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Environmental Challenges to Astronomy

Human activities are changing our environment on all scales. These global changes are increasingly interfering with scientific investigations, also in astronomy. The sources of interference are numerous and rapidly proliferating, both on the ground and in space, and international measures to protect the possibilities for future generations to continue the exploration of the Universe are becoming urgent. Disseminating information about these issues to the public in general and to policymakers in particular is a key priority item for the IAU.

These issues are further described in an article which appeared as a "Policy Forum" on p. 443 of the April 21, 2000 issue of Science Magazine.

In continuation of Resolution A1 of the XXIIIrd IAU General Assembly (see IB81), the IAU Executive Committee has issued the Policy Statement reproduced below. Based on this policy, the IAU will continue to work with all interested organizations, international and national, governmental, intergovernmental, and non-governmental, to protect the night sky as one of the few remaining natural resources available to all mankind. The statement below may be reproduced by organizations and individuals cooperating in this endeavour, provided credit is given to the IAU.

As part of the efforts of the IAU to call attention to the environmental challenges to astronomy, IAU Symposium 196: "Preserving the Astronomical Sky", an IAU/COSPAR/UN Special Environmental Symposium was held in Vienna July 12-16, 1999, in conjunction with the United Nations' Third Conference on the Exploration and Peaceful Uses of Outer Space (UNISPACE III). The Proceedings of IAU Symposium 196 willl be published in the IAU Symposium Series; the Observations and Recommendations from the Symposium, the related IAU Press Release 02/99, and a short preliminary Report are available here.

As an important step towards specific action in the field of ground-based light pollution, a Working Group on "Controlling Light Pollution" has been appointed under IAU Commission 50 to collect and disseminate information on all aspects of the light pollution problem, including its scientific, technical, educational, and political implications. Correspondents are urged to contact the Working Group with information on light pollution problems as well as for obtaining advice on suitable technical solutions and effective channels through which to promote their application.

This statement is also available in a French Version. Ce document existe aussi en Version Française.

IAU Policy Statement on Environmental Challenges to Astronomy

During the 20th century, astronomy has made great progress on the most fundamental questions concerning the origin and evolution of the Universe and our place in it. Within subjects ranging from the origin and evolution of the Solar System, the formation and evolution of stars and the origin of the chemical elements, the nature and evolution of galaxies, up to the structure, origin, and evolution of the Universe itself, sound physical theories have been developed and tested against a wealth of increasingly detailed observational facts.

Except in the Solar System, astronomers cannot conduct experiments on the subjects of their studies. Thus, our understanding of the Universe is primarily based on observations of the electromagnetic and other kinds of radiation emitted by stars and galaxies. The dramatic recent progress is due to a series of observational breakthroughs, made with ground and space based observatories and closely linked to the development of cutting-edge technologies. In order to probe the diverse range of astronomical objects, observations must cover all wavelengths from radio via infrared and optical to X- and gamma-rays, some of which are only accessible from space.

The phenomena thus discovered include the most violent events known in the Universe. Yet, these objects are so far away that the signals recorded by astronomical telescopes when capturing radiation from the early phases of the Universe are vastly fainter than those familiar from everyday life. This fact makes astronomy especially vulnerable to, but also a very sensitive indicator of, environmental degradation affecting the night sky at all wavelengths.

At the threshold of the third millennium, progress in the further exploration of the depths of the universe is threatened by human activities affecting the night sky. Briefly, these adverse effects are fourfold:

  1. Pollution by scattered light from ground based light sources.
    To millions of people living in or near great cities or industrial centres, the sight of the dark night sky is unknown. Plainly visible from space, this light not only obliterates the faint signals reaching us from the Universe, it also represents the useless waste of much fossil or nuclear fuel. Thus, economic incentive and scientific interest go hand in hand in this matter. Simple measures exist to direct light where it is needed, and thus both conserve energy and keep the night sky pristine; they need to be implemented more widely. The IAU values and supports the numerous national and local initiatives taken to promote understanding and action on this issue. IAU actions in this field are coordinated by the Working Group on "Controlling Light Pollution" under IAU Commission 50.
  2. Interference from man-made radio noise.
    Radio astronomy has contributed several of the most fundamental discoveries of the past century. Now, however, it is under relentless and increasing pressure, above all from the communications industry, to give up the protected wavebands containing the astrophysically most important frequencies. Considering that an ordinary portable telephone, if placed on the Moon, would be one of the very brightest sources in the radio sky at its wavelength, even sideband radiation from transmissions in a permitted waveband may be fatal to astronomy. Continued efforts by the IAU and URSI (Union de Radio Science Internationale), as represented by the Inter-Union Committee on the Allocation of Frequencies for Radio Astronomy and Space Science (IUCAF) within the International Telecommunications Union (ITU), are vital for radio astronomy to survive in the face of this competition.
  3. Space debris.
    Space debris from spacecraft and launchers has two kinds of deleterious effects on astronomy: First, it leaves luminous trails on the sky which ruin astronomical observations. Second, direct hits by spacecraft debris are a threat to the survival of scientific satellite observatories, including the International Space Station, somewhat analogous to the effects of swarms of small natural meteorites. The former effect is mainly felt by astronomers; the latter problem affects all satellites regardless of their purpose. For this reason, international efforts are under way to control the growth of space debris, which will hopefully also benefit astronomy.
  4. Technology experiments and artistic or commercial displays in space.
    Experiments continue to be proposed which would place strongly luminous objects in space, whether for technology assessment (generation and transmission of illumination or power), or for artistic or commercial purposes. Responsibly executed and carefully controlled experiments should, of course be allowed, but malfunctions may occur. Moreover, at the moment, no international regulations exist to prevent uncontrolled private and other enterprises from launching objects into space that would ruin the night sky for people of all nations, potentially for many generations: Unlike ground-based art or advertising displays, space displays respect no national sovereignty or environmental regulations. An international treaty is needed to prevent unbridled proliferation of such displays to the irreparable detriment of scientific progress in astronomy.

The IAU, therefore, urgently appeals to the nations of the world to negotiate and implement an international treaty regulating space activities that would unnecessarily endanger what is perhaps the last natural resource available to all mankind: The night sky. Clearly, nations should be free to develop potentially beneficial space technology in a controlled and responsible manner as defined by internationally recognised guidelines. The IAU urges, however, that such guidelines be defined with due regard to the protection of peaceful scientific investigation, following the models set by, e.g. the Antarctic Treaty or the international agreements on radio frequency allocations.

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