After 14 years of staring at a dead star, astronomers have reaffirmed Einstein's theory of general relativity. The PSR J1906 + 0746, a pulsar at 25,000 light-years, shakes slightly as it rotates – an effect that can see its pulses disappear from our skies in less than a decade.
It is called precession – a phenomenon predicted by general relativity, which is observed only with very few pulsars. The new findings could help us determine the limit on the number of binary pulsars in the galaxy, and in turn help us understand the expected collision speed of binary neutron stars.
The pulsars are probably the most useful stars in the sky. They quickly spin neutron stars with jets of bright radio waves emitting from their magnetic poles. As they rotate, these rays can sweep past the Earth, depending on how the star is oriented: a bit like a headlight.
They are also incredibly precise, with rotations that can be predicted to the scale of milliseconds. These so called. Millisecond pulsars can keep time so precise that they can guide future space navigation.
But even the majority of pulsars ̵
When the spin orientation is not properly aligned with the orientation of the binary orbit, this must pull the rotation of the pulsar into axial precession. Such discrepancy is thought to be caused, for example, by an asymmetric supernova explosion.
So, as the pulsar is swinging along its axis, we should be able to detect changes in its impulse profile.
When PSR J1906 + 0746 was discovered in 2004, it shows two clearly rotated or polarized rotational emissions. However, when a team of astronomers led by Gregory Desvines of the Max Planck Institute for Radio Astronomy went to look for archival data collected by the Parks observatory radio telescope, they found only one beam.
To find out what was going on with their subject of study, between 2005 and 2009 using Nançay and Arecibo radio telescopes, and between 2012 and 2018 with Arecibo, the team monitored PSR J1906 + 0746.
When they began observing the star in 2005, they saw both beams of rotation, which was discovered in 2004. Gradually, the beam from the north pole of the star became weaker; by 2016, it had completely disappeared.
The team predicts that the polarization data contains pulsar precession information. They modeled this data, extending it back in time to 50 years, and then compared it to the pulsar observations.
It coincided with an uncertainty level of only five percent, completely coinciding with estimates of general relativity – as well as estimates of the polarization properties of pulsars published 50 years ago by Venkatraman Radhakrishnan and David Cook.
The team also realized that the Earth's line of sight had intersected the magnetic pole of the pulsar from north to south, which meant that it could map the pulsar beam – which in turn allowed them to determine the ratio of the sky illuminated by the beam. .
This helps to estimate the number of binary neutron stars in the galaxy, which can help determine how many of them must collide. producing gravitational waves.
And their model doesn't just work backwards. If I saw how it fit into the observation data, it meant that they too could forecast ahead. The team believes that the southern ray will also disappear from view, sometime around 2028.
It should reappear between 2070 and 2090, with the northern ray reappearing between 2085 and 2105.
can provide gravity tests that cannot be otherwise done, "said astronomer Ingrid Stalby of the University of British Columbia. "This is another beautiful example of such a test."
The study was published in Science .