ESA Space Science

The European Space Agency (ESA) reacted promptly to the discovery of comet 3I/ATLAS on 1 July 2025. Soon after they were alerted to its existence by automated detection systems, ESA astronomers began using ground-based telescopes in Hawaii, Chile, and Australia to monitor its progress.

Since then, the comet has been observed by space telescopes close to Earth, including the NASA/ESA Hubble Space Telescope and the NASA/ESA/CSA James Webb Space Telescope.

In the coming months, ESA will turn interplanetary voyagers such as Mars Express, ExoMars Trace Gas Orbiter and the Jupiter Icy Moons Explorer (Juice) in the direction of the comet to make further observations from excellent vantage points.

Follow the links below for more information.

The European Space Agency’s Plato spacecraft has safely arrived at ESTEC, ESA’s technical heart in the Netherlands. There, engineers will complete the spacecraft by connecting its solar panels and sunshield, and carry out a series of critical tests to confirm that Plato is fit for launch and ready for its planet-hunting mission in space.

The European Space Agency-led Solar Orbiter mission has split the flood of energetic particles flung out into space from the Sun into two groups, tracing each back to a different kind of outburst from our star.

For this new Picture of the Month feature, the NASA/ESA/CSA James Webb Space Telescope has provided a fantastic new view of IRAS 04302+2247, a planet-forming disc located about 525 light-years away in a dark cloud within the Taurus star-forming region. With Webb, researchers can study the properties and growth of dust grains within protoplanetary discs like this one, shedding light on the earliest stages of planet formation.

The NASA/ESA/CSA James Webb Space Telescope has revealed new details in the core of the Butterfly Nebula, NGC 6302. From the dense, dusty torus that surrounds the star hidden at the centre of the nebula to its outflowing jets, the Webb observations reveal many new discoveries that paint a never-before-seen portrait of a dynamic and structured planetary nebula.

In the past decade, the European Space Agency’s Gaia mission has revealed the nature, history, and behaviour of billions of stars. Our pioneering stargazer has reshaped our view of the skies around us like no other, revealing that star clusters are more connected than expected over vast distances.

*Click here for the latest updates on ESA observations of comet 3I/ATLAS*

A team of astronomers has taken the sharpest-ever picture of the unexpected interstellar comet 3I/ATLAS, using the crisp vision of the NASA/ESA Hubble Space Telescope.

ESA's Planetary Defence Office responded promptly to the discovery of the comet, and has been tracking it since the beginning of July.

Now, Hubble's observations from space are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 km, but it could be as small as 320 m across, researchers report.

Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Further observations, including by the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.

Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data show that the comet is losing dust in a similar manner to that from previously seen Sun-bound comets originating within our Solar System.

The big difference is that this interstellar visitor originated in some other stellar systems, elsewhere in our Milky Way galaxy.

3I/ATLAS is traveling through our Solar System at roughly 210 000 km per hour, the highest speed ever recorded for a Solar System visitor. This breathtaking sprint is evidence that the comet has been drifting through interstellar space for many billions of years. The gravitational slingshot effect from innumerable stars and nebulae the comet passed added momentum, ratcheting up its speed. The longer 3I/ATLAS was out in space, the higher its speed grew.

This comet was discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) on 1 July 2025 at a distance of 675 million km from the Sun. 3I/ATLAS should remain visible to ground-based telescopes until September, after which it will pass too close to the Sun to observe. It is expected to reappear on the other side of the Sun by early December.

Icy wanderers such as 3I/ATLAS offer a rare, tangible connection to the broader galaxy. To actually visit one would connect humankind with the Universe on a far greater scale. To this end, ESA is preparing the Comet Interceptor mission. The spacecraft will be launched in 2029 into a parking orbit, lying in wait for a suitable target – a pristine comet from the distant Oort Cloud that surrounds our Solar System, or, unlikely but highly appealing, an interstellar object.

While it is improbable that we will discover an interstellar object that is reachable for Comet Interceptor, as a first demonstration of a rapid response mission that waits in space for its target, it will be a pathfinder for possible future missions to intercept these mysterious visitors.

The research paper based on Hubble observations will be published in The Astrophysical Journal Letters.

[Image description: At the center of the image is a comet that appears as a teardrop-shaped bluish cocoon of dust coming off the comet’s solid, icy nucleus and seen against a black background. The comet appears to be heading to the bottom left corner of the image. About a dozen short, light blue diagonal streaks are seen scattered across the image, which are from background stars that appeared to move during the exposure because the telescope was tracking the moving comet.]

