A pulsar is a celestial object that is thought to be a rapidly rotating neutron star. The incredibly dense leftovers of a supernova, a pulsar emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second. Sometimes, pulsars are locked in a ridiculously tight orbit with another star. When that happens, things can get very interesting very fast, if you’re in the right position to observe it.
When a pulsar is locked in an orbit with another star, the gravity between them can become intense, so intense that it is believed by scientists to emit waves and to actually bend space-time itself, making the pulsar “wobble” in the process.
Scientists at the Netherlands Institute for Radio Astronomy have been watching Pulsar J1906 for the last five years. In that time, the astronomers determined the pulsar’s weight and quantified the gravitational disturbance between it and it’s paired star.
Then, all at once, the pulsar disappeared in the wink of an eye. Its beams of radio waves, like a lingering scream, are now passing by the Earth, and scientists are saying that the vanishing of Pulsar J1906 can be explained by something called “precession.” Precession is when a star actually wobbles far enough that it dips into the space-time bend that its own orbit created.
Having observed this incredible occurrence firsthand, the astronomers published a paper on it in The Astrophysical Journal and were presented at the 225th meeting of the American Astronomical Society.
The lead author of the study, Joeri van Leeuwen, discussed the properties of pulsars with reporters.
“They pack more mass than our Sun has in a sphere that’s only 10 miles across.”
Dr. van Leeuwen continued to explain what happens when pulsars occur as binaries. He said that neutron stars “come hard up against Einstein’s theory of general relativity,” and generate space-time ripples called gravitational waves in the process. Though undetectable now, astronomers hope that one day they will be able to find solid evidence of the phenomenon.
The lead author said that Pulsar J1906 popped up unexpectedly during a routine survey of the sky.
“It was strange, because that part of the sky’s been surveyed lots of times – and then something really bright and new appears.”
The astronomers discovered the pulsar was accompanied by a companion star, and between the two of them, they were pushing the bounds of physics. The two stars circled each other in just four-hour rotations, which is the second fastest orbit ever observed. The pulsar itself spun seven times per second, blinking its two radio wave beams across space to Earth.
For the next five years, Dr. van Leeuwen’s team observed over one billion rotations of the pulsar using the world’s five biggest radio telescopes.
Co-author of the study, Professor Ingrid Stairs of the University of British Columbia, Canada, spoke of how the pulsar was observed.
“By precisely tracking the motion of the pulsar, we were able to measure the gravitational interaction between the two highly compact stars with extreme accuracy.”
She said that both the pulsar and its binary are approximately 1.3 times heavier than our Sun, but they are only separated by one solar diameter.
“The resulting extreme gravity causes many remarkable effects.”
Chief among those is the time-space warp and the wobble that has now caused J1906 to shine its light elsewhere in time — for the time being.
The pulsar’s axis drifts by two degrees every year, and according to Dr. van Leeuwen’s calculations, it should swing back around to shine on Earth again by about 2170.
[Image via Jantoniadis]