NASA has issued a chilling update on the mysterious ‘interstellar object’ racing through our solar system.
The visitor from another star, dubbed 3I/ATLAS, was first spotted on July 1 as it reached 420 million miles from the sun.
Now, the Hubble Space Telescope has captured the sharpest images ever taken of 3I/ATLAS as it makes its way into the inner solar system.
These groundbreaking images reveal that 3I/ATLAS is moving at a staggering speed of 130,000 miles per hour (209,000 km/h) – making it the fastest interstellar object ever detected.
Using Hubble’s observations, astronomers have also been able to make a new estimate for the size of the object’s icy core.
Previously, scientists at the Vera C. Rubin Observatory estimated that the alien comet was roughly seven miles (11.2 km) across.
We now know that 3I/ATLAS is at most 3.5 miles (5.6 km) wide and possibly as small as 1,000 feet (320 metres).
However, that would still make 3I/ATLAS the largest interstellar object ever found, and up to 14 times larger than the second–biggest.
The Hubble Space Telescope has captured the clearest images ever taken of the mysterious interstellar object, 3I/ATLAS, that has been hurtling through our solar system
These images reveal that 3I/ATLAS (artist’s impression) is likely smaller than previously thought. NASA estimates that it is at most 3.5 miles (5.6 km) wide and possibly as small as 1,000 feet (320 metres).
Scientists and space agencies around the world are now almost certain that the object 3I/ATLAS is a comet rather than a solid piece of rock.
That means it is a relatively small lump of ice, frozen gases, and dust surrounded by a large cloud of evaporating material, which grows as it approaches the heat of the sun.
When objects are extremely far away, scientists estimate their size by how much light they reflect.
However, astronomers weren’t initially sure whether 3I/ATLAS was a very large but dull space rock or a smaller and highly reflective comet surrounded by bright gases.
Now, thanks to Hubble’s observations, we can see the tell–tale glow of a frozen comet and get a good estimate of its true size.
Hubble’s image reveals a dust plume streaming out of the sun–warmed side of the comet and the hint of a tail stretching out behind.
This amount of dust loss matches what scientists find in other comets around 300 million miles from the sun.
As 3I/ATLAS gets closer to the sun and becomes even warmer, the tail and dust plumes should also grow more pronounced.
The observations also confirm earlier theories that 3I/ATAS is a comet rather than a large solid rock. That means the object has a smaller core surrounded by a glowing halo of gas, which made it appear larger in initial observations. Pictured: 3I/ATLAS as seen by the Hubble Space Telescope
These observations also show that 3I/ATLAS is moving at a staggering 130,000 miles per hour (209,000 km/h) – making it the fastest interstellar object ever detected. Pictured: Multiple images of 3I/ATLAS taken by the Very Large Telescope (VLT), showing the object’s passage as a row of dots
It will reach its closest point to the sun in late October at a distance of 130 million miles (210 million km), passing just inside the orbit of Mars.
Thankfully, the object poses no threat whatsoever to Earth and will be on the opposite side of the sun during this close encounter.
This is only the third time that scientists have managed to detect an object approaching from another star system, and astronomers are working hard to gather as much data as they can while it is still here.
Science team leader for the Hubble observations, Dr David Jewitt, of the University of California, says: ‘No one knows where the comet came from. It’s like glimpsing a rifle bullet for a thousandth of a second.
‘You can’t project that back with any accuracy to figure out where it started on its path.’
3I/ATLAS’ extreme speed relative to the sun also confirms that it has likely been travelling through the cosmos for many billions of years.
As the comet passed planets, stars, and nebulae, the ‘gravitational slingshot effect’ added to its momentum.
The longer an object spends drifting through space, the faster it will become.
Scientists believe that 3I/ATLAS has been orbiting the Milky Way (possible orbits shown in red) for at least eight billion years. That makes it around twice as old as our own solar system
The object will reach its closest point to the sun in late October at a distance of 130 million miles (210 million km), passing just inside the orbit of Mars
Previous studies have suggested that 3I/ATLAS is likely to be at least eight billion years old, making it the oldest comet ever seen.
That means the comet is potentially twice as old as our 4.6 billion–year–old solar system.
3I/ATLAS follows just two other interstellar objects, 1I/’Oumuamua, which was discovered in 2017, and 2I/Borisov in 2019.
However, researchers believe that recent advances in telescope technology mean we will soon start spotting more interstellar visitors.
Dr Jewitt says: ‘This latest interstellar tourist is one of a previously undetected population of objects bursting onto the scene that will gradually emerge.
‘This is now possible because we have powerful sky survey capabilities that we didn’t have before. We’ve crossed a threshold.’
Hubble is just the first powerful space telescope lined up to observe 3I/ATLAS’ journey through our stellar neighbourhood, with the James Webb Space Telescope, TESS (Transiting Exoplanet Survey Satellite), and the Neil Gehrels Swift Observatory all scheduled to make observations.
3I/ATLAS should remain visible to ground–based telescopes through September, after which it will pass too close to the Sun to observe, and is expected to reappear on the other side of the Sun by early December.
