HIP 21421

E140930

HIP 21421 is the Hipparcos catalog designation for Aldebaran, the bright orange giant star that marks the eye of the constellation Taurus.

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All labels observed (1)

Label Occurrences
HIP 21421 canonical 4

Statements (48)

Predicate Object
instanceOf Hipparcos catalog entry
star
absoluteMagnitudeV −0.63
alsoKnownAs Aldebaran
Alpha Tauri
angularSeparationFromCompanion about 31 arcseconds
apparentMagnitudeV 0.85
bayerDesignation Aldebaran
surface form: α Tauri
belongsToAsterism Hyades
surface form: Hyades region (foreground to Hyades cluster)
catalog Hipparcos satellite
surface form: Hipparcos
chineseAsterism Net (畢宿, Bì Xiù)
colorIndexBminusV 1.54
companionPhysicalAssociation optical double only
constellation Taurus
declination +16° 30′ 33.49″
distanceFromEarth about 65 light-years
effectiveTemperature about 3900 K
equatorialCoordinateSystem International Celestial Reference System
surface form: ICRS
evolutionaryStage red giant branch star
flamsteedDesignation 87 Tauri
galacticLatitude −20.0° (approx)
galacticLongitude 180.97° (approx)
hasChineseName 畢宿五 (Bìxiù wǔ)
hasExoplanetCandidate Aldebaran planetary system
surface form: Aldebaran b (disputed)
hasHenryDraperNumber HD 29139
hasHipparcosNumber 21421
hasHRNumber HR 1457
hasSAONumber SAO 94027
isBrightestStarIn Taurus
isForegroundTo Hyades
surface form: Hyades open cluster
isNakedEyeObject true
isOneOf brightest stars in the night sky
isPrimaryStandardStar yes, for spectral type K5 III
luminosity about 400 times solar luminosity
marksFeatureOfConstellation eye of the Bull in Taurus
mass about 1.2 solar masses
metallicityFeH about −0.34
parallax 48.94 mas
parallaxError 0.77 mas
properMotionDec −188.94 mas/yr
properMotionRA +62.78 mas/yr
radialVelocity +54.2 km/s
radius about 44 times solar radius
rightAscension 04h 35m 55.239s
spectralType K5 III
traditionalNameOrigin Arabic al-dabarān (the follower)
variableStarType slow irregular variable
visualCompanion HIP 21432

How these facts were elicited

The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.

Instruction
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10.

# Requirements
- If you don't know the subject at all, return an empty list.
- If the subject is not a named entity, return an empty list.
- Include at least one triple where predicate is "instanceOf".
- Do not get too wordy.
- Separate several objects into multiple triples with one object.
Input
Subject: HIP 21421
Description of subject: HIP 21421 is the Hipparcos catalog designation for Aldebaran, the bright orange giant star that marks the eye of the constellation Taurus.

Referenced by (4)

Full triples — surface form annotated when it differs from this entity's canonical label.