Even pulsars — the rapidly spinning cores of dead stars — get kicked around sometimes. A billion-ton asteroid may have recently plunged into one such stellar remnant, which is 37,000 light-years from Earth. The collision interrupted the pulsar’s rhythmic beacon, researchers report in the January 10 Astrophysical Journal Letters.
Pulsars are the lighthouses of the universe; as they spin, they sweep out a beam of radiation. As seen from Earth, the star appears to grow brighter and then fainter with exquisite precision, sometimes up to thousands of times a second. As electromagnetic energy is dumped into space, the pulsar’s spin gradually slows down over time. Researchers hope to use the rhythm of pulsars as a tool for detecting the faint, long-sought signals of gravitational waves.
Astronomers at the University of Oxford analyzed 24 years of radio wave data from a pulsar called PSR J0738-4042 in the constellation Puppis. They noticed that in 2005, the steady beat of the pulsar faltered. A second blip appeared just as the spin-down rate suddenly increased. The researchers argue that they most likely witnessed the pulsar vaporizing something very massive, such as an asteroid.
The finding could have implications for the search for gravitational waves. If pulsars aren’t as steady as has been thought, astronomers might need to rethink the use of the dead stars to probe gravity’s secrets.