Her parents also bought her a small telescope. As a little girl Colleen and her dad studied the Moon with a small telescope. Simulation of a pulsar X-ray pulsars are neutron stars, tiny stars only about 10 miles across. Neutron stars are created when a big star explodes and then collapses back onto itself to form a tiny ball. A neutron star has such strong gravity that a human would be squashed flat.
Young neutron stars spin very fast, and give off radio waves.
Because their magnetic field is so strong, the radio waves can only come out at the north and south pole of the star. If the star's radio beam swings past the earth, we see it as a pulse of radio energy, going on and off very fast. X-ray pulsars are older neutron stars that spin more slowly. They give off X-rays and gamma rays instead of radio waves. That's what the two new stars are that Colleen discovered.