A supermassive black hole, that mysterious tombstone of light, matter and time predicted in the theory of general relativity, may be right under our noses.
Researchers have been suspecting for some time that such an entity lies in the centre of our galaxy. But if black holes can’t be observed directly, how can scientists spot them?
Well, their presence can be determined and measured by observing the behaviour of nearby stars.
In 2002, a young blue star named S2 – known as an O-type star, which is particularly rare, has high mass and is very bright – caught the attention of astronomers when it was seen making an unnaturally sharp turn. The star was moving so unusually fast, scientists estimate only the gravity force from 4 million suns could’ve kept it on its usual course.
It turns out S2 comes back to the same location every sixteen years – a point some 26,000 light-years away from Earth – and exhibits the same behaviour.
The last time S2 encountered this location, the blue star survived the mysterious and frightening pull, but it’s a lucky twist of fate not shared by other celestial bodies. Just a few years ago, scientists observed how an approaching gas cloud was heated, stretched and violently torn apart like fairy floss.
Two teams of astronomers have been observing the star for the last two decades. This year, one of those teams, an international collaboration between Chile and Germany led by Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics, claim to have found the strongest evidence yet that the mysterious area of huge gravitational pull “is indeed a massive black hole” known as Sagittarius A*.
The research group published their findings in the European journal Astronomy & Astrophysics with the title, “Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA.”
The above image of Sagittarius A*, or rather a series of gas clouds swirling around it, was produced by combining infrared light from a series of telescopes at the European Southern Observatory’s Very Large Telescope in Chile.
The colourful streaks show flares of radiation emanating from the hot gas clouds as they are pulled into the black hole at 30 per cent of the speed of light, or 324 million km/h.
“This is the closest yet we have come to see the immediate zone around a supermassive black hole with direct, spatially resolved techniques,” Dr Genzel says.
Today, there is a scientific consensus that the universe is full of these elusive phenomena.
Black holes are objects so dense that not even light can escape they attraction. According to Einstein’s general theory of relativity, when too much matter or energy is concentrated in one spot, space-time distorts. Time slows and matter just vanishes into oblivion.
In 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) confirmed the existence of smaller black holes in the universe when it detected and recorded the sound of two black holes colliding a billion light-years away. The breakthrough fulfilled the predictions in Einstein’s general theory of relativity.
Located in Hanford Site, Livingston, LIGO is a large-scale physics observatory created to detect cosmic gravitational waves.