Answer to Question #306256 in Astronomy | Astrophysics for Rohan

Question

Why is the orbit of the telescope stable nonetheless? What otherforces need to be considered?

Answer 1

This orbit is unique in that it allows the telescope to remain aligned with the Earth as it orbits the Sun. This permits the enormous sunshield on the satellite to protect the telescope from the Sun's and Earth's heat and light (and Moon). The orbit of the telescope is usually stable because of balance of the Sun's and Earth's combined gravitational pulls at the L2 point which enable the Webb to keep up with the Earth as it orbits the Sun. At this time, the gravitational forces of the Sun and the Earth are essentially enough to sustain a spacecraft in orbit about L2, requiring only a small amount of rocket energy to hold the spacecraft in orbit around L2. Webb will also orbit L2, rather than sit perfectly still at L2. The telescope is kept out of the shades of both the Moon and Earth by this orbit (which takes Webb around 6 months to complete).

The precise balance between a satellite's speed and gravity's pull is what keeps it all afloat. If they're going at the right speed, they will fall at same pace that the Earth's arc falls away from them. That is, rather than speeding further into orbit or plummeting down to Earth, they remain in orbit around the earth. The gravitational pull of the Earth is greater in some locations than in others. The moon, the sun, and even the planet Jupiter may all drag spacecraft together. You would imagine that gravitation would be sufficient to cope with. Spacecraft in low earth orbit, such as the Hubble Space Telescope, can, nonetheless, be dragged out of their orbit by atmospheric drag.