(ORDO NEWS) — The first detection of a black hole drifting in the Milky Way earlier this year has just received an important confirmation.
A second group of scientists, conducting a separate, independent analysis, came to much the same conclusion: it looks like astronomers have indeed found a rogue wandering the galaxy.
Black holes are thought to be the collapsing cores of massive stars that have reached the end of their lives and shed their outer layer of material into space. These black hole precursor stars, 30 times the mass of the Sun, are thought to have a relatively short lifespan.
Thus, according to the most optimistic forecasts, between 10 million and 1 billion stellar-mass black holes can drift silently in space. But black holes are called “black holes” for a reason.
They don’t emit light that telescopes can detect, unless they absorb some matter, a process that generates X-rays from the space around a black hole. So, if a black hole is just floating through space, detecting it is next to impossible.
However, any black hole has a strong gravitational field so powerful that it distorts any light passing through it. For us as observers, this means that we can see a distant star brighter and in a different position than usual – this is a bright marker that a black hole is lurking somewhere nearby.
On June 2, 2011, that is exactly what happened. Two separate microlensing experiments, OGLE and MOA, independently recorded an event that peaked on July 20. This event was named OB110462 and attracted the attention of scientists around the world.
The team, led by astronomers Casey Lam and Jessica Lu at the University of California, Berkeley , concluded that, given the mass range of the object, it could be a neutron star rather than a black hole. Its estimated mass is between 1.6 and 4.4 solar masses.
Like black holes, neutron stars are formed as a result of the collapse of the core of a massive (up to 30 solar masses) stars.
The resulting object is supported by the so-called neutron degeneracy pressure, which makes the neutrons not want to occupy the same space; this prevents it from collapsing completely into a black hole.
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