A team of astronomers using the MeerKAT radio telescope in South Africa has discovered a mysterious object in the Milky Way galaxy that could be either the lightest black hole ever detected or the heaviest neutron star. The object, dubbed "M33 X-7," is located about 10,000 light-years from Earth in the constellation Sagittarius.

Black holes are formed when massive stars collapse at the end of their lives. Neutron stars are formed when the cores of massive stars collapse, but not to the point of forming a black hole. Neutron stars are extremely dense, with a teaspoon of neutron star material weighing billions of tons.

The object's mass is estimated to be about 6.9 times the mass of the Sun, making it too massive to be a neutron star and too light to be a black hole. This puts it in a class of objects known as "intermediate-mass black holes" (IMBHs), which are thought to be relatively rare.

If M33 X-7 is confirmed to be an IMBH, it would be the closest one to Earth ever discovered. The closest known black hole to Earth is V616 Monocerotis, which is about 3,000 light-years away.

The discovery of M33 X-7 could help astronomers learn more about the formation and evolution of black holes and neutron stars. It could also shed light on the mystery of missing mass in the universe. Missing mass is the matter that is thought to exist in the universe but cannot be seen. Some astronomers believe that IMBHs could account for some of the missing mass.

Further observations of M33 X-7 are needed to confirm its nature. If it is indeed an IMBH, it would be a major discovery that would have important implications for our understanding of the universe.