In 2019, Heino Falcke presented the first image of a black hole’s shadow. This column first ran in The Tablet in April, 2019.
In the aftermath of World War I, a group of astronomers met at the Academy Palace in Brussels to set up the International Astronomical Union (IAU), fostering cooperation among astronomers across national borders. The time for such collaboration was ripe; a few months later, the English astronomer Eddington would observe bent starlight during a solar eclipse that validated the work of the German theorist, Einstein.
The work of the IAU is mostly technical. How we designate star names or universal time standards is arbitrary; that we all use the same designations, is essential. Most people would never have heard of the IAU except for its (arbitrary, but essential) definition of a planet back in 2006, which appeared to “demote” Pluto — to the outrage of small children and others who equate science with memorizing facts.
That outcry, however, pushed the IAU to become more sensitive to the vast interest in astronomy among the general public. Since then it has greatly increased the ways that ordinary folks can participate in its work: running contests for naming new astronomical features, encouraging “citizen science” efforts like the Galaxy Zoo, and promoting to everyone the joy of looking at the stars.
[In April, 2019] the IAU met again in that same Palace in Brussels to celebrate its hundredth birthday. We heard of new outreach efforts to bring astronomy to Africa and to disadvantaged folks like the blind. And we heard how contacts made among scientists collaborating across borders can develop networks of mutual trust and provide avenues for diplomacy. From a purely technical organization, the IAU has evolved into a tool for global engagement.
By coincidence, on the day before the IAU’s birthday party, the EU headquarters in Brussels hosted the Event Horizon Telescope (EHT) announcement of their first image of a black hole’s shadow (as described in my April, 2017, column).
The chair of the EHT science team, Heino Falcke, is an old friend — we’d attended the Vatican Observatory summer school together in 1993. Since I already happened to be in Brussels for the IAU celebration, he got me into the auditorium where he unveiled the image of an orange ring of light, soon to be famous across the internet… illustrating both Einstein’s theories, once again, and that wide public interest in astronomy.
In fact, the EHT targeted two different black holes. The one in the distant galaxy M87, revealed this month, will be joined eventually by an image of the black hole at the center of our Milky Way. The M87 black hole is two thousand times farther away, but by coincidence it is also two thousand times bigger. Thus each looks to be about the same size to us.
The mustard seed
Huge as they are, each black hole covers just a tiny fraction of our sky. Heino compared it to a mustard seed in Washington, DC, as seen from Brussels. To resolve such a tiny speck requires a telescope as big as the Earth. Indeed, Earth’s diameter provides, by coincidence, just the right distance between the different radio telescopes to make these images possible.
Astronomy is full of coincidences. It just happens that the size of the Moon and the Sun as seen in our sky are so well matched that the Moon can exactly cover the Sun. The resulting spectacular solar eclipses encouraged the ancients to develop astronomy, and allowed Eddington to observe faint stars near the eclipsed Sun and confirm Einstein’s Relativity theory.
Sometimes events coincide by chance; sometimes by design. And sometimes even our science can’t tell the difference.