Gliese 581b
extrasolar planet
Gliese 581b or Gl 581b is an exoplanet orbiting within the Gliese 581 system, located 20.5 light-years (6.3 parsecs) away from Earth in the Libra constellation. It is the first planet discovered of three confirmed in the system so far, and the second in order from the star.
Discovery
The planet was discovered by a team of French and Swiss astronomers, who announced their findings on November 30, 2005, as a discovery of one of the smallest exoplanets then found, with one conclusion being that planets may be more common around the smallest stars. It was the fifth planet found around a red dwarf star (after Gliese 876's first three planets and Gliese 436 b).
The planet was discovered using the HARPS instrument, with which they found the host star to have a wobble that implied the existence of the planet.
The astronomers published their results in Astronomy and Astrophysics Letters.
Orbit and mass
Gliese 581b has a minimum mass of approximately 15.8 times the Earth's mass, similar to Neptune's mass. It does not transit its star, implying that its orbital inclination is less than 88.1 degrees. A 2024 study determined the inclination of the planet, allowing its true mass to be determined, which is about 30% greater than the minimum mass at about 20.5 Earth masses.
The planet is rather close to Gliese 581 and completes a full orbit in only 5.37 days at a mean distance of about 6 million kilometers (0.04 AU).
The public source identifies “Gliese 581b” as extrasolar planet. This brief keeps that definition visible, then builds a research path around Gliese, 581b and extrasolar.
Why this record matters
A short description can identify a subject without explaining its stakes. For “Gliese 581b”, the useful work is to connect “extrasolar planet” to the records capable of establishing context and consequence.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 9, 2026. The linked authority identifier is Q817196. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2005 and 2024.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Gliese 581b”, its source revision and the description used here.
- Expand the search: follow Gliese 581b primary sources, Gliese 581b archive and Gliese research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Gliese 581b”?
- Which cited source is closest to the event, object or claim?
- Which institution is responsible for the underlying evidence?
Search terms from this dossier
This entry incorporates text from “Gliese 581b” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.