Interstellar Objects

Scientists announced on July 11 that 3I/Atlas, a mysterious interstellar object discovered earlier in July, could be the oldest comet ever seen, potentially more than seven billion years old – three billion years older than our Solar System. It’s only the third interstellar object identified to date.

Understanding Interstellar Objects:

• Origin: Interstellar objects are celestial bodies that originate outside our Solar System and merely travel through it.
• Gravitational Binding: Unlike planets, asteroids, and comets within a star system, these objects are not gravitationally bound to any single star.
• Journey: They can be ejected from other solar systems due to collisions or slingshotted by a planet’s or star’s gravity, sending them into interstellar space (the vast area between stars).
• Previous Discoveries: The first two interstellar objects discovered were 1I/ʻOumuamua (found in 2017) and 2I/Borisov (found in 2019).

How Scientists Determine Interstellar Trajectory:

Scientists compute an object’s trajectory to determine if it is interstellar:

• Solar System Objects: All planets, asteroids, and comets within our Solar System follow closed elliptical orbits.
  • They move fastest at their closest point to the Sun (perihelion) but are eventually slowed down by solar gravity, bringing them back.
  • At their farthest point from the Sun (aphelion), solar gravity pulls them back towards the Sun.
• Interstellar Objects: Their trajectory is fundamentally different:
  • They move in an open-ended hyperbolic orbit.
  • They have a perihelion point (closest to the Sun) but no aphelion (farthest point where they return).
  • This is because they travel at such immense speeds that the Sun’s gravitational pull isn’t strong enough to slow them down sufficiently during their outbound journey, allowing them to escape our Solar System.
• Observation Factors: Scientists determine these trajectories by observing several factors, including:
  • The speed at which the object is moving.
  • Its distance compared to background stars. A fast-moving object at a faraway distance is indicative of a hyperbolic orbit.

(Source: IE)