On October 19th, 2017 at the Hawaiian island of Maui, at Haleakala Observatory, astronomers using the pan-starrs survey telescope detected a mysterious object travelling at high speed through our solar system, the trajectory of this object is unlike that has been ever discovered. The object was found in a highly unusual hyperbolic orbit suggesting that it was traveling at such a high rate of speed that it was not being pulled into more of a circular orbit by a force of gravity. Scientists have never seen such an object come through our solar system. At first, they thought it was a comet, then an asteroid, and then the International Astronomical Union has reclassified it as something new entirely, an interstellar object. They named it OUMUAMUA, a Hawaiian word meaning messenger was the first object of its kind to be officially recognized as INTERSTELLAR. So let's find some of the most intriguing theories and find out whether it was some celestial body or some alien activity? 

Oumuamua had some theories as to what it is and where it came from, researchers have tried to identify the star system where Oumuamua came from. They were able to combine data from the European Space Agency's Gaia mission that pinpoints the precise location of stars. Using this data it was identified that it likely came from a binary star system that has two stars that orbit a centre, unlike our single Sun which is around 80 light-years from Earth. 

At first, astronomers thought that Oumuamua was a comet but there was no cloud of gas or dust enveloping the object as most comets have so it was then reclassified as an asteroid but there was also a problem with this as the researchers realized the object was moving faster than an asteroid should be as if it were getting a boost from volatile materials evaporating off of its surface exactly like a comet's surrounding cloud or tail that you would see in photographs but Oumuamua had no tail. Whether or not it's a comet or an asteroid one thing remains clear Oumuamua is not quite like anything seen before besides the fact that, unlike most cosmic objects which are generally big lumps, the cigar-shaped object was spinning strangely like a stick.

 It was estimated to be bigger than the Eiffel Tower, some 1312ft long and 130ft thick. It was a kind of elongated cigar-shaped object tumbling through space. It wasn't discovered until it was on its way out of our solar system 40 days after passing the closest point to the sun on September 9, 2017, and it was moving incredibly fast, about 196.0 mph. And the way it was whipping around the sun told scientists that this object had to have come from somewhere beyond our solar system. The unusual brightness variations also suggest the object does not rotate around just one axis. Instead, it is tumbling -- not just end over end, but about a second axis at a different period, too. The object flew past the Earth so fast that its speed couldn't be from the gravity of the sun alone.

'Oumuamua's position revealed that there was something affecting its motion other than the gravitational forces of the Sun and planets. In this latest study, Researchers tracked ‘Oumuamua’ as it moved through the solar system and found that its trajectory cannot be explained solely by the gravitational attraction of the Sun, planets and large asteroids. Analyzing the trajectory of the interstellar visitor, found that the speed boost was consistent with the behaviour of a comet. Oumuamua had been boosted by 25,000 miles (40,000 kilometres) compared to where it would have been if only gravitational forces were affecting its motion. Comets normally eject large amounts of dust and gas when warmed by the Sun. But according to team scientist Olivier Hainaut of the European Southern Observatory, "There were no visible signs of outgassing from 'Oumuamua, so these forces were not expected.", they concluded that Oumuamua accelerated due to “comet-like outgassing.” This means that Oumuamua vents gases when heated in a similar manner to a comet. 

Some researchers have come to exotic conclusions as to what this first interstellar visitor could have been and where it might have come from. A Harvard Professor of astronomy, Avi Loeb, said that Oumuamua is indeed an alien spacecraft that is powered by a light sail. The method of propelling a spacecraft using radiation pressure given off by the sun or huge mirrors. The only way to make sense of Oumuamua's strange acceleration, without resorting to some sort of undetectable outgassing, is to assume that the object was propelled by solar radiation by photons bouncing off  and the only way the object could be propelled by solar radiation is if it were no thicker than a millimeter and have a very low density with a large surface area, this object could function as a sail-powered by light rather than by wind. Such an object could not be produced naturally, leaving the only other explanation that Oumuamua must have been designed, built, and launched by extraterrestrial intelligence. He further explained that the non-gravitational acceleration is a sign of deliberate maneuvering, and Oumuamua has no comet tail showing any outcasting. 

But another theory has now surfaced that might explain what Oumuamua really is. It's now believed the object could be like a pancake or a giant cookie-shaped piece of debris, a piece of shrapnel from an exoplanet like Pluto. Some researchers argue that the object could be a hydrogen iceberg. The iceberg theory can also explain ‘Oumuamua’s weird cigar shape. After the core of the giant molecular cloud dissipates and the iceberg is set adrift in the void, it is constantly bombarded by cosmic radiation. The problem was that it was hard to explain how the hydrogen, which freezes at a temperature around 3 degrees Kelvin, barely above absolute zero, would stay frozen on the long trip from its birth to here. 

Inspired by the hydrogen ice idea, scientists investigated other kinds of icebergs that might fill the bill. They finally hit on nitrogen. When the New Horizons spacecraft went past the previously unexplored Pluto in 2015, it found a world awash in nitrogen glaciers. The shininess of Oumuamua is about the same as the surfaces of Pluto and Triton, which are also covered in nitrogen ice. A key advantage of the proposal we advance here of a nitrogen ice fragment is that it can simultaneously explain all of the important observational characteristics of Oumuamua, and that material of this composition is found in the solar system. 

Therefore it can be concluded that Oumuamua is an example of an uncommon but certainly not exotic object: a fragment of a Pluto-like planet from another stellar system.

References -

• https://www.nasa.gov/gateway

• https://www.nasa.gov/specials/artemis/

• https://spacenews.com/intuitive-machines-first-lunar-lander-mission-slips-to-2022/

• https://www.nasa.gov/press-release/nasa-publishes-artemis-plan-to-land-first-woman-next-man-on-moon-in-2024