There was an interesting announcement today from the world of extra-galactic astronomy, as a team from the European Southern Observatory's Very Large Telescope (a name which I think sums up the creativity of scientists perfectly) have published evidence of the first black hole to be detected outside of our own Milky Way galaxy.

(For those few who do not yet know what a black hole is, it is a region of space and time that is so strongly curved, or has such a strong gravitational field, that not even light can escape from it. Aside from some arguments utilizing quantum mechanics, nothing that enters a black hole can ever exit again. The modern theory of black holes dates back just over a hundred years, and experimental evidence has only existed for the past few decades)

The team made the observation by carefully tracking how stars near the black hole were moving. Black holes themselves cannot be viewed directly, as no light can escape from them, but their powerful gravitational fields cause stars and other objects to move in odd ways. At present there is no other object or phenomena in the Universe that can create gravitational fields that are strong enough to explain these movements. The method used at the ESO VLT has not been tried before, but now that it has been proven it could be useful for surveying a number of other potential black holes both in our own galaxy and beyond to other galaxies or intergalactic space.

In this example, a small black hole was detected in NGC 1850, a cluster of a few thousand of stars that exists 160,000 light-years away in the Large Magellanic Cloud, a neighbor galaxy of the Milky Way. (And by small, they mean that it is a mere eleven times heavier than our own Sun). The astronomers were able to observe five stars, each comparable in size to our own Sun, and determined that they were orbiting something massive and invisible - a black hole.

Astronomers have previously detected this type of small, stellar-mass black hole in other galaxies only by picking up the X-ray glow emitted as they absorb matter, or from the gravitational waves generated as black holes collide with one another or with neutron stars. However we know from previous theories and observations that most stellar-mass black holes don’t generate enough X-rays or gravitational waves to be detected. This new method will allow many of these hidden black holes to be detected as well.

And the next few years promise more such discoveries, as the ESO’s Extremely Large Telescope in Chile (another creative name offered by the scientific community), is set to start operating later this decade, and will allow astronomers to find even more hidden black holes.  

It is truly amazing how much one species living on a pale blue dot in an unremarkable Solar System in an unremarkable galaxy can learn about the Universe through a few simple observations.