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On record 2025 as one of the most amazing years in contemporary astronomy, providing findings that would turn our collective understanding of our planet and our place within our galaxy on its head. Ranging from finding a rare interstellar comet passing through our solar system to hints that point towards signs of past life on Mars, this year promised to hold not only moments of wonder but also moments of scientific upheaval. Data collection from next-generation equipment like the James Webb Space Telescope, Dark Energy Spectroscopic Instrument, or NASA’s Perseverance rover called into question long-held beliefs about our galaxy, our Black Holes, or our ability to sustain life. However, new planets were discovered orbiting our closest stars, or on our collision course with our neighbouring Andromeda galaxy.
Top space discoveries of 2025
| Discovery |
Observatory or Mission |
Why it mattered |
| Interstellar comet 3I/ATLAS | ATLAS, Hubble, ESA spacecraft | Offered direct insight into material from another star system |
| Birth of supermassive black holes | James Webb Space Telescope | Challenged theories of early galaxy formation |
| Weakening dark energy | DESI survey | Questioned the fate and expansion of the universe |
| Evidence of past life on Mars | Perseverance rover | Strongest biosignatures detected so far |
| Biosignatures on exoplanets | James Webb Space Telescope | Raised hopes of life beyond the solar system |
| New nearby exoplanets | JWST, ground telescopes | Expanded known planetary systems close to Earth |
| Milky Way–Andromeda future | Computational simulations | Rewrote predictions of galactic collision |
| Vera C. Rubin Observatory first light | Rubin Observatory | Opened a new era of deep-sky observation |
Source: Space.com
8 discoveries that changed how scientists see the universe in 2025
Interstellar comet 3I/ATLAS stuns astronomers
One of the highlights of the year was the discovery of Comet 3I/ATLAS. The fact that the comet was found moving with high speed on a hyperbolic trajectory made it the third interstellar object seen crossing the solar system. The 3I/ATLAS comet was composed of different elements in a way that seemed similar to that of comets in the solar system. It was composed of another star; therefore, the building blocks of planets could be common in the entire galaxy. The levels of carbon dioxide and metal elements helped the scientists understand the environment outside the solar system.
Supermassive black holes may form far earlier than expected
“Little red dots” observed by the James Webb telescope appeared to be nascent supermassive black holes within dense gas clouds in the early universe, defying previous assumptions that black holes took billions of years to evolve from smaller bodies. These observations rather indicated that massive black holes formed relatively fast, within less than a billion years after the Big Bang, to account for the early emergence of massive galaxies within the universe.
Dark energy shows signs of weakening
The Dark Energy Spectroscopic Instrument yielded a surprising discovery, which was one of the most unsettling findings of 2025. This was the fact that dark energy, which accelerates the expansion of the universe, did not remain constant. Instead, it was found to be more prevalent billions of years ago and has been dwindling down since then. If this was true, then the world would need to revise its theories about the future of the universe.
Perseverance rover finds compelling signs of ancient Martian life
The NASA rover named ‘Perseverance’ spotted ‘leopard spots’ on old rocks on Mars, which are commonly associated with the presence of microorganisms on Earth. The rover also found ‘organic compounds’ that are buried within ‘clay sediments.’ Although not conclusive, these are the most compelling signs yet that Mars had the potential to support life billions of years ago, at least at some point in time.
Possible biosignatures detected on distant exoplanets
Telescopes, in particular the James Webb Space Telescope, provided evidence of the presence of dimethyl sulphide in the planet K2-18b. This compound is biogenic in nature because it is produced by biological organisms on Earth. K2-18b is a water-world planet, also known as a ‘hycean planet,’ which has a large ocean below a massive atmosphere.
New planets discovered around nearby stars
In the year 2025, planets of a rocky nature were confirmed to be circling Barnard’s Star, and tantalising signs of a gas giant planet were found to be orbiting Alpha Centauri A. Notably, the discovery of planetary bodies showed that planetary systems are aplenty, even within our own Sun’s immediate neighbours.
The Milky Way’s collision with Andromeda is no longer certain
New simulations factoring in the gravitational influence of neighbouring galaxies revealed that the Milky Way and Andromeda may not collide after all. Instead, there is now a roughly equal chance they will narrowly miss each other, reshaping long-standing predictions about the distant future of our galaxy.
A new era begins with the Vera C. Rubin Observatory
But new simulations, taking into account the gravitational pull of nearby galaxies, have found there is a possible realisation that the Milky Way and the Andromeda galaxy will no longer experience a collision. Instead, there is an equal probability of the Milky Way narrowly missing the Andromeda galaxy, as well as the reverse scenario.A new era begins for the Vera C. Rubin Observatory. After many decades of planning, the Vera C. Rubin Observatory finally took its first images in 2025. With the largest digital camera in the world, it is expected to produce an enormous amount of data each night, from asteroids, supernovas, and changes in the cosmos.
