Source: http://www.wired.com/2015/10/guys-lots-o...

When you’re searching the vast expanse of space, lots of things look like they could be signs of extraterrestrial life. Astronomical observers are constantly looking for tiny glimmers of information in the mess of noise that streams through space toward Earth, and often, things that at first look like signals end up being mirages. This has all happened before; it will all happen again. For example:

Pulsars In 1967, astronomer Jocelyn Bell was monitoring signals from the Mullard Radio Astronomy Observatory, trying to analyze the behavior of quasars, energy-spewing regions surrounding supermassive black holes within distant galaxies. What she found, though, was a series of regular pulses, always from the same part of the sky, that she labeled LGM-1: Little Green Men. Soon, though, she found similar signals coming from another part of the sky, and realized that she wasn’t seeing messages from two different alien civilizations: It was radiation from a spinning, magnetized neutron star—the first measured pulsar.