sailfish.physics.kepler.PointMass

class sailfish.physics.kepler.PointMass(mass: float, position_x: float, position_y: float, velocity_x: float, velocity_y: float)[source]

Bases: NamedTuple

The mass, 2D position, and 2D velocity of a point-like particle

__init__()

Methods

`__init__`()
`count`(value, /)	Return number of occurrences of value.
`gravitational_acceleration`(x, y, ...)	Return the gravitational acceleration due to a point mass.
`gravitational_potential`(x, y, softening_length)	Return the gravitational potential of a point mass, with softening.
`index`(value[, start, stop])	Return first index of value.
`perturb`([dm, dpx, dpy])	Perturb the mass and momentum of a point mass.

Attributes

`angular_momentum`	The angular momentum of a point mass
`kinetic_energy`	The kinetic energy of a point mass
`mass`	Alias for field number 0
`position_x`	Alias for field number 1
`position_y`	Alias for field number 2
`velocity_x`	Alias for field number 3
`velocity_y`	Alias for field number 4

property angular_momentum: float: The angular momentum of a point mass

count(value, /): Return number of occurrences of value.

gravitational_acceleration(x: float, y: float, softening_length: float) -> (<class 'float'>, <class 'float'>)[source]: Return the gravitational acceleration due to a point mass.

gravitational_potential(x: float, y: float, softening_length: float) → float[source]: Return the gravitational potential of a point mass, with softening.

index(value, start=0, stop=9223372036854775807, /)

Return first index of value.

Raises ValueError if the value is not present.

property kinetic_energy: float: The kinetic energy of a point mass

mass: float: Alias for field number 0

perturb(dm: float = 0.0, dpx: float = 0.0, dpy: float = 0.0) → PointMass[source]

Perturb the mass and momentum of a point mass.

Since the point mass maintains a velocity rather than momentum, the velocity is changed according to

dv = (dp - v dm) / m

position_x: float: Alias for field number 1

position_y: float: Alias for field number 2

velocity_x: float: Alias for field number 3

velocity_y: float: Alias for field number 4