StarClusterRelated Interpreter »
represents an entity of type "StarCluster".
gives the value of a specified property.
gives the value of a list of properties.
gives the value of a specified property modified by qualifier rules quali->vali.
gives the value of a property associated with a particular date specification.
represents a class of entities with values of propi defined by speci.
Sample Entity Classes
AlphanumericName alphanumeric name AlternateNames alternate names Altitude altitude AltitudeTransit next transit altitude AngularDiameterFromEarth angular diameter AngularRadiusFromEarth angular radius ApparentAltitude apparent altitude ApparentMagnitude apparent magnitude Azimuth azimuth AzimuthRise azimuth at rise AzimuthSet azimuth at set BlueBandMagnitude blue band magnitude BooleanRise above the horizon Classes classes Constellation constellation DailyTimeAboveHorizon daily time above horizon Declination declination Diameter average diameter DistanceFromEarth distance from Earth DistanceFromSun distance from Sun EntityClasses entity classes GalacticLatitude galactic latitude GalacticLongitude galactic longitude GeocentricEclipticLatitude geocentric ecliptic latitude GeocentricEclipticLongitude geocentric ecliptic longitude GlobularClusterType Shapley–Sawyer concentration class GreenwichHourAngle Greenwich hour angle HeliocentricEclipticLatitude heliocentric ecliptic latitude HeliocentricEclipticLongitude heliocentric ecliptic longitude HelioCoordinates heliocentric XYZ coordinates ICNumber IC number Image image LocalHourAngle local hour angle MajorAxis major axis MaximalAltitudeTime next maximum altitude time MinorAxis minor axis Name name NGCNumber NGC number ObjectType object type RadialVelocity radial velocity Radius average radius Redshift redshift RightAscension right ascension RiseTime next rise SetTime next set SiderealHourAngle sidereal hour angle TransitTime next transit time VisualBandMagnitude visual band magnitude ZenithAngle zenith angle
- "StarCluster" entities include the majority of star clusters from the Revised New General Catalogue and Index Catalogue, including members of the Messier Catalog.
- "StarCluster" entity classes include groups based on star cluster type, such as "open star clusters" and "globular clusters", as well as groups related to catalog membership, such as "Messier objects".
- Some properties are available for the "StarCluster" entity type as a whole and can be given using the form EntityValue["StarCluster",property]. Such properties include:
"Properties" the list of available properties "PropertyCanonicalNames" the standard names of available properties "SampleEntities" a sample list of available entities (typically of length 10) "SampleEntityClasses" a sample list of available entity classes (typically of length 10) "EntityCount" number of entities available "Entities" the list of available entities "EntityCanonicalNames" the standard names of available entities "EntityClasses" the list of available entity classes "EntityClassCanonicalNames" the standard names of available entity classes "PropertyClasses" the list of available property classes "PropertyClassCanonicalNames" the standard names of available property classes "PropertyCount" number of properties available
- The following annotations can be used in the third argument of EntityValue["StarCluster",property,annotation]:
"Source" source information for the property "Date" the date associated with the entity-property value (if any) "EntityAssociation" an association of entities and entity-property values "PropertyAssociation" an association of properties and entity-property values "EntityPropertyAssociation" an association in which the specified entities are keys, and values are a nested association of properties and entity-property values "PropertyEntityAssociation" an association in which the specified properties are keys, and values are a nested association of entities and entity-property values "Dataset" a dataset in which the specified entities are keys, and values are an association of property names and entity-property values
- The following annotations can be used in the second argument of EntityValue[property,annotation]:
"Qualifiers" the list of possible qualifiers for the property "QualifierValues" the list of possible values that can be given to each qualifier "DefaultQualifierValues" the list of default values for the property's qualifiers "Description" a brief textual description of the property "Definition" a detailed textual definition of the property "PhysicalQuantity" the physical quantity associated with the entity-property value "Unit" the unit associated with the entity-property value
- A qualifier value of Automatic indicates that an applicable format of values can be used; e.g. for the "Date" qualifier, this includes a proper date or date span.
Examplesopen allclose all
Basic Examples (6)
Implicit Entity Classes (1)
Property Classes (1)
Some properties accept qualifiers:
The "Location" qualifier, which specifies the location of the observer, can accept an explicit GeoPosition, location-based Entity objects or queries that evaluate to one of these:
Date qualifiers can accept an explicit DateObject or queries that evaluate to a DateObject:
Date qualifiers can also be specified using Dated:
Globular clusters are distributed spherically around the center of the galaxy. Before radio and infrared astronomy, which allow you to see through all the dust that obscures your view of the center of the galaxy, globular clusters could be used to estimate the location of the galactic center.
First, obtain the 3D coordinates of the globular star clusters:
Convert the coordinates into Cartesian coordinates and remove outliers:
Obtain the coordinates of the actual galactic center:
Plot the center as a + with the actual center in black, the centroid in red and the location of the Sun as a large black point:
Globular star clusters are distributed spherically around the center of the galaxy, but open star clusters are mainly confined to the galactic plane. You can use the location of open star clusters to find the galactic plane.
First, obtain the 3D coordinates of the globular star clusters:
Obtain the 3D coordinates of the open star clusters:
Fit the open star cluster positions to a 3D plane:
Determine the normal to the galactic plane, find its center and create a graphical representation:
Plot all star clusters, with open clusters in blue and globular clusters in red, along with the galactic plane: