Present and future astronomy sites and the World Heritage List
Richard Wainscoat
University of Hawaii, Institute for Astronomy
President, IAU Commission 50
(Protection of existing and potential observatory sites)
Article 2 of the 1972 Convention Concerning the Protection of the World Cultural and
Natural Heritage defines one of the criteria for “natural heritage” as:
natural sites or precisely delineated natural areas of outstanding universal value
from the point of view of science, conservation or natural beauty
The International Astronomical Union Commission 50 (protection of existing and
potential observatory sites) urges the conference participants to consider how
sites of outstanding scientific value can be added to the World Heritage List.
1. Optical Astronomy
The Earthʼs atmosphere is a major limiting factor for astronomy at optical
wavelengths (i.e., wavelengths similar to what the human eye can see).
Turbulence in the air produces blurring of images. Although astronomy from
space does not suffer from this blurring, space astronomy is extremely
expensive; the vast majority of our knowledge of astronomy has come from
ground-based telescopes.
Because the predominant air circulation in the upper atmosphere is from west to
east, the very best astronomical sites are located on the west coasts of
continents, or on isolated islands. In these locations, the air in the upper
atmosphere flows over the observatory in a smooth manner, with little turbulence,
leading to sharp images of stars. These locations also have less air pollution
than continental or east coast sites, where high aerosol content of the air is a
major problem.
Additionally, observatories need to be located at relatively high altitudes
(preferably at least 2,000 meters) to raise them above the moist marine air layer.
They must also be located at latitudes with good weather — eliminating latitudes
where tropical or temperate rain forests are found on the western sides of
continents.
These requirements lead to a very limited list of the very best sites for optical
astronomy:
a. The coastal mountains of Chile
b. Canary Islands (La Palma)
c. Hawaiian Islands (Mauna Kea, Haleakala)
Present and future astronomy sites and the World Heritage List
d. Baja California and coastal mountains of southern California
e. Namibia, where there is a high plateau
Namibia has not been explored for astronomy; it is not clear whether a plateau
will yield adequate image quality. The famous observatories of southern
California — Mount Wilson and Palomar — are very good sites, but suffer from
serious light pollution problems. Baja California has been explored as a site for
astronomy, including recent tests for the Large Synoptic Survey Telescope and
the Thirty Meter Telescope, but has been found to be inferior to Mauna Kea and
the Chilean sites.
This leaves the following list of the very best astronomical sites in the world:
a. Present and future observatory sites in Chile
b. La Palma in the Canary Islands (Spain)
c. Mauna Kea and Haleakala in the Hawaiian islands (USA)
These sites have been proven to be the very best in recent site testing
experiments for future telescopes. Mauna Kea and Chile remain as the only
sites under consideration for the Thirty Meter Telescope. Chile is the the likely
site for the European Extremely Large Telescope. Haleakala was recently
chosen as the site for the Advanced Technology Solar Telescope, which will be
the largest telescope ever built to study the Sun. This recognizes Haleakala as
the very best site in the world for studying the Sun.
2. Radio Astronomy
Millimeter and submillimeter wavelength astronomy relies on a very dry
atmosphere. An exhaustive search led to choice of the high plain in the Atacama
desert for the site of the Atacama Large Millimeter/Submillimeter Array (ALMA).
This site is by far the best site in the world for this type of astronomy.
The other major radio astronomy project in development is the Square Kilometer
Array (SKA). Site selection of this telescope has been dominated by the need to
find some location on the Earth that have little or no radio interference. And so,
only uninhabited places are suitable, with the remaining choice being South
Africa and Western Australia. It seems likely that the final choice will be the
outback of Western Australia.
3. The need for protection
The optical observatories are under tremendous threat. Optical astronomy
needs dark skies. Artificial lights (e.g., from cities, urban developments, roads
etc.) hit air molecules or dust particles in the air, and scatter back down to the
Present and future astronomy sites and the World Heritage List
telescopes. A 10% brightening of the night sky from artificial sources (relative to
the natural sky brightness) results in an effective 10% smaller aperture for
telescopes, and a corresponding loss of sensitivity and inability to do research.
Light pollution — the artificial brightening of the sky from man-made light sources
— is pervading the entire Earth. In a dark sky, the human eye can see about
2,000 stars. In a dark sky, the Milky Way — the Galaxy in which we live — is a
glorious band across the night sky. Dark skies are part of our heritage. The vast
majority of the Earthʼs population now lives in places where there is significant
light pollution. The majority of the Earthʼs population can no longer see the Milky
Way. There are precious few remaining places where the dark night sky is visible
in all its magnificence.
Astronomical observatories by their nature are extremely sensitive to light
pollution. IAU Commission 50 hopes that listing of the very best optical
observatory sites on the World Heritage List will bring renewed emphasis to the
important need to preserve the dark night sky, particularly over these
observatories.
