Campus & Community

Telescopes search for beacons from E.T.

7 min read
This 61-inch telescope in Harvard, Mass., is used to search for light beacons from advanced civilizations in the universe and for finding planets that orbit different sun-like stars. Standing by it are (left to right) Costas Papaliolios, professor of physics; Charles “Chip” Coldwell, research assistant; Paul Horowitz, professor of physics; and Jonathan Wolff, a graduate student. (Photo by Harvard-Smithsonian Oak Ridge Observatory)

Every morning Paul Horowitz checks his e-mail to see if he has any messages from E.T.

The professor of physics at Harvard University has his office computer wired to telescopes that scan the skies seeking radio and light signals from advanced civilizations beyond Earth. So far, he and his colleagues have found some possibilities.

To speed up the search, Harvard has broken ground for a new telescope to look for extraterrestrial beacons. This instrument will be capable of covering a million times more celestial space than the present instrument the University uses for its alien search.

“A high-intensity pulsed laser, teamed with a moderate sized telescope, forms an efficient interstellar beacon,” Horowitz says. “To a distant observer in the direction of its slender beam, it would appear as a brief pulse a thousand times brighter than our sun. We’ve had such technology for years, so we presume anyone interested in contacting us would also have it.”

The project, known as Optical Search for Extraterrestrial Intelligence (OSETI), has been going on since October 1998 with the use of a 61-inch telescope located about 40 miles west of Boston at the Harvard-Smithsonian Oak Ridge Observatory. Harvard astronomers David Latham and Robert Stefanik use the same instrument to look for planets orbiting stars beyond our solar system. Both the 61-inch and the new 72-inch telescopes are limited to looking for light signals. OSETI doesn’t have a budget (or permission from the United Nations) to send beacons into outer space.

At the same Harvard site sits an 84-foot radio antenna that has been searching for extraterrestrial radio broadcasts since 1985. Part of the original search was funded by Steven Spielberg, director of the movie “E.T The Extraterrestrial.

The new 72-inch telescope will be the first earthly “eye” ever built to continuously search the skies for light that would change our world like nothing else in history.

A universe full of life

Horowitz has been trying to make contact with intelligent aliens for 23 years without much luck. “We never thought it was going to be easy,” says the youthful-looking 58-year-old physicist. “We have every reason to believe that the universe is full of life; every reason to believe at least some of it has evolved to intelligence. We developed radio communications about a hundred years ago and lasers about 40 years ago. There might be a civilization out there 1,000 years or more ahead of us. It’s amazing what you can do in 1,000 years.”

What the OSETI team would like to find are bursts of light from sun-like stars in our own or other galaxies. “There are billions sun-like stars in the Milky Way galaxy alone,” Horowitz points out. “To be seen, they would need to send beams a thousand times brighter than our sun. That’s not too hard to do; even we can do it.”

The Harvard OSETI telescope boasts two light detectors to eliminate counting artificial flashes caused by one malfunctioning detector. The sky spies must also make sure that light flashes they record are not just spurious bursts from cosmic rays hitting our atmosphere, or errant sparks from a power line. “And you need to rule out jokers in the trees with flashlights,” adds Andrew Howard, a graduate student working on the project.

Searchers also must ascertain that the light is not natural. In 1967, British astronomers discovered a pulsing radio beam they quickly labeled “Little Green Men #1.” It turned out to be a rapidly rotating star that emits a regular radio signal similar to the beam of a lighthouse. Sky watchers have since found many of these natural beacons, some of which emit light as well as radio waves.

After more than two years of watching with their 61-inch telescope, the Harvard team has found 21 locations where they’ve spotted more than one flash. Two pulses have been seen at 16 different places, three at two locations, two at three sites, and one has been detected five times.

“We see about one random event per night from misbehaving detectors, cosmic rays, or unknown sources,” notes Horowitz. “Therefore, all these multiple sightings might be part of this static, or background noise. But we don’t want to throw out the baby with the bath water, so we keep looking at repeat sites. We’ve looked a lot at the spot where flashes have been seen five different times. As far as we know, it’s bath water, but you can’t be sure.”

A greater degree of certainty would occur if two different telescopes saw such flashes at the same time. To do that, the Harvard group is cooperating with Princeton University to put the same kind of dual detectors on a 36-inch telescope in New Jersey, approximately 300 miles from Harvard.

“The Princeton telescope is far enough away to avoid confusing local flashes, but near enough to have comparable weather,” Horowitz notes.

The most positive way to identify a call from E.T. would be to see some kind of artificial pattern in the signal. Suppose earthly astronomers saw a series of equally spaced pulses, say three, five, seven, 11, then 13 flashes. That would mean someone out there is sending prime numbers: 3, 5, 7, 11, 13, etc. These are numbers that cannot be divided evenly by other numbers higher than one. Receiving that kind of light or radio signal is what Horowitz calls “a clincher.”

Lengthy conversations

The 72-inch telescope will be able detect flashes in any part of the sky visible from the northeastern United States, a task Horowitz called “hopeless” for the present 61-inch instrument. The most interesting targets include stars that show evidence of planets orbiting them. More than 50 such planets have been discovered to date.

Horowitz figures his team can check all the stars visible from Harvard in about a year that has a minimum of 200 clear nights. Each night, the telescope would stare at a strip of sky. Imagine the sky as a striped hemispheric roof with Earth’s rotation carrying the telescope past a part of one stripe each night. Every object in that overhead arc could be looked at for about a minute.

Each night the telescope would move to another stripe. About one-third of a stripe can be observed each night. The other two-thirds would be surveyed later in the year after the sun has moved.

Most of the targets lie in our Milky Way galaxy. Beacons from other galaxies could be detected, but it’s too difficult to hold conversations with beings so far away. Even at speeds of 186,000-plus miles a second, it would take light more than four years to travel to the nearest star, alfa-centuri. The closest galaxy like our own, Andromeda, is so far away that it would take about 2 million years for a “hello” to reach us.

A Milky Way civilization, a scant 60 trillion miles away could get us a message in a mere 10 years. After we build an answering machine, a reply would take another 10 years. Even so, such a protracted conversation could change our knowledge and expectations forever.

“Who knows what’s out there?” Horowitz asks rhetorically. “We’re stuck in a crummy 100 years of technology, trapped in prisons of what we think can be or can’t be. In the past, communications among ourselves has enabled us get out of such boxes. It’s hard to imagine the impact of communicating with a civilization 1,000 years, even 10,000, ahead of us.”

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