Haze, heat, and city lights dim our view into space
ASTRONOMERS around the world are banding together to save the nighttime sky. Besides their old enemies of light pollution and radio interference that drowns out cosmic radio waves, they now have to cope with a growing haze of orbiting space junk and even with urban heat. US Naval Observatory officials, for example, are concerned that heat from proposed high-rise buildings near their Washington, D.C., site would cause enough air turbulence to disrupt their traditional precision measurements of star positions.
So the International Astronomical Union has called a special meeting to consider ways to preserve our view of the cosmos. It will convene in Washington Aug. 13 to 16.
We all have a stake in this discussion because the sky belongs to everyone. As the IAU notes: ``The view of the night sky that our grandparents had is rapidly disappearing. ... Only in a few areas can the real night sky still be seen and all of these are far from cities. A whole generation is growing up that has never seen the Milky Way.''
As world population grows and cities spread, a certain amount of sky lighting is inevitable. But much of the brightening is excessive. It's a thoughtless use of lighting due to general unawareness of its sky-obscuring effect. For example, lighting billboards from below throws the light up into the sky. Lighting the billboards from the top down greatly reduces the glare.
Some observatories, such as the Kitt Peak National Observatory near Tucson, Ariz., have been able to control light pollution by working closely with local communities. Through careful display lighting, better streetlight shielding, and other measures, interference from urban lighting can be minimized. It amounts to only about 8 percent of the night sky brightness at Kitt Peak now.
Radio astronomy sites can also work to curb local sources of radio noise. But radio astronomers face a greater challenge in trying to keep key frequency bands clear for their use. These are the frequencies of natural cosmic radio emissions. There is strong pressure from a variety of radio users to gain access to as much of the radio spectrum as possible for earthly communications.
The space junk haze is part of the larger problem of orbital debris that threatens satellites and manned spacecraft. Here astronomers share a common cause with all space users in trying to find ways to reduce orbital trash. The debris could, of course, ruin orbiting observatories such as the Hubble Space Telescope, now due to be launched next year. But it also hurts ground-based equipment when reflected light ruins observations or even damages sensitive detectors.
Astronomers meeting next August are unlikely to come up with a comprehensive plan to solve all these problems, although they may have some specific practical suggestions. It will be accomplishment enough if they can begin to build an international awareness of the need for sky protection. Gaining that protection requires widespread cooperation locally, nationally, and internationally. And that means general agreement that it is an important common goal.
Loss of our view into space would be a tragedy for everyone. Who wants to live in a cocoon?
A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.