Most accurate cosmic clocks show unexpected instability

Millisecond pulsars are the Universe's most accurate natural clocks. A glitch, once thought rare, just occurred twice in the closest one. A combination of X-ray, optical, and infrared data reveal the central pulsar at the core of the Crab Nebula, including the winds and outflows that the pulsars carry in the surrounding matter.

The central bright purplish-white spot is, indeed, the Crab pulsar, which itself spins at about 30 times per second, but will speed up over time. The material shown here spans about 5 light-years in extent, originating from a star that went supernova about 1,000 years ago, teaching us that the typical speed of the ejecta is around 1,500 km/s. The neutron star originally reached a temperature of ~1 trillion K, but even now, it's already cooled to "only" about 600,000 K.

NASA/STScI; Infrared: NASA-JPL-Caltech In all the cosmos, pulsars are the most precise long-term way to measure time. The rate of orbital decay of a binary pulsar is highly dependent on the speed of gravity and the orbital parameters of the binary system. We have used binary pulsar data to constrain the speed of gravity to be equal to the speed of light to a precision of 99.8%, and to infer the existence of gravitational waves decades before LIGO and Virgo detected them.

Here, double pulsar J0737-3039 is illustrated, with the observed relativistic time delay shown at right. Each time these magnetized neutron stars complete a rotation, a pulse of radiation emerges. This most up-to-date view of the nebula MSH 15-52 in X-ray light comes courtesy of NASA’s Chandra X-ray observatory.

Note that the pulsar, at the center of the “base” of the hand, is offset from the supernova remnant itself, near the top-right of the image, indicating that the neutron star has been blown aside with an incredibly rapid kick at about 5% of the speed of light. When pulses intersect your line-of-sight, you’ll observe rapid, periodic bursts. With a very strong surrounding magnetic field, pulsars accelerate matter around them and collimate them in jets that get emitted around two poles.

As the neutron star rotates, the emitted jets rotate, and each time one of the jets crosses your line-of-sight, you observe a pulse of emissions: typically at radio frequencies, but often also at other frequencies as well. The fastest-spinning ones, millisecond pulsars, are the most accurate and stable pulsars for timekeeping purposes. Using the combined data from NASA’s Chandra (X-ray), Hubble (visible light), and IXPE (X-ray polarization, in light blue), pulsar winds coming off of the Vela pulsar, a neutron star just ~10,000 years old, can easily be seen.