LSR

class astropy.coordinates.LSR(*args, copy=True, representation_type=None, differential_type=None, **kwargs)

Bases: BaseRADecFrame

A frame in the Local Standard of Rest (LSR).

For Earth-bound observers it is often convenient to use a reference frame that is tied to the Solar System barycenter, but such frames are not very useful for describing galactic dynamics. The dynamical LSR is instead tied to the circular velocity at the Sun’s location, but defining a circular velocity in a non-axisymmetric galaxy requires non-trivial averaging. The kinematic LSR is understood as a frame in which the average motion of the stars in the solar neighborhood is zero, but in practice that is not straightforward either because the average motion is different for different spectral types.

The default parameters of this frame are those of the dynamical LSR of Schönrich et al. (2010), meaning the Galactic (right-handed) Cartesian velocity components of the solar motion are \((U, V, W) = (11.1, 12.24, 7.25)~{{\rm km}}~{{\rm s}}^{{-1}}\), but a different solar motion can be specified with the v_bary argument. The frame is axis-aligned and co-spatial with ICRS.

The frame attributes are listed under Other Parameters.

Parameters:

dataBaseRepresentation subclass instance

A representation object or None to have no data (or use the coordinate component arguments, see below).

raAngle, optional, keyword-only

The RA for this object (dec must also be given and representation must be None).

decAngle, optional, keyword-only

The Declination for this object (ra must also be given and representation must be None).

distanceQuantity [:ref: ‘length’], optional, keyword-only

The Distance for this object along the line-of-sight. (representation must be None).

pm_ra_cosdecQuantity [:ref: ‘angular speed’], optional, keyword-only

The proper motion in Right Ascension (including the cos(dec) factor) for this object (pm_dec must also be given).

pm_decQuantity [:ref: ‘angular speed’], optional, keyword-only

The proper motion in Declination for this object (pm_ra_cosdec must also be given).

radial_velocityQuantity [:ref: ‘speed’], optional, keyword-only

The radial velocity of this object.

representation_typeBaseRepresentation subclass, python:str, optional

A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing representation_type='cartesian' will make the classes expect position data with cartesian names, i.e. x, y, z in most cases unless overridden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

differential_typeBaseDifferential subclass, python:str, python:dict, optional

A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing differential_type='cartesian' will make the classes expect velocity data with the argument names v_x, v_y, v_z unless overridden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

copybool, optional

If True (default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.

Other Parameters:

v_baryCartesianDifferential

The velocity of the solar system barycenter with respect to the LSR, in Galactic cartesian velocity components.

Attributes Summary

default_differential	Default representation for differential data (e.g., velocity)
default_representation	Default representation for position data
frame_attributes
frame_specific_representation_info	Mapping for frame-specific component names
name
v_bary	The relative velocity of the solar-system barycenter

Attributes Documentation

default_differential

Default representation for differential data (e.g., velocity)

default_representation

Default representation for position data

frame_attributes = {'v_bary': <astropy.coordinates.attributes.DifferentialAttribute object>}

frame_specific_representation_info

Mapping for frame-specific component names

name = 'lsr'

v_bary

The relative velocity of the solar-system barycenter

Default: (11.1, 12.24, 7.25) km / s