In 2017, a mysterious interstellar object called Oumuamua whizzed past Earth, and scientists were perplexed by its unusual characteristics. Comets typically come from a bank of frozen objects situated at the outer solar system know as the "Oort Cloud" and accelerate when they get close to the sun because the ice inside them turns to water vapor, which is ejected outwards, acting as a thruster. This expulsion of gas results in a dust tail or a bright halo called a coma, but Oumuamua had neither of these things and was still accelerating more than it should. This led many to suggest it was an alien spacecraft being powered by an extraterrestrial engine.
However, researchers from the University of California, Berkeley, and Cornell University in the US have come up with a new, more straightforward explanation. Oumuamua came from interstellar space, meaning it was bombarded with cosmic radiation. This radiation penetrated deep into its rock, reaching the ice trapped inside. This converted the water into hydrogen gas, which remained locked within it until it got near the sun. The warmth caused the comet to expel the hydrogen, which was enough to accelerate it off its trajectory. The gas would have formed a very thin shell around the comet, but would have been too small to see from telescopes on Earth.Thus, the theory that Oumuamua is an alien spacecraft has been debunked, and the researchers have concluded that it was an interstellar comet.
One interesting fact about Oumuamua is its unusual shape. Observations suggest that it is highly elongated and has a cigar-like shape with an estimated length of 1km, and the object has a reddish appearance, which is quite different from any natural object in our solar system. In fact, its shape has led some researchers to suggest that it may be an artificial object or probe sent by an extraterrestrial civilization, although this idea is highly speculative and has not been supported by any evidence.
Oumuamua's trajectory suggests that it came from the direction of the constellation Lyra and was traveling at a high speed relative to the Sun. It is believed to have originated from another star system outside of our own solar system, making it the first known interstellar object to have passed through our solar system.
However, scientists have not been able to determine exactly where Oumuamua came from or how long it had been traveling through interstellar space before it was detected. Its origins remain a mystery, and scientists are still studying the data to learn more about this fascinating object.
Oumuamua passed by the Earth at a distance of about 85 times the distance from the Earth to the Moon, or about 33 million kilometers (20.7 million miles) away. Currently, Oumuamua is no longer visible from Earth and is very far away, traveling through the depths of space. Oumuamua is currently about 34.9 astronomical units away from Earth, which is roughly 5.2 billion kilometers. It is moving away from the Sun and Earth at a speed of about 315,000 kilometers per hour. Its exact location and trajectory are constantly changing due to its motion through space and the gravitational influence of other objects in the solar system, so its current position and distance from Earth will change over time.