About ʻOumuamua
The first object known to have come from outside the Solar System, found in 2017 — and briefly suggested to be an alien probe.
- 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)
The full story, section by section
The story of ʻOumuamua in 4 parts. Tap any part to read it in full.
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An unusual visitorIts speed and path showed it was not bound to the Sun: it came from interstellar space and is leaving for good.Read this part → Illustration drawn for this site — not a photograph.
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The "alien light sail" ideaIn 2018 Harvard astronomers Shmuel Bialy and Avi Loeb suggested the push could come from sunlight on a thin, artificial light sail.Read this part → Illustration drawn for this site — not a photograph.
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Natural explanationsProposed 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.Read this part → Illustration drawn for this site — not a photograph.
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Later interstellar objectsTwo more interstellar objects have since been found: the comet 2I/Borisov in 2019, and 3I/ATLAS in 2025.Read this part → Illustration drawn for this site — not a photograph.
Key people
The people at the centre of the story — witnesses, investigators, officials and sceptics:
- Avi LoebAbraham Avi Loeb is an Israeli-American theoretical physicist and professor at Harvard University who has researched astrophysics and cosmology. He became widely known for arguing that interstellar o…
Related cases & events
Events and sightings linked to ʻOumuamua:
Programs, organizations & documents
The official programs, groups and papers involved:
🏛️ Program or study · 5 min readGalileo ProjectThe Galileo Project is a privately funded research project founded in July 2021 and led by Harvard astrophysicist Avi Loeb to search for physical evidence of extraterrestrial technology. By late 2025, the project operated sky-watching observatories in Cambrid…
🏛️ Program or study · 2 min readSETIThe Search for Extraterrestrial Intelligence: listening for signals from civilisations on other worlds.🏛️ Official records
- AAWSAP DIRD, Aneutronic Fusion Propulsion II, November 2010Department of War · 2010-11-01This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIR…
- Apollo 17 Crew Debriefing for Science, 1973NASA · 1973Apollo 17 was the ninth crewed U.S. mission to the Moon, and the sixth to land Astronauts on the lunar surface. This document is an excerpt from the Apollo 17 Crew Debriefing for Science on January 8, 1973, in which Dic…
🛸 UFO sightings about ʻOumuamua
Sightings that mention ʻOumuamua
More in the encyclopedia
Other articles that link to or mention ʻOumuamua:
- Wow! signalA strong radio signal recorded in 1977 that looked like what SETI was searching for, and was never heard again.
- UAP hearingsPublic hearings in the U.S. Congress on UFOs and UAP, from 1966 to the whistleblower hearings of 2023–2025.
Questions & answers
What is ʻOumuamua?
ʻOumuamua: The first object known to have come from outside the Solar System, found in 2017 — and briefly suggested to be an alien probe. Read: ʻOumuamua →
What else is ʻOumuamua called?
ʻOumuamua is also known as Oumuamua, 1I/2017 U1.
Who is Avi Loeb?
Avi Loeb: Abraham Avi Loeb is an Israeli-American theoretical physicist and professor at Harvard University who has researched astrophysics and cosmology. He became widely known for arguing that interstellar objects passing through the Solar System, such as ʻOumuamua, could be alien technology. His claims have been widely rejected by other scientists and led to professional isolation, though he founded the Galileo Project and was named chair of the UAP Science Advisory Council in June 2026. Read: Avi Loeb →
What was 3I/ATLAS?
3I/ATLAS: The third known interstellar object, a comet found in July 2025 that sparked claims of alien technology. Read: 3I/ATLAS →
What is Galileo Project?
Galileo Project: The Galileo Project is a privately funded research project founded in July 2021 and led by Harvard astrophysicist Avi Loeb to search for physical evidence of extraterrestrial technology. By late 2025, the project operated sky-watching observatories in Cambridge, Massachusetts, Pennsylvania, and Las Vegas to photograph unidentified aerial phenomena, study interstellar objects, and search for alien satellites. The project has drawn strong criticism and mixed reactions from other scientists regarding its methods, claims, and findings. Read: Galileo Project →
What is SETI?
SETI: The Search for Extraterrestrial Intelligence: listening for signals from civilisations on other worlds. Read: SETI →