Oumuamua Return: A Story Of The Cigar-Shaped Asteroid

19th Apr 2025

Sometimes, space brings us such mysteries that scientists from all over the world have been racking their brains over them for years. One of them is the story of an interstellar visitor named Oumuamua. In 2017, this unusual object flew through our solar system, leaving us with many unanswered questions. In this article, we will tell you the details of this mysterious space wanderer and try to answer the main question that worries many: Will Oumuamua return?

What Is Oumuamua, And Why Is NASA Terrified Of It?

Let’s move back to October 19, 2017, to Hawaii. The Pan-STARRS 1 telescope discovers an unidentified object that probably came to us… from beyond the Solar System. The discovery causes an unprecedented excitement in scientific and pseudo-scientific circles. And why not! After all, this is the first interstellar object registered in the history of space observations. The unexpected visitor is given a name to match: Oumuamua, which in Hawaiian means “first scout from afar.” And then the continuous mysteries begin.

Getting Oumuamua real image turned out to be almost impossible. The asteroid was small (about 400 m long and about 50 m wide), and at the time of discovery it had already passed its closest point to the Sun (perihelion) and was quickly moving away. Measurements made by ground-based observatories were more or less successful, but Oumuamua Hubble images turned to be unsuitable, so the Hubble official site had to limit itself to an artist’s illustration.

oumuamua asteroid — Oumuamua Artist’s impression. Credit: hubblesite

At first, the mysterious guest was classified as a comet, but later, it became clear that something was wrong. The “First Scout” showed no signs of a coma (a cloud of gas and dust) typical of comets. A reasonable question arose: Is Oumuamua an asteroid? But even here, everything turned out to be complicated.

Instead of the usual “boulder” (which is exactly what most asteroids in the Solar System look like, as you could read about in our articles What are Asteroids and Asteroid vs Meteor), our object turned out to be elongated, like a cigar, and slightly flattened. In addition, the cigar-shaped asteroid was moving with abnormal acceleration and along a hyperbolic trajectory, which indicated that it had never been gravitationally bound to our Sun and was simply flying by.

This data raised the boldest hypotheses about the origin of the “First Scout”. In particular, Harvard University professor Abraham “Avi” Loeb suggested that the mysterious interstellar visitor could be an alien probe. Mass media immediately picked up this version and seriously distorted it. This is where the rumours about “NASA’s scare” came from. NASA, like other space agencies and scientists, were more intrigued than scared. After all, the object did not pose a danger of collision with Earth or other planets of the Solar System, but the very fact of its arrival was a truly unique event.

Where Did Oumuamua Come From? Scientific Hypotheses On The Origin

oumuamua origin — Origin’s story for ‘Oumuamua, using images from NASA and ESO/L. Calçada. Credit:planetplanet.net

No matter how hard scientists tried, they could not define the exact place of origin of the “First Scout”. The trajectory analysis showed that it arrived from the direction where the star Vega (the Lyra constellation) is located. But, given the average speed of the object (44 km/s) and the time of its travel (probably hundreds of millions or even billions of years), Vega itself was in a completely different place at the time of the launch of the Oumuamua object. Most likely, our wanderer wandered around the Milky Way for a very long time before getting into the Solar System. But what made it leave its home?

1. Gravitational Slingshot Or “Grand Tack” Hypothesis

One of the most likely versions suggests that the first scout was thrown into interstellar space as a result of close gravitational interaction with a massive gas giant planet in its forming star system, similar as it was with Jupiter that threw out small bodies (planetesimals) from our Solar System.

2. Exoplanet Fragment

Another intriguing hypothesis suggests that the “First Scout” is a fragment of an exoplanet similar to Pluto, composed primarily of nitrogen ice. A collision in its home system could have ejected the fragment, and sublimation of nitrogen as it approached our Sun could explain its strange acceleration.

3. Comet Remnant

Some researchers have suggested that Oumuamua could be the remnant of a comet that was tidally disrupted or otherwise destroyed during its journey.

The real reason for Oumuamua’s journey is still a mystery, and perhaps future missions to interstellar objects will be able to shed light on it.

Where Is Oumuamua Now In 2025?

oumuamua trajectory — This NASA animation depicts the trajectory of ‘Oumuamua, as it moves through the inner solar system.
Credit: NASA/JPL-Caltech

It is impossible to answer exactly where is Oumuamua right now, since its location is constantly changing. It is known that about 5 years ago it left the Kuiper belt, and now it is moving far beyond our Solar System (at a distance of more than 100 AU from Earth) towards the constellation of Pegasus. However, due to the huge distance and great dimness, even such a powerful telescope as the James Webb is not able to see Oumuamua. It is like trying to look for a needle in a haystack.

