In the autumn of 1967 Jocelyn Bell Burnell was working on her Ph.D in the Astronomy Department at Cambridge University, analysing the printout charts of the huge amount of data that was coming in from the department's radio telescope. One day she spotted what she described as 'scruff' on the printout. Looking back at the records she found that this signal always appeared in the same patch of sky. When she made more detailed recordings from that area of space she discovered that the 'scruff' was a series of regular pulses exactly 1.3 seconds apart. Once she had eliminated the explanations that this might be a man-made satellite or a message from aliens she concluded that the signal was coming from a distant star. Jocelyn had discovered pulsars, the rapidly spinning remains of exploded stars which throw out a beam of radiation. As the beam sweeps past us we detect a pulse of radiation. It's like watching a cosmic lighthouse. Dame Jocelyn Bell Burnell is Adam Walton's special guest on this week's Science Cafe. After the discovery of pulsars Jocelyn went on to carve out a distinguished career in astronomy. She's a talented communicator of science, a passionate advocate for women in science and in 2008 she became the first female president of the Institute of Physics. She recently came to Wales as one of the keynote speakers at the Wrexham Science Festival and while she was there she joined Adam to discuss women in science, her religious faith, poetry and, of course, the discovery that made her name.