Smile is a brand-new space mission currently in the making. It will study how Earth responds to the solar wind and solar storms.

At the European Space Agency’s technical heart in the Netherlands, engineers have spent the last four months carrying out ‘spacecraft environment testing’ – putting Smile through its paces to make sure it is ready for the shaky rocket launch, the vacuum of space and the extreme temperatures it will face in orbit around Earth.

Now all complete, Smile is one step closer to launch in 2026.

This video provides a glimpse into the testing process. It is the third episode in a series of short videos, and includes interviews with David Agnolon (ESA Smile Project Manager), Chris Runciman (ESA Smile System Engineer), Laura Malena Lottes (ESA Smile Mechanical Engineer), Benjamin Vanoutryve (ESA Smile AIT/AIV and Launcher Interface Principal Engineer), Li Jing (CAS Smile Project Manager), He Tau (CAS Smile Mechanical Engineer) and Zhu Xiaofei (CAS Smile Thermal Engineer). 

Smile (the Solar wind Magnetosphere Ionosphere Link Explorer) is a joint mission between the European Space Agency and the Chinese Academy of Sciences. Smile is due to launch on a European Vega-C rocket in 2026. Follow the latest mission news via esa.int/smile.

Access the related broadcast quality video material

Access the other episodes of ‘Let’s Smile’

Completing the spacecraft – Let’s Smile (episode 2)

Introducing the Smile mission – Let’s Smile (episode 1)

Smile’s other half arrives – Let’s Smile (action snippet)

On 11 June, engineers at OHB’s facilities in Germany joined together the two main parts of ESA’s Plato mission. 

They used a special crane to lift Plato’s payload module, housing its 26 ultra-sensitive cameras, into the air and carefully line it up over the service module. The supporting service module contains everything else that the spacecraft needs to function, including subsystems for power, propulsion and communication with Earth. 

With millimetre-level precision, the engineers gently lowered the payload module into place. Once perfectly positioned, the team tested the electrical connections. 

Finally, they securely closed a panel that connects the payload module to the service module both physically and electronically (seen ‘hanging’ horizontally above the service module in this image). This panel, which opens and closes with hinges, also contains the electronics to process data from the cameras. 

Now in one piece, Plato is one step closer to beginning its hunt for Earth-like planets.  

In the coming weeks, the spacecraft will undergo tests to ensure its cameras and data processing systems still work perfectly. 

Then it will be driven from OHB’s cleanrooms to ESA’s technical heart (ESTEC) in the Netherlands. At ESTEC, engineers will complete the spacecraft by fitting it with a combined sunshield and solar panel module. 

Following a series of essential tests to confirm that Plato is fit for launch and ready to work in space, it will be shipped to Europe’s launch site in French Guiana. 

The mission is scheduled to launch on an Ariane 6 in December 2026. 

Access the related broadcast quality video footage. 

ESA’s Plato (PLAnetary Transits and Oscillations of stars) will use 26 cameras to study terrestrial exoplanets in orbits up to the habitable zone of Sun-like stars.  

Plato's scientific instrumentation, consisting of the cameras and electronic units, is provided through a collaboration between ESA and the Plato Mission Consortium. This Consortium is composed of various European research centres, institutes and industries, led by the German Aerospace Center (DLR). The spacecraft is being built and assembled by the industrial Plato Core Team led by OHB together with Thales Alenia Space and Beyond Gravity. 

What if we could look at the Sun from a whole new angle, one we've never seen before? 

From Earth, we always look towards the Sun's equator. This year, the ESA-led Solar Orbiter mission broke free of this ‘standard’ viewpoint by tilting its orbit to 17° – out of the ecliptic plane where the planets and all other Sun-watching spacecraft reside. Now for the first time ever, we can clearly see the Sun’s unexplored poles.  

Using different instruments, Solar Orbiter can see what happens throughout the Sun's outer layers. The material in these layers never stays still, being pushed outward and (usually) falling back to the Sun.  

Interestingly, it saw that the Sun's magnetic field has its north and south all tangled up, with patches of both magnetic polarities present right up to the Sun's south pole. This only happens once every 11 years, at the point in the solar cycle when the Sun's magnetic field flips.  

Solar Orbiter will keep a close eye on the Sun – including its poles – for the years to come. Its unique viewing angle will change our understanding of the Sun’s magnetic field, the solar cycle and the workings of space weather. 

Read the full story here. 

Solar Orbiter is a space mission of international collaboration between ESA and NASA.