Quick answer: Gaia is the European Space Agency’s star-mapping space observatory. It was launched in 2013 and switched off on 27 March 2025 after charting nearly two billion stars and other objects. It is in the news because, on 5 November 2026, the Ministry of Science and Technology said an Indian-led team had used Gaia data to show that the star cluster UBC 63 is actually two separate clusters.
Why the Gaia mission is in the news
A press release from the Ministry of Science and Technology (PIB, 5 November 2026) described a study led by researchers from Gauhati University and the Indian Institute of Astrophysics (IIA), an autonomous body under the Department of Science and Technology. The team set out to study star formation inside a loose open cluster called UBC 63, about 4,892 light years from Earth. Gaia’s precise measurements of stellar positions and motions showed them something unexpected: the “single” cluster is really two, now named UBC 63A and UBC 63B.
The finding, published in The Astronomical Journal, comes as Gaia’s science team prepares its fourth data release. ESA’s Gaia news page says Data Release 4 is due on 2 December 2026, so the mission keeps producing results even though the spacecraft itself is silent.
What the UBC 63 study found
| Parameter | UBC 63A | UBC 63B |
|---|---|---|
| Approximate age | 21 million years (young) | 562 million years (old) |
| Separation when 63A formed | About 60 parsecs (about 196 light years) | |
| Closest approach | About 7 parsecs (about 23 light years), roughly 6 million years ago | |
| Separation today | About 26 parsecs (about 85 light years), moving apart; not gravitationally bound | |
Because the two groups differ in age by more than 500 million years, they cannot have formed together. The researchers first noticed two separate sequences on a colour-magnitude diagram, a plot of star brightness against colour. Machine learning and orbit simulations then confirmed the split. Catching two clusters soon after a close flyby is rare, so the result helps explain how clusters evolve.
Key facts about the Gaia mission
- Agency and launch: Built and operated by the European Space Agency (ESA); launched on 19 December 2013 on a Soyuz-Fregat rocket.
- Where it worked: A Lissajous-type orbit around the second Lagrange point (L2) of the Sun-Earth system.
- Goal: To build the largest and most precise 3D map of the Milky Way by measuring the position, distance and motion of nearly two billion objects.
- Scale of work: Between 27 July 2014 and 15 January 2025 it made more than three trillion observations. Two billion stars is only about 1% of the Milky Way’s stars.
- Hardware: Two identical telescopes fed one focal plane carrying the largest digital camera ever flown in space, with nearly one billion pixels. Its functions were astrometry, blue and red photometry, and a radial-velocity spectrometer.
- Retirement: On 27 March 2025, ESA’s control centre (ESOC) pushed it away from L2 into a “retirement orbit” around the Sun, switched off its systems and corrupted its software so it could never restart. It had been planned for five years but ran for over a decade.
Gaia data releases: a quick timeline
| Release | Date |
|---|---|
| Data Release 1 | 14 September 2016 |
| Data Release 2 | 25 April 2018 |
| Early Data Release 3 | 3 December 2020 |
| Full Data Release 3 | 13 June 2022 |
| Focused Product Release | 10 October 2023 |
| Data Release 4 | 2 December 2026 (scheduled) |
| Final legacy catalogue | No earlier than end of 2030 |
ESA credits Gaia data with showing that the Milky Way merged with another large galaxy about 10 billion years ago, and with tracking hundreds of thousands of asteroids. Its Euclid telescope uses Gaia’s star map to orient itself.
Exam angle: how NDA, CDS and CAPF can ask this
- Lagrange points are a favourite: ESA notes that Gaia, Euclid and Webb all orbit the Sun-Earth L2 point. Learn what L1 and L2 are and which missions use them.
- Match-the-agency questions are common, so link Gaia, Euclid and Plato to ESA.
- Astronomy units and terms such as light year, parsec and open cluster suit NDA general science questions.
Practice MCQs
Q1. The Gaia space observatory was operated by:
(a) NASA (b) ISRO (c) European Space Agency (d) JAXA
Answer: (c) – Gaia is an ESA mission designed and built by European industry.
Q2. Gaia observed the sky from an orbit around which point?
(a) Sun-Earth L1 (b) Sun-Earth L2 (c) Earth-Moon L4 (d) Geostationary orbit
Answer: (b) – ESA describes a Lissajous-type orbit around L2.
Q3. Using Gaia data, an Indian-led team found that UBC 63 is:
(a) a black hole pair (b) a spiral galaxy (c) two separate star clusters (d) a supernova remnant
Answer: (c) – It splits into UBC 63A and UBC 63B of very different ages.
Q4. Gaia Data Release 4 is scheduled for:
(a) 27 March 2025 (b) 15 January 2025 (c) 2 December 2026 (d) 19 December 2027
Answer: (c) – ESA has fixed 2 December 2026 for DR4.
Frequently asked questions
Is the Gaia spacecraft still working?
No. ESA ended science observations on 15 January 2025 and switched the spacecraft off on 27 March 2025. Scientists continue to analyse its data.
How many stars did Gaia map?
Nearly two billion stars and other objects, through more than three trillion observations.
What is UBC 63?
It is a loosely bound open star cluster about 4,892 light years away. Gaia data now show it is two clusters, UBC 63A and UBC 63B, that recently passed close to each other.
Which Indian institutions were involved in the UBC 63 study?
Gauhati University and the Indian Institute of Astrophysics led the work, with a DST INSPIRE research fellow among the authors.
When is Gaia’s next data release?
Data Release 4 is scheduled for 2 December 2026.
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Sources: PIB (Ministry of Science and Technology), ESA: Farewell Gaia, ESA Gaia factsheet, ESA Gaia news 2026. Facts as reported up to 7 November 2026.
Featured image background: European Space Agency / Wikimedia Commons, CC BY-SA 3.0 igo.
