ʻOumuamua
From the UAP Encyclopedia, the open encyclopedia of UFO and UAP history · 🗓️ Event
Contents 5
| Type | Event |
|---|---|
| Also known as | Oumuamua, 1I/2017 U1 |
| Discovered | 19 October 2017 |
| By | Robert Weryk, Pan-STARRS1 telescope, Hawaii |
| Designation | 1I/2017 U1 |
| Name means | "Scout" or "messenger" (Hawaiian) |
ʻOumuamua (officially 1I/2017 U1) is the first object confirmed to have entered the Solar System from interstellar space. It was found on 19 October 2017 by Robert Weryk using the Pan-STARRS1 telescope on Haleakalā, Hawaii, already on its way out after passing the Sun. Its odd shape and an unexplained push away from the Sun led one astronomer to suggest it might be an artificial object, an idea most scientists reject.[1][2]
An unusual visitor
Its speed and path showed it was not bound to the Sun: it came from interstellar space and is leaving for good. Its brightness changed by a factor of about ten as it tumbled, suggesting a very elongated or flat shape, perhaps a few hundred metres long. Unlike a comet, it showed no visible tail or cloud of gas.[1][2]
As it left, careful tracking showed a small extra acceleration that gravity alone did not explain — the kind of push comets get from escaping gas.[1]
The "alien light sail" idea
In 2018 Harvard astronomers Shmuel Bialy and Avi Loeb suggested the push could come from sunlight on a thin, artificial light sail. Loeb defended the idea in his 2021 book Extraterrestrial. Most astronomers consider natural explanations more likely.[1][3]
Natural explanations
Proposed natural causes include a fragment of nitrogen ice chipped off a Pluto-like world, and — in a 2023 study in Nature by Jennifer Bergner and Darryl Seligman — hydrogen gas escaping from ice warmed by the Sun, which would push it without making a visible coma.[4]
Later interstellar objects
Two more interstellar objects have since been found: the comet 2I/Borisov in 2019, and 3I/ATLAS in 2025. Projects such as the Galileo Project now study interstellar objects as part of the search for technology from elsewhere.[1]
References
- ʻOumuamua — Wikipedia · en.wikipedia.org
- Astronomers observe first interstellar asteroid — ESO press release eso1737, 20 November 2017 · eso.org
- Bialy & Loeb, "Could Solar Radiation Pressure Explain ʻOumuamua's Peculiar Acceleration?" (2018) · arxiv.org
- Bergner & Seligman, "Acceleration of 1I/ʻOumuamua from radiolytically produced H2 in H2O ice", Nature (2023) · nature.com
Facts in this article are drawn in part from the Wikipedia articles “ʻOumuamua”, available under the CC BY-SA 4.0 licence.
This page was last edited on 14 November 2026. Articles are written in our own words from the sources listed under References; disputed claims are attributed to the people who made them.
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