For illustrative purposes, we have compiled a table of all the Oumuamua asteroid journey stages through our Solar System:

Stage	Date	Event	Distance from Sun (AU)	Heliocentric Velocity (km/s)	Observations/Findings
Entry into the Solar System	Before the 1990s	The object enters the Sun’s sphere of influence	>> 1000 AU	~26.33	Interstellar velocity, hyperbolic trajectory. Object too distant and faint to be observed.
Neptune Orbit Crossing	Early Sept 2017	Crosses Neptune’s orbit, moving inward towards the Sun	~30.1 AU	Increasing	Object not yet detected.
Perihelion	Sept 9, 2017	Passes perihelion (closest point to the Sun)	0.255 AU	87.71	Maximum velocity. No cometary activity was observed.
Mars Orbit Crossing	October 1, 2017	Crosses Mars’ orbit on its way out from the Sun	~1.5 AU	~66	The object is moving outward.
Closest Approach to Earth	October 14, 2017	The object is at its closest point to Earth	~0.162 AU	~26.81 (relative to Earth)	–
Earth Orbit Crossing	October 16, 2017	Crosses the orbit of Earth, moving away from the Sun	~1 AU	~45 (relative to the Sun)	The object is moving away.
Discovery	October 19, 2017	Discovered by the Pan-STARRS1 telescope (Hawaii)	~1.49 AU (from Sun)	~44 (relative to Earth)	First detection of an interstellar object. Unusual elongated shape, reddish colour.
Intensive Observations	October-November 2017	Observations with various ground-based and space telescopes (CFHT, VLT, WHT, Gemini, Keck, Hubble, Spitzer)	1.5 – 2.5 AU	Decreasing	Refinement of shape (highly elongated, ~1:10 axis ratio), size (hundreds of meters long), rotation period (~7-8 hours), Confirmed lack of coma. Non-gravitational acceleration was detected.
Jupiter Orbit Crossing	~May 2018	Crosses Jupiter’s orbit, moving outward from the Sun	~5.2 AU	Decreasing	Estimated date, based on trajectory extrapolation.
Saturn Orbit Crossing	~January 2019	Crosses Saturn’s orbit, moving outward from the Sun	~9.54 AU	Decreasing	Estimated date, based on trajectory extrapolation.
Loss of Observability	Late 2017–2018	Becomes too faint to be observed by even the most powerful telescopes	> 4 AU	Approaching ~26.33	The last reliable data was obtained in early 2018.
Kuiper Belt Exit	No later than 2019	Leaves the Kuiper Belt region	>55 AU	~26.33	–
Current Status	March 2025	Very far beyond the Solar system	>>100 AU	~26.33	Not observable. Moving towards the Pegasus constellation
Exit from the Solar System	After 2038	Leaves the Sun’s heliosphere	>> 1000 AU	~26.33	Object permanently escapes into interstellar space.

Is The Asteroid Oumuamua Coming Back? Farewell, Mysterious Wanderer!

And now, finally, we come to the burning question: will Oumuamua return? Unfortunately, the fans of sensations will have to be disappointed, no matter how hard they tried to pull the non-existent words of Elon Musk that “Oumuamua Has Suddenly Returned, and It’s Not a MISTAKE!” This is nothing more than a clickbait headline.

The object is moving along an open, hyperbolic trajectory, inexorably moving away from the Solar System into interstellar space. Approximately by 2038, it will reach the heliopause (the boundary of the heliosphere) and finally leave the gravitational influence of the Sun. In other words, scientists should not expect an Oumuamua return date. The first scout will never return.

Oumuamua Impact: Lessons From An Interstellar Guest

Although our unexpected guest was not planning to collide with the Earth, its visit (let’s call it the Oumuamua impact on science) is extremely important. It showed that such interstellar objects are not unique (Borisov comet, which flew 2 years after Oumuamua, is a clear confirmation of this), and that we need to be ready for their appearance. After all, who knows what they could bring?

Imagine that an interstellar asteroid did crash into the Earth… We wrote about the consequences of such a collision in detail in our article Will an Asteroid Hit Earth. Taking into account the enormous speed and size of the object, the explosion would have been thousands of megatons of TNT, which would have formed a giant crater, dust, tsunamis, and earthquakes… In general, a real Armageddon with all that it entails.

Was The Cigar-Shaped Asteroid An Occasional Visitor Or A Warning?

So, now that the Oumuamua return question is solved, we can only wait for the next guests and hope that they will not have hostile intentions. In the meantime, all we can do while we wait is study asteroids and other similar objects not only for asteroid mining but also for protection against them. Who knows, maybe this was the “First Scout” mission.