NASA’s Nancy Grace Roman Space Telescope team has unveiled ambitious plans for a groundbreaking survey that promises to reveal the Milky Way in unprecedented detail. Scheduled to commence in 2027, this survey will span two years, capturing tens of billions of stars and unearthing previously hidden structures within our galaxy.
“The Galactic Plane Survey will revolutionize our understanding of the Milky Way,” stated Julie McEnery, Roman’s senior project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’ll be able to explore the mysterious far side of our galaxy and its star-studded heart. Because of the survey’s breadth and depth, it will be a scientific mother lode.”
Revolutionizing Galactic Observation
The Galactic Plane Survey marks Roman’s first selected general astrophysics survey, supplementing its three core surveys and Coronagraph technology demonstration. At least 25% of Roman’s five-year primary mission is dedicated to proposals from astronomers worldwide, allowing for additional surveys that leverage Roman’s full capabilities.
Roman is slated for launch by May 2027, with the possibility of an earlier launch in the fall of 2026. This development follows the European Space Agency’s Gaia spacecraft, which mapped approximately two billion Milky Way stars in visible light. However, many parts of the galaxy remain obscured by dust, a challenge Roman aims to overcome using infrared light.
“It blows my mind that we will be able to see through the densest part of our galaxy and explore it properly for the first time,” said Rachel Street, a senior scientist at Las Cumbres Observatory in Santa Barbara, California, and a co-chair of the committee that selected the Galactic Plane Survey design.
Exploring Cosmic Cradles
The survey will cover nearly 700 square degrees, equivalent to the area of about 3,500 full moons, along the glowing band of the Milky Way. Scientists anticipate mapping up to 20 billion stars and detecting minute positional shifts through repeated high-resolution observations. This will be accomplished in just 29 days spread over the mission’s initial two years.
Stars are born from clouds of gas and dust. Roman will peer through these cosmic cradles to observe millions of stellar embryos, newborn stars, and young stars potentially forming planetary systems. This comprehensive study will encompass every phase of a star’s evolution, providing insights into the forces shaping them.
“This survey will study such a huge number of stars in so many different stellar environments that we’ll be sampling every phase of a star’s evolution,” Street noted.
Understanding Star Formation
Star formation involves a complex interplay of gravity, radiation, magnetism, and turbulence. Roman’s observations will help determine how these forces influence the formation of stars, brown dwarfs, and new worlds. The survey will also examine nearly 2,000 young, loosely bound open clusters and dozens of ancient, densely packed globular clusters near the galaxy’s center, offering clues to the Milky Way’s early history.
Comparing Roman’s snapshots of clusters scattered throughout the galaxy will enable scientists to study nature versus nurture on a cosmic scale. Because a cluster’s stars generally share the same age, origin, and chemical makeup, analyzing them allows astronomers to isolate environmental effects very precisely.
Pulses and Pathways
When stars exhaust their fuel, they leave behind cores known as white dwarfs, or collapse into neutron stars and black holes. Roman will detect these stellar remnants through microlensing, a phenomenon where light from a background star curves around an intervening object, temporarily brightening the star.
A separate survey, Roman’s Galactic Bulge Time-Domain Survey, will focus on deep microlensing observations in the Milky Way’s heart. The Galactic Plane Survey will complement this by providing a broader view of the galaxy’s center, helping to unravel the origins of its central bar and study ultratight binary objects.
“Compact binaries are particularly interesting because they’re precursors to gravitational-wave sources,” said Robert Benjamin, a visiting professor at the University of Wisconsin-Whitewater, and a co-chair of the committee that selected the Galactic Plane Survey design.
Roman’s repeated observations will also monitor stars that flicker. Ground-based surveys detect thousands of bright stellar outbursts, but often can’t see the faint, dust-obscured stars that produce them. Roman will pinpoint the culprits plus take high-resolution snapshots of the aftermath.
Enhancing Cosmic Measurements
Some stars throb rhythmically, and the speed of their pulsing is directly linked to their intrinsic brightness. By comparing their true brightness to how bright they appear from Earth, astronomers can measure distances across the galaxy. Roman will find these blinking stars farther away than ever before and track them over time, helping astronomers improve their cosmic measuring sticks.
“Pairing Roman’s Galactic Plane Survey with other Milky Way observations will create the best portrait of the galaxy we’ve ever had,” Benjamin said.
The announcement comes as astronomers eagerly anticipate the wealth of data Roman will provide, promising to deepen our understanding of the galaxy and its myriad mysteries. As Roman prepares for launch, the scientific community is poised to unlock new chapters in the story of the Milky Way, offering insights that could reshape our comprehension of the cosmos.
