Scientists have yet to explain the cigar-shaped object in space.

Scientists say the cigar-shaped object has many complex elements. It could be an alien spacecraft, given its features that do not resemble a comet.

In October 2017, astronomer Robert Weryck and his colleague Marco Micheli at the European Space Agency (ESA) discovered a cigar-shaped object flying past the Sun on September 9 of the same year, at a speed of about 315,000 km/h and quickly heading out of the Solar System.

By calculating its trajectory, they determined that the object must have come from outside the Solar System. Initially labeled a comet and then an asteroid, the cigar-shaped object had characteristics that puzzled scientists.

Oumuamua's unusual orbit caught scientists' attention. (Photo: BBC).

Specifically, scientists estimate it to be no more than 914 meters long and about 121 meters wide. Overall, this rust-colored, cigar-shaped object is seven times longer than it is wide and rotates on its axis every 7.4 hours, according to NBC News . Of course, this is an anomaly that has never been recorded before. So it has been nicknamed 'Oumuamua' , which means "first distant messenger" in Hawaiian.

After analyzing its trajectory, astronomers believe that Oumuamua came from the direction of the constellation Lyra, home to the bright star Vega. As it reached the Solar System, the object was steered toward the Sun by a gravity assist, taking it past Mars, Jupiter, and Saturn. If it followed this trajectory, it would have reached the constellation Pegasus.

As it hurtled away, however, scientists discovered that Oumuamua was accelerating at an unusual rate. In a paper co-authored by Micheli for the journal Nature , he and astronomers concluded that something was affecting Oumuamua's trajectory and speed.

Co-author Davide Farnocchia from the Center for Near-Earth Object Studies (CNEOS) suggests the unusual speed is the result of natural jets of gas ejected from the surface (known as outgassing), which act like thrusters on a spacecraft.

But it's worth noting that Oumuamua is believed to be completely hollow inside. Karen Mectors, another co-author of the paper and an astronomer at the University of Hawaii, and ESA scientist Olivier Hainaut both agree that the object shows no signs of escaping gas. Therefore, the hypothesis is not valid.

The cigar-shaped object is made of a material that is very rare in the universe. (Photo: Getty Images).

In addition, some recent discoveries indicate that the size of this object is much smaller than initially estimated. Specifically, according to the latest estimates, Oumuamua is only about 458 m long and no more than 121 m wide. When observed closely, the shape of this object is more like a pancake than a cigar.

Some scientists believe that Oumuamua is made of solid nitrogen, a form of ice seen on the surfaces of Pluto and its natural satellite Triton. Others say this is unlikely because pure nitrogen is rare in the universe.

Finally, Harvard astronomer Avi Loeb suggests that Oumuamua is some sort of alien technology. It could be an old probe or a sail, which would explain its unusual acceleration as it left the solar system.