Researchers have proposed a new detection method to discover about 10 black holes per year. At this rate, the number of known black holes can double within two years.
Black holes are known to absorb all light and matter. They also emit zero radiation which makes it difficult to image and detect them amid a black background in space. Now, researchers proposed a new method that may accelerate the discovery of more black holes.
New Method To Accelerate Discovery Of More Black Holes
Avery Broderick, from the University of Waterloo, and colleagues proposed a new approach that would detect and study black holes not as individual entities but as a system. The researchers would do this by combining microlensing and radio wave interferometry, standard astrophysical tools that are used today.
Gravitational Microlensing
Gravitational microlensing is an astronomical event that occurs because of the gravitational lens effect. It happens when a dark object such as a black hole passes a light source such as a star. Microlensing allows the study of objects that emit little or no light making the method an ideal technique for studying the galactic populations of planets, neutron stars and black holes.
During transit of the dark object, the background star's light bends around the gravitational field of the object, which makes the star appear brighter. The biggest telescopes currently used to observe microlensing in visible light though have limited resolution so they relay little information about the the objects that passed by.
Interferometry
Broderick and colleagues proposed that instead of visible light, radio waves will be used to take a number of snapshots of the microlensing event in real time.
By looking at the same microlensing event using a radio telescope such as the Very Long Baseline Array (VLBA) interferometer, astronomers would be able to resolve not just one image, which would allow them to extract all kinds of parameters such as mass, velocity and distance of the object.
Using a series of radio images taken over time and turning these into a movie would allow researchers to gather another set of information about the black hole itself.
"Future radio microlensing surveys conducted with upcoming radio telescopes combined with modest improvements in the VLBA could increase the rate of Galactic black hole events to roughly 10 , sufficient to double the number of known stellar mass black holes in a couple of years, and permitting the construction of distribution functions of stellar mass black hole properties," the researchers wrote on The Astrophysical Journal.
