Trojan Asteroid: Could It Affect Future Space Missions?

by TK Sanders

Scientists recently determined that an asteroid shares Earth’s orbit around the Sun — only the second such celestial body ever to have been discovered. The asteroid measures about a kilometer in length and spins approximately two months ahead of Earth in the orbit.

Known as 2020 XL5, the asteroid appeared for scientists in December of 2020. Scientists used advanced telescopes stationed atop a mountain in Hawaii to research the asteroid. Other experts in Chile then studied the projectile more closely using a 4.1 meter SOAR telescope.

Planetary scientist Toni Santana-Ros of the University of Alicante in Spain used the data to determine the path and behavior of the asteroid. Santana-Ros said that 2020 XL5 is trapped for at least the next several thousand years in an orbit fixed upon one of the Sun-Earth “Lagrange points.”

These points designate stability based on gravitational forces between the Earth and Sun. Therefore, the object keeps pace with the Earth as it goes round the Sun; and should not waver in its own path for millinea.

More specifically, Lagrange points are equilibrium points for any objects with small mass under the influence of any two much more massive bodies. They are important because spacecraft can occupy these points for a “free ride” throughout space without needing much fuel. The known points in Earth’s immediate proximity were discovered in the 18th century by mathematicians.

How did math determine the points, and how can the points help future missions?

Scientists figured out that small points 60 degrees ahead of Earth and 60 degrees behind Earth provided stable equilibriums. Because 60 degrees equates to one-sixth of the Earth’s orbit (360 degrees), then one-sixth of a calendar year, or full cycle orbit, is about two months. Simple math, really.

Inhabitants of Earth need not fear debris stuck in a Lagrange point. Polar gravity of the Sun and Earth won’t let the floating mass escape the point. The debris tries to meander from the orbit. But is immediately drawn back, with the flight path resembling that of a kidney bean — oblong and a bit curved.

Scientists refer to 2020 XL5 as a Trojan asteroid as a form of shorthand. Actual “Trojan” asteroids only exist in Jupiter’s orbit, but scientists borrowed the lingo in this instance. Similar asteroids exist all across the galaxy; but 2020 XL5 is just the second Trojan in Earth’s orbit.

Though 2020 XL5 poses some difficult process risks in terms of exploration, scientists remain hopeful that Trojan asteroids could help us understand space better. Ideally, a spacecraft could one day dock on such an asteroid. From there, the asteroid would serve as a home base to explore other parts of the galaxy. We could mine the asteroids for minerals, or use them as low gravity launchpads, too.