope observes the universe), as well as increased risk of wildfires and the need for more power-consuming air conditioning to keep the telescope’s mirrors cool. Includes being.

“In the long run, we are concerned about how climate change will affect the feasibility of certain stations,” said Paranal, Chile and others. Travis Lector, University of Alaska Anchorage Astronomer, American Astronomical Society Sustainability Committee.. “Can we enjoy the same quality of observations years in the future?”

Evaluation of VLT as a test case

Paranal is the first observatory where scientists studied the question. The Cantalloube team has compiled over 30 years of meteorological observations made on the site, including temperature, wind speed and direction, and humidity. The study also included a reanalysis of information from two European climate databases up to 1980.

Records revealed a temperature rise of 1.5 ° C during the study period. This change is important because the VLT dome cools during the day to match the expected ambient temperature at sunset. If the telescope’s mirror is warmer than the temperature, heat waves will undulate over the mirror and blur your view, much like it would be on a desert highway on a summer afternoon.

VLT’s current cooling system was designed to maintain temperatures below 16 ° C, as the sunset temperature exceeded that value by about 10% when the telescope was designed. But in 2020, it took about a quarter of the time. As a result, Cantalloube said that as temperatures continue to rise (perhaps up to 4 ° C by the end of the century), the air conditioning and cooling capacities of many telescope equipment need to be increased in the future. , According to some models).

The study also found that changes in jet stream caused a periodic increase in wind shear in the upper troposphere, producing a blurring effect known as wind-induced halos, especially during the El Nino phenomenon. The four components of the VLT, the 8-meter telescope, are equipped with adaptive optics. Adaptive optics uses lasers and deformable mirrors to create and focus artificial “guide stars” in the upper atmosphere to correct most blurring. However, wind shear eddy makes the system difficult to operate. The study states that this is particularly troublesome for efforts to image extrasolar planets that require both high resolution and high contrast.

“Monitoring weather parameters in the field is one way to get the most out of the telescope’s time thanks to a coordinated observation schedule,” says Cantalloube. For example, “Some observations are less affected by humidity, while others are less affected by humidity, so if you know the content of atmospheric humidity in advance, you can schedule your observation program accordingly.”

Cantalloube said her team continues to evaluate paranal data as it expands its work to study the state of major observatories in Hawaii, Arizona and the Canary Islands.

Ground threat

The president points out that climate challenges are not limited to view quality. “The most obvious threat is wildfires,” he said. “In recent years, we’ve seen several large-scale fires near the observatory, especially in California.”

For example, last August Fire on Mount Hamilton, California Burned one dwelling and damaged the other dwelling Lick Observatory I hardly missed some of the telescopes. After a month, another fire could break out Mount Wilson Observatory, Near Pasadena. Siding Spring Observatory In Australia, in 2013 the lodge for visiting astronomers and other buildings was lost, and in 2003 the country’s Mount Stromlo Observatory lost several major telescopes.

Satellite image of Australia's Siding Spring Observatory surrounded by burnt landscapes
The aftermath of the fire at the Siding Spring Observatory in Australia is shown in brown in this false-colored image from NASA’s Terra satellite. The observatory forms a small patch of red spots with white spots near the center. The image was taken in February 2013, three weeks after the fire. credit: NASA Earth Observatory Image by Jesse Allen. Data from NASA / METI / ERSDAC / JAROS, USA / Japan ASTER Science Team

“Many observatories are remote and have limited access, so protecting them from wildfires can be very difficult,” Lector said. “They are the most vivid threats.”

Proposed solution

One of the proposed solutions to climate change could actually cause even more problems in astronomy, Lector said. Some climate scientists Aerosol injection Entering the upper atmosphere reduces the amount of sunlight that reaches the surface of the earth, which can possibly reverse the trend of warming. However, it will also reduce the amount of light from stars and other celestial bodies that reach the surface. “Aerosols are probably best preserved as the last ditch of Ave Maria,” Lector said.

Cantalloube et al. Say that astronomers need to reduce carbon dioxide emissions by reducing travel, reducing their reliance on energy-intensive supercomputers, and taking other steps. I did. “Technology development can address these subtle effects of climate change,” said Cantalube. “I’m more worried about how to do that. How can we make our observatory more environmentally friendly?”

—Damond Benningfield ([email protected]), Science writer

This story is part of a week-long coverage of Covering Climate Now, with a focus on “surviving climate emergencies.” Now cover the climate Is a global journalism collaboration aimed at enhancing coverage of climate stories.

Blurring the Universe-Eos Blurring the Universe-Eos

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