Hubble and dark energy
The quest to find dark energy began over 20 years ago
The accelerating expansion of the Universe was discovered in 1998 by studying supernovae in distant galaxies. The initial supernova observations were carried out by telescopes on the ground. However, to learn more about the expansion history of the Universe and the evolving role of dark energy, we want to study supernovas at a wide range of distances, and the most remote ones are hard to observe with ground-based telescopes.
That’s where the Hubble Space Telescope played a decisive role.
As soon as a distant supernova was discovered from the ground, Hubble would observe it in much more detail. Moreover, through repeated observations of a large swathe of sky (known as the GOODS field, for Great Observatories Origins Deep Survey), Hubble discovered dozens of extremely distant supernovas on its own.
Thanks to these high-precision observations from Hubble, astronomers became convinced that the original 1998 claim of an accelerating expansion was real. Apparently, some mysterious force is pushing empty space away from itself. The true nature of this dark energy is still very much a matter of debate. Hubble helped frame the question; whether or not it will also help to provide the answer, only time will tell.