StarCluster

Star clusters from a variety of well‐known catalogs.

Entity["StarCluster",name] or

represents an entity of type "StarCluster".

[prop]

gives the value of a specified property.

[{prop₁,…}]

gives the value of a list of properties.

[prop,{qual_ival_i,…}]

gives the value of a specified property modified by qualifier rules qual_i->val_i.

[Dated[prop,date]]

gives the value of a property associated with a particular date specification.

EntityClass["StarCluster",{prop_ispec_i,…}]

represents a class of entities with values of prop_i defined by spec_i.

Sample Entities

Sample Entity Classes

Properties

	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
	EntityTypeList	entity type list
	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

Details

"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.

Examples

open allclose all

Basic Examples (6)

Use for discovery:

Find the distance to a star cluster:

Retrieve a dataset of all available properties for an entity:

Find the three brightest star clusters:

Find the equatorial coordinates of a star cluster:

Find the current sky position of a star cluster from your location:

Scope (4)

Implicit Entity Classes (1)

Represent the three brightest star clusters:

Get a list of the star clusters:

Property Classes (1)

Represent equatorial coordinate properties associated with star clusters:

Get a list of available property classes for star clusters:

Find the list of properties included in a property class:

Obtain the property values for the properties in a property class for an entity:

Qualifiers (2)

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:

Dates (1)

Date qualifiers can accept an explicit DateObject or queries that evaluate to a DateObject:

Date qualifiers can also be specified using Dated:

Applications (2)

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:

Top