A black hole is an object with such strong gravitational attraction that even light can not escape.
Until very recently, most research into black holes has focused on stellar black holes, which will have a mass of 5 to 100 times the mass of our Sun, and on supermassive black holes, which exist at the center of most galaxies and have masses in the millions or even thousands of millions of solar masses. The black hole in the center of the Milky Way galaxy has a mass of 4 million solar masses. The recently imaged black hole in galaxy M87 has a mass of 6,000 million solar masses. Some research has also assessed intermediate black holes, that would have a mass of 100 to 10,000 solar masses.
The traditional method to detecting a stellar mass black hole requires that the black hole is part of a binary star system, where the second star is a normal star. The black hole pulls matter from the normal star, resulting in the emission of X-rays, which CAN be detected. The presence of X-rays emitted from a binary star where only one star can be observed indicates the presence of a black hole. Detailed analysis can reveal the mass of the black hole.
Many black holes that are part of a binary system are too small or too far from the normal star to produce X-rays. However, a new method has resulted in the detection of a black hole of just 3.3 solar masses. This would have a diameter of about 6 miles. This is approaching the lower limit for the theoretical size of a black hole.
The new method relies on scanning the sky using a telescope designed to look for binary systems. The research team then used data from another telescope system to filter the collection of binaries. One star, located in the constellation Auriga, showed evidence of an unseen second object. There was no evidence of X-ray emissions. Analysis of the data indicated that the unseen object was likely a black hole with a mass of about 3 solar masses. Further research is underway to provide additional evidence.
This new technique expands our ability to detect and study black holes.
Western Slope Skies is produced by members of the Black Canyon Astronomical Society. This episode was written & recorded by Bryan Cashion.