OXON HILL, Md. — Astronomers can peer more deeply into the cosmos than ever before. The key is new technology. But new technology can have a dark side. It can create pollution that interferes with astronomers’ work.
Space debris, light pollution and radio waves are the most worrisome. And the situation is getting worse. These types of pollution could prevent astronomers from getting a clear look at the night sky. This warning came from speakers at the annual meeting of the American Astronomical Society on January 9.
Just six decades have passed since the former Soviet Union launched Sputnik, the first artificial satellite. Back then, there was no terrestrial debris around Earth. But conditions have changed. Today, U.S. government scientists track nearly 18,000 objects orbiting Earth. Most are considered space “junk.” These objects range in size from centimeter-long chunks of metal or other spacecraft debris to bus-sized satellites.
And here’s the problem. All of this junk can damage existing space telescopes. What’s more, many also can reflect light, which could potentially confuse observers using ground-based telescopes. From Earth, a glint of light could be a distant star — or just a hunk of metallic junk.
“The worst is yet to come,” warns Patrick Seitzer. He is an astronomer at the University of Michigan in Ann Arbor. “We're going to double our catalog [of debris] over the next 20 years.” There’s an aerospace company called Boeing, for example, that wants to launch a global network of nearly 3,000 satellites. And collisions between any two of them could cause problems. Any smashup can release thousands of new pieces of debris.
Polluting with light
Down on Earth, light pollution is a well-known problem. Artificial lights can outshine the light of stars. And a shift by many nations to illuminating the environment with light-emitting diodes, or LEDs, isn’t helping.
In 2010, LEDs constituted less than 1 percent of the American lighting market. Today, they account for about half. And their share is expected to grow.
LEDs do have environmental and economic benefits. They are long-lived and energy efficient. But they emit a broad spectrum of light, meaning wavelengths that include many colors. These include blue-rich light, which is especially bad for astronomy. Blue light scatters more easily than longer wavelengths, such as yellow light. That scattering worsens sky glow, a sort of haze of light created as the light reflects off of particles in the air above big cities. Sky glow makes it hard to see the stars.
Radio waves, another source of energy, also pose a problem for star gazers. Astronomers search space for radio waves generated by stars and galaxies. But Earth-based sources of this energy can be confused for those signals. Those terrestrial radio sources can include Wi-Fi and even driverless cars. For instance, the radar on driverless cars could affect radio astronomy operations up to 100 kilometers (62 miles) away, said Harvey Liszt. He is a radio astronomer at the National Radio Astronomy Observatory, based in Charlottesville, Va.
Saving the stars
There is no doubt that technology is affecting the visibility of skies for astronomers across the planet. That’s why the late astronomer Jean Heidmann proposed a radical idea. He suggested putting a telescope on the moon. He’d site it on the far side, away from Earth. There, it would be safe from space debris, light and radio pollution, he noted.
Another, less extreme idea: Impose strict government regulation on radio frequencies. Astronomers may need to expand and secure what are known as “radio quiet” zones. A notable one covers half of West Virginia. It was developed to surround the extremely sensitive Green Bank Observatory. It’s home to the world’s biggest fully steerable radio telescope. In this almost 34,000 square-kilometer (13,000 square-mile) region of radio silence, there is no cell-phone service and almost no radio stations. People here communicate with land-line phones or call from the road at phone booths.
Without a similar effort to safeguard the radio airways, “radio astronomers would lose the ability to observe,” says Liszt. Such action might be the only way, he argues, to preserve a future for Earth-based radio astronomy.
As for artificial light, having none would be best — at least to many astronomers. But most realize that’s almost a futile fight. Still, there are ways to cope. Flagstaff, Ariz., is adopting LED lights. But this city is using what are known as narrow-band amber LEDs. They resemble the yellow, low-pressure sodium lights that many cities have used in the past, and that astronomers prefer. One reason: They limit sky glow.
“Dark skies have become part of the culture here,” said Jeff Hall. He is an astronomer and director of the Lowell Observatory in Flagstaff. He describes it as “a community value. We even have a company called Dark Sky Brewing.”
Such down-to-Earth solutions to pollution may be astronomers’ only hope.
aerospace A research field devoted to the study of Earth’s atmosphere and the space beyond or to aircraft that travel in the atmosphere and space.
astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
cosmos (adj. cosmic) A term that refers to the universe and everything within it.
culture (n. in social science) The sum total of typical behaviors and social practices of a related group of people (such as a tribe or nation). Their culture includes their beliefs, values and the symbols that they accept and/or use. Culture is passed on from generation to generation through learning.
debris Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.
LED (short for light emitting diode) Electronic components that, as their name suggests, emit light when electricity flows through them. LEDs are very energy-efficient and often can be very bright. They have lately been replacing conventional lights for home and commercial lamps.
light pollution The intrusion of unwanted light into areas that would naturally remain dark. Light pollution interferes with our ability to view the night sky. It also alters the circadian rhythms of plants, animals and people.
moon The natural satellite of any planet.
network A group of interconnected people or things.
observatory (in astronomy) The building or structure (such as a satellite) that houses one or more telescopes.
orbit The curved path of a celestial object or spacecraft around a star, planet or moon. One complete circuit around a celestial body.
phenomenon Something that is surprising or unusual.
pristine An adjective referring to something that is in original or near-original condition. It means something is somewhat old but in a seemingly “untouched” or unaltered condition.
radar A system for calculating the position, distance or other important characteristic of a distant object. It works by sending out periodic radio waves that bounce off of the object and then measuring how long it takes that bounced signal to return. Radar can detect moving objects, like airplanes. It also can be used to map the shape of land — even land covered by ice.
radio To send and receive radio waves, or the device that receives these transmissions.
radio waves Waves in a part of the electromagnetic spectrum. They are a type that people now use for long-distance communication. Longer than the waves of visible light, radio waves are used to transmit radio and television signals. They also are used in radar.
range The full extent or distribution of something. For instance, a plant or animal’s range is the area over which it naturally exists. (in math or for measurements) The extent to which variation in values is possible. Also, the distance within which something can be reached or perceived.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
sky glow The dome of light that surrounds cities at night. Sky glow is caused by particles in the air that scatter light from street lights, car lights and other sources of artificial light. Sky glow is one of three types of light pollution.
star The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
telescope Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.
terrestrial Having to do with planet Earth, especially its land. Terra is Latin for Earth.
wavelength The distance between one peak and the next in a series of waves, or the distance between one trough and the next. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.
Meeting: R. Green et al. The triple threat to multi-wavelength observational astronomy. 231st meeting of the American Astronomical Society, Oxon Hill, Md., January 9, 2018.
Journal: J. Heidmann. SETI from the moon: Avoiding radio pollution for future radio-astronomy. Highlights of Astronomy. 1998, p. 996. doi: 10.1007/978-94-011-4778-1_119.