Low-frequency gravitational waves may soon be detectable using pulsars, a new study claims.
Scientists from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) say current radio telescopes may possibly identify the elusive waves, which may provide helpful information to numerous space studies.
The first step is to identify a vast bed of pulsars.
"Detecting this signal is possible if we are able to monitor a sufficiently large number of pulsars spread across the sky," says lead author Stephen Taylor.
What Are Pulsars?
Pulsars are neutron stars with high magnetic properties. Neutron stars are swiftly rotating cores of stars that resulted from the explosion of a huge star as a supernova.
The authors have been investigating how to use these pulsars in identifying signals from low-frequency gravitational waves.
What Are Gravitational Waves?
Gravitational waves include a wide array of frequencies that can also be detected using various technologies.
In Einstein's General Theory of Relativity, he predicted that gravitational waves ripple and spread from speeding huge objects.
Nanohertz gravitational waves are those that come from two supermassive black holes that are moving around each other. Each of these black holes are millions to billion times larger in mass than the ones recently detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO).
The Role Of Black Holes
LIGO identified gravitational waves from two black holes, each of which measures 30 times higher than the Sun's mass.
Such black holes came from the core of separate galaxies that slam against each other. These black holes inch closer to each other and eventually, it will merge and form one enormous black hole.
As they move near each other, the black holes create a pulling action in space and generate a weak signal that travels toward different outward directions.
Pulsars' Specialty: Vibrations From Black Holes
When the vibrations created by the black holes pass the Earth, it shakes the planet a little, resulting in a deviation with respect to distant pulsars. The resulting gravitational waves take months or years to pass by the Earth and need a long period of observations for scientists to detect.
"Pulsars will allow us to see these massive objects as they slowly spiral closer together," says co-author Joseph Lazio.
The situation becomes different, though, when the black holes become too near each other. This is because the gravitational waves emitted by the black holes become very short that pulsars cannot detect it anymore. Fortunately, the European Space Agency and NASA are developing space-based laser interferometers, which would work in the frequency band that can identify signs of supermassive holes combining.
Because the center of galaxies contain many stars and black holes are very small compared to the solar system, looking for evidence of supermassive black hole merger has been a tough challenge for astronomers.
Gravitational Signals Instead
Astronomers then settled looking for gravitational signals from mergers instead. So, they look for pulsars to do just that. Experts at NANOGrav began looking for the fastest-rotating pulsars to determine shifts due to gravitational waves.
At present, NASA JPL's Michele Vallisneri says NANOGrav is monitoring 54 pulsars. The fewest pulsars are detected from the southern hemisphere, hence collaboration with experts from Australia and Europe for the entire coverage would be valuable.
The study was published in The Astrophysical Journal Letters on Tuesday.