Optical observatories also need protection from air pollution. Air pollutants
diminish the transmission of light through the atmosphere, and also scatter back
light from artificial light sources into the telescopes.
Finally, optical observatories need protection from aircraft flying overhead.
Aircraft exhaust often seeds cloud formation (“rooster tails”), and interferes with
atmospheric transmission, as well as adding lights and turbulence. Only La
Palma is presently protected from overflight by aircraft.
The radio telescopes have a very strong need for protection from radio
interference. Listing the sites of ALMA and the SKA on the World Heritage List
will be of tremendous value in the future to help resist efforts to add radio
transmitters at locations that will interfere with these telescopes. Radio
telescopes are also vulnerable to aircraft (and their radio transmitters) and should
also be protected from overflight by aircraft.
4. International involvement
Each of the major observatory sites listed above supports research efforts
involving many countries:
Hawaii: USA, UK, Canada, France, Argentina, Brazil, Australia, Netherlands,
Japan, Taiwan, South Korea, Germany
Chile: Chile, Germany, France, UK, Belgium, Netherlands, Italy, Sweden,
Denmark, Finland, Portugal, Switzerland, Spain, Czech Republic, Argentina,
Australia, Brazil, Canada, USA
Present and future astronomy sites and the World Heritage List
La Palma: Spain, UK, USA, Italy, Denmark, Finland, Norway, Sweden, Iceland
ALMA: Chile, Germany, France, UK, Belgium, Netherlands, Italy, Sweden,
Denmark, Finland, Portugal, Switzerland, Spain, Czech Republic, USA, Canada,
Japan, Taiwan
SKA: Argentina, Australia, Canada, China, Italy, Netherlands, UK, India, New
Zealand, South Africa, USA
The extremely wide international involvement at each of these observatory sites
is testament to the tremendous universal value that these sites have.
5. The type of protection
The protection that is being sought from World Heritage for these scientific sites
is unlike the typical protection afforded to a World Heritage Site. Most
importantly, it is the scientific site itself for which protection/recognition is being
sought. It is not the structures that are there; nor is it the landscape itself. In
fact, the usable areas at these locations for science is often very restricted.
Therefore, it should be possible to demolish existing observatories at these sites
(for example to make way for a new more capable observatory), or to build new
observatories at the sites. As an example, Mauna Kea has a science reserve
near its summit, with a small area devoted to astronomy. The Pan-STARRS 4
telescope is a powerful survey telescope planned for Mauna Kea that will likely
be built on the present site of the University of Hawaii 2.2-meter telescope.
6. Other properties of these sites
Many of the best sites for astronomy are worthy candidates for the World
Heritage list for their natural properties. For example, Haleakala National Park is
on the United States tentative list. Haleakala Observatory is adjacent to this
park. The Roque de los Muchachos Observatory on La Palma is adjacent to the
Caldera de Taburiente National Park.
7. Specific threats
By far the biggest threat that the optical astronomy sites face is population
growth, and the concomitant growth in artificial light that is associated with urban
development. Each of the three optical observatory sites — Chile, Hawaii, and
the Canary Islands — is experiencing rapid population growth.
Present and future astronomy sites and the World Heritage List
Listing these sites on the World Heritage List brings additional pressure on local,
state and national governments to limit artificial light, and to install high-quality
light fixtures that have minimal effect on the night sky. It will bring international
help and international recognition to the need to preserve our heritage of dark
skies.
The Chilean sites face dangers from mining. Chile is rich in minerals, and mines
operate on a 24-hour schedule, using bright lights for nighttime operations.
Listing of the Chilean astronomy sites on the World Heritage List will additional
protection and international pressure on the Chilean government to limit mining
near the optical astronomy sites and also near the ALMA site where radio
emissions would interfere with the radio astronomy research there.
If these very special optical astronomy sites are lost due to light pollution or radio
frequency interference, there will be no good place left on the Earth for
astronomy research. Space astronomy cannot replace ground-based astronomy.
There is no way to launch a large telescope into orbit, and the cost of even a
small telescope such as the Hubble Space Telescope or the proposed James
Webb Space Telescope is enormous.
8. The special case of Antarctica
Antarctica is also a wonderful site for astronomy, due to its high elevation, and
dry and cold air, and the 24-hour nights that occur during winter. It is also a
wonderful site for many other kinds of science. It has not been discussed above
because it does not fit into the standard World Heritage List model of being
nominated by a country.
9. Other sites
The list of astronomy sites developed above is an elite list of the very best sites
for astronomy. It could easily be expanded to afford protection to other
observatories, such as the optical observatories in Arizona, the Very Large Array
(radio telescope in New Mexico), and other important facilities.
Present and future astronomy sites and the World Heritage List
The Milky Way seen from Mauna Kea Observatory.
Present and future astronomy sites and the World Heritage List
The Earth seen at night from the Defense Meteorological Satellite.