Light pollution from large cities affects astronomical observation

The astronomical observation has been harmed in the last decades due to the illumination of roads, properties and houses. called light pollution increased 9.6% year over year from 2011 to 2021, according to studies.

Besides the already known atmospheric pollution, the phenomenon also contributed to change the appearance of the night sky, specialists say.

“Light pollution is the inability to see the night sky as it is naturally due to the artificial lighting of cities, houses and streets. Isso é bem common in modern life, but something that people have thought about in the history of humanity, is very recent. There are no more than a century, perhaps less than isso, in most two places”, explains Roberto Dell’Aglio Dias da Costa, professor of the Department of Astronomy of the Institute of Astronomy, Geophysics and Atmospheric Sciences of the University of São Paulo (USP). , in communication.

Increase in apparent light

One of the most intense forms of light pollution is called “skyglow”, in that the particles that make up light, called photons, are emitted mainly by street lights, among other sources of light produced by human hair.

The skyglow is marked by the increase in the apparent light, not the darkness, and can be observed over distances. The excess of illumination causes the particles of light to scatter into the atmosphere, or makes it difficult to observe stars and planets in astronomy. The problem is aggravated by the presence of satellites and space shuttles in orbit.

The light emissions detected by satellites will increase from 1992 to 2017 by less than 49%. No meanwhile, the index could be even higher considering that the measurement of atmospheric pollution is made from a satellite that does not capture the frequencies of blue light, emitted by LED lights.

Meanwhile, the global LED market grew from 1% in 2011 to 47% in 2019. Which means that most of the lamps are LED, especially those used on the streets.

The skyglow can also be affected by the appearance of new sources of light in a country, rather than by exchanging one lamp for another. What impacts the most is either so much light that it ends up dispersing two poles, or it gives lighting to houses and establishments that, instead of being well directed at or alone, for example, ends up going directly to what is.

astronomical observation

In the observatories, images are captured from time intervals of exposure to the lights of the two stars, as explained by the USP researcher.

“O nosotros olho does not have an exposure time adjustment, so it is not useful for modern professional astronomical observations. I have served immensely at the piss of the 19th century; Due to the invention of photography, around 1840, all the astronomical observations were feitas a olho nu. Porém, isso é pastado, isso é história. Now, professional observatories need image recorders, because most of the information that they see from an astronomical alveus does not see in the form of an image, they fear that light decomposes its components to observe or what is called the spectrum of light says Dell’Aglio.

External light interferences from stars and astronomy impact the quality of the light spectrum to be observed and studied by astronomers. At the same time, light reflected from city dust particles can interfere with observation. For this reason, the observatories are built far from the cities.

“Optical astronomy depends, however, on ter ceus muito obscuros, or mais obscuro possível. For this reason, the professional astronomical observatories are always installed in places far from human activity, normally mountains or deserts, more remote places. More and more ear pollution [luminosa] It begins to be a problem in the large professional astronomical observatories”, says the professor.

In addition to harming astronomy, light pollution has negative effects on human and animal life. It confuses the circadian timing, affects the production of melatonin, the migration patterns – tartarugas, birds and insects are attracted to light, or that make them migrate for the right time or risk in unnaturally lit areas, more artificially, being able to take them to death. Also, marine ecosystems are being altered by pollution.

Reduction of light pollution

It is estimated that currently more than 80% of the population is affected by light pollution. In some places, such as Chile, the United States and Hawaii, there are initiatives to reduce the lighting around two observatories.

Além disso, reserves of darkness with the use of adequate lighting seek to minimize the problem. Among the solutions, there is the installation of light poles that barely illuminate the street, not dispersing to the eye, and with little overlapping of light fixtures, in addition to fewer lighting resources at night.

“Ter céu escuro is not just a quest to do astronomy research. Because of how dark it is to be able to follow the natural cycles, or that it is part of culture, part of education, part of our civility”, says Dell’Aglio.

(With information from Julia Estanislau, from Jornal da USP)