Mysterious interstellar object spotted hurtling through our solar system could be an ALIEN SPACECRAFT, experts claim

A mysterious visitor from another solar system could be an alien spacecraft, according to a leading Harvard astronomer.

The enormous interstellar object, now officially dubbed 3I/ATLAS, is already speeding through the solar system at 41 miles per second, or 150,000 miles per hour.

Estimated to be 12 miles wide, A11pl3Z is far larger and brighter than the two previous interstellar objects to visit our solar system - 'Oumuamua and Borissov.

This has sparked speculation that 3I/ATLAS's intense brightness might not have a natural explanation.

Professor Avi Loeb, an astrophysicist at Harvard University, says it is 'difficult to understand' how the object could be so large unless it is either a comet or an alien craft.

While Professor Loeb says that follow-up observations may prove the object to be a naturally forming comet, an alien spacecraft remains a strong possibility.

'If it is not a comet, then its large brightness would be a big surprise and potentially signal a non-natural origin, perhaps from artificial light,' he told MailOnline. 

However, other astronomers say that much stronger evidence would be needed to prove the solar system has its first alien guests.

The object, originally named A11pl3Z, was first spotted by NASA's Asteroid Terrestrial-impact Last Alert System on July 1.

But astronomers were able to trace back the first sighting of 3I/ATLAS to June 14 in a set of images that had too many stars in the background to see the object initially.

Arriving from the direction of the constellation Sagittarius, 3I/ATLAS is currently about 420 million miles (670 million kilometres) away from Earth.

NASA predicts that it will reach its closest point to the sun on October 30, at a distance of 130 million miles (210 million km) - passing just within the orbit of Mars.

Thankfully, the object poses no threat to Earth and will pass harmlessly at around 150 million miles (240 million km) away at its closest point.

Now that enough observations have been gathered, the Minor Planets Centre - the official body for recording objects in space - has confirmed that this is an interstellar visitor.

Based on 3I/ATLAS's elliptical orbit, astronomers predict that the object will pass straight through our solar system before continuing on with its journey through the stars.

This makes it only the third interstellar object to ever be recorded passing through the solar system.

Just like 'Oumuamua, some scientists have already suggested that 3I/ATLAS could be an alien craft.

After 'Oumuamua was spotted in 2017, Professor Loeb speculated that it might be a probe 'meant to scan signals from all viewing directions'.

This was primarily based on the fact that 'Oumuamua did not produce a 'coma' - a cloud of evaporating gas and ice produced by comets as they approach the sun.

Scientists struggled to explain why the space rock sped up as it approached the sun - an effect normally produced by the 'off gassing' of evaporating material.

Now, as 3I/ATLAS approaches, keen alien hunters will be looking intently for 'technosignatures' - signs produced by the presence of technology.

Dr Eliot Gillum, director of the Optical SETI (Search for Extraterrestrial Intelligence) Program at the SETI Institute, told MailOnline that these could include 'following a path not governed solely by gravity' or an abnormal reflection pattern.

However, although Dr Gillum says it is 'possible' that 3I/ATLAS is alien in origin, he says it is unlikely that scientists will find any evidence to support this.

'It would have to be a heck of an observation to seriously open the door to aliens,' says Dr Gillum.

Likewise, early observations are beginning to suggest that the object is likely to be a comet.

A few telescopes claim to have already seen the object's tail of ice and gas, leading the Minor Planets Centre and NASA to label it a comet.

This would provide a natural explanation for why the object appears to be so bright and rule out the possibility of being an alien craft.

Even Professor Loeb suggests that a comet is now the more likely scenario, adding: 'If it ends up being a comet, it is no different qualitatively than natural icy rocks or dirty snowballs which are found in the Solar system.'

Likewise, Dr Mark Norris, an astronomer at the University of Lancashire, told MailOnline that the chances of 3I/ATLAS being an alien craft are now 'as close to zero as things get'.

However, Dr Norris suggests that this interstellar visitor still might hold the key to understanding alien life.

According to the 'panspermia' theory, the seeds of life are spread through the universe of debris ejected from one solar system to another.

Dr Norris says: 'Before we knew about these objects, most people would have said the chances of that happening are basically zero.

'Now that we know that rocks do survive passing through the stars, that number is still very small, but it's not zero.'

If scientists were able to get a sample of one of these objects and could show it contains the same basic building blocks found here on Earth, the chance of finding life on other planets is suddenly much greater.

Unfortunately, it's already too late to send a mission to intercept 3I/ATLAS, but there may be many more chances in the future.

Scientists believe there could be up to 10,000 interstellar objects in our solar system at any time, but most are simply too faint to see.

And with powerful new telescopes like the Vera C. Rubin Observatory coming online, scientists may get a chance to sample a visitor from another sun in the near future.