Scientists have discovered a rapidly spinning neutron star with an unconventional living arrangement. This pulsar cohabitates with two white dwarfs, and the three are smashed together in a space smaller than Earth’s orbit around the Sun. The system is gravitationally extreme, with the three members all tugging on one another.
The arrangement will allow astronomers to test the limits of general relativity and find out if their theories of gravity break down in the face of such a force. The results appeared online January 5 in Nature.
Pulsars are the remnants of massive stars that have exploded as supernovae. City-sized but slightly more than solar-mass, they are as dense as atomic nuclei and can rotate hundreds of times per second, sending lighthouse-like beams of radiation Earth’s way with each spin. White dwarfs, on the other hand, are the leftovers of average-sized stars — stellar corpses squished to Earth’s radius but containing the mass of the Sun.
This pulsar’s extremely regular pulses allow astronomers to measure gravitational perturbations precisely.
“While Einstein’s theory of general relativity has so far been confirmed by every experiment, it is not compatible with quantum theory,” says Scott Ransom of the National Radio Astronomy Observatory, which operates the Green Bank Telescope, the instrument he and his team used to make the discovery.
“Because of that, physicists expect that it will break down under extreme conditions.” With precise measurements of how the dead stars affect one another, the team will find out whether Einstein’s century-old predictions hold up to the scrutiny of stellar systems he could not have imagined.
Portrait of a weird moon Often called a “cantaloupe” for its weirdly variegated surface, marked by twisting, crumpled ridges, Triton is a bizarre world. The most distant of the major moons in the solar system, Triton has characteristics of both classes of satellites — the big spherical ones and the tiny irregular ones.
Triton is spherical and spans 1,682 miles (2,707 kilometers), making it one of the largest moons known. The moon orbits Neptune in a retrograde motion — that is, it travels in a direction opposite that of the planet’s rotation at all times.
What makes Triton even stranger is its surface. It is young, contains geysers that vent nitrogen and dust, and has few craters. The twisting cantaloupe terrain seems to have formed from cold ammoniarich material seeping upward.