Astronomy (Symbols)
===================

Symbols related to astronomy.

.. py:currentmodule:: symplyphysics.symbols.astronomy

.. py:data:: absolute_magnitude

    **Absolute magnitude** is a measure of the luminosity of a celestial object on an inverse
    logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be
    equal to the apparent magnitude that the object would have if it were viewed from a
    distance of exactly 10 parsecs, without extinction or dimming of its light due to
    absorption by interstellar matter and cosmic dust.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Absolute_magnitude>`__.

Symbol:
    :code:`M`

Latex:
    :math:`M`

Dimension:
    :code:`dimensionless`


.. py:data:: apparent_magnitude

    **Apparent magnitude** is a measure of the brightness of a star, astronomical object or other
    celestial objects like artificial satellites. Its value depends on its intrinsic luminosity,
    its distance, and any extinction of the object's light caused by interstellar dust along the
    line of sight to the observer.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Apparent_magnitude>`__.

Symbol:
    :code:`m`

Latex:
    :math:`m`

Dimension:
    :code:`dimensionless`


.. py:data:: luminosity

    In astronomy, **luminosity** is the total amount of electromagnetic energy emitted per unit of
    time by a star, galaxy, or other astronomical objects.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Luminosity#>`__.

Symbol:
    :code:`L`

Latex:
    :math:`L`

Dimension:
    :code:`power`


.. py:data:: illuminance

    In photometry, **illuminance** is the total luminous flux incident on a surface, per unit area.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Illuminance#>`__.

Symbol:
    :code:`E_v`

Latex:
    :math:`E_\text{v}`

Dimension:
    :code:`luminous_intensity/area`


.. py:data:: irradiance

    In radiometry, **irradiance**, or **flux density**, is the radiant flux received by a
    surface per unit area.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Irradiance>`__.

Symbol:
    :code:`E_e`

Latex:
    :math:`E_\text{e}`

Dimension:
    :code:`power/area`


.. py:data:: eccentricity

    The **eccentricity** of a conic section is a non-negative real number that uniquely
    characterizes its shape. 

Symbol:
    :code:`e`

Latex:
    :math:`e`

Dimension:
    :code:`dimensionless`


.. py:data:: zenith_angle

    The **zenith angle**, or **zenith angular distance**, is the angle between a direction of
    interest (e.g. a star) and the local zenith.

Symbol:
    :code:`theta`

Latex:
    :math:`\theta`

Dimension:
    :code:`angle`


.. py:data:: declination

    **Declination** is one of the two angles that locate a point on the celestial sphere in
    the equatorial coordinate system, measured north (positive) or south (negative) of the
    celestial equator.

Symbol:
    :code:`delta`

Latex:
    :math:`\delta`

Dimension:
    :code:`angle`


.. py:data:: altitude

    **Altitude**, sometimes referred to as **elevation** or **apparent height**, is the angle
    between the object and the observer's local horizon.

    **Links:**

    #. `Wikipedia <https://en.wikipedia.org/wiki/Horizontal_coordinate_system#Definition>`__.

Symbol:
    :code:`h`

Latex:
    :math:`h`

Dimension:
    :code:`angle`