The interstellar comet that has had scientists around the world mesmerised for months safely passed Earth this morning.
At roughly 06:00 GMT, 3I/ATLAS reached its closest point to Earth, coming within 168 million miles (270 million km) of our planet.
To put that into perspective, that is still nearly twice the average distance between Earth and the sun.
The comet is now whizzing towards Jupiter, where it will make a relatively close pass of the gas giant at a distance of 33 million miles (53 million km) on March 16, 2026.
From there, 3I/ATLAS will make its way past the orbit Saturn by July, without coming close to the planet, and cross the orbit of Uranus in June 2027.
In 2028, the interstellar object will travel beyond the last of the planets as it shoots by Neptune at 137,000 miles per hour (221,000 km/h).
Astronomers predict that the comet will reach the orbit of Pluto in April 2029, before striking out into the outer reaches of the solar system.
Finally, 3I/ATLAS will wave goodbye to our stellar neighbourhood as it returns to interstellar space sometime in the mid 2030s.
The interstellar comet 3I/ATLAS safely passed Earth this morning, reaching its closest distance to our planet at 168 million miles (270 million km) away
3I/ATLAS was discovered in July and marks only the third time that astronomers have been able to find an object that formed around another star in our own solar system
3I/ATLAS was discovered on July 1 by the NASA-funded ATLAS telescope in Chile.
When scientists traced back the approaching object’s trajectory, they made the startling discovery that it had arrived from outside the solar system.
This was just the third time astronomers had detected a visitor from another solar system, following 1I Oumuamua in 2017 and 2I Borisov in 2019.
Scientists believe that 3I/ATLAS formed around a distant star around eight billion years ago.
That makes the comet older than our solar system, and the oldest thing that we have ever been able to study close up.
On October 3, the comet reached its closest distance to Mars as it passed just 19 million miles (30 million km) from the Red Planet.
Then, on October 29, the interstellar object reached its closest point to the sun at a distance of 130 million miles (210 million km).
While some immediately leapt to wild conclusions about alien spacecraft, this was actually a fantastic opportunity for scientists to learn more about the history of the galaxy.
Astronomers believe that 3I/ATLAS is around eight billion years old, making it older than our own solar system
All of the objects behaviour is consistent with that of a comet heating up and releasing gas and dust as it approaches the sun
All that time, telescopes on Earth and out in space were redirected towards gathering information about the interstellar traveller.
NASA even used spacecraft orbiting Mars, normally used for recording the planet’s surface, to capture data about the passing object.
Professor Chris Lintott, an astronomer from the University of Oxford, told Daily Mail: ‘We’ve been scrambling to observe 3I/ATLAS with everything we’ve got since it was discovered.
‘So far, it’s a fairly normal, active comet – plenty of carbon monoxide, some water, a sprinkling of Nickel.’
As comets approach the sun, their outer layers of ice and dust evaporate into a glowing cloud known as a coma and several long tails stretching out in different directions.
The closer 3I/ATLAS got to the sun, the brighter and more active the coma and tails became, and the more layers of the comet’s outer surface were burned away.
‘Because it’s being heated by the Sun, it’s changing all the time, and it’ll take some time to work out what it’s really made of,’ says Professor Lintott.
‘One idea is that it’s like a baked Alaska, with a crunchy outer layer affected by the billions of years it spent in outer space, surrounding a nice fresh ice core.’
Scientists have been ‘scrambling’ to observe the comet ever since it was discovered. This diagram shows all the spacecraft the European Space Agency has repurposed for investigating the object
NASA was able to use spacecraft in orbit around Mars to capture to spectrum of light coming from the glowing cloud of gas and dust surrounding the comet (pictured)
And, while it might take scientists months to comb through all the data, researchers have already learned enough to decisively conclude that it is not an alien spacecraft.
All of the object’s supposedly anomalous behaviours, such as changing trajectory or producing jets of sublimating gas, are entirely consistent with what we know about comet behaviour.
Dr Matthew Genge, an expert on near-Earth objects and astrobiology from Imperial College London, says: ‘Suggestions that 3I/Atlas was an alien spacecraft on route to Earth have thus been shown to be very wrong indeed.’
However, one of the most important lessons that scientists have learned from this encounter is that we need to be better prepared for the next interstellar object.
Interstellar objects are not particularly rare, as scientists predict there are around a billion billion billion of them in the galaxy, we are just very bad at spotting them.
But as telescopes like the newly-completed Vera C Rubin Observatory start to survey the sky, we should start to find many more.
Professor Mark Burchell, a space scientist from the University of Kent, told Daily Mail: ‘Now we know how to spot them, it gets easier each time.
‘The next science goal to my mind is to prepare to see a ‘fresh’ comet from the outer solar system, which means parking a spacecraft in space in advance.’
Having passed Earth, 3I/ATLAS is now whizzing towards Jupiter, where it will make a relatively close pass of the gas giant at a distance of 33 million miles (53 million km) on March 16, 2026
Normally, it takes years to plan, build, and launch a new spacecraft – which isn’t possible within the window we have to catch an interstellar object.
Yet with a spacecraft waiting out in space, scientists could simply redirect this interceptor craft to catch suitable comets when they approach.
Professor Burchell says this might be much harder to do with interstellar objects, since they are so much rarer than comets.
But if scientists were suitably prepared, the potential for learning about the formation of the galaxy could be incredible.
