​London, July 5 (IANS) A team of Swedish astronomers has discovered a growing supermassive black hole in the centre of a galaxy located 70 million light years from Earth.

The team, led by astronomers from Sweden's Chalmers University of Technology, discovered the black hole in the centre of galaxy named "NGC 1377" with the help of Atacama Large Millimetre/submillimetre Array (ALMA) telescope in Chile. 

"We were curious about this galaxy because of its bright, dust-enshrouded centre. What we weren't expecting was this: a long, narrow jet streaming out from the galaxy nucleus," said researcher Susanne Aalto from Chalmers.

The observations revealed a jet which is 500 light years long and less than 60 light years across, travelling at a speed of nearly 800,000 km per hour. 

Most galaxies have a supermassive black hole in their centres. 

These black holes can have masses of between a few million to a billion solar masses. 

How they grew to be so massive is a long-standing mystery for scientists.

"The jets we usually see emerging from galaxy nuclei are very narrow tubes of hot plasma. This jet is very different. Instead, it's extremely cool and its light comes from dense gas composed of molecules," said study co-author Francesco Costagliola.

According to the researchers, the jet has ejected molecular gas equivalent to two million times the mass of the Sun over a period of only around half a million years -- a very short time in the life of a galaxy. 

The motion of the gas in the jet also surprised the astronomers. 

"The jet's unusual swirling could be due to an uneven flow of gas towards the central black hole. Another possibility is that the galaxy's centre contains two supermassive black holes in orbit around each other," said Sebastien Muller from Chalmers.​