But there is a problem.
The universe is enormous, and even our most powerful telescopes can examine only limited portions of it at extraordinary detail.
NASA’s Nancy Grace Roman Space Telescope is being built to change that equation.
Roman will combine the sensitivity of a major space observatory with something astronomers desperately want: a much wider view.
Its primary mirror is roughly 2.4 metres across—the same diameter as the Hubble Space Telescope’s main mirror—but Roman’s Wide Field Instrument is designed to capture an area of sky vastly larger than Hubble can see in a single observation.
Think of Hubble as an extraordinarily powerful zoom lens.
Roman is being designed more like an enormous cosmic panorama camera.
That difference could allow scientists to survey hundreds of millions of galaxies and potentially discover thousands of planets beyond our solar system during its mission.
But Roman isn’t being sent into space simply to produce spectacular photographs.
It is being built to investigate a mystery sitting at the centre of modern physics.
Most of the universe is still a mystery
Everything we can directly see—stars, planets, people, oceans and galaxies—accounts for only a small fraction of what scientists believe exists in the universe.
The rest appears to be dominated by two things we still don’t properly understand: dark matter and dark energy.
Dark matter does not shine like ordinary matter, yet its gravitational influence appears throughout galaxies and galaxy clusters.
Dark energy presents an even stranger problem.
Observations indicate that the expansion of the universe is accelerating. Scientists use the term dark energy for whatever is driving that acceleration, but its fundamental nature remains unknown.
Roman will map enormous numbers of galaxies across vast distances, giving astronomers a much larger dataset with which to examine how the universe expanded and how cosmic structures developed.
Those measurements could strengthen our current understanding.
Or they could reveal that something important is missing from it.
Then there are the planets
Roman will also search for worlds far beyond our solar system.
One of its techniques, gravitational microlensing, takes advantage of gravity itself.
When one star passes almost directly in front of another from our perspective, the gravity of the nearer system can briefly magnify the light of the background star. If planets surround the foreground star, they can leave tiny additional signatures in that magnification.
Roman will repeatedly watch huge numbers of stars, looking for those fleeting signals.
That gives it the potential to find planets that are difficult to detect using other techniques—including worlds orbiting far from their stars and possibly even planets travelling through the galaxy without a parent star at all.
But the most exciting discovery may not be on NASA’s list
History has repeatedly shown that major observatories become important for discoveries their designers could not fully anticipate.
Hubble transformed our understanding of the age and expansion of the universe.
Other observatories have revealed galaxies, atmospheres and cosmic structures in ways that were difficult to imagine when they were first designed.
Roman’s enormous surveys could produce something particularly valuable in modern astronomy:
a gigantic map of the changing universe.
Scientists will be able to compare objects across huge regions of space, search for unusual events and identify things that don’t behave as expected.