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  2. Oort constants - Wikipedia

    en.wikipedia.org/wiki/Oort_constants

    Figure 1: Geometry of the Oort constants derivation, with a field star close to the Sun in the midplane of the Galaxy. Consider a star in the midplane of the Galactic disk with Galactic longitude at a distance from the Sun. Assume that both the star and the Sun have circular orbits around the center of the Galaxy at radii of and from the Galactic Center and rotational velocities of and ...

  3. List of common astronomy symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_common_astronomy...

    Distance description for orbital and non-orbital parameters: d - distance d - in km = kilometer; d - in mi = mile; d - in AU = astronomical unit; d - in ly = light-year; d - in pc = parsec; d - in kpc = kiloparsec (1000 pc) D L - luminosity distance, obtaining an objects distance using only visual aspects

  4. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    The astronomical unit of mass is the solar mass. [1] The symbol M ☉ is often used to refer to this unit. The solar mass (M ☉), 1.988 92 × 10 30 kg, is a standard way to express mass in astronomy, used to describe the masses of other stars and galaxies.

  5. Astronomical seeing - Wikipedia

    en.wikipedia.org/wiki/Astronomical_seeing

    In astronomy, seeing is the degradation of the image of an astronomical object due to turbulence in the atmosphere of Earth that may become visible as blurring, twinkling or variable distortion. The origin of this effect is rapidly changing variations of the optical refractive index along the light path from the object to the detector.

  6. David L. Fried - Wikipedia

    en.wikipedia.org/wiki/David_L._Fried

    David L. Fried (April 13, 1933 – May 5, 2022) was an American scientist, best known for his contributions to optics.Fried described what has come to be known as the Fried Parameter, or r0 (often pronounced r-naught, but also r-zero).

  7. Astronomical constant - Wikipedia

    en.wikipedia.org/wiki/Astronomical_constant

    The astronomical unit of time is a time interval of one day (D) of 86400 seconds.The astronomical unit of mass is the mass of the Sun (S).The astronomical unit of length is that length (A) for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and time.

  8. Orbital eccentricity - Wikipedia

    en.wikipedia.org/wiki/Orbital_eccentricity

    In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit , values between 0 and 1 form an elliptic orbit , 1 is a parabolic escape orbit (or capture orbit), and greater than ...

  9. IAU (1976) System of Astronomical Constants - Wikipedia

    en.wikipedia.org/wiki/IAU_(1976)_System_of...

    The astronomical unit of length is known as the astronomical unit (A or au), which in the IAU(1976) system is defined as the length for which the gravitational constant, more specifically the Gaussian gravitational constant k expressed in the astronomical units (i.e. k 2 has units A 3 S −1 D −2), takes the value of 0.017 202 098 95. This ...