Theories Explaining the Discovery of 'Oumuamua: An Exploration of Possible Origins

Since its discovery in 2017, the interstellar object 'Oumuamua has fueled a lot of debate and speculation. Here, we explore seven possible theories behind 'Oumuamua's origin and review the evidence supporting each.

1. A Rock Similar to Asteroids in Our Solar System

When initial spectral data was available in November 2017, 'Oumuamua's spectra were described as being similar to L or D class asteroids. This suggests that 'Oumuamua could be a typical asteroid, similar to those found in our solar system. However, evidence from other observations contradicts this hypothesis.

2. A Comet Similar to Comets in Our Solar System

If 'Oumuamua were a comet, one might expect it to have a coma or tail due to the outgassing of water vapor and carbon dioxide. However, observations by Pan-STARRS, Hubble, and the ESO telescopes failed to detect any such coma or tail.

3. A Comet Not Similar to Comets in Our Solar System

The absence of a coma or tail despite its proximity to the Sun suggests that 'Oumuamua might not follow typical comet behavior. This theory is unsupported by current observations.

4. A Metallic Type M Asteroid

Some have speculated that 'Oumuamua could be a metallic asteroid. However, no observational evidence supports this theory, and its properties are difficult to reconcile with known metallic asteroids.

5. A Natural Object Composed of Unusual Material

A suggestion is that 'Oumuamua could be a natural object composed of material not found in our solar system. One possibility is that it was a refractory substance tidally disrupted by a white dwarf. However, this is purely speculative and lacks concrete evidence.

6. A Solar Sail Devised by Alien Civilization

The idea of an alien solar sail is perhaps the most intriguing theory. An object designed to ride on solar radiation pressure could explain its observed acceleration and absence of outgassing. However, the lack of detectable emissions or signals from 'Oumuamua, despite searches by SETI instruments, remains a significant hurdle for this theory.

7. A Space Probe Designed by Alien Civilization

Similar to the solar sail theory, this suggestion proposes that 'Oumuamua is a space probe sent by an advanced extraterrestrial civilization. Like the solar sail theory, the absence of emissions or signals from 'Oumuamua raises doubts about this theory.

Review of Evidence

Several key observations and facts have emerged that complicate the simple interpretation of 'Oumuamua as a typical asteroid or comet:

It passed remarkably close to the Sun within 0.25 AU, significantly within the orbit of Mercury. This placed it on a gravitational trajectory outside the solar system.

Observations revealed a brightness variation of three magnitudes, typically attributed to its shape rather than albedo changes.

It was not detected by STEREO spacecraft, which are designed to monitor the Sun.

The absence of a coma or tail and the lack of detectable emissions or signals from 'Oumuamua challenge traditional interpretations.

Its acceleration showed a non-gravitational force, which remains unexplained.

Conclusion

While the discovery of 'Oumuamua continues to intrigue and challenge our understanding of the universe, the available evidence does not support any single theory conclusively. The most plausible explanations remain 'Oumuamua being a typical interstellar object, though the lack of clear evidence leaves open the possibility of more exotic origins.