orbit - Periapsis or Periastron? - Astronomy Stack Exchange "Periapsis" is definitely ancient Greek and it derives from peri+apsi (περί+αψη) Apsi is the noun of the verb "άπτομαι" which means touch something Having said that, this word is only being used in astronomy and there is no literal translation to English, so periapsis and periastron could be used interchangeably
orbital elements - Explanation of Longitude of Periapsis - Astronomy . . . In this coordinate system, the longitude of the orbital periapsis starting from the initial point is FOP, which is the sum, as usual, of $\Omega$ the longitude of the node FON and $\omega$ the argument NOP of periapsis, but now they are measured in the same plane -- which was the thing to be illustrated
Whats the difference between semi-major axis and apoapsis? Apoapsis is a + c and periapsis is a - c Ellipse with e approx; 0 78: For the Earth's orbit around the Sun, a = 149 6 million km and e = 0 0167, so c = ea = 2 5 million km; aphelion = a + c = 152 1 million km; perihelion = a - c = 147 1 million km
Perihelion dates and parameters - Astronomy Stack Exchange As such, yes, it will always be 0 when your actual object is at periapsis Argument of Periapsis, on the other hand, is the angle measured in the plane of the orbit, from the Ascending Node to the Periapsis of the orbit, in the direction of travel around the orbit It remains the same regardless of the position of the object in the orbit
Finding the radius of an eccentric orbit at any point Knowing the apoapsis, periapsis and therefore period of an orbit, how can I find the radius of an object in an orbit at a given angle or time, whichever is needed For example, if I have an object m orbiting around object M with an apoapsis of 100m and a periapsis of 50m, what is the distance between m and M after t seconds, or at $\theta$ degrees
orbit - Whats the formula for change in argument of periapsis over . . . A quick google search gave me the equation for the change in longitude of the ascending node over time, given here, but in the site and also through comparing my model to Celestrak it's very clear that the change in the argument of periapsis over time is also significant
orbit - What is exactly the longitude of the perigee - Astronomy . . . Perigee is the Earth-specific name for periapsis People use longitude (which is a composite angle rather than an angle) because this solves the problems of circular and equatorial orbits The reason you need to use an epoch time to specify the Moon's argument of perigee and longitude of ascending node is because the Moon's orbit about the
Why doesnt the moon always follow the same path? Or why arent the . . . The moon takes 27 days to orbit the Earth, but as the Earth moon system is orbiting the sun there are 29 days between full moons This means that if the moon is at periapsis on the day of the full moon (ie there is a "supermoon") in January, then it will be about two days from full when it reaches periapsis in February
orbit - Confused on how you are supposed to calculate eccentricity . . . The semimajor axis can now be calculated once you have the specific orbital energy, and characterizes the distance of the extremes of the orbit; For an elliptical orbit, the semi-major axis is half the distance between the periapsis and the apoapsis, and for a hyperbolic trajectory, it is half the minimum distance between the two lobes
Orbital resonance and the precession of the periapsis The revolution period of a body is the time it takes to return to pericenter So, for example, Io will return to its perijove after 1 769 days, and Europa to its own perijove after 3 551 days