Hyperbolic asteroid facts for kids

A hyperbolic asteroid is a space rock that travels on a special path not bound to our Sun. Imagine throwing a ball so fast it never comes back down—that's similar to the path of a hyperbolic asteroid. Its orbit has a shape called a hyperbola, which means it has an orbital eccentricity (a number that describes the shape of an orbit) greater than 1.

Unlike comets, these asteroids don't have a fuzzy cloud of gas and dust around them, known as a coma. Most of these objects are only slightly hyperbolic and probably started their journey inside our Solar System, rather than coming from another star.

What is a Hyperbolic Orbit?

Most planets and asteroids in our Solar System travel in nearly circular paths around the Sun. These are called elliptical orbits, and their eccentricity is close to 0. An orbit's shape is measured by its eccentricity.

• An eccentricity of 0 is a perfect circle.
• An eccentricity between 0 and 1 is an ellipse (a stretched-out circle).
• An eccentricity of exactly 1 is a parabola (a U-shape).
• An eccentricity greater than 1 is a hyperbola (a wider, open curve).

Because hyperbolic asteroids have an eccentricity greater than 1, their path is an open curve. This means they fly towards the Sun, swing around it, and then head back out into deep space, never to return.

Known Hyperbolic Visitors

Scientists are always on the lookout for these fast-moving objects. Sometimes, an object that is first identified as a hyperbolic asteroid later starts to show comet-like behavior, like releasing gas.

The most famous hyperbolic object is ʻOumuamua. It moved like a comet, but scientists never saw it release any gas or dust. Because of this, it is listed as a hyperbolic asteroid.

Here are some other objects that were first thought to be hyperbolic asteroids but were later found to be comets:

• C/2017 U7 (A/2017 U7)
• C/2018 C2 (Lemmon)
• C/2018 F4 (PANSTARRS)
• C/2019 O3 (Palomar)
• C/2019 G4

Astronomer David Jewitt thinks we might see more of these objects coming from the direction of the Lyra constellation. This is the same part of the sky where ʻOumuamua appeared to come from.

How Do Asteroids Get These Orbits?

An asteroid can be thrown onto a hyperbolic path by the powerful gravity of a giant planet like Jupiter. This is called a gravitational "perturbation," which is like a giant cosmic nudge.

When a small asteroid passes too close to Jupiter, the planet's gravity can act like a slingshot, flinging the asteroid at high speed. This boost in speed can change its orbit from a closed loop into an open hyperbola, sending it on a one-way trip out of the Solar System.

See also

• ʻOumuamua, the first interstellar object detected in our Solar System.
• Hyperbolic comet, a comet with an orbit that escapes the Sun.
• Interstellar object