What is an apsis in astronomy?
Q: What is an apsis in astronomy?
A: An apsis in astronomy is the point of greatest or least distance of the elliptical orbit of an astronomical object from its center of attraction.
Q: What is the point of closest approach in an elliptical orbit called?
A: The point of closest approach in an elliptical orbit is called the periapsis or pericentre.
Q: What is the point of farthest excursion in an elliptical orbit called?
A: The point of farthest excursion in an elliptical orbit is called the apoapsis, apocentre or apapsis.
Q: What is the major axis of an ellipse?
A: The major axis of an ellipse is the line through the longest part of the ellipse, which is drawn through the periapsis and apoapsis and is also known as the line of apsides.
Q: What are the similar words used to identify the body being orbited?
A: The similar words used to identify the body being orbited are perigee and apogee for orbits around the Earth, and perihelion and aphelion for orbits around the Sun.
Q: What are the terms used for referring to the moon during the Apollo program?
A: The terms used for referring to the moon during the Apollo program were pericynthion and apocynthion.
Q: What does the term apoapsis mean etymologically?
A: Etymologically, the term apoapsis comes from the Greek word από (apo) which means "from," and refers to the point farthest away from the center of attraction in an elliptical orbit.
