Q 01/05

What is the boundary around a black hole beyond which nothing can affect an outside observer called?

A) Photon sphere

B) Event horizon

C) Ergosphere

D) Singularity

Answer · why

B) Event horizon

David Finkelstein gave the modern definition in 1958, calling it a perfect one-way membrane.

Q 02/05

What is the name of the supermassive black hole at the centre of the Milky Way?

A) Cygnus X-1

B) Messier 87*

C) Sagittarius A*

D) TON 618

Answer · why

C) Sagittarius A*

It weighs in at roughly 4 million Suns and sits about 26,000 light-years from Earth.

Q 03/05

In which year was the first-ever image of a black hole published?

A) 2011

B) 2015

C) 2017

D) 2019

Answer · why

D) 2019

The result was announced in six simultaneous press conferences around the world on 10 April.

Q 04/05

That first black hole photograph showed the object at the heart of which galaxy?

A) Andromeda

B) Messier 87

C) Centaurus A

D) The Large Magellanic Cloud

Answer · why

B) Messier 87

The galaxy is a supergiant elliptical in Virgo, some 53 million light-years away, with a jet of plasma shooting from its core.

Q 05/05

In which year did astronomers unveil the first image of the black hole at the centre of our own galaxy?

A) 2022

B) 2023

C) 2024

D) 2025

Answer · why

A) 2022

The image had been delayed because data from the South Pole Telescope could not be flown out until the austral winter ended.