Above: The Parkes Observatory, in New South Wales, Australia (Stephen West, Wikimedia Commons)
In 2015, a Russian telescope detected mysterious signals from outer space. They were coming from the direction of HD164595, a star 95 light years from Earth! Journalists began speculating: could these signals be from an alien civilization?
People have always been searching for signs of extraterrestrial (alien) life. The first modern SETI (Search for Extraterrestrial Intelligence) effort was Project Ozma, launched in 1960. Radioastronomer Frank Drake used an 85-foot antenna to look for signs of intelligent alien life. But all he heard was silence and the occasional false alarm.
Still, Project Ozma sparked the interest of other scientists. Since then, researchers have used many different techniques and technologies to try to figure out if humans are alone in the universe.
So how exactly do scientists look for extraterrestrial life? To a large extent, it involves listening for radio waves coming from deep space. And if you’re interested, you can even help researchers sift through the data!
Did you know? The SETI@home program was launched in 1999. Since then, over six million people have participated. That’s a lot of alien hunters!
Radio towers transmit music that can be picked up by the radio in your car. Likewise, alien civilizations might beam signals into space that eventually reach Earth. These aliens might actually be trying to reach us. Or they might be trying to communicate with each other, and the signals end up reaching Earth by accident.
Of course, the reverse could also be true. For decades, TV and radio broadcasts from Earth have been traveling into space. One day, an alien civilization may receive these signals and try to contact us!
That’s why many SETI researchers search the sky for radio waves. This technique is sometimes called radio SETI. In fact, astronomers think that radio waves are an ideal way to communicate across the universe. That’s because they can travel such long distances. Also, they usually aren’t blocked by the gases and dust found in space.
Did you know? SETI - or Search for Extraterrestrial Intelligence - is the scientific practice of searching for intelligent aliens. The SETI Institute is a non-profit organization dedicated to SETI.
How do scientists listen for alien life?
Astronomers often use very large satellite dishes to listen for incoming radio waves. These dishes are very sensitive, and can pick up many different kinds of signals. Recently, researchers have started to use large numbers of small dishes (LNSD). LNSDs are cheaper and easier to operate than large dishes. The individual dishes are about the same size as the satellite dish you might have at home.
Astronomers use these dishes in two main ways:
- Sometimes, they do a targeted search, pointing the dishes toward a specific area. This allows researchers to study objects in more detail.
- The second strategy is a wide-sky survey. By scanning large areas of sky, researchers can monitor a greater number of planets, stars and galaxies. However, there’s a drawback to this technique. Because they spend less time focusing on specific regions of the sky, the dishes can only pick up the most powerful signals.
Many scientists think that it’s best to use a hybrid approach, which means a combination of both methods. Sometimes, researchers believe certain planets are more likely to have alien life, like exoplanets located in the “Goldilocks zone”. In these cases, it make sense to use targeted searches. But no one really knows what alien life might look and act like, or where it might live. Aliens might be living on completely different types of planets. Wide-sky surveys would make sure scientists didn’t miss out on these planets—or these aliens!
Did you know? The Allen Telescope Array (ATA) is an example of the large numbers of small dishes (LNSD) approach to the search for extraterrestrial intelligence (SETI). Eventually, the ATA will use 350 individual dishes to probe the sky for signals from outer space.
What happens if they detect a signal?
When they detect an unusual signal, astronomers usually monitor the region more closely using more telescopes. This is an important step, because signals can often come from non-alien sources!
For example, telescopes at the Parkes Observatory in Australia detected intense radio waves. These waves seemed like they were coming from deep space. But eventually, researchers discovered the true source: the microwave oven in the staff kitchen! People were reheating coffee and opening the door before the timer went off. This releases microwave radiation for about a quarter of a second. And that’s what the telescope was picking up!
Other false alarms have come from military satellites. And that mysterious signal you read about at the start of this article? Scientists determined that it was actually coming from Earth!
Did you know? The largest telescope on Earth was constructed in China in 2016. Its dish is wider than 30 football fields. One of its jobs is to search for radio waves sent by aliens.
How you can help
Scientists haven’t detected a real alien message yet. But the search continues, and you can help!
Telescopes looking for alien signals generate massive amounts of data. Analyzing this data takes a lot of computing power. The crowdsourcing program SETI@home uses home computers around the world to analyze data from the Arecibo telescope in Puerto Rico.
You can participate by installing the free SETI@home program. It automatically downloads data uploaded to the internet by researchers at U.C. Berkeley, and processes it when you’re not using your computer. Rather than running a boring screensaver, your computer can help search for signals sent by intelligent alien life! Happy hunting.