Astrophysics (Index)About

eccentricity

(e)
(degree to which an orbit is non-circular)

The term eccentricity refers to an orbit's non-circularity, and is more specifically used for a numerical quantification (e) of the non-circularity, with zero for a circular orbit, between zero and one for an elliptical orbit, 1 for a parabolic trajectory, and greater than 1 for hyperbolic. The eccentricity of an elliptical orbit is:

    ra - rp
e = ———————
    ra + rp

Where:

Earth's orbit has an eccentricity of 0.0167, the Moon's is 0.0549, and Halley's Comet's is 0.97.

An extra-solar planet's orbital eccentricity can aid in the study of its atmosphere: electromagnetic radiation from the system includes reflected light from the planet, which varies due to the distance between star and planet, including effects of the planet's atmospheric temperature and weather resulting from this varying temperature. Differential spectroscopy through the course of the orbit offers additional clues regarding the atmosphere's constituents.


(orbits,celestial mechanics,measure)
Further reading:
http://en.wikipedia.org/wiki/Orbital_eccentricity

Referenced by pages:
apsis
black hole merger
Ceres
comet
corotation resonance (CR)
damocloid
DQ Tau
Earth
extreme mass ratio inspiral (EMRI)
EXOSAT
exosphere
giant planet
HD 80606 b
Hill radius
Jupiter
Kozai mechanism
Kuiper Belt (K Belt)
late heavy bombardment (LHB)
libration
Mars
mean anomaly
Mercury
moon
Neptune
orbital element
Planet Nine
planet formation
Pluto
precession
Laplace radius (rL)
Saturn
Sedna
semi-major axis (a)
sidereal
solar circle
solar constant
solar time
Solar Orbiter (SolO)
synodic period
tidal heating
tidal Q
trans-Neptunian object (TNO)
Uranus
Venus

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