World eagerly awaits groundbreaking black hole discovery, but what is it?

9 Apr 2019

Image: © Tyler Hulett/

Astronomers at ESO are set to make a mysterious major announcement about a black hole discovery, perhaps even the first ever image of one.

The last time astronomers have been this excited was prior to the announcement of the first detection of gravitational waves. In the speeches that followed, researchers connected with the discovery described this moment as opening a door to a whole new field of research.

Now, we appear to be on the cusp of an announcement of equal gravitas. This possibility was raised by the announcement from the European Southern Observatory (ESO) that it was to hold a press conference to “present a groundbreaking result from the Event Horizon Telescope (EHT)”.

This will be no run-of-the-mill announcement, with a total of six major press conferences being held simultaneously across the world at 2pm IST tomorrow (10 April). ESO added: “Due to the importance of this result, we encourage satellite events in the different ESO member states and beyond.”

While this in itself reveals very little, the fact it is a major EHT announcement will surely lead to the reveal of only one thing: our very first clear image of the event horizon of a black hole. Despite their regular appearance in science fiction movies and being the centre of fascination for many, black holes have been frustratingly elusive to observe.

The EHT was founded with this one mission, as part of an international collaboration to link radio dishes across the world to create an Earth-sized interferometer, rather than trying to build a single, impossibly large dish.

So far, the network of eight dishes has focused its attention on the two supermassive black holes with the largest apparent event horizons: Sagittarius A* at the centre of the Milky Way and M87 in the centre of the Virgo A galaxy.

Best guesses

As you would imagine, the EHT wants to photograph the black hole’s event horizon, the ‘point of no return’ where no matter can escape.

If you were a betting person, the safe choice would be Sagittarius A* as being the focus of the announcement. Two years ago, the EHT announced that terabytes of data had been gathered to try to create clearer images of the black hole with promises of “razor-sharp images” in the years to come.

As AFP (via points out, Sagittarius A* has a mass 4m times that of our sun, generating a black hole about 44m km across. Despite its size, trying to photograph the black hole located about 26,000 light years away is equivalent to trying to snap an image of a golf ball on the moon.

The other, less likely candidate is M87, a monster black hole 1,500 times more massive than Sagittarius A*, located even further away from Earth. However, leaning in its favour as the focus of this announcement is light smog within the Milky Way. As we sit in the plain of our galaxy, astronomers have to observe Sagittarius A* through a filter, making it slightly more difficult.

So, right now we are none the wiser as to what the exact announcement will be, but we can be sure that it will go down in the history books.

Updated, 10.58am, 9 April 2019: This article was amended to clarify that the black hole generated by Sagittarius A* is about 44m km across, not 44km.

Colm Gorey was a senior journalist with Silicon Republic