There are many natural radio signals to be observed in radio astronomy. The glow of gaseous hydrogen, the magnetic field, or the swirl of electrons through pulsars. These signals are often very natural in nature, so astronomers can distinguish them from the artificial chirps and chatter of terrestrial sources. But things can get even more complicated when searching for signals from extraterrestrial civilizations. They must have an artificial nature similar to human radio signals. So how can astronomers distinguish a distant artificial signal from a local one?

This is no easy challenge. Even natural signals can be confused with artificial ones. For example, in 2007 astronomers began detecting bright radio pulses known as Fast Radio Bursts (FRBs). These millisecond bursts are probably caused by magnetars, although we don’t understand much about them. After its discovery, astronomers at Parkes Observatory analyzed its ancient data and discovered FRB-like radio signals known as the peritoneum. Astronomers wondered for a while whether these were similar phenomena, but soon discovered that peritoneums occur when hungry astronomers turn on a still-operating microwave oven and emit a short radio signal before the oven shuts down. By the way, it’s perfectly safe unless you’re at a radio observatory.

The SETI project looks for unusual signals, especially of an artificial nature, and finds most of them. Everything from cars to Starlink satellites can produce a strong artificial signal. Usually, the way to distinguish a local source from a distant source is to move the telescope slightly “out of target” and then back to the source. If you’ve seen the movie before” To contact” is what astronomers did to confirm that the alien signal came from Vega. The problem with this method is that it takes time, that is, it cannot be used for short duration signals. But the team has now developed a different method.