Neutron stars cram more mass than that of the sun into a sphere as wide as a city. A teaspoon's worth of a neutron star weighs in at a billion tons. Exotic though they may be, neutron stars are not what physicists would call strange, according to a study reported this week.
To find out what these ultradense stars are made of, Jean Cottam of NASA's Goddard Space Flight Center in Greenbelt, Md., and her colleagues used an X-ray satellite to determine how light is warped by the extreme gravity of a neutron star partnered with an ordinary star some 30,000 light-years from Earth. This pairing is known as EXO0748-676.
According to the general theory of relativity, light escaping from any strong region of gravity