Artificial light, star bright

The Department of Astronomy will have an open-house event in Tähtitorninmäki today from 12 noon to 7 pm.

 Tähtitorninmäki

Clear skies and bright stars are a rare delight for an increasing number of city dwellers, and others as well. When the sun sets, we sink into a sea of artificial light, which is reflected in the sky as diffused light. This light pollution, also known as luminous pollution, outshines all dimmer sources of light, such as stars.

For a long time now, scientists have been unable to use old observatories in city areas because of this pollution. And light pollution knows no city boundaries: artificial light from Los Angeles has rendered the observatories built in Southern California in the early twentieth century practically unusable.

Astronomers, however, are not the primary victims of light pollution. Researchers make observations in such remote places as the Chilean mountains and Australian deserts. Observatories in these areas are virtually free of external disturbances. “Ordinary city dwellers suffer the most from diffused artificial light. They have lost contact with the stars in the sky,” says Walter Rydman, physicist and spokesman for the Ursa Astronomical Association.

Considering the population of Finland, Ursa is one of the world’s largest astronomical associations, and it continues to arrange public events in its observatory in the center of Helsinki. This is made possible largely by the Baltic Sea, which unfolds before the observatory, unilluminated. “You can still see objects in the solar system and some of the brightest objects in deep space quite well from our observatory, but you cannot see the starry sky in all its glory,” Rydman says.

The Observatory of the University of Helsinki celebrates its 175th anniversary this autumn.

To honour the anniversary, the Department of Astronomy will have an open-house event in Tähtitorninmäki on Tuesday, 3 November, from 12 noon to 7 pm.

The open-house event will be the last opportunity for visitors to familiarise themselves with the Observatory as part of the Department of Astronomy, as the astronomers are already moving to the Department of Physics located on the Kumpula science campus.

Text: Juha Merimaa
Picture: Veikko Somerpuro
3.11.2009
www.helsinki.fi/universitycommunications


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