Roman's first big surveys
The era when Roman's galaxy maps start weighing dark energy and its microlensing census counts hidden worlds.
The story
By around 2030 the first large surveys of the Roman Space Telescope are expected to be accumulating results. It sweeps the sky like a panorama at Hubble resolution, and the scale of the data is different — its field of view is a hundred times Hubble's, so a single high-latitude survey captures hundreds of millions of galaxies. Surveys begin after about a year of commissioning following launch.
The first expectation is dark energy. By measuring the distribution of galaxies and the distortion of their shapes (weak gravitational lensing) statistically, it tests why cosmic expansion is accelerating with the largest sample ever. Supernova observations run alongside, redoing the dark-energy measurement Hubble opened in 1998 an order of magnitude more precisely.
The second is the microlensing exoplanet survey. Watching hundreds of millions of stars toward the galactic centre for months at a time, it catches the brief brightening of a background star when a foreground planet's gravity passes in front. Thousands of planets are expected, including those in wide orbits and free-floating ones. If Kepler proved that planets are common, Roman is the telescope that draws the complete map of planetary systems.
The third pillar is technology demonstration — a coronagraph that suppresses starlight a billion-fold to attempt direct imaging of Jupiter-like exoplanets in reflected light. Success would be the stepping stone to the Habitable Worlds Observatory of the 2040s, built to image Earth-like planets directly. Survey data are released immediately, and citizen-science projects are waiting.
Why it matters
Roman is a wide-field Hubble. Where Hubble and Webb dig deep into narrow fields, Roman photographs large pieces of sky whole at the same resolution. Rare objects — the most distant quasars, the brightest supernovae, the most massive galaxy clusters — are caught only by looking wide, and their statistics set the precision of cosmology.
Dark energy makes up seventy percent of the universe and remains unidentified. Precision has improved steadily since the 1998 discovery, but whether it is a cosmological constant or changes with time is still undecided. Combining Roman's data with those of Euclid (ESA, launched 2023) is expected to approach the answer in the early 2030s.
Microlensing finds the planets other methods miss. Transits (Kepler, TESS) favour planets close to their stars and radial velocity favours heavy ones, but microlensing catches an Earth-mass planet even at Jupiter's distance. Whether arrangements like our own solar system are common or rare will emerge from this survey as statistics for the first time.
How to watch
Roman is to orbit the Sun–Earth L2 point like James Webb, 1.5 million km from Earth and invisible to the naked eye. After launch, zooming in on Earth in the orbit view will show Roman's marker beside Webb at L2.
The microlensing survey field lies toward the galactic centre in Sagittarius. Select the galactic centre in the sky view to see whether that direction is above the horizon from your location and where it sits in the southern summer sky; the 3-D interstellar view draws the 26,000 light-years to the galactic centre at true scale.
Roman's high-latitude survey fields lie far from the galactic plane — toward Ursa Major in the north and near the south celestial pole. Zooming in there in the sky view shows a "clean" sky free of the Milky Way, where background galaxies show best.
Background
Roman's primary mirror is a 2.4 m mirror — Hubble's size — donated to NASA in 2012 by the US National Reconnaissance Office, built for Earth observation and never used. The telescope is named for Nancy Grace Roman, NASA's first chief of astronomy, known as the "mother of Hubble".
Launch is planned on a Falcon Heavy, followed by about a month to L2 and about a year of commissioning before a five-year primary mission. The survey plan was finalised in 2025, with the high-latitude wide-area, time-domain and galactic-bulge microlensing surveys taking 75 percent of observing time.
Roman's data are public the moment they are taken — there is no one-year proprietary period as with Hubble and Webb. Because of this policy the first survey results are expected to come not from one team's paper but from simultaneous analysis by researchers and citizen scientists worldwide.
FAQ
When do the first results come?
Surveys begin after about a year of commissioning following launch, with the first large results expected around 2030.
How does it differ from Hubble and Webb?
A field of view a hundred times Hubble's — large pieces of sky whole at the same resolution: width instead of depth.
How many exoplanets will it find?
Thousands by microlensing, including planets in wide orbits and free-floating ones.
Can anyone use the data?
Yes — data are public immediately, with no proprietary period.
Related
- Roman Space Telescope launch
- James Webb Space Telescope launch
- Hubble Space Telescope launch
- James Webb — object index
- Hubble Space Telescope — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.