The European Space Agency (ESA) has released the latest data from its groundbreaking Gaia mission, providing precise positions, motions, and physical properties for nearly 1.8 billion stars across our Milky Way galaxy. Stellar movements at the galaxy's edges even hint at its turbulent past.
Launched by ESA at the end of 2013, the Gaia spacecraft is dedicated to charting the positions, distances, motions, and physical characteristics of billions of stars in our galaxy. Positioned at the Sun-Earth Lagrange point 2 (L2)—1.5 million kilometers from Earth in the direction away from the Sun—Gaia benefits from a stable gravitational balance for uninterrupted observations.
From this vantage point, Gaia sweeps the sky continuously, capturing data across multiple light spectrum bands and measuring thousands of stars daily. Its billion-pixel camera, the largest ever flown in space, is so sensitive it could measure the width of a human hair from 1,000 kilometers away.
The previous catalog from April 2018 detailed nearly 1.7 billion stars. The new Gaia Early Data Release 3 (EDR3), published on Thursday, December 3, adds precise data on about 100 million more stellar sources—including 300,000 within 326 light-years of the Sun—with significantly improved accuracy.
Gaia's new dataset has enabled astronomers to track distinct stellar populations streaming toward the galaxy's far edge, the galactic anticenter.
Analysis reveals a group of slowly moving stars above the galactic plane drifting downward, paired with fast-moving stars below the plane rising upward. "This striking pattern was entirely unexpected," notes ESA. "It may stem from a close encounter between the Milky Way and the Sagittarius dwarf galaxy in the distant past."
The Sagittarius dwarf galaxy is currently being absorbed by the Milky Way through a process of tidal disruption. Its most recent pass left a lasting impact, perturbing stars without fully destroying the satellite galaxy.
Additionally, Gaia's measurements confirm the Solar System's gentle acceleration around the galactic center—enough to shift its path by one atomic diameter per second, or about 115 kilometers per year. This first direct evidence of orbital curvature aligns perfectly with theoretical models, reassuring us it's all part of normal galactic dynamics.
